Chemistry

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Fenton-Based Treatment of Flax Biomass for Modification of Its Fiber Structure and Physicochemical Properties
(MDPI, 2024-07-15) Aliasgharlou, Nasrin; Cree, Duncan E.; Wilson, Lee
The availability of a sustainable technique for degumming lignocellulose fibers is a challenge for the fiber processing industry. Removal of non-cellulosic content from lignocellulose fibers is essential for improving their mechanical and chemical properties, which makes the fibers more suitable for various applications. Herein, a catalytic Fenton-based oxidation process was employed to isolate microcellulose fibers from raw flax fibers. Various complementary methods such as FT-IR/NMR spectroscopy and TGA were used to obtain insight into the thermal behavior of the treated fibers. The morphology of the fibers was studied using Scanning Electron Microscopy (SEM), whereas the surface chemical properties of the fibers was evaluated by a dye-based adsorption method, along with a potentiometric point-of-zero-charge method. To obtain fibers with suitable properties, such as uniform fiber diameter, several Fenton reaction parameters were optimized: pH (7), reaction time (15 h), iron sulfate (2 wt.%), and hydrogen peroxide (10 wt.%). The results indicate that, under the specified conditions, the average diameter of the raw fibers (12.3 ± 0.5 µm) was reduced by 58%, resulting in an average diameter of 5.2 ± 0.3 µm for the treated fibers. We demonstrate that the treated fibers had a lower dye adsorption capacity for methylene blue, consistent with the smoother surface features of the treated fibers over the raw flax fibers. Overall, this study contributes to utilization of the Fenton reaction an efficient oxidation technique for the production of lignocellulose fibers with improved physicochemical properties, such as reduced fiber diameter distribution, in contrast with traditional alkali-based chemical treatment.
Examining Order–Disorder Structural Transition of Gd2Zr2–xCexO7 Using Synchrotron Techniques
(ASC, 2025-03) Kaur, Khushveer; King, Graham; Grosvenor, Andrew
Depending on the radius ratio of A and B site cations, A2B2O7-type oxides can adopt different crystal structures, including the pyrochlore-, defect fluorite-, or bixbyite-type structures. Gd2Zr2O7 with a rGd3+/rZr4+ ratio of 1.46 is an example that exhibits a polymorphic transition between the pyrochlore- and defect fluorite-type structures. To delve deeper into these polymorphic transitions, Ce was introduced as a substitute in the B-site of Gd2Zr2O7. Gd2Zr2–xCexO7 (0 ≤ x ≤ 2) was synthesized using a coprecipitation method and annealed at 1400 °C. Previous investigations yielded disparate results regarding the structures adopted due to the challenge of detecting the low-intensity superstructural peaks associated with the pyrochlore and bixbyite structures using conventional lab-based X-ray diffraction (XRD) instruments. Utilizing synchrotron XRD with a high signal/noise ratio resolves these contradictions and aids in the structure analysis for Gd2Zr2–xCexO7. Based on synchrotron XRD data, a combination of defect fluorite and pyrochlore phases was observed for x = 0–0.25, the defect fluorite structure was adopted when x = 0.5–1.75, and the bixbyite structure was observed when x = 2. Ce L3 and Zr K-edge X-ray absorption near edge spectroscopy (XANES) spectra revealed that both cations were present in 4+ oxidation states.
