Steric Gating Directs Room-Temperature Hydrosilylation on Silicon Hydride Surfaces

Steric Gating Directs Room-Temperature Hydrosilylation on Silicon Hydride Surfaces | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Steric Gating Directs Room-Temperature Hydrosilylation on Silicon Hydride Surfaces Yit Lung Khung, Peng-Mou Chen, Yi-Jen Lin This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6954985/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Stable formation of Si–C bonded monolayers on hydrogen-terminated silicon at room temperature is often hindered by surface oxidation. We reported a mechanistic study of propargylamine and 1,5-hexadiene grafting on atomically flat, planar, and porous silicon surfaces. Using XPS, FTIR, AFM, and contact angle analysis, we showed that both surface roughness and molecular structure can govern reactivity and oxidation. While 1,5-hexadiene showed minimal oxidation, propargylamine induced oxidation that scales with roughness. Interestingly, on atomically flat silicon, dense Si–H groups sterically gate the surface, favoring alkyne–Si coupling. Notably, the distal amine group in grafted propargylamine promoted localized oxidation of nearby Si–H bonds through dipolar or hydrogen bonding effects—a rarely reported pathway. This revealed a new oxidation mechanism initiated by surface-bound nucleophiles. Our results highlight steric gating and distal-group effects as critical for tailoring silicon surface chemistry, with implications for molecular electronics and interface design. Physical sciences/Chemistry/Surface chemistry/Surface spectroscopy Physical sciences/Chemistry/Surface chemistry/Surface assembly Physical sciences/Chemistry/Physical chemistry/Reaction kinetics and dynamics Room-Temperature Hydrosilylation Steric Gating Silicon Surface Functionalization Surface Oxidation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Room-temperature hydrosilylation has been one of the more attractive strategies for forming stable Si–C bonds 1 – 4 . Performing hydrosilylation under ambient conditions can significantly reduce the risk of surface oxidation, and if the reaction proceeds without a catalyst, the oxidation risk is further minimized. While several approaches have been reported for achieving room-temperature hydrosilylation, the underlying mechanistic consensus remains unclear 3 . However, there is an emerging trend toward the use of polarizing additives to enhance surface reactivity toward unsaturated carbon species. Notably, most academic reports on room-temperature hydrosilylation focus on nanoparticulate silicon 5 – 9 , with relatively little discussion of planar or atomically flat surfaces. This is particularly striking, as planar silicon carries more direct technological relevance and should serve as a principal substrate for understanding surface reaction mechanisms. In terms, achieving high quality monolayer on oxide-free planar silicon via room temperature reactions would be considered as a major advancement in the areas of molecular electronics and hence it is necessary to begin address the intrinsic chemistry underlying these processes. To address how surface roughness may also influence room temperature hydrosilylation, we proposed the grafting of propargylamine at room temperature (in ethyl propionate, an aprotic solvent for 4 hours) on three silicon-based surfaces of different nature, (1) atomically flatten silicon, (2) planar pristine silicon and (3) porous silicon. We want to examine how propargylamine would interact to surfaces of different roughness and to determine the subtle differences the surface roughness would render to the overall hydrosilylation reaction. After the organic grafting, the surfaces were examined via XPS, ATR-FTIR, water goniometry as well as AFM provide a clear picture pertaining to the chemical process of this novel room temperature hydrosilylation. The intrinsic mode of reaction mechanism is also hypothesized and deduced based on our experimental findings. From the different surfaces, we had identified an interesting trend in the form of steric gating, especially how steric access and morphology can influence the reaction notably for atomically flatten silicon surface. These unique findings ultimately provide the all the necessary impetus for this work and a graphical illustration is as prepared below in Fig. 1 . Results Three topographically distinct silicon surfaces were prepared to investigate the influence of surface roughness on room-temperature reactions of oxide-free silicon. Ethyl propionate was selected as the reaction medium due to its moderate dielectric constant (~ 5.7), providing sufficient polarity to enable dipolar interactions with the Si–H surface while remaining non-disruptive to the hydride layer. Such interactions are proposed to facilitate room-temperature coupling between the silicon substrate and unsaturated carbon species, promoting Si–C bond formation without perturbing the intrinsic surface chemistry 3 . Prior to physical experimentation, DFT calculations were first performed on propargylamine, 1,5-hexadiene, and ethyl propionate (Fig. 2 and Supplementary Fig. 1) to examine their electronic structures and electrostatic characteristics. The electrostatic potential (ESP) map of propargylamine revealed two electron-rich regions: one localized at the amine terminus and another at the unsaturated carbon moiety. In contrast, 1,5-hexadiene exhibited a more uniform ESP distribution with no significant dipolar character. Propargylamine also showed a notable dipole moment (0.63 D) compared to the nonpolar 1,5-hexadiene (0.00 D). It is important to note that while the experimental system employed ethyl propionate as the solvent (1.93 D), all DFT calculations were performed in the gas phase to evaluate intrinsic molecular polarity and charge distribution. This comparison remains relevant, as molecule–surface interactions at the solid–liquid interface is primarily governed by local electrostatic environments where bulk solvation effects are mostly attenuated. Potential interference between propargylamine and ethyl propionate was not considered a significant concern, as esters are relatively weak hydrogen bond acceptors and are unlikely to sequester the amine functionality or participate in surface reactivity under the conditions used 10 . These insights were essential for interpreting subsequent reactivity trends and constructing the proposed reaction mechanism. A reaction time of 4 hours was selected to capture early-stage reactivity and oxidation across different silicon surface morphologies. This relatively short duration enabled the resolution of subtle kinetic differences before extensive oxidation could mask initial surface features. Subsequent characterization confirmed that this time frame was sufficient to produce discernible and interpretable surface modifications. Initial physical characterization of the grafted surfaces was conducted using AFM and contact angle measurements (Fig. 3 ). As expected, the three surface types exhibited distinctly different topographies. In addition to freshly etched surfaces used as controls, we also subjected all surfaces to a 4-hour incubation in neat ethyl propionate (without any reactant) to determine whether the aprotic solvent alone would alter surface chemistry (Supplementary Fig. 2). On atomically flat surfaces, step terraces with heights of 0.3–0.4 nm were observed, consistent with the known morphology of chemically etched atomically flat silicon 11 , while the overall RMS roughness was 0.14 nm. Across all modified atomically flat surfaces, RMS roughness remained between 0.1–0.2 nm, in agreement with literature values 12 . Following propargylamine grafting, the overall surface roughness remained similar to that of the control; however, "kinks" were observed at the step edges of the terraces 13 , 14 , indicating the formation of defects on the terraces. In contrast, grafting of 1,5-hexadiene produced no notable structural changes on the atomically flat surfaces. Such structural defects at step edges are often indicative of localized etching or oxidation. Supporting this, contact angle measurements revealed a marked difference in wettability: propargylamine-modified surfaces exhibited a low contact angle (23.9 ± 2.3°), whereas both control and 1,5-hexadiene-modified surfaces showed significantly higher contact angles (81.4 ± 2.9° and 82.7 ± 2.5°, respectively). Given the contrasting wettability profile of propargylamine-modified surfaces, despite otherwise similar physical features, we sought to better understand the origin of this hydrophilicity. To isolate the effect of water-driven oxidation, we incubated freshly etched atomically flat silicon in pure water for 4 hours at room temperature; the resulting contact angle remained in the 40s (Supplementary Fig. 3). The even lower contact angle observed for propargylamine-modified surfaces suggested that the chemical modifications induced by propargylamine had extend beyond simple oxidation, perhaps introducing additional surface functionalities or interactions that would enhance hydrophilicity of the surface. The RMS for the pristine silicon surface (planar) was measured between 0.2–0.3 nm for all the surface chemical modifications, indicating that the topography remains largely unmodulated. But once again, the contact angle for propargylamine was markedly lower (19.8 ± 1.8°) compared to both the control and 1,5-Hexadiene. This corroboration with our previous results from atomically flat silicon had suggested that the introduction of propargylamine had indeed changed the very nature of the surface chemistry although there was little change on surface roughness. On the other hand, the differences in roughness observed on porous silicon surfaces for propargylamine (RMS: 5.76 nm) was very significant when compared to the control (RMS: 1.33 nm) and that of 1,5 Hexadiene (RMS: 2.57 nm). The surface was also completely hydrophilic (4.5 ± 0.3°) and along with the massive change in surface roughness, the reaction of propargylamine to porous silicon surface even for a short duration of only 4 hours at room temperature was observed to cause significant changes to the porous silicon surface material. In conjunction, neat reaction (in the absence of solvent) was also examined to study the roughening effect on the surfaces (Supplementary Fig. 2) The first chemical profiling of the surface chemistry was performed initially with highly sensitive glazing angle FTIR-ATR at 65° angle to determine the effects of room temperature reaction (Fig. 4 ). Due to the sensitivity of our setup, we were able to register and monitor the signal of silicon hydride (Si-H) at ~ 2084 cm − 1 , a signal as reported commonly for Si-H 15 . Freshly prepared surfaces (regardless of form factor) would present predominantly Si-H bonds on the surface and the loss of this signal would indicate either surface oxidation or hydrosilylation to form surface Si-C bonding. The FTIR-ATR measurement would shed light on the “consumption” of Si-H on the surface and the FTIR spectrum was as presented in Fig. 4 . Normalization of baseline was performed for all surfaces to examine the intensity of the Si-H peak comparatively and we noticed that the depletion of Si-H was lowest for atomically flat silicon while porous silicon surface had seemingly lost most of the Si-H on propargylamine grafted surfaces. This was interestingly as the reaction was performed at room temperature for merely 4 hours and this was enough time to observe the depletion of surface Si-H from porous silicon. There had also been substantial reduction of peak intensity for planar silicon surface and from these observations, it was evidently clear that loss of Si-H from propargylamine grafting has also been different and may be influenced by the overall surface roughness, a point that would be addressed in the subsequent section in this report. An in-depth physicochemical characterization of the top surface layer (~ 2–5 nm) was performed using XPS analysis for all the sample (see Supplementary Fig. 4). High-resolution XPS Si2p spectra were acquired for all three surface types (Fig. 5 ). The freshly prepared control surfaces exhibited negligible oxidation, as indicated by the dominant Si⁰ peak (~ 99 eV) and an absence of significant signal in the 103–104 eV region corresponding to Si–O species. The degree of oxidation was quantified by calculating the ratio of the Si–O peak area to the total Si2p spectral area. As an additional control, freshly etched surfaces were subjected to a 4-hour incubation in ethyl propionate. On atomically flat silicon, no measurable oxidation was observed in the Si2p spectrum following incubation (Supplementary Fig. 5A). For planar and porous silicon surfaces, slight increases