Synthesis of Hyperbranched Polyglycerol-Photosensitizer/TiO 2 Nanocomposite for the Photocatalytic Degradation of Methylene Blue

Synthesis of Hyperbranched Polyglycerol-Photosensitizer/TiO 2 Nanocomposite for the Photocatalytic Degradation of Methylene Blue | 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 Research Article Synthesis of Hyperbranched Polyglycerol-Photosensitizer/TiO 2 Nanocomposite for the Photocatalytic Degradation of Methylene Blue Guang-Zhao Li, Shengrong Zhou, Debin Tian, Chengqiang Yang, Gen Liu, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6927801/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 18 Nov, 2025 Read the published version in Journal of Polymers and the Environment → Version 1 posted 15 You are reading this latest preprint version Abstract The escalating environmental challenges posed by organic dye pollution necessitate the development of efficient and sustainable remediation technologies. This study presents a novel strategy to enhance the visible-light photocatalytic performance of TiO₂ through the synthesis of hyperbranched polyglycerol (HPG)-modified nanocomposites functionalized with photosensitizers (hemin and Eosin Y, EY). A sol-gel method was employed to graft HPGs with tailored polymerization degrees and branching architectures onto TiO₂ surfaces, enabling systematic investigation of the effects of modifier content, polymer structure, and light source on photocatalytic activity.The grafted polymers significantly narrowed TiO₂’s bandgap energy (from 2.82 eV for pure TiO₂ to as low as 0.50 eV for HPG2-hemin/TiO₂), extending its light absorption to the visible spectrum. Under optimized conditions, 1% HPG5-EY/TiO₂ achieved a methylene blue (MB) degradation rate of 73.22% within 120 minutes of visible-light irradiation—a 2.11-fold enhancement compared to pristine TiO₂. The composite also demonstrated exceptional recyclability, retaining over 95% of its initial activity after four reuse cycles. Mechanistic studies revealed that the abundant hydroxyl groups in HPG facilitated the generation of reactive oxygen species (•OH and •O₂⁻), which synergistically accelerated MB degradation.This work establishes a robust framework for designing high-performance TiO₂-based photocatalysts by leveraging polymer structural engineering and photosensitizer integration. The approach not only addresses the inherent limitations of TiO₂’s UV-dependent activity but also provides a scalable strategy for sustainable wastewater treatment under solar illumination. Photocatalytic degradation TiO2 Polyhydroxy polymer Photosensitizer Visible light response Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Organic dyes are extensively utilized in modern society, imparting vibrant coloration across numerous applications. However, these compounds exhibit poor environmental degradability, and their wastewater discharge represents a growing environmental challenge. This contamination not only adversely impacts ecosystems but also poses significant risks to human health[ 1 ]. Conventional remediation strategies—including extraction, adsorption, ion exchange, coagulation, and biodegradation—have been employed for wastewater treatment[ 2 – 4 ]. These approaches, however, are often limited by inherent drawbacks [ 5 – 9 ], resulting in generally low treatment efficiencies. In contrast, photocatalysis presents a promising approach requiring only illumination and a photocatalyst, thereby eliminating the need for chemical additives. This technique is operationally simple, low-maintenance, and facilitates rapid degradation of organic pollutants within short durations [ 10 , 11 ]. The efficacy of photocatalytic degradation hinges critically on the selection of an appropriate photocatalyst. Numerous nanomaterials, including TiO₂, ZnO, SnO, ZrO₂, CuO, and Fe₂O₃, have been extensively explored as photocatalytic materials[ 12 ]. Among these, TiO₂, an n-type semiconductor, stands out due to its notable advantages, including non-toxicity, abundance, cost-effectiveness, versatility, and structural stability. Consequently, it remains one of the most widely adopted photocatalysts in current research and applications[ 13 ]. TiO₂ exhibits three distinct crystalline polymorphs: anatase, rutile, and brookite. While brookite demonstrates the highest intrinsic photocatalytic activity, its synthesis in high-purity forms remains technically demanding, thereby limiting systematic investigations[ 14 ]. In contrast, anatase TiO₂, which exhibits superior photocatalytic performance compared to rutile, has garnered significant research interest and practical application[ 15 ]. A critical limitation of TiO₂ lies in its relatively wide bandgap (3.2 eV for anatase), which restricts its ability to harness visible light effectively. This constraint confines its photoreactivity primarily to the ultraviolet (UV) spectrum, accounting for only ~ 5% of solar energy[ 16 ]. Consequently, enhancing the visible-light absorption capacity of TiO₂ is pivotal to broadening its utility in sustainable environmental remediation[ 17 – 20 ]. Strategies to modify or dope TiO₂ with organic/inorganic compounds represent a straightforward yet highly effective approach to augmenting its photocatalytic performance[ 21 , 22 ]. For instance, Sendão et al. synthesized carbon dot-TiO₂ composites, achieving a 367% enhancement in methylene blue (MB) degradation under visible light compared to pristine TiO₂[ 23 ]. Similarly, Neshastehgar et al. developed TiO₂@Silane@SiO₂ hybrids, which demonstrated improved visible-light absorption and efficient MB degradation[ 24 ]. Photosensitizers, a class of compounds capable of absorbing photons and generating reactive oxygen species (ROS) during photocatalytic processes, play a pivotal role in overcoming TiO₂’s UV-dependent limitations[ 25 ]. These sensitizers can harness solar or artificial light in the visible range, exciting electrons to higher energy levels and generating electron-hole pairs (e⁻/h⁺). The excited electrons (e⁻) react with molecular oxygen to form superoxide anion radicals (•O₂⁻), while holes (h⁺) interact with water or hydroxide ions to produce hydroxyl radicals (•OH)[ 26 , 27 ]. These ROS, characterized by strong oxidizing capabilities, effectively decompose organic pollutants[ 28 ]. By extending TiO₂’s photoreactive range to the visible spectrum, photosensitizers enable more efficient utilization of solar energy[ 29 ]. Despite these advancements, several critical challenges remain unresolved. First, the inherent bandgap width of TiO₂ (3.2 eV) inherently limits its activity to the UV region, constraining its practical applicability under visible light[ 30 ]. Second, while photosensitizer integration improves photocatalytic efficiency, the long-term stability and recyclability of modified materials remain significant hurdles[ 31 ]. To address these issues, this study presents a novel strategy for enhancing TiO₂-based photocatalysts through the sol-gel synthesis of hyperbranched polyglycerol (HPG)-modified materials. By compounding HPG with two photosensitizers (hemin and Eosin Y (EY)) at varying degrees of polymerization and branching, the study achieves effective TiO₂ modification[ 32 , 33 ]. Hemin and EY synergistically promote the generation of •O₂⁻ and •OH under light irradiation, significantly enhancing organic pollutant degradation[ 34 ]. A systematic investigation was conducted to evaluate the impact of HPG polymerization degree, branching architecture, photosensitizer grafting density, and light source on photocatalytic performance. Experimental results demonstrate that polymer grafting markedly enhances TiO₂’s activity, particularly under visible light, while maintaining structural stability across multiple cycles. This approach provides a robust framework for TiO₂ modification, offering both scientific insight and practical value in advancing photocatalytic technologies for environmental applications. 