Co-expression of multi-genes for polynary perovskite electrocatalysts for reversible solid oxide cells
(Springer Nature, 2025-03-25) Zhang, Xiaoxin; He, Hongyuan; Chen, Yu; Yang, Guangming; Xiao, Xiao; Lv, Haiping; Xiang, Yongkang; Wang, Shuxiong; Jiang, Chang; Li, Jianhui; Chen, Zhou; Liu, Subiao; Yan, Ning; Yong, Xue; Alodhayb, Abdullah N.; Pan, Yuanming; Chen, Ning; Lin, Jinru; Tu, Xin; Shao, Zongping; Sun, Yifei
High-entropy LnBaCo2O5+δ perovskites are explored as rSOC air electrodes, though high configuration entropy (Sconfig) alone poorly correlates with performance due to multifactorial interactions. We systematically engineer LnBaCo2O5+δ perovskites (Ln = lanthanides) with tunable Sconfig and 20 consistent parameters, employing Bayesian-optimized symbolic regression to decode activity descriptors. The model identifies synergistic contributions from Sconfig, ionic radius, and electronegativity, enabling screening of 177,100 compositions. Three validated oxides exhibit superior activity/durability, particularly (Pr0.05La0.4Nd0.2Sm0.1Y0.25)BaCo2O5+δ, showing enhanced oxygen vacancy concentration and disordered transport pathways. First-principles studies reveal optimized charge transfer kinetics via cobalt-oxygen bond modulation. Further, the interplay between first ionization energy, atomic mass, and ionic Lewis acidity dictates stability. This data-driven approach establishes a quantitative framework bridging entropy engineering and catalytic functionality in complex oxides.
Isolated iridium oxide sites on modified carbon nitride for photoreforming of plastic derivatives
(Springer Nature, 2025-03-24) Kumar, Pawan; Zhang, Hongguang; Yohannes, Asfaw G.; Wang, Jiu; Zeraati, Ali Shayesteh; Roy, Soumyabrata; Wang, Xiyang; Kannimuthu, Karthick; Askar, Abdelrahman M.; Miller, Kirsten A.; Ling, Kexin; Adnan, Muflih; Hung, Sung-Fu; Ma, Jian-Jie; Huang, Wei-Hsiang; Trivedi, Dhwanil; Molina, Maria; Zhao, Heng; Martí, Angel A.; Leontowich, Adam F. G.; Shimizu, George K. H.; Sinton, David; Adachi, Michael M.; Wu, Yimin A.; Ajayan, Pulickel M.; Siahrostami, Samira; Hu, Jinguang; Kibria, Md Golam
The rising concentration of plastics due to extensive disposal and inefficient recycling of plastic waste poses an imminent and critical threat to the environment and ecological systems. Photocatalytic reforming of plastic derivatives to value-added chemicals under ambient conditions proceeds at lower oxidation potential which galvanizes the hydrogen evolution. We report the synthesis of a narrow band gap NCN-functionalized O-bridged carbon nitride (MC) through condensation polymerization of hydrogen-bonded melem (M)-cyameluric acid (C) macromolecular aggregate. The MC scaffold hosts well-dispersed Ir single atom (MCIrSA) sites which catalyze oxidative photoreforming of alkali-treated polylactic acid (PLA) and polyethylene terephthalate (PET) derivatives to produce H2 at a rate of 147.5 and 29.58 μmol g−1cat h−1 under AM1.5G irradiation. Solid-state electron paramagnetic resonance (EPR) and time-resolved photoluminescence (TRPL) reveals efficient charge carrier generation and separation in MCIrSA. X-ray absorption spectroscopy (XAS) and Bader charge analysis reveal undercoordinated IrN2O2 SA sites pinned in C6N7 moieties leading to efficient hole quenching. The liquid phase EPR, in situ FTIR and density functional theory (DFT) studies validate the facile generation of •OH radicals due to the evolution of O-Ir-OH transient species with weak Ir--OH desorption energy barrier.
High-Sensitivity and Flexible Motion Sensing Enabled by Robust, Self-Healing Wood-Based Anisotropic Hydrogel Composites
(Wiley, 2025-02-07) Teng, Youchao; Zhang, Zhilei; Cui, Yunqi; Su, Zhe; Godwin, Matthew; Chung, TzuChun; Zhou, Yongzan; Leontowich, Adam L.G.; Islam, Muhammad Shahidul; Tam, Kam C.; Wu, Yimin A.