in oxidation were detected after 4 hours in ethyl propionate, calculated at 5.21% and 5.84%, respectively (Supplementary Fig. 5B and 5C respectively). These results indicate that under the mildly polar conditions of ethyl propionate at room temperature, the silicon surfaces remain largely inert, with most Si–H moieties preserved. In contrast, the introduction of propargylamine led to a pronounced increase in surface oxidation, even after only 4 hours at room temperature. On atomically flat silicon, the oxidation level rose to 14.5% (Fig. 5 B). On planar silicon, an even higher oxidation level of 24.4% was observed. Notably, on porous silicon, the Si⁰ signal (~ 99 eV) was nearly absent, suggesting extensive oxidation or possible complete loss of the underlying Si–Si network. Conversely, grafting with 1,5-hexadiene resulted in minimal oxidation. On atomically flat silicon, negligible oxidation was detected, while planar and porous silicon exhibited only slight increases (4.7% and 4.3%, respectively). This outcome is consistent with expectations, as 1,5-hexadiene is likely to undergo hydrosilylation through one of its terminal unsaturated carbons to form Si–C bonds, which are known to impart significant resistance to subsequent oxidation of the underlying silicon surface. The complete loss of Si-Si signature from porous silicon on propargylamine grafting was rather unexpected as the reaction had occurred at room temperature for a short duration of 4 hours (Fig. 5 H). From the data obtained, it is envisaged that the presence of the nucleophilic propargylamine could have driven the complete oxidation on the porous surface. When the chemical profiling was examined in tandem with the AFM and FTIR data, it was clear that propargylamine may have caused both extensive structural reshaping of the porous architecture as well as the complete loss of the Si-H. This adherently altered the wettability profile along the principles of Wenzel effect for hydrophilic surface. However, what was more interesting was that subjecting the porous silicon material in water for 4 hours at room temperature did not exhibit similar drastic changes (Supplementary Fig. 3) and the influence from propargylamine should be considered as a chemical reaction on the surface. It was clear that even at room temperature, there was sufficient impetus for propargylamine to alter and affect the surface chemistry on porous silicon to the point of reshaping the topography of the material. By comparing the various Si2p spectrums, it was clear that this chemical effect on the surface by propargylamine was dependent on the roughness of the silicon substratum, with atomically flat resisting physical changes on the surface while porous silicon experiencing extensive structural reshaping. However, there was evidence to suggest that atomically flat silicon had also underwent notable chemical changes as well in the form of surface oxidation. In principle, it is possible to elucidate the nature of surface grafting by examining the high-resolution C1s spectra of the samples. However, the high oxidation levels present on both planar and porous silicon surfaces complicate interpretation of the C1s chemical signals, making it difficult to unambiguously assign surface chemistry for these substrates. In contrast, the near absence of oxidation on the atomically flat silicon surface provided a valuable opportunity to investigate the reaction processes on an oxide-free silicon hydride surface at room temperature. Analysis of the C1s spectrum for atomically flat silicon (Fig. 6 A-C) revealed that, in addition to the expected C–C peak at 285.0 eV, deconvolution identified a clear Si–C signal at 283.9 eV for 1,5-hexadiene and a broader peak centered at 283.4 eV for propargylamine. These results indeed suggested that a 4-hour room-temperature interaction was sufficient to drive hydrosilylation at the unsaturated carbon terminus, forming covalent Si–C bonds. The detail of the C1s for planar and porous silicon was also as shown in Supplementary Fig. 6. To gain further insight into the molecular orientation of grafted propargylamine, we examined the N 1s spectra in both the presence and absence of the polar solvent (ethyl propionate) to study the difference in terms of promoting reactivity (Fig. 6 D). Under standard 1:1 reaction condition, the N1s peak maximum shifted to 399.9 eV in the presence of the solvent, compared to 399.4 eV for neat propargylamine in the absence of solvent. This shift toward higher binding energy suggests that the distal amine groups are engaged in hydrogen bonding interactions 16 , whereas the lower binding energy observed in the neat case is consistent with physisorbed, free and non-interacting amines on the surface 17 . Given that hydrogen bonding would require proximity between the amine and the surface Si–H groups, this supports the conclusion that propargylamine grafting proceeds via reaction of the unsaturated carbon end with the silicon surface. However, as the shift was rather subtle, at ~ 0.5 eV, this may also suggest that the distal amine interaction to neighboring surface hydride was relatively localized. Notably, this interaction appears to enhance local surface oxidation, an effect not previously reported in the literature. Complementary FTIR analysis further confirmed these findings, showing slight depletion of the Si–H stretching band at 2084 cm⁻¹, consistent with consumption of surface Si–H during grafting. The near-complete disappearance of the Si–H signal in the propargylamine-modified sample, combined with the XPS data, strongly suggests that propargylamine promotes surface oxidation, whereas 1,5-hexadiene exhibits minimal impact on surface oxidation under identical conditions. To minimize the formation of a thick underlying oxide layer—which would compromise accurate estimation of the organic monolayer—we deliberately limited the reaction time to 4 hours, even at room temperature. This had help obtain the ideally near-zero oxidation for 1,5-Hexadiene and hence provided the opportunity to compared the surface chemistry between propargylamine and 1,5-Hexadiene. Herein, we relied on the XPS information to estimate the average effective thickness of organic monolayer using standard Beer–Lambert attenuation law, adapted to photoelectron attenuation 18 : $$\:d=\:-\lambda\:\text{cos}\left(\theta\:\right)\text{ln}\frac{I}{{I}_{o}}$$ 1 Where d is the overlayer thickness in nanometer, \(\:\lambda\:\) is the effective attenuation length that is typically taken at 3.3 nm for Si2p through thin organic carbon layer, \(\:\theta\:\) being the photoelectron take-off angle (45°) and \(\:\frac{I}{{I}_{o}}\) is the experimentally measured photoelectron intensity of Si2p before modification ( \(\:{I}_{o}\) ) and after modification ( \(\:I\) ). From the determined areas under the peak, we estimated the monolayer thickness for propargylamine grafting on atomically flat silicon to be approximately 0.59 nm, based on attenuation of the Si2p signal. This was only marginally higher than the theoretical length of 0.49 nm for propargylamine and was highly suggestive for a partially passivated silicon surface. In contrast, the average effective thickness measured for 1,5-Hexadiene was approximately 0.38 nm which was lower than the theoretical height of a fully upright 1,5-Hexadiene (0.9 nm). Interestingly this could indicate that the organic chain may be tilted on the surface and that the surface was also partially passivated, an outcome that was consistent to expectation from a short reaction time of 4 hours at room temperature. It is important to note that these values represent apparent thicknesses, averaging over both grafted and non-grafted surface on atomically flat silicon with step terraces averaging 0.30 nm in height. As the silicon surfaces are not fully passivated, the calculated thickness was subtly suggestive of the nature of the surface reactivity and molecular orientation, a discourse that would be further elaborated in latter segments. Yet, determining the surface coverage of the grafting was useful towards understanding the surface grafting at room temperature. The near absence of oxidation as well as the ‘flatness’ of the material had enable for relatively close estimation based on the quenching of the Si (0) signals (Si2p 3/2 + Si2p 1/2 ) for 1,5 Hexadiene and we determine the coverage based on the model as shown below, $$\:Coverage=\left(1-\frac{I}{{I}_{o}}\right)\:\times\:\:100\%$$ 2 Where I o represents the core Si2p area before grafting and I is the area after the surface had been grafted. For 1,5-Hexadiene, we had determined that the area of coverage on the surface was 15% and this had shown that a short 4-hour room temperature grafting may be too brief to obtain higher passivation on the surface. When estimating the surface coverage of propargylamine, it was necessary to account for the oxidation that had occurred in over to avoid over-estimating the surface coverage from the grafting. To do so, we had slightly altered Eq. ( 2 ) to account for the oxidation as shown below, $$\:Coverage=\left(1-\frac{I}{{I}_{o}}\right)\:\times\:\left(\frac{{I}_{o}}{{I}_{o}+{A}_{si-o}}\right)\times\:\:100\%$$ 3 Where \(\:{A}_{si-o}\) accounts for the area of oxidation (Si2p peak centering at 103–104 eV) to prevent Si-O formation being falsely accounted as coverage. From the modified calculations, we had determined that our surface coverage of propargylamine to be ~ 20% of the surface. A recalculation of 1,5-Hexadiene using the modified equation did not show any notable difference in terms of the outcome (~ 14–15%) in terms of surface coverage and hence will be taken as 15% for the rest of the discourse of this work. The overall calculated surface coverage is as tabulated below in Table 1 . From these findings, we were able to construct a more complete understanding of the reaction mechanism occurring on atomically flat silicon surfaces (see Fig. 7 ). Although surface oxidation was observed following grafting with propargylamine, XPS analysis of both the Si2p and N1s spectra unambiguously indicated the formation of Si–C bonds on atomically flat surfaces. This observation suggests that multiple chemical processes were taking place concurrently. We propose that, in the aprotic solvent ethyl propionate at room temperature, initial interactions between the amine nitrogen and the silicon surface—further influenced by solvent’s moderate polarity—may not be insufficiently energetic to drive direct Si–N bond formation 19 , 20 unless the silicon surface is under an electron deficient condition 21 . Hence, we did not observed the characteristics of Si-N bonding on the surface 22 . Moreover, this interaction was sterically hindered by the densely packed Si–H layer, which imposed a gating effect that limited the approach of the nitrogen atom to the surface. As a result, the molecule likely adopted an alternative orientation, with the unsaturated carbon moiety directed toward the surface. This orientation enabled covalent grafting via Si–C bond formation through a hydrogen abstraction pathway, ultimately yielding a monolayer with distal amine groups protruding from the surface. Because of these observations, we define steric gating as a surface-imposed steric constraint that selectively influences molecular orientation and accessibility of reactive sites in this work. Yet, this was not the end of the surface chemistry. We further proposed that the distal NH₂ groups perturb the local electronic environment of adjacent Si–H bonds, either through hydrogen bonding or dipole–dipole interactions, thereby increasing the susceptibility of these sites to nucleophilic attack by trace water or oxygen. This, in turn, promoted localized oxidation of the surface. Moreover, a partially passivated amine monolayer could attract water molecules closer to the surface, further accelerating oxidation processes. To support this rationale, we also grafted propiolic acid (replacing the amine with a carboxylic acid group) onto the silicon hydride surface 23 (Supplementary Fig. 7). In this case, surface oxidation was substantially lower with notable Si–C bond formation detected. This result was consistent with our hypothesis: the bulkier and more sterically hindered COOH group, combined with the poor donor characteristics of Si–H 24 , limits both close approach between the COOH and Si atom which subsequently causes the molecule to reorientate itself in similar fashion and ultimately forming Si-C bonding although COOH distal group should cause less electronic perturbation of adjacent Si–H bonds, as previously reported by Imanishi et. al 23 . Thus, the comparative behavior between propargylamine and propiolic acid confirms our proposed steric gating model and highlights how molecular orientation