2. Results and Discussion 2.1. Structure and Morphology Polyhydroxy polymer-modified TiO₂ photocatalysts were fabricated via the sol-gel method. The nomenclature and composition details of HPG-hemin/TiO₂ and HPG-EY/TiO₂ photocatalysts are detailed in the Supplementary Information. To elucidate the polymerization degree and branching architecture of the synthesized hyperbranched polyglycerol (HPG), ¹H nuclear magnetic resonance (¹H-NMR) and ¹³C NMR analyses were performed. As illustrated in Figures S1 and S2, the ¹H-NMR spectra of HPG1–HPG5 revealed distinct hydrogen atom assignments, as annotated in the figures. Calculations based on Eq. (1) (Supplementary Information) yielded polymerization degrees of 138, 178, 264, 131, and 123 for HPG1–HPG5, respectively. The variation in polymerization degrees among HPG1, HPG2, and HPG3 demonstrates that the polymerization extent can be precisely modulated by adjusting the initiator concentration. Notably, the polymerization degrees of HPG1, HPG4, and HPG5 exhibit a near 1:1:1 ratio, indicating that polymerization temperature has negligible influence on the polymerization degree. Figure S3 presents the ¹³C NMR spectra of HPG1, HPG4, and HPG5, with peak integration data summarized in Table S1 . The branching degrees of these samples, calculated as 0.15, 0.19, and 2.16, respectively, confirm that elevated reaction temperatures significantly enhance the branching architecture of HPG. This high degree of branching provides an increased number of hydroxyl groups, thereby enhancing photocatalytic activity. To verify the successful grafting of photosensitizers onto the polymer backbone, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FT-IR) were conducted. The polydispersity index (PDI) of the synthesized polymers and their grafted derivatives ranged from 1.35 to 1.83 (Fig. 1 a), indicating a relatively narrow molecular weight distribution for all HPG samples. The mass fractions of EY in HPG1-EY and HPG5-EY were approximately 25.86% and 32.45%, while hemin contents in HPG1-hemin and HPG2-hemin were 9.58% and 14.22%, respectively. The observed increase in average molecular weight (Mₙ) of grafted products compared to unmodified polymers confirms effective photosensitizer immobilization. TGA profiles (Fig. 1 c and 1 d) reveal that HPG1-hemin, HPG2-hemin, HPG1-EY, and HPG5-EY reach maximum decomposition rates at 369°C, 302°C, 312°C, and 283°C, respectively. The residual mass fractions at 700°C—representing the proportion of successfully grafted photosensitizers—were 3.42% (HPG1-hemin), 13.13% (HPG2-hemin), 33.33% (HPG1-EY), and 37.51% (HPG5-EY). These results demonstrate that both higher polymerization degree and branching degree significantly enhance photosensitizer grafting efficiency (Fig. 1 c and 1 d). Increased polymerization degree provides a greater density of hydroxyl groups for photosensitizer attachment, while higher branching increases surface hydroxyl availability, facilitating more complete interfacial contact during grafting. FT-IR spectroscopy further validates the grafting process. The spectra of HPG-hemin and HPG exhibit similar overall features, but HPG-hemin displays stronger peak intensities (Fig. 1 b). The hydroxyl absorption peak at 3417 cm⁻¹ is attenuated in HPG-hemin due to esterification between HPG hydroxyls and hemin carboxyl groups. The emergence of a carbonyl peak at 1660 cm⁻¹ and enhanced C–O–C vibrations at 1104 cm⁻¹ confirm successful hemin grafting[ 35 ]. In contrast, the FT-IR spectra of HPG-EY and HPG remain largely similar[ 36 ]. However, HPG-EY exhibits a distinct carbonyl peak at 1645 cm⁻¹ and a ketocarbonyl peak of EY at 1563 cm⁻¹, alongside retained hydroxyl absorption at 3417 cm⁻¹. This spectral profile indicates that esterification between HPG hydroxyls and EY carboxyl groups generates new hydroxyl functionalities, further corroborating efficient EY grafting with high immobilization efficiency. X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM) were employed to assess whether the modification process altered the structural integrity of TiO₂. The XRD patterns revealed nine distinct diffraction peaks corresponding to anatase TiO₂ (Fig. 2 a), indicating that the synthesis of HPG-hemin/TiO₂ and HPG-EY/TiO₂ did not induce crystalline phase transformation. In contrast, the Raman spectra (Fig. 2 b) displayed a broad peak at 576 cm⁻¹ from hyperbranched polyglycerol (HPG), which overlapped with the characteristic TiO₂ anatase peaks, rendering them indistinguishable[ 37 ]. Notably, Raman peaks associated with the photosensitizers (hemin and Eosin Y) were detected across the 1000–4000 cm⁻¹ spectral range, confirming that the grafting of these species did not perturb the TiO₂ crystal lattice (Fig. 2 b). These findings are consistent with the XRD analysis, collectively demonstrating that the modification strategy preserved the anatase phase of TiO₂ while enabling successful photosensitizer immobilization. SEM imaging revealed uniform spherical particles with consistent size distribution across all samples (Fig. 3 ), suggesting that the polymer grafting process preserves the surface morphology of TiO₂. However, minor agglomeration was observed in some regions (Fig. 3 b–d)[ 34 ]. This phenomenon is primarily attributed to interfacial hydrogen bonding between surface hydroxyl groups on TiO₂ particles and water molecules adsorbed during hydrolysis. The hydrogen bonds can transiently link adjacent particles, resulting in localized clustering. Additionally, insufficient photosensitizer grafting may contribute to this behavior. Incomplete surface coverage leaves exposed hydroxyl groups, which are more prone to hydrogen-bond-mediated aggregation. Furthermore, non-uniform distribution of grafted polymers—likely due to low photosensitizer content—may exacerbate aggregation by creating heterogeneous surface interactions. Notably, the observed agglomeration does not significantly compromise photocatalytic performance. While excessive clustering can hinder charge transfer, moderate aggregation may enhance catalytic activity by creating localized microstructures that concentrate reactive species or provide additional active sites for pollutant adsorption and degradation. These findings highlight the delicate balance between structural integrity and functional optimization in polymer-modified TiO₂ systems. To evaluate the optical absorption properties of the grafted materials, UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) was conducted. All samples—TiO₂, HPG-hemin/TiO₂, and HPG-EY/TiO₂—exhibited strong absorption in the ultraviolet (UV) region (200–330 nm; Fig. 4 ). However, as the wavelength of incident light increased, the absorption capacity of all samples progressively diminished. Notably, the UV absorbance of HPG-hemin/TiO₂ and HPG-EY/TiO₂ was slightly lower than that of pure TiO₂. This phenomenon can be attributed to two factors: (1) the relatively low grafting densities of hemin in HPG-hemin and Eosin Y (EY) in HPG-EY, and (2) the inherently weak UV absorbance of hyperbranched polyglycerol (HPG) itself[ 36 ]. Among the hemin-grafted systems, HPG2-hemin/TiO₂ demonstrated superior light absorption compared to HPG1-hemin/TiO₂, owing to its higher hemin grafting density. Similarly, HPG5-EY/TiO₂ exhibited marginally improved absorption over HPG1-EY/TiO₂ in the visible light range, consistent with its elevated EY grafting efficiency. Consequently, both HPG-hemin/TiO₂ and HPG-EY/TiO₂ displayed significantly enhanced visible light absorption relative to bare TiO₂. The bandgap energy (E₉) of each photocatalyst was calculated using the Kubelka-Munk transformation in conjunction with DRS data, as detailed in the following section:[ 38 , 39 ]: ( αhν ) 2 = A( hν - E g ) n where α , h , ν , A, and E g represent the absorption coefficient, Planck's constant, optical frequency, another constant, and bandgap energy, respectively. For the indirect bandgap semiconductor like TiO 2 , n = 2. The Tauc plots of TiO 2 , HPG1-hemin/TiO 2 , HPG2-hemin/TiO 2 , HPG1-EY/TiO 2 and HPG5-EY/TiO 2 are shown in Fig. 4 b, with E g values of 2.82 eV, 0.96 eV, 0.50 eV, 0.70 eV and 0.63 eV. The modification of TiO 2 by grafting polymers significantly reduces the bandgap energy, allowing the composite materials to absorb lower-energy light and more easily form e − /h + under illumination. 2.2. Photocatalytic Performance To investigate the influence of polymer mass fraction on adsorption behavior, methylene blue (MB) adsorption kinetics were evaluated for composites with varying HPG content. As shown in Figure S4, polymer loading significantly modulates the adsorption capacity of TiO₂-based photocatalysts under fixed experimental conditions. All composites exhibited parabolic adsorption profiles. Notably, pristine TiO₂ demonstrated limited adsorption affinity toward MB, whereas optimal HPG incorporation enhanced adsorption performance. Although HPG molecules themselves exhibit negligible adsorption capacity, excessive polymer content (> 1 wt%) reduced adsorption efficacy due to diminished TiO₂ active site accessibility. Beyond the adsorption maximum, further increases in HPG mass fraction progressively degraded adsorption performance. 