By integrating polyvinyl alcohol (PVA)-borate-tannic acid (TA)-sodium sulfate into cellulosic wood matrices, a novel wood-basedPVA-borate-TA-sodium sulfate (WPBTS) hydrogel is successfully synthesized. Through a multicomponent synergistic design combining natural lignocellulose, PVA, borax, TA, and sodium sulfate, multiple dynamic cross-linking mechanisms—dynamic borate bonding, hydrogen bonding, and metal-ligand interactions—are established, resulting in WPBTS hydrogels with exceptional mechanical properties and self-healing capabilities. The mechanical strength of the WPBTS hydrogel reached an impressive 19.8 MPa, a 45-fold increase compared to PVA-borax-tannic acid (PBTS) hydrogels. Furthermore, the assembled WPBTS hydrogel-based flexible sensor demonstrates a remarkably fast response time of just 20 ms and maintains excellent performance in challenging simulated saline environments. This innovation represents a significant advancement in sensor technology and highlights the potential for transformative applications in complex and demanding scenarios.
High-Sensitivity and Flexible Motion Sensing Enabled byRobust, Self-Healing Wood-Based Anisotropic Hydrogel Composites
(Small, 2025-02) Teng, Youchao; Zhang, Zhilei; Cui, Yunqi; Su, Zhe; Godwin, Matthew; Chung, TzuChun; Zhou, Yongzan; Leontowich, Adam F. G.; Islam, Muhammad Shahidul; Tam, Kam C.; Wu, Yimin A.
By integrating polyvinyl alcohol (PVA)-borate-tannic acid (TA)-sodium sulfate into cellulosic wood matrices, a novel wood-basedPVA-borate-TA-sodium sulfate (WPBTS) hydrogel is successfully synthesized. Through a multicomponent synergistic design combining natural lignocellulose, PVA, borax, TA, and sodium sulfate, multiple dynamic cross-linking mechanisms—dynamic borate bonding, hydrogen bonding, and metal-ligand interactions—are established, resulting in WPBTS hydrogels with exceptional mechanical properties and self-healing capabilities. The mechanical strength of the WPBTS hydrogel reached an impressive 19.8 MPa, a 45-fold increase compared to PVA-borax-tannic acid (PBTS) hydrogels. Furthermore, the assembled WPBTS hydrogel-based flexible sensor demonstrates a remarkably fast response time of just 20 ms and maintains excellent performance in challenging simulated saline environments. This innovation represents a significant advancement in sensor technology and highlights the potential for transformative applications in complex and demanding scenarios.
Scalable Bulk Synthesis of Phase-Pure γ-Sn3N4 as a Model for an Argon-Flow-Mediated Metathesis Reaction
(Wiley, 2024-11-18) Zipkat, Mirjam ; Koldemir, Aylin; Block, Theresa; Ceniza, Claude; Boyko, Teak; Kläger, Sebastian; Pritzl, Reinhard; Moewes, Alexander; Pöttgen, Rainer; Rudel, Stefan Sebastian; Schnick, Wolfgang
Nitrides represent a promising class of materials for a variety of applications. However, bulk synthesis remains a challenging task due to the stability of the N2 molecule. In this study, we introduce a simple and scalable approach for synthesizing nitride bulk materials. Moderate reaction temperatures are achieved by using reactive starting materials, slow and continuous mixing of the starting materials, and by dissipating heat generated during the reaction. The impact on the synthesis of using different starting materials as nitrogen source and the influence of a flux were examined. γ-Sn3N4 was selected as the model compound. The synthesis of pure γ-Sn3N4 bulk material on a large scale has still been a challenge, although a few synthesis methods were already described in the literature. Here we synthesized γ-Sn3N4 by metathesis reaction of argon-diluted SnCl4 with Li3N, Mg3N2 or Ca3N2 as nitrogen sources. Products were characterized by powder X-ray diffraction, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, dynamic flash combustion analysis, hot gas extraction analysis, X-ray photoelectron spectroscopy, Mössbauer spectroscopy and X-ray absorption and emission spectroscopy. Additionally, single-crystal diffraction data of γ-Sn₃N₄, previously unavailable, were successfully collected.