at room temperature critically influences both grafting efficiency and surface stability. One of the more interesting aspects from our data was the evidential reshaping of porous silicon micro-architecture after propargylamine was introduced at room temperature. High resolution XPS C1s spectrum did not reveal the presence of Si-C bonding on the surface with the Si2p spectrum showing a complete loss of the Si-Si core signal. This had indicated that amine had catalyze oxidation and assisted in the nucleophilic attack on surfaces which was expedited by the presence of strained bonds existing on the pore edges of the porous material. Unlike atomically flat silicon, porous silicon did not present a dense enough hydride layer to provide the steric gating effect that would discourage interaction between the NH 2 groups and the silicon atom. Hence, from our survey spectrum, we were able to detect for the presence of nitrogen on the surface although the total oxidation from Si2p had rendered the direct observations of Si-N rather challenging. Thus, it was also possible that the curvature of the surface did not provide the necessary steric gating and thus permit for direct inclusion to form Si-N bonding to the surface at room temperature although this reaction was not considered to be productive for the intentions of room temperature hydrosilylation. Furthermore, as NH 2 groups are rather basic and can deprotonate surface species, this may accelerate etching and oxidation of the material and hence we noticed that loss or enlargement of the overall porous architecture network. Interestingly this topographical change was also not observed when propiolic acid was applied to the porous silicon, thus suggesting that the nucleophilic NH 2 was responsible for the physical changes to the surface. Finally, the grafting of planar silicon had shown elevated levels of oxidation although much of the surface morphology remains relatively intact. From our detailed experimentation of the surface, there are several important observations made. Firstly, while room temperature reaction on silicon hydride is feasible for aliphatic alkenes/alkynes, nucleophilic amines represent a more complex picture whereby the grafting of these moieties had triggered a series of chemical processes on the surface that ultimate yield a range of different distal moieties on the surface. These detailed interplay of molecular structure and surface affinity had not been previously described in literature to the best of the author’s knowledge and what was most interesting about the work was that all these described processes had occurred at room temperature. Furthermore, the roughness of the surface was found to be a major consideration, with atomically flat silicon being able to provide the necessary steric gating effects to orientate the incoming molecule and this was very much in consistent with literature where atomically flatten surface tends to resist oxidation 22 , 25 . More importantly, the grafting of propargylamine at room temperature on porous silicon material was non-ideal as the surface of porous silicon was less stable compared to planar and this resulted in the etching events that reshaped the micro-architecture of the material. Significant academic insights emerged from the experimental data and hypothesized mechanism regarding the room-temperature grafting of amine-based alkynes. Firstly, it is well recognized that grafting organic monolayers bearing free amine functional groups onto oxide-free silicon remains a challenging task. Our initial approach was to leverage room temperature to mitigate the reactivity of amines toward the silicon surface, as previous studies had shown that elevated temperatures promote direct amine insertion. However, the results obtained in this study were unexpected: the amine groups remained highly interactive with Si-H surfaces. Notably, the presence of distal amines was found to alter the chemistry of neighboring silicon atoms—an observation not previously documented in the literature. On roughened substrates such as porous silicon, these effects were even more pronounced, leading to enhanced self-etching phenomena. In contrast, UV-assisted hydrosilylation, which generates surface radicals to drive reactions with alkenes or delocalized π-systems, tends to favor a more uniform and "ideal" passivation of the silicon surface. However, the notion that nucleophilic amines merely act as passive spectators in radical-based processes is misleading; amines can effectively trap and quench surface radicals, introducing defects and even promoting dimerization. Thus, while the prospect of achieving a monolayer with distal amines in a single step is appealing for surface passivation, our findings highlight the inherent complexities of amine interactions with oxide-free silicon, even under mild, room-temperature conditions. Discussion In this work, three types of silicon surfaces—atomically flat silicon, planar Si(111), and porous silicon—were prepared and grafted with propargylamine and 1,5-hexadiene at room temperature using ethyl propionate as the solvent. Our initial objective was to investigate whether hydrosilylation could proceed in the absence of any catalytic agents at room temperature. While 1,5-hexadiene successfully grafted onto all surfaces with varying degrees of surface coverage, propargylamine induced a markedly different chemical response, significantly altering the surface chemistry across all substrates. Using atomically flat silicon as a model, we were able to conduct a detailed analysis of how the amine functional group interacts with the surface and how hydrosilylation can be guided through steric gating imposed by the densely packed hydride layer. More notably, we observed that when amine is introduced as a distal functional group, it can profoundly modify the chemistry of neighboring silicon hydrides. This room-temperature observation of such adjacent-molecule effects is significant, as it prompts a reevaluation of how amine-functionalized organic monolayers behave on oxide-free silicon surfaces under mild conditions. Room-temperature hydrosilylation continues to be an important strategy for achieving stable, covalently bonded monolayers on silicon surfaces via Si–C linkage. Given the central role of silicon in modern semiconductor technologies, developing robust, well-passivated surfaces is of considerable technological and commercial relevance. Traditionally, research in this area has focused on relatively simple aliphatic unsaturated carbon species, where surface chemistry is more predictable. In contrast, this work explored how nucleophilic amines influence room-temperature hydrosilylation. Somewhat unexpectedly, we found that amines play a much more complex role than previously appreciated, exerting diverse chemical effects on neighboring silicon hydrides that depend on both surface structure and roughness. These findings contribute important new insights that should help refine our understanding of amine interactions on silicon surfaces and guide the rational design of advanced functional monolayers for a range of silicon-based applications. Methods Unless otherwise noted, all reagents were purchased from Sigma-Aldrich and used without additional purification. Ultrapure HPLC grade water was obtained J.T Bakers and all used in this experiment for washing and other cleaning processes. P-type (111) silicon wafers with a resistivity of 0.001–0.005 ohm.cm were purchased from Semiconductor Wafer, Inc., Taiwan (SWI), and N-type (111) silicon wafers with a resistivity of 1–10 ohm.cm were obtained from Ruilong, Taiwan. Preparation for Planar and Atomically flat silicon Silicon wafers (111) (N-type, 1–10 ohm.cm) were diced into 10 mm × 10 mm pieces using a diamond cutter, followed by sequential ultrasonic cleaning in acetone, ethanol, and HPLC-grade water. The samples were then treated in hot piranha solution for 30 minutes to remove carbon-based contaminants and thoroughly rinsed with HPLC-grade water to eliminate residual acid. For planar surfaces, wafers were etched in 5% HF solution for 10 minutes to remove the native oxide layer. For atomically flat surfaces, wafers were etched in a 40% aqueous NH₄F solution (pH adjusted to ~ 8 with NH₄OH), supplemented with 5% ammonium sulfite as an oxygen scavenger. The etching solution was degassed by argon purging for 15 minutes prior to use. Wafers were etched for 14 minutes and then rinsed with HPLC-grade water Preparation for porous silicon To obtain porous silicon thin films on the surface, electrochemical anodization strategy using DPS-2303DF linear DC power source was used in this work in a setup similar to previous report 26 . In brief, silicon wafers (111) (P-type, 0.001–0.005 ohm-cm) were ultrasonically cleaned for 2 minutes each in acetone, ethanol, and HPLC-grade water, then dried under a nitrogen stream. The wafers were further treated with a plasma cleaner to remove residual carbon impurities. The etching solution was prepared by mixing 70% ethanol, 30% hydrofluoric acid (HF), and 5% Triton X-100 (volume ratio 70:30:5) in a Teflon beaker, with appropriate safety precautions due to HF handling. A custom Teflon etching cell was assembled, with the silicon wafer mounted on a 2.5 cm × 8 cm aluminum foil anode. An O-ring was placed between the wafer and the Teflon container to ensure a tight seal. The assembly was leak-tested with a few drops of ethanol before proceeding. Electrodes were connected with a platinum wire as the cathode (centered in the cell) and a thick aluminum foil as the anode. The power supply (DPS-2303DF) was configured with a fixed current of 0.03 A at maximum voltage. After introducing 4.8 mL of the etching solution into the cell, the etching process was carried out for 1 minute. Following etching, the HF solution was carefully removed, and the porous silicon (pSi) wafer was rinsed five times with 2 mL aliquots of ethanol to ensure complete removal of residual HF. The wafer was then rinsed with cupious amounts of HPLC-grade water and dried under nitrogen. Surface modification All surface reactions were performed immediately after the silicon material had been etched and without delay. In brief, a solution of ethyl propionate and propargylamine (at aratio 1:1) was prepared and sealed in a customized Schlenk reactor vessel. The rectant solution then underwent at least 10 cycles of freeze-pump thaw under constant vacuum to remove most of the oxygen in the system, in a process similar to previous report from our group 22 , 27 . Nitrogen gas was subsequently introduced slowly to the reactant mix and the freshly prepared silicon sample were carefully introduced and sealed with parafilm for 4 hours at room temperature. After the reaction time, the surfaces were removed from the Schlenk reactor and were washed with copious amounts of methanol, ethanol, acetone, and water in sequential order. The surfaces were then dried with nitrogen and were packed in specially prepared vacuum packages to prevent contamination and oxidation prior to further analysis. Contact angle measurement After the grafting reaction, the surfaces were detected to have a contact angle via a computerized Contact Angle Goniometer (Contact Angle Analyzer from High View Innovation, Taiwan). All contact angle images were acquired via a CCD camera (hVI Series Camera, Taiwan) at a resolution of 2560 × 1920 automatically captured via software built into this equipment. Each chemically grafted surface’s contact angle was performed using a 2 µl stationary droplet. Post-capture, the contact angle images were analyzed using the Dropsnake 2.1 add-on in ImageJ software (version 1.52k). X-ray Photoelectron Spectroscopy (XPS) For all grafted sample X-ray Photoelectron Spectroscopy (XPS) studies, a PHI 5000 VersaProbe (ULVAC-PHI) fitted with an Al Kα X-ray source (1486.6 eV) was used. High-resolution spectra for N1s, Si2p, C1s, and O1s were obtained by recording all changed surfaces at a 45° take-off angle relative to the surfaces. Subequently, all spectra were processed for clarity using XPSpeak to resolve each peak position, the area under the peak, and FHWM. CASAXPS was used to manually classify and specify the baseline (Shirley) for each elemental peak from the survey spectrum to assess the precise atomic composition of all modified samples. Subsequently, the corresponding atomic concentrations were determined using specified relative sensitivity factors (RSFs) for the elements as shown (O1s = 2,93, C1s = 1.00, Si2p = 0.82, and N1s = 1.80). Atomic Force Microscopy (AFM) The physical topography of the modified surfaces were analyzed with Atomic Force Microscopy (AFM) via multimode AFM equipment (Nanoview 1000, Utek Materials, Taiwan). AFM tapping mode was employed for surface investigation, and