2.2.1. Ultraviolet Photocatalysis To evaluate the UV-light photocatalytic degradation kinetics of methylene blue (MB) by grafted composites, systematic experiments were conducted across varying polymer mass fractions as illustrated in Fig. 5 . As evidenced in Fig. 5 a and 5 b, all samples exhibited progressively enhanced MB degradation rates under UV irradiation. Initial degradation efficiency was elevated, attributable to high dye concentration and maximized photocatalyst activity, accelerating reaction kinetics. Subsequently, diminished dye concentration during later stages reduced reaction rates. Photocatalytic performance for MB displayed a volcano-type trend with increasing HPG1-EY loading. Optimal activity occurred at 3% HPG1-EY/TiO₂, achieving 56.15% MB degradation after 120 min—a 1.36-fold enhancement over pristine TiO₂ (41.26%). Conversely, 1% HPG5-EY/TiO₂ demonstrated superior efficiency (88.96% degradation; 2.16× pristine TiO₂). Mechanistically, abundant hydroxyl groups in HPG-EY systems participated in photocatalytic reactions, generating •OH radicals that significantly augmented degradation efficiency (Fig. 6 ). However, excessive polymer loading (> 3%) reduced TiO₂ content, impairing photocatalytic activity. Similar degradation trends were observed for HPG-hemin/TiO₂ composites (Fig. 5 c and 5 d). The 1% HPG1-hemin/TiO₂ and 3% HPG2-hemin/TiO₂ achieved 64.32% and 72.17% MB degradation, representing 1.56-fold and 1.75-fold improvements over pristine TiO₂, respectively. Analogous •OH-mediated enhancement mechanisms were confirmed (Fig. 6 ). Comparative analysis between grafted and control samples (Figure S5) revealed significantly enhanced photocatalytic efficiency in the functionalized composites. This indicates that HPG-photosensitizer grafting generates synergistic effects. Under UV irradiation, photogenerated electrons (e⁻) and holes (h⁺) from TiO₂ underwent more efficient conversion to reactive oxygen species (•O₂⁻ and •OH). The suppressed e⁻-h⁺ recombination rate substantially promoted photocatalytic reaction kinetics, thereby elevating degradation efficiency. 2.2.2. Visible Light Photocatalysis Visible-light photocatalytic experiments were performed on grafted composites with varying polymer mass fractions to evaluate methylene blue (MB) degradation kinetics. As depicted in Fig. 7 a and 7 b, HPG1-EY/TiO₂ and HPG5-EY/TiO₂ exhibited degradation trends analogous to their UV-light performance. The 3% HPG1-EY/TiO₂ and 1% HPG5-EY/TiO₂ composites demonstrated optimal activity, achieving 41.15% and 73.22% MB degradation after 120 min of visible-light irradiation—representing 1.18-fold and 2.11-fold enhancements over pristine TiO₂ (34.74%), respectively. Similarly, HPG-hemin/TiO₂ composites (Fig. 7 c and 7 d) showed consistent trend alignment between visible and UV regimes. The 1% HPG1-hemin/TiO₂ and 3% HPG2-hemin/TiO₂ attained 42.32% and 63.17% degradation, corresponding to 1.22-fold and 1.82-fold improvements versus pristine TiO₂. Notably, visible-light degradation efficiencies were substantially lower than UV-driven performance, primarily attributable to reduced photon utilization efficiency within the visible spectrum. 2.3. Stability and Reusability To evaluate the operational stability of the photocatalysts, cycling experiments were conducted under both UV and visible light irradiation. After four consecutive cycles (Fig. 8 ), all four composite samples exhibited negligible degradation in photocatalytic performance under both illumination regimes. This retention of activity across reuse cycles is critical for practical implementation, as it enables catalyst reuse without significant efficiency loss—delivering economic and environmental advantages [ 40 ]. The demonstrated stability confirms the potential of HPG-hemin/TiO₂ and HPG-EY/TiO₂ as robust photocatalysts for sustainable wastewater treatment, offering viable long-term environmental remediation solutions. 3. Conclusions This study successfully synthesized a series of hyperbranched polyglycerol (HPG)-modified TiO₂ composite photocatalysts. Functionalization with photosensitizers and HPGs of tailored polymerization degrees/branching architectures substantially enhanced TiO₂'s visible-light photocatalytic activity. For instance, 1% HPG5-EY/TiO₂ achieved 88.96% and 73.22% methylene blue (MB) degradation under UV and visible irradiation within 120 min, respectively—representing 2.11-fold and 2.11-fold enhancements over pristine TiO₂. These findings establish a novel modification strategy for TiO₂-based photocatalysts. Through optimized catalyst design and reaction parameter control, both photocatalytic efficiency and robust recyclability were significantly improved, providing scientific foundations and technical frameworks for addressing efficiency-stability trade-offs in practical applications. Future investigations will expand composite applications to broader-spectrum organic pollutant degradation while refining catalyst synthesis protocols to enhance industrial feasibility. Declarations The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Author Contribution G.L: Resources, Supervision, Funding acquisition, Conceptualization, Methodology, Formal analysis, Project Administration. S.Z.: Software, Investigation, Formal Analysis, Writing - Original Draft. D.T.: Conceptualization, Methodology, Software, Investigation, Formal Analysis, Writing - Original Draft. C.Y.: Formal Analysis. G.L.: Conceptualization, Methodology, Data Curation, Supervision, Formal analysis, Writing - Review & Editing. W.W.: Investigation. D.F.: Formal Analysis. J.Z.: Formal Analysis. R.H.: Formal Analysis. All authors have read and agreed to the published version of the manuscript. Acknowledgements This work was supported by the Opening Project of State Key Laboratory of Polymer Materials Engineering (Sichuan University) (Grant No. 2018-4-22), the Open Foundation of Hypervelocity Impact Research Center of CARDC (No. 20190102), the Key Scientific Research Fund of Xihua University (No. Z1620118), the Chunhui Project, Ministry of Education, China (Z2016128), the Xihua University Science and Technology Innovation Competition Project for Postgraduate Students (No. YK20240052, No. YK20240067, No. YK20240064 & No.YK20240079) and the Quality Project of Graduate Education, Xihua University (No. YJD202404). Data Availability The datasets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request, as the authors obtained all the data analyzed. 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Catal Reviews 66:1951–1991. https://doi.org/10.1080/01614940.2023.2169451 Khojastegi A, Khosropour A, Auras F, Abbaspourrad A (2025) 3D Interlocking Metallo-COFs as a Visible Light Responsive Photocatalyst. Small 21:2408151. https://doi.org/10.1002/smll.202408151 Wu Y, Zang Y, Xu L et al (2021) Synthesis of functional conjugated microporous polymer/TiO 2 nanocomposites and the mechanism of the photocatalytic degradation of organic pollutants. J Mater Sci 56:7936–7950. https://doi.org/10.1007/s10853-021-05790-9 Liao W, Zhao M, Rong H et al (2022) Photocatalyst immobilized by hydrogel, efficient degradation and self regeneration: A review. Mater Sci Semiconduct Process 150:106929. https://doi.org/10.1016/j.mssp.2022.106929 Li G-Z, Zhang S, Tian D et al (2024) Improving the Visible Light Absorption and Photocatalytic Degradation Activity of TiO 2 Particles Towards MB by Organic Sensitizer Decoration. Catal Lett 154:3896–3910. https://doi.org/10.1007/s10562-024-04622-0 Dörr S, Schade U, Hellwig P (2008) Far infrared spectroscopy on hemoproteins: A model compound study from 1800–100cm – 1. Vib Spectrosc 47:59–65. https://doi.org/10.1016/j.vibspec.2008.02.003 Zhou S, Tian D, Li G et al (2024) Hyperbranched Polymer-Hemin/TiO 2 Composite Photocatalyst and Its Photocatalytic Performance. Acta Materiae Compositae Sinica 43:1–12 Albiter E, Barrera-Andrade JM, Calzada LA et al (2022) Enhancing Free Cyanide Photocatalytic Oxidation by rGO/TiO 2 P25 Composites. Materials 15:5284. https://doi.org/10.3390/ma15155284 Satti UQ, Zaidi SJA, Riaz A et al (2023) Simple two-step development of TiO 2 /Fe 2 O 3 nanocomposite for oxygen evolution reaction (OER) and photo-bio active applications. Colloids Surf A 671:131662. https://doi.org/10.1016/j.colsurfa.2023.131662 Ren X, Chen R, Ding S, Fu N (2023) Preparation and photocatalytic performance of a magnetically recyclable ZnFe 2 O 4 @TiO 2 @Ag 2 O p-n/Z-type tandem heterojunction photocatalyst: Degradation pathway and mechanism. Colloids Surf A 658:130604. https://doi.org/10.1016/j.colsurfa.2022.130604 Zhu Z, Zhou S, Tian D et al (2025) Fabrication of Polydopamine/hemin/TiO 2 Composites with Enhanced Visible Light Absorption for Efficient Photocatalytic Degradation of Methylene Blue. Polymers 17:311. https://doi.org/10.3390/polym17030311 Additional Declarations No competing interests reported. Supplementary Files TiO2GLYphotocatalyticSI.docx Graphicabstract.docx Cite Share Download PDF Status: Published Journal Publication published 18 Nov, 2025 Read the published version in Journal of Polymers and the Environment → Version 1 posted Editorial decision: Revision requested 06 Jul, 2025 Reviews received at journal 05 Jul, 2025 Reviews received at journal 03 Jul, 2025 Reviews received at journal 02 Jul, 2025 Reviews received at journal 28 Jun, 2025 Reviews received at journal 26 Jun, 2025 Reviewers agreed at journal 25 Jun, 2025 Reviewers agreed at journal 25 Jun, 2025 Reviewers agreed at journal 25 Jun, 2025 Reviewers agreed at journal 25 Jun, 2025 Reviewers agreed at journal 25 Jun, 2025 Reviewers invited by journal 25 Jun, 2025 Editor assigned by journal 20 Jun, 2025 Submission checks completed at journal 20 Jun, 2025 First submitted to journal 19 Jun, 2025 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. 