A comparative study of the long-term aqueous durability of brannerite (Ce0.94Ti2O6–δ) and glass-brannerite (Fe-Al-BG-Ce0.94Ti2O6–δ) composite materials
(Applied Surface Science, 2025-01) Mikhchian, Mehrnaz; Grosvenor, Andrew
The long-term aqueous corrosion behavior of Fe-Al borosilicate glass-brannerite (Fe-Al-BG- Ce0.94Ti2O6–δ) composite material as a potential nuclear wasteform has been investigated to understand how the corrosion behavior of these materials can be compared to current nuclear wasteforms (i.e., borosilicate glass). It was found that the aqueous corrosion behavior of the Fe-Al-BG-Ce0.94Ti2O6–δ composite material resulted from a combined corrosion behavior of the individual Fe-Al-BG and Ce0.94Ti2O6–δ phases when these materials were exposed to deionized water. A combination of surface and bulk analyses has demonstrated that the surface composition and chemistry of Ce0.94Ti2O6–δ and Fe-Al-BG-Ce0.94Ti2O6–δ composite materials were affected by aqueous corrosion, whereas the long-range (i.e., bulk) structure of these materials remained stable over 365 days of exposure to deionized water. This study has shown that the corrosion resistance of Fe-Al-BG-Ce0.94Ti2O6–δ composite material is comparable to Fe-Al-BG, which suggests that this composite material could be further investigated as a potential substitute for borosilicate glass nuclear wasteforms.
Bioinspired complex cellulose nanorod-architectures: A model for dual-responsive smart carriers
(Elsevier, 2024-12-17) Heidari Nia, Marzieh ; Garzia, Livia; Jawhar, Wajih; Wilson, Lee; van de Ven, Theo
The synergy between nanomaterials as solid supports and supramolecular concepts has resulted in nanomaterials with hierarchical structure and enhanced functionality. Herein, we developed and investigated innovative supramolecular functionalities arising from the synergy between organic moieties and the preexisting nanoscale soft material backbones. Based on these complex molecular nano-architectures, a new nanorod carbohydrate polymer carrier was designed with bifunctional hairy nanocellulose (BHNC) to reveal dual-responsive advanced drug delivery (ADD). This carrier scavenges K+-ions within cancer cells, while simultaneously releasing doxorubicin, combining ion homeostasis disruption with targeted drug delivery. The BC ADD system resulted from cross-linking dibenzo-18-crown-6-ether (DB18C6) with BHNC particles. To enhance cellular internalization and facilitate tracking of uptake, the cellulose nanorod carrier was labeled with biotin and fluorescein isothiocyanate, referred to as BCFB. The BHNC serves as the backbone, while the immobilized DB18C6 moieties can capture doxorubicin via complex formation. The BCFB complex molecular nanorod carriers exhibit distinct ADD profiles with pH and K+-responsiveness. They were evaluated as biocompatible carriers for ADD in MDA-MB-231 breast cancer cells, including quantification of nanoparticle uptake and flow cytometry with KHOS cells. These cellulose-based carriers possess unique structure and properties with potential utility as phase transfer catalysts and as adsorbents for diverse waterborne contaminants.
Aloe vera mucilage as a sustainable biopolymer flocculant for efficient arsenate anion removal from water
(The Royal Society of Chemistry, 2024-07-24) Venegas-García, Deysi J.; Wilson, Lee; De la Cruz Guzmán , Paola Mayela
In recent years, utilization of biopolymers as natural coagulant–flocculant (CF) systems has become an area of interest, due to their sustainable nature (renewable, biodegradable, and non-toxic) and potential utility as alternative systems to replace synthetic flocculants. Herein, a biopolymer extracted from Aloe vera mucilage (AVM) was investigated for its arsenic(V) removal properties in a CF water treatment process. Structural characterization of AVM was supported by spectroscopy (FTIR, 13C solids NMR & XPS), TGA, rheology, and pHpzc. The arsenic(V) removal process was optimized by employing the Box–Behnken design under three main factors (coagulant, flocculant dosage and initial arsenic(V) concentration), which led to a reduction of the initial arsenic(V) concentration to levels below the Maximum Acceptable Concentration (MAC; 10 μg L−1). The kinetics and thermodynamics of arsenic(V) removal were analyzed with a one-pot in situ method, where the kinetic profiles followed a pseudo-first-order model. The thermodynamic parameters are characteristic of a spontaneous (entropy-driven) and endothermic physisorption removal process. Flocs isolated from the process were analyzed by XPS, where the results reveal that calcium and amide groups of AVM contribute to the arsenic(V) removal mechanism.