a cantilever set to 150 kHz and 5 N/m of force was used. Images were digitally acquired at a scan rate of 0.8 Hz with a resolution of 512 × 512 pixels, adhering to the developer's recommended automatic integral and proportional gain settings. The scan area for each surface was pre-set to 0.5 µm × 0.5 µm or 1 µm × 1 µm. Gwyddion (MacOS version 2.38) was used to calculate the root-mean-square (RMS) surface roughness for post-image processing. Fourier Transform Infrared Spectroscopy (FTIR) Fourier Transform Infrared Spectroscopy (FTIR) with Attenuated Total Reflectance (ATR) was conducted using a JASCO FT/IR-4700 spectrometer equipped with a liquid nitrogen-cooled Mercury Cadmium Telluride (MCT) detector. A VariGATR™ grazing-angle accessory (Harrick) fitted with a 65° angled germanium prism was employed to enhance surface sensitivity. Spectra were recorded using p-polarized light across the range of 2000–2200 cm⁻¹ to monitor changes in silicon hydride (Si–H) vibrations following surface modification. Each spectrum was collected from 200 scans at a resolution of 8 cm⁻¹. Unmodified Si (N-type 111), atomically flat Si (N-111), and porous Si (P-111) surfaces served as controls corresponding to each modified sample. All spectra were baseline-corrected, normalized, and analyzed using Spectrograph software (version 1.2.16.1). Energy minimization and Density Functional Theory (DFT) analysis DFT energy minimization and geometry optimization of propargylamine and 1,5-hexadiene derivatives were performed using the RB3LYP/6-311G(d,p) + + level of theory in Gaussian 09W. Molecular visualizations were prepared with GaussView. All calculations were conducted under gas-phase conditions (no solvent), employing standard formal charges. Electrostatic potential (ESP) maps were generated from the total electron density, and Mulliken atomic charges were extracted for each optimized structure. Declarations Author Contributions P. M. Chen had performed the surface reactions on both atomically flat and planar silicon while Y. J. Lin had performed the surface reactions on porous silicon. Analysis of FTIR was performed by both P.M. Chen and Y. J. Lin while XPS was collectively analysed by all authors. Most graphical illustrations were prepared by P.M. Chen as well as the description of the experimental and supplementary section. Y. L. Khung is the principal investigator who had envisioned the project concept, provided all necessary funding along with analysis of the data as well as having written majority of the manuscript. Funding and Acknowledgements The work was carried out with funding from China Medical University grant (CMU113-MF-82) as well as grant under Ministry of Science and Technology in Taiwan (NSTC-111-2221-E-039-015-MY3). Conflict of Interest Herein, the authors had declared no conflict of interest References Fanizza, E. et al. UV-light-driven immobilization of surface-functionalized oxide nanocrystals onto silicon. Advanced Functional Materials 17 , 201-211 (2007). https://doi.org/10.1002/adfm.200600288 Purkait, T. K. et al. Borane-Catalyzed Room-Temperature Hydrosilylation of Alkenes/Alkynes on Silicon Nanocrystal Surfaces. Journal of the American Chemical Society 136 , 17914-17917 (2014). https://doi.org/10.1021/ja510120e Yu, Y. X. et al. Room Temperature Hydrosilylation of Silicon Nanocrystals with Bifunctional Terminal Alkenes. Langmuir 29 , 1533-1540 (2013). https://doi.org/10.1021/la304874y Yu, Y. X. & Korgel, B. A. Controlled Styrene Monolayer Capping of Silicon Nanocrystals by Room Temperature Hydrosilylation. Langmuir 31 , 6532-6537 (2015). https://doi.org/10.1021/acs.langmuir.5b01291 Buriak, J. M. et al. Lewis acid mediated hydrosilylation on porous silicon surfaces. Journal of the American Chemical Society 121 , 11491-11502 (1999). https://doi.org/10.1021/ja992188w Schmeltzer, J. M., Porter, L. A., Stewart, M. P. & Buriak, J. M. Hydride abstraction initiated hydrosilylation of terminal alkenes and alkynes on porous silicon. Langmuir 18 , 2971-2974 (2002). https://doi.org/10.1021/la0156560 Sun, Q. Y. et al. Covalently attached monolayers on crystalline hydrogen-terminated silicon:: Extremely mild attachment by visible light. Journal of the American Chemical Society 127 , 2514-2523 (2005). https://doi.org/10.1021/ja045359s Malumbres, A. et al. Facile production of stable silicon nanoparticles: laser chemistry coupled to in situ stabilization via room temperature hydrosilylation. Nanoscale 7 , 8566-8573 (2015). https://doi.org/10.1039/c5nr01031d Small, J. C. et al. Alkyl-functionalization of porous silicon via multimode microwave-assisted hydrosilylation. Polyhedron 114 , 225-231 (2016). https://doi.org/10.1016/j.poly.2015.12.030 Vijayadas, K. N. et al. An unusual conformational similarity of two peptide folds featuring sulfonamide and carboxamide on the backbone. Chemical Communications 48 , 9747-9749 (2012). https://doi.org/10.1039/c2cc34533a Kawaguchi, R., Eguchi, T. & Suto, S. Atomistic investigation on the initial stage of growth and interface formation of Fe on H-terminated Si(111)-(1 x 1) surface. Surface Science 686 , 52-57 (2019). https://doi.org/10.1016/j.susc.2019.04.002 Wagner, P. et al. Bioreactive self-assembled monolayers on hydrogen-passivated Si(111) as a new class of atomically flat substrates for biological scanning probe microscopy. Journal of Structural Biology 119 , 189-201 (1997). https://doi.org/10.1006/jsbi.1997.3881 Yoshida, S., Sekiguchi, T. & Itoh, K. M. Atomically straight steps on vicinal Si(111) surfaces prepared by step-parallel current in the kink-up direction. Applied Physics Letters 87 (2005). https://doi.org/10.1063/1.1995946 Wei, J., Wang, X. S., Bartelt, N. C., Williams, E. D. & Tung, R. T. THE PRECIPITATION OF KINKS ON STEPPED SI(111) SURFACES. Journal of Chemical Physics 94 , 8384-8389 (1991). https://doi.org/10.1063/1.460070 Niwano, M., Terashi, M. & Kuge, J. Hydrogen adsorption and desorption on Si(100) and Si(111) surfaces investigated by in situ surface infrared spectroscopy. Surface Science 420 , 6-16 (1999). https://doi.org/10.1016/s0039-6028(98)00772-9 O'Shea, J. N. et al. Hydrogen-bond induced surface core-level shift in pyridine carboxylic acids. Surface Science 486 , 157-166 (2001). https://doi.org/10.1016/s0039-6028(01)01058-5 Li, B. J. et al. A new strategy to stabilize the heavy metals in carbonized MSWI-fly ash using an acid-resistant oligomeric dithiocarbamate chelator. Journal of Hazardous Materials 467 (2024). https://doi.org/10.1016/j.jhazmat.2024.133686 Ciampi, S. et al. The rapid formation of functional monolayers on silicon under mild conditions. Physical Chemistry Chemical Physics 16 , 8003-8011 (2014). https://doi.org/10.1039/c4cp00396a Tian, F. Y. & Teplyakov, A. V. Silicon Surface Functionalization Targeting Si-N Linkages. Langmuir 29 , 13-28 (2013). https://doi.org/10.1021/la303505s Tung, J., Ching, J. Y., Ng, Y. M., Tew, L. S. & Khung, Y. L. Grafting of Ring-Opened Cyclopropylamine Thin Films on Silicon (100) Hydride via UV Photoionization. ACS Appl. Mater. Interfaces 9 , 31083-31094 (2017). https://doi.org/10.1021/acsami.7b08343 Tao, F. & Xu, G. Q. Attachment chemistry of organic molecules on Si(111)-7x7. Accounts of Chemical Research 37 , 882-893 (2004). https://doi.org/10.1021/ar0400488 Hsiao, Y. S., Chen, P. M. & Khung, Y. L. Thermal reactivity of pyrrole and its methyl derivatives on silicon (111) hydride surfaces. Applied Surface Science 613 (2023). https://doi.org/10.1016/j.apsusc.2022.156005 Imanishi, A., Yamane, S. & Nakato, Y. Si(111) surface modified with α,β-unsaturated carboxyl groups studied by MIR-FTIR. Langmuir 24 , 10755-10761 (2008). https://doi.org/10.1021/la801586d Alkorta, I., Rozas, I. & Elguero, J. Theoretical study of the Si-H group as potential hydrogen bond donor. International Journal of Quantum Chemistry 86 , 122-129 (2002). https://doi.org/10.1002/qua.1613 Bensliman, F., Sawada, Y., Tsujino, K. & Matsumura, M. Oxidation of atomically flat and hydrogen-terminated Si(111) surfaces by hydrogen peroxide. Journal of the Electrochemical Society 154 , F102-F105 (2007). https://doi.org/10.1149/1.2717381 Khung, Y. L., Barritt, G. & Voelcker, N. H. Using continuous porous silicon gradients to study the influence of surface topography on the behaviour of neuroblastoma cells. Experimental Cell Research 314 , 789-800 (2008). https://doi.org/10.1016/j.yexcr.2007.10.015 Lee, C. H. & Khung, Y. L. Molecular geometry influencing thermal-based nucleophilic reactions on silicon (111) hydride surfaces Applied Surface Science 527 (2020). Table 1 Additional Declarations There is NO Competing Interest. Supplementary Files Supplementaryinformationnaturecomm.pdf Steric Gating Directs Room-Temperature Hydrosilylation on Silicon Hydride Surfaces Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6954985","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":484120769,"identity":"5dbf2762-b4ba-46fe-8871-48b3b64f7d37","order_by":0,"name":"Yit Lung Khung","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0001-6571-3034","institution":"China Medical University","correspondingAuthor":true,"prefix":"","firstName":"Yit","middleName":"Lung","lastName":"Khung","suffix":""},{"id":484120770,"identity":"61dcba30-9df0-4990-8af5-d4bfaa7cbab8","order_by":1,"name":"Peng-Mou Chen","email":"","orcid":"","institution":"China Medical University","correspondingAuthor":false,"prefix":"","firstName":"Peng-Mou","middleName":"","lastName":"Chen","suffix":""},{"id":484120771,"identity":"d9c70393-16ae-4081-b653-389841ccdf2a","order_by":2,"name":"Yi-Jen Lin","email":"","orcid":"","institution":"China Medical University","correspondingAuthor":false,"prefix":"","firstName":"Yi-Jen","middleName":"","lastName":"Lin","suffix":""}],"badges":[],"createdAt":"2025-06-23 09:15:44","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6954985/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6954985/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":86638432,"identity":"3c888476-1cca-4f87-a8b3-66ea381d29db","added_by":"auto","created_at":"2025-07-14 07:49:50","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":972879,"visible":true,"origin":"","legend":"\u003cp\u003eGraphical illustration of the room temperature hydrosilylation reaction performed on silicon substrates of different form factors, namely atomically flat, planar and porous silicon and the subsequent chemical profiling of the material.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-6954985/v1/1fc397845dec0f84ca3d41c8.png"},{"id":86638131,"identity":"4f66edc1-491f-4e87-91ac-f388f8110d7b","added_by":"auto","created_at":"2025-07-14 07:41:50","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":659762,"visible":true,"origin":"","legend":"\u003cp\u003eElectrostatic potential (ESP) surface maps and calculated dipole moments of propargylamine and 1,5-hexadiene, obtained at the RB3LYP/6-311++G(d,p) level of theory. ESP surfaces are mapped onto the electron density isosurface (0.002 a.u.) with a color scale ranging as shown above\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-6954985/v1/45128b8e5307023530fbcbb2.png"},{"id":86638132,"identity":"40f14172-29e4-42fc-9e7f-4d67a688996a","added_by":"auto","created_at":"2025-07-14 07:41:50","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":3600173,"visible":true,"origin":"","legend":"\u003cp\u003eAFM and contact angle measurements for all the different silicon surfaces grafted with propargylamine and 1,5-Hexadiene. All RMS and contact angle measurement were derived from n=3 sampling on the surface.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-6954985/v1/9f87034060e5ec1a974e736f.png"},{"id":86637298,"identity":"6bb3410a-e1d9-4c88-b4ed-f889cf4bf147","added_by":"auto","created_at":"2025-07-14 07:33:50","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":514650,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR centering at 2100 cm\u003csup\u003e-1\u003c/sup\u003e to capture the depletion of the surface hydride as a marker for Si-H consumption, either through Si-C bonding or via oxidation for (A) Atomically Flat Silicon, (B) Planar and (C) Porous Silicon.\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-6954985/v1/d72d58c20952dc0f84ed2507.png"},{"id":86638134,"identity":"0e73a66d-35b9-4237-9a94-3c8abef06649","added_by":"auto","created_at":"2025-07-14 07:41:50","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1206393,"visible":true,"origin":"","legend":"\u003cp\u003eHigh-resolution Si2p XPS spectra of atomically flat, planar, and porous silicon surfaces following grafting with propargylamine and 1,5-hexadiene at room temperature. Spectra for untreated control surfaces are also included for comparison. Corresponding peak positions, FWHM values, and integrated areas are listed in the insets. The panels are arranged to reflect increasing surface roughness from top to bottom, allowing comparison of oxidation levels and chemical state evolution across different surface morphologies.