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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-6927801","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":477770962,"identity":"c1baeb4b-9926-4073-86fd-13e10602a8b5","order_by":0,"name":"Guang-Zhao Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/ElEQVRIiWNgGAWjYPCCA0DM3HDgYwOIw9h4gEgtjA0HZzYwSIAYxGth5gVrgXBxAvmI5GcPv/y5I88PdM9h2x02dbrth4G21NhE49JieCPN3FiG55nhzAbGhsO5Z9IkzM4kArUcS8ttwKVlRoKZtITEYcYNB0Ba2g5LmB0AagGxcWtJ/yYtYXDYHqzFEqTl/EP8WuQlcswkPyQcTgRrYQRpuUHAFgOeN2XSDAcOJ89sBgZyb1ua5LYbQFsS8PhFvj19m+SPP4dt+9mbD3/42WbDb3Y+/eGDDzU2uG05AIx2HhCLGVk4AYdysC1Asxh/4FEwCkbBKBgFo4ABAEbGaTLjeZwJAAAAAElFTkSuQmCC","orcid":"","institution":"Xihua University","correspondingAuthor":true,"prefix":"","firstName":"Guang-Zhao","middleName":"","lastName":"Li","suffix":""},{"id":477770963,"identity":"a6c55809-9d21-430a-8b58-2e668d82e374","order_by":1,"name":"Shengrong Zhou","email":"","orcid":"","institution":"Xihua University","correspondingAuthor":false,"prefix":"","firstName":"Shengrong","middleName":"","lastName":"Zhou","suffix":""},{"id":477770967,"identity":"c40311ed-e94c-4d66-9f08-ded1789c2480","order_by":2,"name":"Debin Tian","email":"","orcid":"","institution":"Xihua University","correspondingAuthor":false,"prefix":"","firstName":"Debin","middleName":"","lastName":"Tian","suffix":""},{"id":477770968,"identity":"ad5de535-b987-4169-b520-b6410f559f80","order_by":3,"name":"Chengqiang Yang","email":"","orcid":"","institution":"Xihua University","correspondingAuthor":false,"prefix":"","firstName":"Chengqiang","middleName":"","lastName":"Yang","suffix":""},{"id":477770970,"identity":"4ef2a61c-d4e5-4c97-82e5-f2f19950093c","order_by":4,"name":"Gen Liu","email":"","orcid":"","institution":"Xihua University","correspondingAuthor":false,"prefix":"","firstName":"Gen","middleName":"","lastName":"Liu","suffix":""},{"id":477770973,"identity":"775b8251-fdf2-4009-a520-701035326386","order_by":5,"name":"Wenyan Wang","email":"","orcid":"","institution":"Xihua University","correspondingAuthor":false,"prefix":"","firstName":"Wenyan","middleName":"","lastName":"Wang","suffix":""},{"id":477770976,"identity":"cfbe5337-2ad8-43fb-a600-f5b898a7c011","order_by":6,"name":"Dong Fang","email":"","orcid":"","institution":"Xihua University","correspondingAuthor":false,"prefix":"","firstName":"Dong","middleName":"","lastName":"Fang","suffix":""},{"id":477770977,"identity":"04685708-7833-41dc-8503-45c568105531","order_by":7,"name":"Jinyu Zhou","email":"","orcid":"","institution":"Xihua University","correspondingAuthor":false,"prefix":"","firstName":"Jinyu","middleName":"","lastName":"Zhou","suffix":""},{"id":477770978,"identity":"726ccc27-a5c0-4df5-9358-31f8f30eef18","order_by":8,"name":"Rui Han","email":"","orcid":"","institution":"Xihua University","correspondingAuthor":false,"prefix":"","firstName":"Rui","middleName":"","lastName":"Han","suffix":""}],"badges":[],"createdAt":"2025-06-19 05:53:33","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6927801/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6927801/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10924-025-03682-6","type":"published","date":"2025-11-18T15:58:05+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":85794739,"identity":"b984a031-43b3-421f-a90f-5fea918b307f","added_by":"auto","created_at":"2025-07-01 19:02:58","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":4082585,"visible":true,"origin":"","legend":"\u003cp\u003e(a) GPC Curves of Polymers for the HPG Series Products HPG-hemin and HPG-EY. (b) FT-IR spectra of HPG-hemin composites and HPG-EY. TG curve and DTG curve of HPG-hemin and HPG-EY (c) HPG-hemin, (d) HPG-EY.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6927801/v1/5096cb61d3a375879ce82e61.png"},{"id":85794736,"identity":"7b5978f8-eea7-4276-9d90-226012e51a86","added_by":"auto","created_at":"2025-07-01 19:02:58","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2070527,"visible":true,"origin":"","legend":"\u003cp\u003e(a) XRD patterns of TiO\u003csub\u003e2\u003c/sub\u003e, HPG-hemin/TiO\u003csub\u003e2\u003c/sub\u003e,\u003csub\u003e \u003c/sub\u003eand HPG-EY/TiO\u003csub\u003e2\u003c/sub\u003e composites. (b) Raman spectra of HPG-hemin/TiO\u003csub\u003e2 \u003c/sub\u003eand HPG5-EY/TiO\u003csub\u003e2 \u003c/sub\u003ecomposites.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6927801/v1/751ad83ab87401bc1f09ccaa.png"},{"id":85794738,"identity":"164f71e2-4a36-48ee-bc7a-64c4d48721a4","added_by":"auto","created_at":"2025-07-01 19:02:58","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2310004,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of HPG1-hemin/TiO\u003csub\u003e2\u003c/sub\u003e, HPG2-hemin/TiO\u003csub\u003e2\u003c/sub\u003e, HPG1-EY/TiO\u003csub\u003e2\u003c/sub\u003e and HPG5-EY/TiO\u003csub\u003e2\u003c/sub\u003e (a) HPG1-hemin/TiO\u003csub\u003e2 \u003c/sub\u003e3000x, (b) HPG2-hemin/TiO\u003csub\u003e2\u003c/sub\u003e 3000x, (c) HPG1-EY/TiO\u003csub\u003e2 \u003c/sub\u003e3000x, (d) HPG5-EY/TiO\u003csub\u003e2 \u003c/sub\u003e3000x, (e) HPG1-hemin/TiO\u003csub\u003e2\u003c/sub\u003e 7000x, (f) HPG2-hemin /TiO\u003csub\u003e2\u003c/sub\u003e 7000x, (g) HPG1-EY /TiO\u003csub\u003e2\u003c/sub\u003e 7000x, (h) HPG5-EY /TiO\u003csub\u003e2\u003c/sub\u003e 7000x.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6927801/v1/25e7a3375e9b2e43861f7015.png"},{"id":85794740,"identity":"2c474ecb-7858-459f-9903-1352d44a3a3d","added_by":"auto","created_at":"2025-07-01 19:02:58","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1911762,"visible":true,"origin":"","legend":"\u003cp\u003e(a) UV-Vis DRS spectra of HPG1-hemin/TiO\u003csub\u003e2\u003c/sub\u003e, HPG2-hemin/TiO\u003csub\u003e2\u003c/sub\u003e, HPG1-EY/TiO\u003csub\u003e2\u003c/sub\u003e, HPG5-EY/TiO\u003csub\u003e2\u003c/sub\u003e composites and TiO\u003csub\u003e2\u003c/sub\u003e. (b) The Tauc plots of HPG1-hemin/TiO\u003csub\u003e2\u003c/sub\u003e, HPG2-hemin/TiO\u003csub\u003e2\u003c/sub\u003e, HPG1-EY/TiO\u003csub\u003e2\u003c/sub\u003e, HPG5-EY/TiO\u003csub\u003e2\u003c/sub\u003e, and TiO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6927801/v1/e293bd4215ca744d3b2e87d1.png"},{"id":85794746,"identity":"02f82463-c28c-4baf-af51-5d7f039ef6e1","added_by":"auto","created_at":"2025-07-01 19:02:58","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":3907141,"visible":true,"origin":"","legend":"\u003cp\u003e(a) UV photocatalytic data of HPG1-EY/TiO\u003csub\u003e2\u003c/sub\u003e series samples, (b) UV photocatalytic data of HPG5-EY/TiO\u003csub\u003e2\u003c/sub\u003e series samples, (c) UV photocatalytic data of HPG1-hemin/TiO\u003csub\u003e2\u003c/sub\u003e series samples, (d) UV photocatalytic data of HPG2-hemin/TiO\u003csub\u003e2\u003c/sub\u003e series samples.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6927801/v1/82c68d65bf566e360f21ae6e.png"},{"id":85794742,"identity":"85705050-2637-4cd5-9dcf-7b0c75145ea5","added_by":"auto","created_at":"2025-07-01 19:02:58","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":4940531,"visible":true,"origin":"","legend":"\u003cp\u003ePhotocatalytic Reaction Mechanism Diagram.