Sustainable agro-waste pellets as granular slow-release fertilizer carrier systems for ammonium sulfate
(Royal Society of Chemistry, 2024) Steiger, Bernd; Bui, Nam; Babalola, Bolanle; Wilson, Lee
In this study, several granular biocomposite carrier systems were prepared that contain biomaterials (chitosan, torrefied wheat straw and avian eggshells) as additive components at variable composition. The biocomposites were loaded with ammonium sulfate (AS) by two methods: (1) in situ addition of AS during pellet preparation, and (2) an adsorption method of AS after pellet preparation. Characterisation was carried out via spectroscopy (XRD, FT-IR) and complementary methods (TGA, acid stability). The pellet system (C1) by method (1) contained ca. 22 mg per g NH4+, whereas pellet systems by method (2) contained up to ca. 40 mg per g NH4+. The mol-ratio of NH4+ : SO42− varied from 2.18 (C1) to 2.72 (CW72), 2.97 (CW20), 2.64 (CW21) and 3.20 (CW22). Release studies in water showed that C1 pellets released almost 100% NH4+ within 3 h, while release varied from ca. 60% (CW72), ca. 40% (C20), 20% (C21) to 10% (CW22). By comparison, the systems prepared through method (2) showed a marginal increase of the release profiles up to 96 h. Granular AS carrier systems prepared by method (2) displayed greater mechanical stability and AS content versus the systems prepared by method (1). We demonstrated the ability to tailor the physico-chemical properties of such biocomposite carriers and highlight their promising potential as slow-release fertilizer systems.
Valorization of Eggshell as Renewable Materials for Sustainable Biocomposite Adsorbents—An Overview
(MDPI, 2024-10-08) Babalola, Bolanle; Wilson, Lee
The production and buildup of eggshell waste represents a challenge and an opportunity. The challenge is that uncontrolled disposal of generated eggshell waste relates to a sustainability concern for the environment. The opportunity relates to utilization of this biomass resource via recycling for waste valorization, cleaner production, and development of a circular economy. This review explores the development of eggshell powder (ESP) from eggshell waste and a coverage of various ESP composite sorbents with an emphasis on their potential utility as adsorbent materials for model pollutants in solid–liquid systems. An overview of literature since 2014 outlines the development of eggshell powder (ESP) and ESP composite adsorbents for solid–liquid adsorption processes. The isolation and treatment of ESP in its pristine or modified forms by various thermal or chemical treatments, along with the preparation of ESP biocomposites is described. An overview of the physico-chemical characterization of ESP and its biocomposites include an assessment of the adsorption properties with various model pollutants (cations, anions, and organic dyes). A coverage of equilibrium and kinetic adsorption isotherm models is provided, along with relevant thermodynamic parameters that govern the adsorption process for ESP-based adsorbents. This review reveals that ESP biocomposite adsorbents represent an emerging class of sustainable materials with tailored properties via modular synthetic strategies. This review will serve to encourage the recycling and utilization of eggshell biomass waste and its valorization as potential adsorbent systems. The impact of such ESP biosorbents cover a diverse range of adsorption-based applications from environmental remediation to slow-release fertilizer carrier systems in agricultural production.
Stabilization of Oil-in-Water Pickering Emulsions by Surface-Functionalized Cellulose Hydrogel
(Gels, 2024-10) Udoetok, Inimfon; Mohamed, Mohamed H.; Wilson, Lee
An amphiphilic cellulose (CLH) hydrogel was synthesized via grafting of quaternary ammonium groups onto cellulose. The structural properties of CLH were characterized via Fourier transform infrared (FTIR)/13C solid-state NMR spectroscopy, elemental (CHN) analysis, particle size distribution (PSD), thermogravimetric analysis (TGA), and wettability was assessed through contact angle measurements. Pickering emulsions of apolar oils in water were prepared using variable weights of the CLH hydrogel as the stabilizing agent, along with different methods of agitation (mechanical shaking and sonication). The characterization results for CLH provide support for the successful grafting of quaternary ammonium groups onto cellulose to produce hydrogels. Different methods of agitation of an oil/water mixture revealed the formation of an oil-in-water (O/W) Pickering emulsion that was stable to coalescence for over 14 days. The resulting emulsions showed variable droplet sizes and stability according to the dosage of CLH in the emulsion and the agitation method, where the emulsion droplet size is related to the particle size of CLH. The addition of methyl orange (MO), a probe to evaluate the phase partitioning of the dye, had minor effects on the emulsion droplet size, and the emulsion prepared with 0.8 wt.% of CLH and agitated via sonication exhibited the smallest droplet size and greatest stability. This study is anticipated to catalyze further research and the development of low-cost and sustainable biopolymer hydrogels as stabilizers for tunable Pickering emulsion. Grafted cellulose materials of this type represent versatile stabilizing agents for foods, agrochemicals, and pharmaceutical products and technologies.