\u003c/p\u003e","description":"","filename":"Figure5.png","url":"https://assets-eu.researchsquare.com/files/rs-6954985/v1/c0ab02eae81a8a8fd3c9c805.png"},{"id":86638431,"identity":"62ba95c1-227b-4c1d-8c4b-df96ac548941","added_by":"auto","created_at":"2025-07-14 07:49:50","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":937082,"visible":true,"origin":"","legend":"\u003cp\u003eC1s spectrum after 4-hours of room temperature grafting for (A) unmodified control, (B) Propargylamine and (C) 1,5-Hexadiene. In conjunction, we observed a shift in N1s for propargylamine in the absence of solvent which can only promote physiosorption on the surface.\u003c/p\u003e","description":"","filename":"Figure6.png","url":"https://assets-eu.researchsquare.com/files/rs-6954985/v1/717d352845f8c53d59843324.png"},{"id":86637303,"identity":"3e5bbb12-d6ea-444d-96f7-7fc5c0c48fd3","added_by":"auto","created_at":"2025-07-14 07:33:50","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1215233,"visible":true,"origin":"","legend":"\u003cp\u003eThe hypothesized mechanism governing steric gating as well as the reorientation of the propargylamine at room temperature. Interestingly, upon the hydrosilylation of propargylamine, the amine group was observed to have expedited the oxidation of the adjacent silicon hydride, a phenomenon attributed by the affinity of distal amine to form intermolecular interactions.\u003c/p\u003e","description":"","filename":"Figure7.png","url":"https://assets-eu.researchsquare.com/files/rs-6954985/v1/d7d4b0508cdd3619f5433700.png"},{"id":90985863,"identity":"c7986379-b728-473e-90f0-74d902edc636","added_by":"auto","created_at":"2025-09-10 09:58:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":10010241,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6954985/v1/8c726812-837b-45d7-b7d4-51dfcd88f8d8.pdf"},{"id":86637307,"identity":"a2390e92-0357-49ba-9a5c-066290f15702","added_by":"auto","created_at":"2025-07-14 07:33:50","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":5602225,"visible":true,"origin":"","legend":"Steric Gating Directs Room-Temperature Hydrosilylation on Silicon Hydride Surfaces","description":"","filename":"Supplementaryinformationnaturecomm.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6954985/v1/4fad6eecbbbaa12e4ea961c0.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Steric Gating Directs Room-Temperature Hydrosilylation on Silicon Hydride Surfaces","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRoom-temperature hydrosilylation has been one of the more attractive strategies for forming stable Si\u0026ndash;C bonds\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Performing hydrosilylation under ambient conditions can significantly reduce the risk of surface oxidation, and if the reaction proceeds without a catalyst, the oxidation risk is further minimized. While several approaches have been reported for achieving room-temperature hydrosilylation, the underlying mechanistic consensus remains unclear\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. However, there is an emerging trend toward the use of polarizing additives to enhance surface reactivity toward unsaturated carbon species. Notably, most academic reports on room-temperature hydrosilylation focus on nanoparticulate silicon\u003csup\u003e\u003cspan additionalcitationids=\"CR6 CR7 CR8\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e, with relatively little discussion of planar or atomically flat surfaces. This is particularly striking, as planar silicon carries more direct technological relevance and should serve as a principal substrate for understanding surface reaction mechanisms. In terms, achieving high quality monolayer on oxide-free planar silicon via room temperature reactions would be considered as a major advancement in the areas of molecular electronics and hence it is necessary to begin address the intrinsic chemistry underlying these processes.\u003c/p\u003e \u003cp\u003eTo address how surface roughness may also influence room temperature hydrosilylation, we proposed the grafting of propargylamine at room temperature (in ethyl propionate, an aprotic solvent for 4 hours) on three silicon-based surfaces of different nature, (1) atomically flatten silicon, (2) planar pristine silicon and (3) porous silicon. We want to examine how propargylamine would interact to surfaces of different roughness and to determine the subtle differences the surface roughness would render to the overall hydrosilylation reaction. After the organic grafting, the surfaces were examined via XPS, ATR-FTIR, water goniometry as well as AFM provide a clear picture pertaining to the chemical process of this novel room temperature hydrosilylation. The intrinsic mode of reaction mechanism is also hypothesized and deduced based on our experimental findings. From the different surfaces, we had identified an interesting trend in the form of steric gating, especially how steric access and morphology can influence the reaction notably for atomically flatten silicon surface. These unique findings ultimately provide the all the necessary impetus for this work and a graphical illustration is as prepared below in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eThree topographically distinct silicon surfaces were prepared to investigate the influence of surface roughness on room-temperature reactions of oxide-free silicon. Ethyl propionate was selected as the reaction medium due to its moderate dielectric constant (~\u0026thinsp;5.7), providing sufficient polarity to enable dipolar interactions with the Si\u0026ndash;H surface while remaining non-disruptive to the hydride layer. Such interactions are proposed to facilitate room-temperature coupling between the silicon substrate and unsaturated carbon species, promoting Si\u0026ndash;C bond formation without perturbing the intrinsic surface chemistry\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. Prior to physical experimentation, DFT calculations were first performed on propargylamine, 1,5-hexadiene, and ethyl propionate (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Supplementary Fig.\u0026nbsp;1) to examine their electronic structures and electrostatic characteristics. The electrostatic potential (ESP) map of propargylamine revealed two electron-rich regions: one localized at the amine terminus and another at the unsaturated carbon moiety. In contrast, 1,5-hexadiene exhibited a more uniform ESP distribution with no significant dipolar character. Propargylamine also showed a notable dipole moment (0.63 D) compared to the nonpolar 1,5-hexadiene (0.00 D). It is important to note that while the experimental system employed ethyl propionate as the solvent (1.93 D), all DFT calculations were performed in the gas phase to evaluate intrinsic molecular polarity and charge distribution. This comparison remains relevant, as molecule\u0026ndash;surface interactions at the solid\u0026ndash;liquid interface is primarily governed by local electrostatic environments where bulk solvation effects are mostly attenuated. Potential interference between propargylamine and ethyl propionate was not considered a significant concern, as esters are relatively weak hydrogen bond acceptors and are unlikely to sequester the amine functionality or participate in surface reactivity under the conditions used\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. These insights were essential for interpreting subsequent reactivity trends and constructing the proposed reaction mechanism. A reaction time of 4 hours was selected to capture early-stage reactivity and oxidation across different silicon surface morphologies. This relatively short duration enabled the resolution of subtle kinetic differences before extensive oxidation could mask initial surface features. Subsequent characterization confirmed that this time frame was sufficient to produce discernible and interpretable surface modifications.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eInitial physical characterization of the grafted surfaces was conducted using AFM and contact angle measurements (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). As expected, the three surface types exhibited distinctly different topographies. In addition to freshly etched surfaces used as controls, we also subjected all surfaces to a 4-hour incubation in neat ethyl propionate (without any reactant) to determine whether the aprotic solvent alone would alter surface chemistry (Supplementary Fig.\u0026nbsp;2). On atomically flat surfaces, step terraces with heights of 0.3\u0026ndash;0.4 nm were observed, consistent with the known morphology of chemically etched atomically flat silicon\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e, while the overall RMS roughness was 0.14 nm. Across all modified atomically flat surfaces, RMS roughness remained between 0.1\u0026ndash;0.2 nm, in agreement with literature values\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Following propargylamine grafting, the overall surface roughness remained similar to that of the control; however, \"kinks\" were observed at the step edges of the terraces\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e, indicating the formation of defects on the terraces. In contrast, grafting of 1,5-hexadiene produced no notable structural changes on the atomically flat surfaces. Such structural defects at step edges are often indicative of localized etching or oxidation. Supporting this, contact angle measurements revealed a marked difference in wettability: propargylamine-modified surfaces exhibited a low contact angle (23.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u0026deg;), whereas both control and 1,5-hexadiene-modified surfaces showed significantly higher contact angles (81.4\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u0026deg; and 82.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5\u0026deg;, respectively). Given the contrasting wettability profile of propargylamine-modified surfaces, despite otherwise similar physical features, we sought to better understand the origin of this hydrophilicity. To isolate the effect of water-driven oxidation, we incubated freshly etched atomically flat silicon in pure water for 4 hours at room temperature; the resulting contact angle remained in the 40s (Supplementary Fig.\u0026nbsp;3). The even lower contact angle observed for propargylamine-modified surfaces suggested that the chemical modifications induced by propargylamine had extend beyond simple oxidation, perhaps introducing additional surface functionalities or interactions that would enhance hydrophilicity of the surface.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe RMS for the pristine silicon surface (planar) was measured between 0.2\u0026ndash;0.3 nm for all the surface chemical modifications, indicating that the topography remains largely unmodulated. But once again, the contact angle for propargylamine was markedly lower (19.8 \u0026plusmn; 1.8\u0026deg;) compared to both the control and 1,5-Hexadiene. This corroboration with our previous results from atomically flat silicon had suggested that the introduction of propargylamine had indeed changed the very nature of the surface chemistry although there was little change on surface roughness. On the other hand, the differences in roughness observed on porous silicon surfaces for propargylamine (RMS: 5.76 nm) was very significant when compared to the control (RMS: 1.33 nm) and that of 1,5 Hexadiene (RMS: 2.57 nm). The surface was also completely hydrophilic (4.5 \u0026plusmn; 0.3\u0026deg;) and along with the massive change in surface roughness, the reaction of propargylamine to porous silicon surface even for a short duration of only 4 hours at room temperature was observed to cause significant changes to the porous silicon surface material. In conjunction, neat reaction (in the absence of solvent) was also examined to study the roughening effect on the surfaces (Supplementary Fig.