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6927801/v1/add755e724954d51f6eb76b6.png"},{"id":85795199,"identity":"0128f008-4744-424b-9a54-17f4772bf238","added_by":"auto","created_at":"2025-07-01 19:10:58","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":3874052,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Visible light photocatalytic data of HPG1-EY/TiO\u003csub\u003e2\u003c/sub\u003e series samples, (b) Visible light photocatalytic data of HPG5-EY/TiO\u003csub\u003e2\u003c/sub\u003e series samples. (c) Visible light photocatalytic data of HPG1-hemin/TiO\u003csub\u003e2\u003c/sub\u003e series samples, (d) Visible light photocatalytic data of HPG2-hemin/TiO\u003csub\u003e2\u003c/sub\u003e series samples.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-6927801/v1/6213bfd0a3339781647ee316.png"},{"id":85795204,"identity":"e0cbf108-32c1-48a7-954d-034f2116d436","added_by":"auto","created_at":"2025-07-01 19:10:58","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":2117111,"visible":true,"origin":"","legend":"\u003cp\u003ePhotocatalytic cycle experiments data of HPG1-EY/TiO\u003csub\u003e2\u003c/sub\u003e, HPG5-EY/TiO\u003csub\u003e2\u003c/sub\u003e, HPG1-hemin/TiO\u003csub\u003e2\u003c/sub\u003e samples and HPG2-hemin/TiO\u003csub\u003e2\u003c/sub\u003e. (a) HPG1-EY/TiO\u003csub\u003e2\u003c/sub\u003e Ultraviolet light, (b) HPG5-EY/TiO\u003csub\u003e2\u003c/sub\u003e Ultraviolet light, (c) HPG1-hemin/TiO\u003csub\u003e2\u003c/sub\u003e Ultraviolet light, (d) HPG2-hemin/TiO\u003csub\u003e2\u003c/sub\u003e Ultraviolet light. (e) HPG1-EY/TiO\u003csub\u003e2\u003c/sub\u003e visible light, (f) HPG5-EY/TiO\u003csub\u003e2\u003c/sub\u003e visible light, (g) HPG1-hemin/TiO\u003csub\u003e2\u003c/sub\u003e visible light, (h) HPG2-hemin/TiO\u003csub\u003e2\u003c/sub\u003e visible light.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-6927801/v1/9cf30c63e125dfaf616a520f.png"},{"id":96650339,"identity":"5ccb1d43-c5b4-4dec-97be-d21764daf15e","added_by":"auto","created_at":"2025-11-24 16:11:18","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":25812072,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6927801/v1/bd30b301-8271-4a67-ab0f-da83a9469bac.pdf"},{"id":85795676,"identity":"a5027521-2979-4abf-bd28-5b924efc575e","added_by":"auto","created_at":"2025-07-01 19:26:58","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":3377274,"visible":true,"origin":"","legend":"","description":"","filename":"TiO2GLYphotocatalyticSI.docx","url":"https://assets-eu.researchsquare.com/files/rs-6927801/v1/0664686b8b9ca1ed4f6a5825.docx"},{"id":85795241,"identity":"6f12a0c7-daeb-4ee6-89f3-5dba1b55d9ee","added_by":"auto","created_at":"2025-07-01 19:18:58","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":230199,"visible":true,"origin":"","legend":"","description":"","filename":"Graphicabstract.docx","url":"https://assets-eu.researchsquare.com/files/rs-6927801/v1/17237a3f877eaf4eac9bf08a.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Synthesis of Hyperbranched Polyglycerol-Photosensitizer/TiO 2 Nanocomposite for the Photocatalytic Degradation of Methylene Blue","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eOrganic dyes are extensively utilized in modern society, imparting vibrant coloration across numerous applications. However, these compounds exhibit poor environmental degradability, and their wastewater discharge represents a growing environmental challenge. This contamination not only adversely impacts ecosystems but also poses significant risks to human health[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Conventional remediation strategies\u0026mdash;including extraction, adsorption, ion exchange, coagulation, and biodegradation\u0026mdash;have been employed for wastewater treatment[\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. These approaches, however, are often limited by inherent drawbacks [\u003cspan additionalcitationids=\"CR6 CR7 CR8\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], resulting in generally low treatment efficiencies. In contrast, photocatalysis presents a promising approach requiring only illumination and a photocatalyst, thereby eliminating the need for chemical additives. This technique is operationally simple, low-maintenance, and facilitates rapid degradation of organic pollutants within short durations [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe efficacy of photocatalytic degradation hinges critically on the selection of an appropriate photocatalyst. Numerous nanomaterials, including TiO₂, ZnO, SnO, ZrO₂, CuO, and Fe₂O₃, have been extensively explored as photocatalytic materials[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Among these, TiO₂, an n-type semiconductor, stands out due to its notable advantages, including non-toxicity, abundance, cost-effectiveness, versatility, and structural stability. Consequently, it remains one of the most widely adopted photocatalysts in current research and applications[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. TiO₂ exhibits three distinct crystalline polymorphs: anatase, rutile, and brookite. While brookite demonstrates the highest intrinsic photocatalytic activity, its synthesis in high-purity forms remains technically demanding, thereby limiting systematic investigations[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. In contrast, anatase TiO₂, which exhibits superior photocatalytic performance compared to rutile, has garnered significant research interest and practical application[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. A critical limitation of TiO₂ lies in its relatively wide bandgap (3.2 eV for anatase), which restricts its ability to harness visible light effectively. This constraint confines its photoreactivity primarily to the ultraviolet (UV) spectrum, accounting for only\u0026thinsp;~\u0026thinsp;5% of solar energy[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Consequently, enhancing the visible-light absorption capacity of TiO₂ is pivotal to broadening its utility in sustainable environmental remediation[\u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eStrategies to modify or dope TiO₂ with organic/inorganic compounds represent a straightforward yet highly effective approach to augmenting its photocatalytic performance[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. For instance, Send\u0026atilde;o et al. synthesized carbon dot-TiO₂ composites, achieving a 367% enhancement in methylene blue (MB) degradation under visible light compared to pristine TiO₂[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Similarly, Neshastehgar et al. developed TiO₂@Silane@SiO₂ hybrids, which demonstrated improved visible-light absorption and efficient MB degradation[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Photosensitizers, a class of compounds capable of absorbing photons and generating reactive oxygen species (ROS) during photocatalytic processes, play a pivotal role in overcoming TiO₂\u0026rsquo;s UV-dependent limitations[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. These sensitizers can harness solar or artificial light in the visible range, exciting electrons to higher energy levels and generating electron-hole pairs (e⁻/h⁺). The excited electrons (e⁻) react with molecular oxygen to form superoxide anion radicals (\u0026bull;O₂⁻), while holes (h⁺) interact with water or hydroxide ions to produce hydroxyl radicals (\u0026bull;OH)[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. These ROS, characterized by strong oxidizing capabilities, effectively decompose organic pollutants[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. By extending TiO₂\u0026rsquo;s photoreactive range to the visible spectrum, photosensitizers enable more efficient utilization of solar energy[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Despite these advancements, several critical challenges remain unresolved. First, the inherent bandgap width of TiO₂ (3.2 eV) inherently limits its activity to the UV region, constraining its practical applicability under visible light[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Second, while photosensitizer integration improves photocatalytic efficiency, the long-term stability and recyclability of modified materials remain significant hurdles[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTo address these issues, this study presents a novel strategy for enhancing TiO₂-based photocatalysts through the sol-gel synthesis of hyperbranched polyglycerol (HPG)-modified materials. By compounding HPG with two photosensitizers (hemin and Eosin Y (EY)) at varying degrees of polymerization and branching, the study achieves effective TiO₂ modification[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Hemin and EY synergistically promote the generation of \u0026bull;O₂⁻ and \u0026bull;OH under light irradiation, significantly enhancing organic pollutant degradation[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. A systematic investigation was conducted to evaluate the impact of HPG polymerization degree, branching architecture, photosensitizer grafting density, and light source on photocatalytic performance. Experimental results demonstrate that polymer grafting markedly enhances TiO₂\u0026rsquo;s activity, particularly under visible light, while maintaining structural stability across multiple cycles. This approach provides a robust framework for TiO₂ modification, offering both scientific insight and practical value in advancing photocatalytic technologies for environmental applications.