Hybrid Chitosan Biosorbents: Tunable Adsorption at Surface and Micropore Domains
(Biomimetics, 2024-11) Udoetok, Inimfon; Mohamed, Mohamed H.; Wilson, Lee
Herein, we report a study that provides new insight on the knowledge gaps that relate to the role of biopolymer structure and adsorption properties for chitosan adsorbents that are cross-linked with glutaraldehyde. The systematic modification of chitosan cross-linked with glutaraldehyde (CG) and its quaternized forms (QCG) was studied in relation to the reaction conditions: mole ratios of reactants and pH conditions. Complementary adsorbent characterization employed 13C NMR/FTIR spectroscopy, TGA and DSC, point-zero-charge (PZC), solvent swelling, and sorption studies using selected dye probes. The spectral and thermal techniques provide complementary evidence that affirm the key role of cross-linker content and quaternization on variation of the physicochemical properties of chitosan. The PZC results reveal a neutral surface charge for the modified materials between pH 6.0 to 6.3 ± 0.3, as compared with pH 8.7 ± 0.4 for pristine chitosan. Solvent swelling in water decreased with greater cross-linking, while the QCG materials had greater swelling over CG materials due to enhanced hydration. The adsorption results reveal variable dye uptake properties according to the cross-linker content. Similarly, surface versus micropore adsorption was demonstrated, according to the nature and ionization state of the dye for the modified adsorbents, where the CG and QCG materials had tunable sorption properties that exceeded that of unmodified chitosan. A key step in tuning the structure and surface chemical properties of cross-linked chitosan involves pH control during synthesis. The facile tunability of the physicochemical properties of the modified biopolymers reported herein means that they possess features of biomimetics that are relevant to advanced drug delivery, antimicrobial materials for wound healing, biosensors, and biosorbents for biomedical applications.
Chemical activation of atom-precise Pd3 nanoclusters on γ-Al2O3 supports for transfer hydrogenation reactions
(Royal Society of Chemistry, 2024-09-30) Singh, Siddhant; Wi, Dami; Salem, Kholoud E.; Higgins, Drew
Deposition of atom-precise nanoclusters onto solid supports is a promising route to synthesize model heterogeneous catalysts. However, to enhance nanocluster-support interactions, activation of the nanoclusters by removal of surface ligands is necessary. Thermal treatment to remove surface ligands from supported metal nanoclusters can yield highly active heterogeneous catalysts, however, the high temperatures employed can lead to poor control over the final size and speciation of the nanoclusters. As an alternative to high-temperature thermal treatments, chemical activation of [Pd3(μ-Cl)(μ-PPh2)2(PPh3)3]+ (Pd3) nanoclusters on γ-Al2O3 supports under mild reaction conditions has been demonstrated in this work. Hydride-based reducing agents such as NaBH4, LiBH4, and LiAlH4 have been examined for the activation of the Pd3 nanoclusters. The structural evolution and speciation of the nanoclusters after activation have been monitored using a combination of XAS, XPS, STEM-EDX mapping, and solid-state NMR techniques. The results indicate that treatment with borohydride reducing agents successfully removed surface phosphine and chloride ligands, and the extent of size growth of the nanoclusters during activation is directly correlated with the amount of borohydride used. Borate side products remain on the γ-Al2O3 surface after activation; moreover, exposure to high amounts of NaBH4 resulted in the incorporation of B atoms inside the lattice of the activated Pd nanoclusters. LiAlH4 treatment, on the other hand, led to no significant size growth of the nanoclusters and resulted in a mixture of Pd single-atom sites and activated nanoclusters on the γ-Al2O3 surface. Finally, the catalytic potential of the activated nanoclusters has been tested in the transfer hydrogenation of trans-cinnamaldehyde, using sodium formate/formic acid as the hydrogen donor. The catalytic results showed that smaller Pd nanoclusters are much more selective for hydrogenating trans-cinnamaldehyde to hydrocinnamaldehyde, but overall have lower activity compared to larger Pd nanoparticles. Overall, this study showcases chemical activation routes as an alternative to traditional thermal activation routes for activating supported nanoclusters by offering improved speciation and size control.