\u0026nbsp;2)\u003c/p\u003e \u003cp\u003eThe first chemical profiling of the surface chemistry was performed initially with highly sensitive glazing angle FTIR-ATR at 65\u0026deg; angle to determine the effects of room temperature reaction (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Due to the sensitivity of our setup, we were able to register and monitor the signal of silicon hydride (Si-H) at ~\u0026thinsp;2084 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, a signal as reported commonly for Si-H\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Freshly prepared surfaces (regardless of form factor) would present predominantly Si-H bonds on the surface and the loss of this signal would indicate either surface oxidation or hydrosilylation to form surface Si-C bonding. The FTIR-ATR measurement would shed light on the \u0026ldquo;consumption\u0026rdquo; of Si-H on the surface and the FTIR spectrum was as presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. Normalization of baseline was performed for all surfaces to examine the intensity of the Si-H peak comparatively and we noticed that the depletion of Si-H was lowest for atomically flat silicon while porous silicon surface had seemingly lost most of the Si-H on propargylamine grafted surfaces. This was interestingly as the reaction was performed at room temperature for merely 4 hours and this was enough time to observe the depletion of surface Si-H from porous silicon. There had also been substantial reduction of peak intensity for planar silicon surface and from these observations, it was evidently clear that loss of Si-H from propargylamine grafting has also been different and may be influenced by the overall surface roughness, a point that would be addressed in the subsequent section in this report.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAn in-depth physicochemical characterization of the top surface layer (~\u0026thinsp;2\u0026ndash;5 nm) was performed using XPS analysis for all the sample (see Supplementary Fig.\u0026nbsp;4). High-resolution XPS Si2p spectra were acquired for all three surface types (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The freshly prepared control surfaces exhibited negligible oxidation, as indicated by the dominant Si⁰ peak (~\u0026thinsp;99 eV) and an absence of significant signal in the 103\u0026ndash;104 eV region corresponding to Si\u0026ndash;O species. The degree of oxidation was quantified by calculating the ratio of the Si\u0026ndash;O peak area to the total Si2p spectral area. As an additional control, freshly etched surfaces were subjected to a 4-hour incubation in ethyl propionate. On atomically flat silicon, no measurable oxidation was observed in the Si2p spectrum following incubation (Supplementary Fig.\u0026nbsp;5A). For planar and porous silicon surfaces, slight increases in oxidation were detected after 4 hours in ethyl propionate, calculated at 5.21% and 5.84%, respectively (Supplementary Fig.\u0026nbsp;5B and 5C respectively). These results indicate that under the mildly polar conditions of ethyl propionate at room temperature, the silicon surfaces remain largely inert, with most Si\u0026ndash;H moieties preserved. In contrast, the introduction of propargylamine led to a pronounced increase in surface oxidation, even after only 4 hours at room temperature. On atomically flat silicon, the oxidation level rose to 14.5% (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB). On planar silicon, an even higher oxidation level of 24.4% was observed. Notably, on porous silicon, the Si⁰ signal (~\u0026thinsp;99 eV) was nearly absent, suggesting extensive oxidation or possible complete loss of the underlying Si\u0026ndash;Si network. Conversely, grafting with 1,5-hexadiene resulted in minimal oxidation. On atomically flat silicon, negligible oxidation was detected, while planar and porous silicon exhibited only slight increases (4.7% and 4.3%, respectively). This outcome is consistent with expectations, as 1,5-hexadiene is likely to undergo hydrosilylation through one of its terminal unsaturated carbons to form Si\u0026ndash;C bonds, which are known to impart significant resistance to subsequent oxidation of the underlying silicon surface.\u003c/p\u003e \u003cp\u003eThe complete loss of Si-Si signature from porous silicon on propargylamine grafting was rather unexpected as the reaction had occurred at room temperature for a short duration of 4 hours (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eH). From the data obtained, it is envisaged that the presence of the nucleophilic propargylamine could have driven the complete oxidation on the porous surface. When the chemical profiling was examined in tandem with the AFM and FTIR data, it was clear that propargylamine may have caused both extensive structural reshaping of the porous architecture as well as the complete loss of the Si-H. This adherently altered the wettability profile along the principles of Wenzel effect for hydrophilic surface. However, what was more interesting was that subjecting the porous silicon material in water for 4 hours at room temperature did not exhibit similar drastic changes (Supplementary Fig.\u0026nbsp;3) and the influence from propargylamine should be considered as a chemical reaction on the surface. It was clear that even at room temperature, there was sufficient impetus for propargylamine to alter and affect the surface chemistry on porous silicon to the point of reshaping the topography of the material. By comparing the various Si2p spectrums, it was clear that this chemical effect on the surface by propargylamine was dependent on the roughness of the silicon substratum, with atomically flat resisting physical changes on the surface while porous silicon experiencing extensive structural reshaping. However, there was evidence to suggest that atomically flat silicon had also underwent notable chemical changes as well in the form of surface oxidation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn principle, it is possible to elucidate the nature of surface grafting by examining the high-resolution C1s spectra of the samples. However, the high oxidation levels present on both planar and porous silicon surfaces complicate interpretation of the C1s chemical signals, making it difficult to unambiguously assign surface chemistry for these substrates. In contrast, the near absence of oxidation on the atomically flat silicon surface provided a valuable opportunity to investigate the reaction processes on an oxide-free silicon hydride surface at room temperature. Analysis of the C1s spectrum for atomically flat silicon (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eA-C) revealed that, in addition to the expected C\u0026ndash;C peak at 285.0 eV, deconvolution identified a clear Si\u0026ndash;C signal at 283.9 eV for 1,5-hexadiene and a broader peak centered at 283.4 eV for propargylamine. These results indeed suggested that a 4-hour room-temperature interaction was sufficient to drive hydrosilylation at the unsaturated carbon terminus, forming covalent Si\u0026ndash;C bonds. The detail of the C1s for planar and porous silicon was also as shown in Supplementary Fig.\u0026nbsp;6.\u003c/p\u003e \u003cp\u003eTo gain further insight into the molecular orientation of grafted propargylamine, we examined the N 1s spectra in both the presence and absence of the polar solvent (ethyl propionate) to study the difference in terms of promoting reactivity (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eD). Under standard 1:1 reaction condition, the N1s peak maximum shifted to 399.9 eV in the presence of the solvent, compared to 399.4 eV for neat propargylamine in the absence of solvent. This shift toward higher binding energy suggests that the distal amine groups are engaged in hydrogen bonding interactions\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e, whereas the lower binding energy observed in the neat case is consistent with physisorbed, free and non-interacting amines on the surface\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Given that hydrogen bonding would require proximity between the amine and the surface Si\u0026ndash;H groups, this supports the conclusion that propargylamine grafting proceeds via reaction of the unsaturated carbon end with the silicon surface. However, as the shift was rather subtle, at ~\u0026thinsp;0.5 eV, this may also suggest that the distal amine interaction to neighboring surface hydride was relatively localized. Notably, this interaction appears to enhance local surface oxidation, an effect not previously reported in the literature. Complementary FTIR analysis further confirmed these findings, showing slight depletion of the Si\u0026ndash;H stretching band at 2084 cm⁻\u0026sup1;, consistent with consumption of surface Si\u0026ndash;H during grafting. The near-complete disappearance of the Si\u0026ndash;H signal in the propargylamine-modified sample, combined with the XPS data, strongly suggests that propargylamine promotes surface oxidation, whereas 1,5-hexadiene exhibits minimal impact on surface oxidation under identical conditions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo minimize the formation of a thick underlying oxide layer\u0026mdash;which would compromise accurate estimation of the organic monolayer\u0026mdash;we deliberately limited the reaction time to 4 hours, even at room temperature. This had help obtain the ideally near-zero oxidation for 1,5-Hexadiene and hence provided the opportunity to compared the surface chemistry between propargylamine and 1,5-Hexadiene. Herein, we relied on the XPS information to estimate the average effective thickness of organic monolayer using standard Beer\u0026ndash;Lambert attenuation law, adapted to photoelectron attenuation\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:d=\\:-\\lambda\\:\\text{cos}\\left(\\theta\\:\\right)\\text{ln}\\frac{I}{{I}_{o}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere d is the overlayer thickness in nanometer, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\lambda\\:\\)\u003c/span\u003e\u003c/span\u003e is the effective attenuation length that is typically taken at 3.3 nm for Si2p through thin organic carbon layer, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\theta\\:\\)\u003c/span\u003e\u003c/span\u003e being the photoelectron take-off angle (45\u0026deg;) and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{I}{{I}_{o}}\\)\u003c/span\u003e\u003c/span\u003e is the experimentally measured photoelectron intensity of Si2p before modification (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{I}_{o}\\)\u003c/span\u003e\u003c/span\u003e) and after modification (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:I\\)\u003c/span\u003e\u003c/span\u003e). From the determined areas under the peak, we estimated the monolayer thickness for propargylamine grafting on atomically flat silicon to be approximately 0.59 nm, based on attenuation of the Si2p signal. This was only marginally higher than the theoretical length of 0.49 nm for propargylamine and was highly suggestive for a partially passivated silicon surface. In contrast, the average effective thickness measured for 1,5-Hexadiene was approximately 0.38 nm which was lower than the theoretical height of a fully upright 1,5-Hexadiene (0.9 nm). Interestingly this could indicate that the organic chain may be tilted on the surface and that the surface was also partially passivated, an outcome that was consistent to expectation from a short reaction time of 4 hours at room temperature. It is important to note that these values represent apparent thicknesses, averaging over both grafted and non-grafted surface on atomically flat silicon with step terraces averaging 0.30 nm in height. As the silicon surfaces are not fully passivated, the calculated thickness was subtly suggestive of the nature of the surface reactivity and molecular orientation, a discourse that would be further elaborated in latter segments.\u003c/p\u003e \u003cp\u003eYet, determining the surface coverage of the grafting was useful towards understanding the surface grafting at room temperature. The near absence of oxidation as well as the \u0026lsquo;flatness\u0026rsquo; of the material had enable for relatively close estimation based on the quenching of the Si\u003csup\u003e(0)\u003c/sup\u003e signals (Si2p\u003csup\u003e3/2\u003c/sup\u003e + Si2p\u003csup\u003e1/2\u003c/sup\u003e) for 1,5 Hexadiene and we determine the coverage based on the model as shown below,\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:Coverage=\\left(1-\\frac{I}{{I}_{o}}\\right)\\:\\times\\:\\:100\\%$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere \u003cem\u003eI\u003c/em\u003e\u003csub\u003e\u003cem\u003eo\u003c/em\u003e\u003c/sub\u003e represents the core Si2p area before grafting and \u003cem\u003eI\u003c/em\u003e is the area after the surface had been grafted. For 1,5-Hexadiene, we had determined that the area of coverage on the surface was 15% and this had shown that a short 4-hour room temperature grafting may be too brief to obtain higher passivation on the surface. When estimating the surface coverage of propargylamine, it was necessary to account for the oxidation that had occurred in over to avoid over-estimating the surface coverage from the grafting. To do so, we had slightly altered Eq.