\u003c/p\u003e"},{"header":"2. Results and Discussion","content":" \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Structure and Morphology\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003ePolyhydroxy polymer-modified TiO₂ photocatalysts were fabricated via the sol-gel method. The nomenclature and composition details of HPG-hemin/TiO₂ and HPG-EY/TiO₂ photocatalysts are detailed in the Supplementary Information.\u003c/p\u003e \u003cp\u003eTo elucidate the polymerization degree and branching architecture of the synthesized hyperbranched polyglycerol (HPG), \u0026sup1;H nuclear magnetic resonance (\u0026sup1;H-NMR) and \u0026sup1;\u0026sup3;C NMR analyses were performed. As illustrated in Figures \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e and S2, the \u0026sup1;H-NMR spectra of HPG1\u0026ndash;HPG5 revealed distinct hydrogen atom assignments, as annotated in the figures. Calculations based on Eq.\u0026nbsp;(1) (Supplementary Information) yielded polymerization degrees of 138, 178, 264, 131, and 123 for HPG1\u0026ndash;HPG5, respectively. The variation in polymerization degrees among HPG1, HPG2, and HPG3 demonstrates that the polymerization extent can be precisely modulated by adjusting the initiator concentration. Notably, the polymerization degrees of HPG1, HPG4, and HPG5 exhibit a near 1:1:1 ratio, indicating that polymerization temperature has negligible influence on the polymerization degree. Figure S3 presents the \u0026sup1;\u0026sup3;C NMR spectra of HPG1, HPG4, and HPG5, with peak integration data summarized in Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e. The branching degrees of these samples, calculated as 0.15, 0.19, and 2.16, respectively, confirm that elevated reaction temperatures significantly enhance the branching architecture of HPG. This high degree of branching provides an increased number of hydroxyl groups, thereby enhancing photocatalytic activity.\u003c/p\u003e \u003cp\u003eTo verify the successful grafting of photosensitizers onto the polymer backbone, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FT-IR) were conducted. The polydispersity index (PDI) of the synthesized polymers and their grafted derivatives ranged from 1.35 to 1.83 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea), indicating a relatively narrow molecular weight distribution for all HPG samples. The mass fractions of EY in HPG1-EY and HPG5-EY were approximately 25.86% and 32.45%, while hemin contents in HPG1-hemin and HPG2-hemin were 9.58% and 14.22%, respectively. The observed increase in average molecular weight (Mₙ) of grafted products compared to unmodified polymers confirms effective photosensitizer immobilization. TGA profiles (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed) reveal that HPG1-hemin, HPG2-hemin, HPG1-EY, and HPG5-EY reach maximum decomposition rates at 369\u0026deg;C, 302\u0026deg;C, 312\u0026deg;C, and 283\u0026deg;C, respectively. The residual mass fractions at 700\u0026deg;C\u0026mdash;representing the proportion of successfully grafted photosensitizers\u0026mdash;were 3.42% (HPG1-hemin), 13.13% (HPG2-hemin), 33.33% (HPG1-EY), and 37.51% (HPG5-EY). These results demonstrate that both higher polymerization degree and branching degree significantly enhance photosensitizer grafting efficiency (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). Increased polymerization degree provides a greater density of hydroxyl groups for photosensitizer attachment, while higher branching increases surface hydroxyl availability, facilitating more complete interfacial contact during grafting.\u003c/p\u003e \u003cp\u003eFT-IR spectroscopy further validates the grafting process. The spectra of HPG-hemin and HPG exhibit similar overall features, but HPG-hemin displays stronger peak intensities (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). The hydroxyl absorption peak at 3417 cm⁻\u0026sup1; is attenuated in HPG-hemin due to esterification between HPG hydroxyls and hemin carboxyl groups. The emergence of a carbonyl peak at 1660 cm⁻\u0026sup1; and enhanced C\u0026ndash;O\u0026ndash;C vibrations at 1104 cm⁻\u0026sup1; confirm successful hemin grafting[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. In contrast, the FT-IR spectra of HPG-EY and HPG remain largely similar[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. However, HPG-EY exhibits a distinct carbonyl peak at 1645 cm⁻\u0026sup1; and a ketocarbonyl peak of EY at 1563 cm⁻\u0026sup1;, alongside retained hydroxyl absorption at 3417 cm⁻\u0026sup1;. This spectral profile indicates that esterification between HPG hydroxyls and EY carboxyl groups generates new hydroxyl functionalities, further corroborating efficient EY grafting with high immobilization efficiency.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eX-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM) were employed to assess whether the modification process altered the structural integrity of TiO₂. The XRD patterns revealed nine distinct diffraction peaks corresponding to anatase TiO₂ (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea), indicating that the synthesis of HPG-hemin/TiO₂ and HPG-EY/TiO₂ did not induce crystalline phase transformation. In contrast, the Raman spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb) displayed a broad peak at 576 cm⁻\u0026sup1; from hyperbranched polyglycerol (HPG), which overlapped with the characteristic TiO₂ anatase peaks, rendering them indistinguishable[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Notably, Raman peaks associated with the photosensitizers (hemin and Eosin Y) were detected across the 1000\u0026ndash;4000 cm⁻\u0026sup1; spectral range, confirming that the grafting of these species did not perturb the TiO₂ crystal lattice (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). These findings are consistent with the XRD analysis, collectively demonstrating that the modification strategy preserved the anatase phase of TiO₂ while enabling successful photosensitizer immobilization.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSEM imaging revealed uniform spherical particles with consistent size distribution across all samples (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), suggesting that the polymer grafting process preserves the surface morphology of TiO₂. However, minor agglomeration was observed in some regions (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb\u0026ndash;d)[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. This phenomenon is primarily attributed to interfacial hydrogen bonding between surface hydroxyl groups on TiO₂ particles and water molecules adsorbed during hydrolysis. The hydrogen bonds can transiently link adjacent particles, resulting in localized clustering. Additionally, insufficient photosensitizer grafting may contribute to this behavior. Incomplete surface coverage leaves exposed hydroxyl groups, which are more prone to hydrogen-bond-mediated aggregation. Furthermore, non-uniform distribution of grafted polymers\u0026mdash;likely due to low photosensitizer content\u0026mdash;may exacerbate aggregation by creating heterogeneous surface interactions.\u003c/p\u003e \u003cp\u003eNotably, the observed agglomeration does not significantly compromise photocatalytic performance. While excessive clustering can hinder charge transfer, moderate aggregation may enhance catalytic activity by creating localized microstructures that concentrate reactive species or provide additional active sites for pollutant adsorption and degradation. These findings highlight the delicate balance between structural integrity and functional optimization in polymer-modified TiO₂ systems.