A Highly Sensitive Chitosan-Based SERS Sensor for the Trace Detection of a Model Cationic Dye
(MDPI, 2024-08-28) Vafakish, Bahareh; Wilson, Lee
The rapid detection of contaminants in water resources is vital for safeguarding the environment, where the use of eco-friendly materials for water monitoring technologies has become increasingly prioritized. In this context, the role of biocomposites in the development of a SERS sensor is reported in this study. Grafted chitosan was employed as a matrix support for Ag nanoparticles (NPs) for the surface-enhanced Raman spectroscopy (SERS). Chitosan (CS) was decorated with thiol and carboxylic acid groups by incorporating S-acetyl mercaptosuccinic anhydride (SAMSA) to yield CS-SAMSA. Then, Ag NPs were immobilized onto the CS-SAMSA (Ag@CS-SAMSA) and characterized by spectral methods (IR, Raman, NIR, solid state 13C NMR with CP-MAS, XPS, and TEM). Ag@CS-SAMSA was evaluated as a substrate for SERS, where methylene blue (MB) was used as a model dye adsorbate. The Ag@CS-SAMSA sensor demonstrated a high sensitivity (with an enhancement factor ca. 108) and reusability over three cycles, with acceptable reproducibility and storage stability. The Raman imaging revealed a large SERS effect, whereas the MB detection varied from 1–100 μM. The limits of detection (LOD) and quantitation (LOQ) of the biocomposite sensor were characterized, revealing properties that rival current state-of-the-art systems. The dye adsorption profiles were studied via SERS by fitting the isotherm results with the Hill model to yield the ΔG°ads for the adsorption process. This research demonstrates a sustainable dual-function biocomposite with tailored adsorption and sensing properties suitable for potential utility in advanced water treatment technology and environmental monitoring applications.
Cu(II) Ion Adsorption by Aniline Grafted Chitosan and Its Responsive Fluorescence Properties
(MDPI, 2020-02-26) Vafakish, Bahareh; Wilson, Lee
The detection and removal of heavy metal species in aquatic environments is of continued interest to address ongoing efforts in water security. This study was focused on the preparation and characterization of aniline grafted chitosan (CS-Ac-An), and evaluation of its adsorption properties with Cu(II) under variable conditions. Materials characterization provides support for the grafting of aniline onto chitosan, where the kinetic and thermodynamic adsorption properties reveal a notably greater uptake (>20-fold) of Cu(II) relative to chitosan, where the adsorption capacity (Qm) of CS-Ac-An was 106.6 mg/g. Adsorbent regeneration was demonstrated over multiple adsorption-desorption cycles with good uptake efficiency. CS-Ac-An has a strong fluorescence emission that undergoes prominent quenching at part per billion levels in aqueous solution. The quenching process displays a linear response over variable Cu(II) concentration (0.05–5 mM) that affords reliable detection of low level Cu(II) levels by an in situ “turn-off” process. The tweezer-like chelation properties of CS-Ac-An with Cu(II) was characterized by complementary spectroscopic methods: IR, NMR, X-ray photoelectron (XPS), and scanning electron microscopy (SEM). The role of synergistic effects are inferred among two types of active adsorption sites: electron rich arene rings and amine groups of chitosan with Cu(II) species to afford a tweezer-like binding modality.