\u0026nbsp;(\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) to account for the oxidation as shown below,\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:Coverage=\\left(1-\\frac{I}{{I}_{o}}\\right)\\:\\times\\:\\left(\\frac{{I}_{o}}{{I}_{o}+{A}_{si-o}}\\right)\\times\\:\\:100\\%$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{A}_{si-o}\\)\u003c/span\u003e\u003c/span\u003e accounts for the area of oxidation (Si2p peak centering at 103\u0026ndash;104 eV) to prevent Si-O formation being falsely accounted as coverage. From the modified calculations, we had determined that our surface coverage of propargylamine to be ~\u0026thinsp;20% of the surface. A recalculation of 1,5-Hexadiene using the modified equation did not show any notable difference in terms of the outcome (~\u0026thinsp;14\u0026ndash;15%) in terms of surface coverage and hence will be taken as 15% for the rest of the discourse of this work. The overall calculated surface coverage is as tabulated below in Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eFrom these findings, we were able to construct a more complete understanding of the reaction mechanism occurring on atomically flat silicon surfaces (see Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e). Although surface oxidation was observed following grafting with propargylamine, XPS analysis of both the Si2p and N1s spectra unambiguously indicated the formation of Si\u0026ndash;C bonds on atomically flat surfaces. This observation suggests that multiple chemical processes were taking place concurrently. We propose that, in the aprotic solvent ethyl propionate at room temperature, initial interactions between the amine nitrogen and the silicon surface\u0026mdash;further influenced by solvent\u0026rsquo;s moderate polarity\u0026mdash;may not be insufficiently energetic to drive direct Si\u0026ndash;N bond formation\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e unless the silicon surface is under an electron deficient condition\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. Hence, we did not observed the characteristics of Si-N bonding on the surface\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Moreover, this interaction was sterically hindered by the densely packed Si\u0026ndash;H layer, which imposed a gating effect that limited the approach of the nitrogen atom to the surface. As a result, the molecule likely adopted an alternative orientation, with the unsaturated carbon moiety directed toward the surface. This orientation enabled covalent grafting via Si\u0026ndash;C bond formation through a hydrogen abstraction pathway, ultimately yielding a monolayer with distal amine groups protruding from the surface. Because of these observations, we define steric gating as a surface-imposed steric constraint that selectively influences molecular orientation and accessibility of reactive sites in this work.\u003ctable id=\"Tab1\" border=\"1\" class=\"fr-table-selection-hover\"\u003e\u003c/table\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003eYet, this was not the end of the surface chemistry. We further proposed that the distal NH₂ groups perturb the local electronic environment of adjacent Si\u0026ndash;H bonds, either through hydrogen bonding or dipole\u0026ndash;dipole interactions, thereby increasing the susceptibility of these sites to nucleophilic attack by trace water or oxygen. This, in turn, promoted localized oxidation of the surface. Moreover, a partially passivated amine monolayer could attract water molecules closer to the surface, further accelerating oxidation processes. To support this rationale, we also grafted propiolic acid (replacing the amine with a carboxylic acid group) onto the silicon hydride surface\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e (Supplementary Fig. 7). In this case, surface oxidation was substantially lower with notable Si\u0026ndash;C bond formation detected. This result was consistent with our hypothesis: the bulkier and more sterically hindered COOH group, combined with the poor donor characteristics of Si\u0026ndash;H\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e, limits both close approach between the COOH and Si atom which subsequently causes the molecule to reorientate itself in similar fashion and ultimately forming Si-C bonding although COOH distal group should cause less electronic perturbation of adjacent Si\u0026ndash;H bonds, as previously reported by Imanishi et. al\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. Thus, the comparative behavior between propargylamine and propiolic acid confirms our proposed steric gating model and highlights how molecular orientation at room temperature critically influences both grafting efficiency and surface stability.\u003c/p\u003e\n\n\u003cp\u003eOne of the more interesting aspects from our data was the evidential reshaping of porous silicon micro-architecture after propargylamine was introduced at room temperature. High resolution XPS C1s spectrum did not reveal the presence of Si-C bonding on the surface with the Si2p spectrum showing a complete loss of the Si-Si core signal. This had indicated that amine had catalyze oxidation and assisted in the nucleophilic attack on surfaces which was expedited by the presence of strained bonds existing on the pore edges of the porous material. Unlike atomically flat silicon, porous silicon did not present a dense enough hydride layer to provide the steric gating effect that would discourage interaction between the NH\u003csub\u003e2\u003c/sub\u003e groups and the silicon atom. Hence, from our survey spectrum, we were able to detect for the presence of nitrogen on the surface although the total oxidation from Si2p had rendered the direct observations of Si-N rather challenging. Thus, it was also possible that the curvature of the surface did not provide the necessary steric gating and thus permit for direct inclusion to form Si-N bonding to the surface at room temperature although this reaction was not considered to be productive for the intentions of room temperature hydrosilylation. Furthermore, as NH\u003csub\u003e2\u003c/sub\u003e groups are rather basic and can deprotonate surface species, this may accelerate etching and oxidation of the material and hence we noticed that loss or enlargement of the overall porous architecture network. Interestingly this topographical change was also not observed when propiolic acid was applied to the porous silicon, thus suggesting that the nucleophilic NH\u003csub\u003e2\u003c/sub\u003e was responsible for the physical changes to the surface. Finally, the grafting of planar silicon had shown elevated levels of oxidation although much of the surface morphology remains relatively intact.\u003c/p\u003e\n\u003cp\u003eFrom our detailed experimentation of the surface, there are several important observations made. Firstly, while room temperature reaction on silicon hydride is feasible for aliphatic alkenes/alkynes, nucleophilic amines represent a more complex picture whereby the grafting of these moieties had triggered a series of chemical processes on the surface that ultimate yield a range of different distal moieties on the surface. These detailed interplay of molecular structure and surface affinity had not been previously described in literature to the best of the author\u0026rsquo;s knowledge and what was most interesting about the work was that all these described processes had occurred at room temperature. Furthermore, the roughness of the surface was found to be a major consideration, with atomically flat silicon being able to provide the necessary steric gating effects to orientate the incoming molecule and this was very much in consistent with literature where atomically flatten surface tends to resist oxidation\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. More importantly, the grafting of propargylamine at room temperature on porous silicon material was non-ideal as the surface of porous silicon was less stable compared to planar and this resulted in the etching events that reshaped the micro-architecture of the material.\u003c/p\u003e\n\u003cp\u003eSignificant academic insights emerged from the experimental data and hypothesized mechanism regarding the room-temperature grafting of amine-based alkynes. Firstly, it is well recognized that grafting organic monolayers bearing free amine functional groups onto oxide-free silicon remains a challenging task. Our initial approach was to leverage room temperature to mitigate the reactivity of amines toward the silicon surface, as previous studies had shown that elevated temperatures promote direct amine insertion. However, the results obtained in this study were unexpected: the amine groups remained highly interactive with Si-H surfaces. Notably, the presence of distal amines was found to alter the chemistry of neighboring silicon atoms\u0026mdash;an observation not previously documented in the literature. On roughened substrates such as porous silicon, these effects were even more pronounced, leading to enhanced self-etching phenomena. In contrast, UV-assisted hydrosilylation, which generates surface radicals to drive reactions with alkenes or delocalized \u0026pi;-systems, tends to favor a more uniform and \u0026quot;ideal\u0026quot; passivation of the silicon surface. However, the notion that nucleophilic amines merely act as passive spectators in radical-based processes is misleading; amines can effectively trap and quench surface radicals, introducing defects and even promoting dimerization. Thus, while the prospect of achieving a monolayer with distal amines in a single step is appealing for surface passivation, our findings highlight the inherent complexities of amine interactions with oxide-free silicon, even under mild, room-temperature conditions.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this work, three types of silicon surfaces\u0026mdash;atomically flat silicon, planar Si(111), and porous silicon\u0026mdash;were prepared and grafted with propargylamine and 1,5-hexadiene at room temperature using ethyl propionate as the solvent. Our initial objective was to investigate whether hydrosilylation could proceed in the absence of any catalytic agents at room temperature. While 1,5-hexadiene successfully grafted onto all surfaces with varying degrees of surface coverage, propargylamine induced a markedly different chemical response, significantly altering the surface chemistry across all substrates. Using atomically flat silicon as a model, we were able to conduct a detailed analysis of how the amine functional group interacts with the surface and how hydrosilylation can be guided through steric gating imposed by the densely packed hydride layer. More notably, we observed that when amine is introduced as a distal functional group, it can profoundly modify the chemistry of neighboring silicon hydrides. This room-temperature observation of such adjacent-molecule effects is significant, as it prompts a reevaluation of how amine-functionalized organic monolayers behave on oxide-free silicon surfaces under mild conditions.\u003c/p\u003e \u003cp\u003eRoom-temperature hydrosilylation continues to be an important strategy for achieving stable, covalently bonded monolayers on silicon surfaces via Si\u0026ndash;C linkage. Given the central role of silicon in modern semiconductor technologies, developing robust, well-passivated surfaces is of considerable technological and commercial relevance. Traditionally, research in this area has focused on relatively simple aliphatic unsaturated carbon species, where surface chemistry is more predictable. In contrast, this work explored how nucleophilic amines influence room-temperature hydrosilylation. Somewhat unexpectedly, we found that amines play a much more complex role than previously appreciated, exerting diverse chemical effects on neighboring silicon hydrides that depend on both surface structure and roughness. These findings contribute important new insights that should help refine our understanding of amine interactions on silicon surfaces and guide the rational design of advanced functional monolayers for a range of silicon-based applications.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eUnless otherwise noted, all reagents were purchased from Sigma-Aldrich and used without additional purification. Ultrapure HPLC grade water was obtained J.T Bakers and all used in this experiment for washing and other cleaning processes. P-type (111) silicon wafers with a resistivity of 0.001\u0026ndash;0.005 ohm.cm were purchased from Semiconductor Wafer, Inc., Taiwan (SWI), and N-type (111) silicon wafers with a resistivity of 1\u0026ndash;10 ohm.cm were obtained from Ruilong, Taiwan.