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo evaluate the optical absorption properties of the grafted materials, UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) was conducted. All samples\u0026mdash;TiO₂, HPG-hemin/TiO₂, and HPG-EY/TiO₂\u0026mdash;exhibited strong absorption in the ultraviolet (UV) region (200\u0026ndash;330 nm; Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). However, as the wavelength of incident light increased, the absorption capacity of all samples progressively diminished. Notably, the UV absorbance of HPG-hemin/TiO₂ and HPG-EY/TiO₂ was slightly lower than that of pure TiO₂. This phenomenon can be attributed to two factors: (1) the relatively low grafting densities of hemin in HPG-hemin and Eosin Y (EY) in HPG-EY, and (2) the inherently weak UV absorbance of hyperbranched polyglycerol (HPG) itself[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Among the hemin-grafted systems, HPG2-hemin/TiO₂ demonstrated superior light absorption compared to HPG1-hemin/TiO₂, owing to its higher hemin grafting density. Similarly, HPG5-EY/TiO₂ exhibited marginally improved absorption over HPG1-EY/TiO₂ in the visible light range, consistent with its elevated EY grafting efficiency. Consequently, both HPG-hemin/TiO₂ and HPG-EY/TiO₂ displayed significantly enhanced visible light absorption relative to bare TiO₂.\u003c/p\u003e \u003cp\u003eThe bandgap energy (E₉) of each photocatalyst was calculated using the Kubelka-Munk transformation in conjunction with DRS data, as detailed in the following section:[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]:\u003c/p\u003e \u003cp\u003e(\u003cem\u003eαhν\u003c/em\u003e)\u003csup\u003e2\u003c/sup\u003e = A(\u003cem\u003ehν\u003c/em\u003e - \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eg\u003c/em\u003e\u003c/sub\u003e)\u003csup\u003en\u003c/sup\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cem\u003eα\u003c/em\u003e, \u003cem\u003eh\u003c/em\u003e, \u003cem\u003eν\u003c/em\u003e, A, and \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eg\u003c/em\u003e\u003c/sub\u003e represent the absorption coefficient, Planck's constant, optical frequency, another constant, and bandgap energy, respectively. For the indirect bandgap semiconductor like TiO\u003csub\u003e2\u003c/sub\u003e, n\u0026thinsp;=\u0026thinsp;2. The Tauc plots of TiO\u003csub\u003e2\u003c/sub\u003e, HPG1-hemin/TiO\u003csub\u003e2\u003c/sub\u003e, HPG2-hemin/TiO\u003csub\u003e2\u003c/sub\u003e, HPG1-EY/TiO\u003csub\u003e2\u003c/sub\u003e and HPG5-EY/TiO\u003csub\u003e2\u003c/sub\u003e are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, with \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eg\u003c/em\u003e\u003c/sub\u003e values of 2.82 eV, 0.96 eV, 0.50 eV, 0.70 eV and 0.63 eV. The modification of TiO\u003csub\u003e2\u003c/sub\u003e by grafting polymers significantly reduces the bandgap energy, allowing the composite materials to absorb lower-energy light and more easily form e\u003csup\u003e\u0026minus;\u003c/sup\u003e/h\u003csup\u003e+\u003c/sup\u003e under illumination.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Photocatalytic Performance\u003c/h2\u003e \u003cp\u003eTo investigate the influence of polymer mass fraction on adsorption behavior, methylene blue (MB) adsorption kinetics were evaluated for composites with varying HPG content. As shown in Figure S4, polymer loading significantly modulates the adsorption capacity of TiO₂-based photocatalysts under fixed experimental conditions. All composites exhibited parabolic adsorption profiles. Notably, pristine TiO₂ demonstrated limited adsorption affinity toward MB, whereas optimal HPG incorporation enhanced adsorption performance. Although HPG molecules themselves exhibit negligible adsorption capacity, excessive polymer content (\u0026gt;\u0026thinsp;1 wt%) reduced adsorption efficacy due to diminished TiO₂ active site accessibility. Beyond the adsorption maximum, further increases in HPG mass fraction progressively degraded adsorption performance.\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e \u003ch2\u003e2.2.1. Ultraviolet Photocatalysis\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo evaluate the UV-light photocatalytic degradation kinetics of methylene blue (MB) by grafted composites, systematic experiments were conducted across varying polymer mass fractions as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. As evidenced in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, all samples exhibited progressively enhanced MB degradation rates under UV irradiation. Initial degradation efficiency was elevated, attributable to high dye concentration and maximized photocatalyst activity, accelerating reaction kinetics. Subsequently, diminished dye concentration during later stages reduced reaction rates. Photocatalytic performance for MB displayed a volcano-type trend with increasing HPG1-EY loading. Optimal activity occurred at 3% HPG1-EY/TiO₂, achieving 56.15% MB degradation after 120 min\u0026mdash;a 1.36-fold enhancement over pristine TiO₂ (41.26%). Conversely, 1% HPG5-EY/TiO₂ demonstrated superior efficiency (88.96% degradation; 2.16\u0026times; pristine TiO₂). Mechanistically, abundant hydroxyl groups in HPG-EY systems participated in photocatalytic reactions, generating \u0026bull;OH radicals that significantly augmented degradation efficiency (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). However, excessive polymer loading (\u0026gt;\u0026thinsp;3%) reduced TiO₂ content, impairing photocatalytic activity. Similar degradation trends were observed for HPG-hemin/TiO₂ composites (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed). The 1% HPG1-hemin/TiO₂ and 3% HPG2-hemin/TiO₂ achieved 64.32% and 72.17% MB degradation, representing 1.56-fold and 1.75-fold improvements over pristine TiO₂, respectively. Analogous \u0026bull;OH-mediated enhancement mechanisms were confirmed (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eComparative analysis between grafted and control samples (Figure S5) revealed significantly enhanced photocatalytic efficiency in the functionalized composites. This indicates that HPG-photosensitizer grafting generates synergistic effects. Under UV irradiation, photogenerated electrons (e⁻) and holes (h⁺) from TiO₂ underwent more efficient conversion to reactive oxygen species (\u0026bull;O₂⁻ and \u0026bull;OH). The suppressed e⁻-h⁺ recombination rate substantially promoted photocatalytic reaction kinetics, thereby elevating degradation efficiency.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.2.2. Visible Light Photocatalysis\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eVisible-light photocatalytic experiments were performed on grafted composites with varying polymer mass fractions to evaluate methylene blue (MB) degradation kinetics. As depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb, HPG1-EY/TiO₂ and HPG5-EY/TiO₂ exhibited degradation trends analogous to their UV-light performance. The 3% HPG1-EY/TiO₂ and 1% HPG5-EY/TiO₂ composites demonstrated optimal activity, achieving 41.15% and 73.22% MB degradation after 120 min of visible-light irradiation\u0026mdash;representing 1.18-fold and 2.11-fold enhancements over pristine TiO₂ (34.74%), respectively. Similarly, HPG-hemin/TiO₂ composites (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ed) showed consistent trend alignment between visible and UV regimes. The 1% HPG1-hemin/TiO₂ and 3% HPG2-hemin/TiO₂ attained 42.32% and 63.17% degradation, corresponding to 1.22-fold and 1.82-fold improvements versus pristine TiO₂. Notably, visible-light degradation efficiencies were substantially lower than UV-driven performance, primarily attributable to reduced photon utilization efficiency within the visible spectrum.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Stability and Reusability\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo evaluate the operational stability of the photocatalysts, cycling experiments were conducted under both UV and visible light irradiation. After four consecutive cycles (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e), all four composite samples exhibited negligible degradation in photocatalytic performance under both illumination regimes. This retention of activity across reuse cycles is critical for practical implementation, as it enables catalyst reuse without significant efficiency loss\u0026mdash;delivering economic and environmental advantages [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. The demonstrated stability confirms the potential of HPG-hemin/TiO₂ and HPG-EY/TiO₂ as robust photocatalysts for sustainable wastewater treatment, offering viable long-term environmental remediation solutions.