Supramolecular Chemistry of Polymer-Based Molecular Tweezers: A Minireview
(MDPI, 2024-09-14) Vafakish, Bahareh; Wilson, Lee
Polymer-based molecular tweezers have emerged as a prominent research area due to their enhanced ability to form host–guest complexes, driven by advancements in their design and synthesis. The impact of the spacer structure on the tweezers is predominant. They can be rigid, flexible, and stimuli-responsive. Herein, a new generation of molecular tweezers is introduced as polymer-based molecular tweezers. The integration of molecular tweezers onto biopolymers has significantly expanded their potential applications, making them promising candidates, especially in drug delivery, owing to their biocompatibility, adaptive structural features, and versatile interaction capabilities. The unique structure of polymer-based molecular tweezers, particularly when integrated with biopolymers, creates a unique nano-environment that enhances their interaction with guest molecules. This minireview focuses on the synthesis and applications of polymer-based molecular tweezers and examines how the incorporation of various spacers affects their binding affinity and specificity. These features highlight the advancement of these polymer-based systems, emphasizing their potential applications, particularly in drug delivery, water treatment technology, and future research opportunities.
Surface-Modified Chitosan: An Adsorption Study of a “Tweezer-Like” Biopolymer with Fluorescein
(MDPI, 2019-08-18) Vafakish, Bahareh; Wilson, Lee
Tweezer-like adsorbents with enhanced surface area were synthesized by grafting aniline onto the amine sites of a chitosan biopolymer scaffold. The chemical structure and textural properties of the adsorbents were characterized by thermogravimetric analysis (TGA) and spectral methods, including Fourier transform infrared (FT-IR), nuclear magnetic resonance (1H- and, 13C-NMR) and scanning electron microscopy (SEM). Equilibrium solvent swelling results for the adsorbent materials provided evidence of a more apolar biopolymer surface upon grafting. Equilibrium uptake studies with fluorescein at ambient pH in aqueous media reveal a high monolayer adsorption capacity (Qm) of 61.8 mg·g−1, according to the Langmuir isotherm model. The kinetic adsorption profiles are described by the pseudo-first order kinetic model. 1D NMR and 2D-NOESY NMR spectra were used to confirm the role of π-π interactions between the adsorbent and adsorbate. Surface modification of the adsorbent using monomeric and dimeric cationic surfactants with long hydrocarbon chains altered the hydrophile-lipophile balance (HLB) of the adsorbent surface, which resulted in attenuated uptake of fluorescein by the chitosan molecular tweezers. This research contributes to a first example of the uptake properties for a tweezer-like chitosan adsorbent and the key role of weak cooperative interactions in controlled adsorption of a model anionic dye.
Flax fiber-chitosan biocomposites with tailored structure and switchable physicochemical properties
(Elsevier, 2023-11-21) Mir, Mariam; Wilson, Lee D.
A facile and sustainable synthesis of unique flax fiber composites (FFCs) is reported, where raw flax fiber (FFR) was immobilized with variable chitosan content. FFCs were structurally characterized via TGA, XRD, SEM analysis, and spectroscopy (IR, NMR, and Raman mapping). Physicochemical characterization of FFCs enabled estimation of the point-of-zero-charge (PZC), solvent swelling at variable pH. Dye adsorption with Rose Bengal (RB) and Methylene Blue (MB) afforded characterization of the surface chemistry of the materials. This contribution study is a first reported example that highlights the unique structure-property relationships of FFC materials and the role of electrostatic interactions between the pristine fiber substrate and chitosan. FFCs with incremental chitosan content display the following trends: (i) greater solvent swelling at variable pH (350 % for FFCs and ca. 100 % for FFR and commercial absorbents), (ii) two-fold enhanced adsorption of RB (FFC 0.5 to FFC 2.0) and (iii) 1.5-fold decreased adsorption of MB (FFC 2.0 to FFC 0.5). The unique “switchable” sorption properties of the FFCs toward solvent and dyes was revealed upon facile and noncovalent immobilization of chitosan onto FFR. The sustainable composites reported herein offer a potential adsorption-based technology suitable for filter-based applications in “smart textiles” to biomedical sorbents for wound healing.

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