\u003c/p\u003e\n\u003ch3\u003ePreparation for Planar and Atomically flat silicon\u003c/h3\u003e\n\u003cp\u003eSilicon wafers (111) (N-type, 1\u0026ndash;10 ohm.cm) were diced into 10 mm \u0026times; 10 mm pieces using a diamond cutter, followed by sequential ultrasonic cleaning in acetone, ethanol, and HPLC-grade water. The samples were then treated in hot piranha solution for 30 minutes to remove carbon-based contaminants and thoroughly rinsed with HPLC-grade water to eliminate residual acid. For planar surfaces, wafers were etched in 5% HF solution for 10 minutes to remove the native oxide layer. For atomically flat surfaces, wafers were etched in a 40% aqueous NH₄F solution (pH adjusted to ~\u0026thinsp;8 with NH₄OH), supplemented with 5% ammonium sulfite as an oxygen scavenger. The etching solution was degassed by argon purging for 15 minutes prior to use. Wafers were etched for 14 minutes and then rinsed with HPLC-grade water\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003ePreparation for porous silicon\u003c/h2\u003e \u003cp\u003eTo obtain porous silicon thin films on the surface, electrochemical anodization strategy using DPS-2303DF linear DC power source was used in this work in a setup similar to previous report\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. In brief, silicon wafers (111) (P-type, 0.001\u0026ndash;0.005 ohm-cm) were ultrasonically cleaned for 2 minutes each in acetone, ethanol, and HPLC-grade water, then dried under a nitrogen stream. The wafers were further treated with a plasma cleaner to remove residual carbon impurities. The etching solution was prepared by mixing 70% ethanol, 30% hydrofluoric acid (HF), and 5% Triton X-100 (volume ratio 70:30:5) in a Teflon beaker, with appropriate safety precautions due to HF handling. A custom Teflon etching cell was assembled, with the silicon wafer mounted on a 2.5 cm \u0026times; 8 cm aluminum foil anode. An O-ring was placed between the wafer and the Teflon container to ensure a tight seal. The assembly was leak-tested with a few drops of ethanol before proceeding. Electrodes were connected with a platinum wire as the cathode (centered in the cell) and a thick aluminum foil as the anode. The power supply (DPS-2303DF) was configured with a fixed current of 0.03 A at maximum voltage. After introducing 4.8 mL of the etching solution into the cell, the etching process was carried out for 1 minute. Following etching, the HF solution was carefully removed, and the porous silicon (pSi) wafer was rinsed five times with 2 mL aliquots of ethanol to ensure complete removal of residual HF. The wafer was then rinsed with cupious amounts of HPLC-grade water and dried under nitrogen.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSurface modification\u003c/h3\u003e\n\u003cp\u003eAll surface reactions were performed immediately after the silicon material had been etched and without delay. In brief, a solution of ethyl propionate and propargylamine (at aratio 1:1) was prepared and sealed in a customized Schlenk reactor vessel. The rectant solution then underwent at least 10 cycles of freeze-pump thaw under constant vacuum to remove most of the oxygen in the system, in a process similar to previous report from our group\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. Nitrogen gas was subsequently introduced slowly to the reactant mix and the freshly prepared silicon sample were carefully introduced and sealed with parafilm for 4 hours at room temperature. After the reaction time, the surfaces were removed from the Schlenk reactor and were washed with copious amounts of methanol, ethanol, acetone, and water in sequential order. The surfaces were then dried with nitrogen and were packed in specially prepared vacuum packages to prevent contamination and oxidation prior to further analysis.\u003c/p\u003e\n\u003ch3\u003eContact angle measurement\u003c/h3\u003e\n\u003cp\u003eAfter the grafting reaction, the surfaces were detected to have a contact angle via a computerized Contact Angle Goniometer (Contact Angle Analyzer from High View Innovation, Taiwan). All contact angle images were acquired via a CCD camera (hVI Series Camera, Taiwan) at a resolution of 2560 \u0026times; 1920 automatically captured via software built into this equipment. Each chemically grafted surface\u0026rsquo;s contact angle was performed using a 2 \u0026micro;l stationary droplet. Post-capture, the contact angle images were analyzed using the Dropsnake 2.1 add-on in ImageJ software (version 1.52k).\u003c/p\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eX-ray Photoelectron Spectroscopy (XPS)\u003c/h2\u003e \u003cp\u003eFor all grafted sample X-ray Photoelectron Spectroscopy (XPS) studies, a PHI 5000 VersaProbe (ULVAC-PHI) fitted with an Al Kα X-ray source (1486.6 eV) was used. High-resolution spectra for N1s, Si2p, C1s, and O1s were obtained by recording all changed surfaces at a 45\u0026deg; take-off angle relative to the surfaces. Subequently, all spectra were processed for clarity using XPSpeak to resolve each peak position, the area under the peak, and FHWM. CASAXPS was used to manually classify and specify the baseline (Shirley) for each elemental peak from the survey spectrum to assess the precise atomic composition of all modified samples. Subsequently, the corresponding atomic concentrations were determined using specified relative sensitivity factors (RSFs) for the elements as shown (O1s\u0026thinsp;=\u0026thinsp;2,93, C1s\u0026thinsp;=\u0026thinsp;1.00, Si2p\u0026thinsp;=\u0026thinsp;0.82, and N1s\u0026thinsp;=\u0026thinsp;1.80).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eAtomic Force Microscopy (AFM)\u003c/h2\u003e \u003cp\u003eThe physical topography of the modified surfaces were analyzed with Atomic Force Microscopy (AFM) via multimode AFM equipment (Nanoview 1000, Utek Materials, Taiwan). AFM tapping mode was employed for surface investigation, and a cantilever set to 150 kHz and 5 N/m of force was used. Images were digitally acquired at a scan rate of 0.8 Hz with a resolution of 512 \u0026times; 512 pixels, adhering to the developer's recommended automatic integral and proportional gain settings. The scan area for each surface was pre-set to 0.5 \u0026micro;m \u0026times; 0.5 \u0026micro;m or 1 \u0026micro;m \u0026times; 1 \u0026micro;m. Gwyddion (MacOS version 2.38) was used to calculate the root-mean-square (RMS) surface roughness for post-image processing.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eFourier Transform Infrared Spectroscopy (FTIR)\u003c/h2\u003e \u003cp\u003eFourier Transform Infrared Spectroscopy (FTIR) with Attenuated Total Reflectance (ATR) was conducted using a JASCO FT/IR-4700 spectrometer equipped with a liquid nitrogen-cooled Mercury Cadmium Telluride (MCT) detector. A VariGATR\u0026trade; grazing-angle accessory (Harrick) fitted with a 65\u0026deg; angled germanium prism was employed to enhance surface sensitivity. Spectra were recorded using p-polarized light across the range of 2000\u0026ndash;2200 cm⁻\u0026sup1; to monitor changes in silicon hydride (Si\u0026ndash;H) vibrations following surface modification. Each spectrum was collected from 200 scans at a resolution of 8 cm⁻\u0026sup1;. Unmodified Si (N-type 111), atomically flat Si (N-111), and porous Si (P-111) surfaces served as controls corresponding to each modified sample. All spectra were baseline-corrected, normalized, and analyzed using Spectrograph software (version 1.2.16.1).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eEnergy minimization and Density Functional Theory (DFT) analysis\u003c/h2\u003e \u003cp\u003eDFT energy minimization and geometry optimization of propargylamine and 1,5-hexadiene derivatives were performed using the RB3LYP/6-311G(d,p)\u0026thinsp;+\u0026thinsp;+\u0026thinsp;level of theory in Gaussian 09W. Molecular visualizations were prepared with GaussView. All calculations were conducted under gas-phase conditions (no solvent), employing standard formal charges. Electrostatic potential (ESP) maps were generated from the total electron density, and Mulliken atomic charges were extracted for each optimized structure.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003eAuthor Contributions\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eP. M. Chen had performed the surface reactions on both atomically flat and planar silicon while Y. J. Lin had performed the surface reactions on porous silicon. \u0026nbsp;Analysis of FTIR was performed by both P.M. Chen and Y. J. Lin while XPS was collectively analysed by all authors. \u0026nbsp;Most graphical illustrations were prepared by P.M. Chen as well as the description of the experimental and supplementary section. \u0026nbsp;Y. L. Khung is the principal investigator who had envisioned the project concept, provided all necessary funding along with analysis of the data as well as having written majority of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding and Acknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe work was carried out with funding from China Medical University grant (CMU113-MF-82) as well as grant under Ministry of Science and Technology in Taiwan (NSTC-111-2221-E-039-015-MY3).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHerein, the authors had declared no conflict of interest\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eFanizza, E.\u003cem\u003e et al.\u003c/em\u003e UV-light-driven immobilization of surface-functionalized oxide nanocrystals onto silicon. \u003cem\u003eAdvanced Functional Materials\u003c/em\u003e \u003cstrong\u003e17\u003c/strong\u003e, 201-211 (2007). https://doi.org/10.1002/adfm.200600288\u003c/li\u003e\n\u003cli\u003ePurkait, T. 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Oxidation of atomically flat and hydrogen-terminated Si(111) surfaces by hydrogen peroxide. \u003cem\u003eJournal of the Electrochemical Society\u003c/em\u003e \u003cstrong\u003e154\u003c/strong\u003e, F102-F105 (2007). https://doi.org/10.1149/1.2717381\u003c/li\u003e\n\u003cli\u003eKhung, Y. L., Barritt, G. \u0026amp; Voelcker, N. H. Using continuous porous silicon gradients to study the influence of surface topography on the behaviour of neuroblastoma cells. \u003cem\u003eExperimental Cell Research\u003c/em\u003e \u003cstrong\u003e314\u003c/strong\u003e, 789-800 (2008). https://doi.org/10.1016/j.yexcr.2007.10.015\u003c/li\u003e\n\u003cli\u003eLee, C. H. \u0026amp; Khung, Y. L. Molecular geometry influencing thermal-based nucleophilic reactions on silicon (111) hydride surfaces \u003cem\u003eApplied Surface Science\u003c/em\u003e \u003cstrong\u003e527\u003c/strong\u003e (2020). \u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table 1","content":"\u003cp\u003e\u003cimg 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\"\u003e\u003c/p\u003e\n"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research 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We reported a mechanistic study of propargylamine and 1,5-hexadiene grafting on atomically flat, planar, and porous silicon surfaces. Using XPS, FTIR, AFM, and contact angle analysis, we showed that both surface roughness and molecular structure can govern reactivity and oxidation. While 1,5-hexadiene showed minimal oxidation, propargylamine induced oxidation that scales with roughness. Interestingly, on atomically flat silicon, dense Si\u0026ndash;H groups sterically gate the surface, favoring alkyne\u0026ndash;Si coupling. Notably, the distal amine group in grafted propargylamine promoted localized oxidation of nearby Si\u0026ndash;H bonds through dipolar or hydrogen bonding effects\u0026mdash;a rarely reported pathway. This revealed a new oxidation mechanism initiated by surface-bound nucleophiles. Our results highlight steric gating and distal-group effects as critical for tailoring silicon surface chemistry, with implications for molecular electronics and interface design.\u003c/p\u003e","manuscriptTitle":"Steric Gating Directs Room-Temperature Hydrosilylation on Silicon Hydride Surfaces","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-14 07:33:45","doi":"10.21203/rs.3.rs-6954985/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"334de601-95df-4779-a11b-382dd7f70d4d","owner":[],"postedDate":"July 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":51405819,"name":"Physical sciences/Chemistry/Surface chemistry/Surface spectroscopy"},{"id":51405820,"name":"Physical sciences/Chemistry/Surface chemistry/Surface assembly"},{"id":51405821,"name":"Physical sciences/Chemistry/Physical chemistry/Reaction kinetics and dynamics"}],"tags":[],"updatedAt":"2025-09-10T09:50:16+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-14 07:33:45","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6954985","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6954985","identity":"rs-6954985","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}