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Conclusions","content":"\u003cp\u003eThis study successfully synthesized a series of hyperbranched polyglycerol (HPG)-modified TiO₂ composite photocatalysts. Functionalization with photosensitizers and HPGs of tailored polymerization degrees/branching architectures substantially enhanced TiO₂'s visible-light photocatalytic activity. For instance, 1% HPG5-EY/TiO₂ achieved 88.96% and 73.22% methylene blue (MB) degradation under UV and visible irradiation within 120 min, respectively\u0026mdash;representing 2.11-fold and 2.11-fold enhancements over pristine TiO₂. These findings establish a novel modification strategy for TiO₂-based photocatalysts. Through optimized catalyst design and reaction parameter control, both photocatalytic efficiency and robust recyclability were significantly improved, providing scientific foundations and technical frameworks for addressing efficiency-stability trade-offs in practical applications. Future investigations will expand composite applications to broader-spectrum organic pollutant degradation while refining catalyst synthesis protocols to enhance industrial feasibility.\u003c/p\u003e"},{"header":"Declarations","content":" \u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eG.L: Resources, Supervision, Funding acquisition, Conceptualization, Methodology, Formal analysis, Project Administration. S.Z.: Software, Investigation, Formal Analysis, Writing - Original Draft. D.T.: Conceptualization, Methodology, Software, Investigation, Formal Analysis, Writing - Original Draft. C.Y.: Formal Analysis. G.L.: Conceptualization, Methodology, Data Curation, Supervision, Formal analysis, Writing - Review \u0026amp; Editing. W.W.: Investigation. D.F.: Formal Analysis. J.Z.: Formal Analysis. R.H.: Formal Analysis. All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThis work was supported by the Opening Project of State Key Laboratory of Polymer Materials Engineering (Sichuan University) (Grant No. 2018-4-22), the Open Foundation of Hypervelocity Impact Research Center of CARDC (No. 20190102), the Key Scientific Research Fund of Xihua University (No. Z1620118), the Chunhui Project, Ministry of Education, China (Z2016128), the Xihua University Science and Technology Innovation Competition Project for Postgraduate Students (No. YK20240052, No. YK20240067, No. YK20240064 \u0026amp; No.YK20240079) and the Quality Project of Graduate Education, Xihua University (No. YJD202404).\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e \u003cp\u003eThe datasets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request, as the authors obtained all the data analyzed.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSahu A, Poler JC (2024) Removal and degradation of dyes from textile industry wastewater: Benchmarking recent advancements, toxicity assessment and cost analysis of treatment processes. 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Polymers 17:311. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/polym17030311\u003c/span\u003e\u003cspan address=\"10.3390/polym17030311\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-polymers-and-the-environment","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jooe","sideBox":"Learn more about [Journal of Polymers and the Environment](https://www.springer.com/journal/10924)","snPcode":"10924","submissionUrl":"https://submission.nature.com/new-submission/10924/3","title":"Journal of Polymers and the Environment","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Photocatalytic degradation, TiO2, Polyhydroxy polymer, Photosensitizer, Visible light response","lastPublishedDoi":"10.21203/rs.3.rs-6927801/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6927801/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe escalating environmental challenges posed by organic dye pollution necessitate the development of efficient and sustainable remediation technologies. This study presents a novel strategy to enhance the visible-light photocatalytic performance of TiO₂ through the synthesis of hyperbranched polyglycerol (HPG)-modified nanocomposites functionalized with photosensitizers (hemin and Eosin Y, EY). A sol-gel method was employed to graft HPGs with tailored polymerization degrees and branching architectures onto TiO₂ surfaces, enabling systematic investigation of the effects of modifier content, polymer structure, and light source on photocatalytic activity.The grafted polymers significantly narrowed TiO₂\u0026rsquo;s bandgap energy (from 2.82 eV for pure TiO₂ to as low as 0.50 eV for HPG2-hemin/TiO₂), extending its light absorption to the visible spectrum. Under optimized conditions, 1% HPG5-EY/TiO₂ achieved a methylene blue (MB) degradation rate of 73.22% within 120 minutes of visible-light irradiation\u0026mdash;a 2.11-fold enhancement compared to pristine TiO₂. The composite also demonstrated exceptional recyclability, retaining over 95% of its initial activity after four reuse cycles. Mechanistic studies revealed that the abundant hydroxyl groups in HPG facilitated the generation of reactive oxygen species (\u0026bull;OH and \u0026bull;O₂⁻), which synergistically accelerated MB degradation.This work establishes a robust framework for designing high-performance TiO₂-based photocatalysts by leveraging polymer structural engineering and photosensitizer integration. The approach not only addresses the inherent limitations of TiO₂\u0026rsquo;s UV-dependent activity but also provides a scalable strategy for sustainable wastewater treatment under solar illumination.\u003c/p\u003e","manuscriptTitle":"Synthesis of Hyperbranched Polyglycerol-Photosensitizer/TiO 2 Nanocomposite for the Photocatalytic Degradation of Methylene Blue","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-01 19:02:53","doi":"10.21203/rs.3.rs-6927801/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-06T12:12:38+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-05T17:26:31+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-03T14:55:30+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-02T23:57:15+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-28T15:05:37+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-26T11:26:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"204353131929637719873634578067727737058","date":"2025-06-25T16:58:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"156109255487058927247040638525079989314","date":"2025-06-25T12:27:31+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"200938665893703683123570830511241171985","date":"2025-06-25T12:12:34+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"220110478924807926317922354019331649562","date":"2025-06-25T11:19:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"266525849483244322039670377673617119142","date":"2025-06-25T10:57:25+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-25T10:49:20+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-20T06:30:52+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-20T06:28:27+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Polymers and the Environment","date":"2025-06-19T05:51:26+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-polymers-and-the-environment","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jooe","sideBox":"Learn more about [Journal of Polymers and the Environment](https://www.springer.com/journal/10924)","snPcode":"10924","submissionUrl":"https://submission.nature.com/new-submission/10924/3","title":"Journal of Polymers and the Environment","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"4e1f7c48-1b43-4c87-ac77-d5cb50777cd4","owner":[],"postedDate":"July 1st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-11-24T16:06:05+00:00","versionOfRecord":{"articleIdentity":"rs-6927801","link":"https://doi.org/10.1007/s10924-025-03682-6","journal":{"identity":"journal-of-polymers-and-the-environment","isVorOnly":false,"title":"Journal of Polymers and the Environment"},"publishedOn":"2025-11-18 15:58:05","publishedOnDateReadable":"November 18th, 2025"},"versionCreatedAt":"2025-07-01 19:02:53","video":"","vorDoi":"10.1007/s10924-025-03682-6","vorDoiUrl":"https://doi.org/10.1007/s10924-025-03682-6","workflowStages":[]},"version":"v1","identity":"rs-6927801","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6927801","identity":"rs-6927801","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}