Reduction Of Au Research Articles

UV light promoted dihydrolipoic acid and its alanine derivative directed rapid synthesis of stable gold nanoparticles and their catalytic activity

In general, colloidal gold nanoparticles (AuNPs) have been synthesized in heated or boiling water containing HAuCl4 precursor with sodium citrate as reducing stabilizing reagent. Although temperature plays a driving for synthesis of AuNPs, elevated temperature in thermal reduction method causes aggregation of the AuNPs. The preferential, rapid and strong binding of dihydro-lipoic acid and its derivatives on surface of AuNPs via thiol − Au chemistry promote the production of very stable AuNPs. In this study, we have developed citric acid (CA), dihydrolipoic acid (DHLA) and DHLA-Alanine (DHLA-Ala) directed rapid synthesis of ultra-stable AuNPs, DHLA@AuNPs and DHLA-Ala@AuNPs, under the UV (311 nm) irradiation at room temperature (RT: 25 °C) in around 10 min (min). CA is used as a potential reducing agent to expedite both reduction of Au3+ ion and AuNP formation, DHLA and DHLA-Ala act as stabilizing agents by replacing CA molecules on surface of AuNPs in order to produce quite stable AuNP. It is worthy to mention that reduction of Au3+ ion, formation and surface stabilization of AuNPs are consequently occurred in one step. We also investigated how experimental parameters including reaction time and temperature, pH of reaction solution, affect formation of the AuNPs. The effects of salt concentration and storage temperature were studied to show stability of the AuNPs. The synthesized DHLA@AuNPs and DHLA-Alanine@AuNPs were characterized via UV-Vis spectrophotometer (UV-Vis), scanning transmission electron microscope (STEM), dynamic light scattering (DLS) and Zeta potential (ZT) devices. The reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) was efficiently catalyzed by the AuNPs in the presence of sodium borohydride in aqueous solution.

Graphene/chitosan nanoreactors for ultrafast and precise recovery and catalytic conversion of gold from electronic waste

The extraction of gold (Au) from electronic waste (e-waste) has both environmental impact and inherent value. Improper e-waste disposal poses environmental and health risks, entailing substantial remediation and healthcare costs. Large efforts are applied for the recovery of Au from e-waste using complex processes which include the dissolution of Au, its adsorption in an ionic state and succeeding reduction to metallic Au. These processes themselves being complex and utilizing harsh chemicals contribute to the environmental impact of e-waste. Here, we present an approach for the simultaneous recovery and reduction of Au3+ and Au+ ions from e-waste to produce solid Au0 forms, thus skipping several technological steps. We develop a nanoscale cross-dimensional composite material via self-assembly of two-dimensional graphene oxide and one-dimensional chitosan macromolecules, capable of acting simultaneously as a scavenger of gold ions and as a reducing agent. Such multidimensional architecture doesn't require to apply any voltage for Au adsorption and reduction and solely relies on the chemisorption kinetics of Au ions in the heterogeneous GO/CS nanoconfinements and their chemical reduction on multiple binding sites. The cooperative phenomena in ionic absorption are responsible for the extremely high efficiency of gold extraction. The extraction capacity reaches 16.8 g/g for Au3+ and 6.2 g/g for Au+, which is ten times larger than any existing gold adsorbents can propose. The efficiency is above 99.5 wt.% (current limit is 75 wt.%) and extraction ability is down to very low concentrations of 3 ppm.

One‐Step DES‐Mediated Synthesis of Au Nanoparticles Using Eysenhardtia polystachya Extract and Evaluation of Their Proapoptotic and Anti‐Inflammatory Activities

AbstractThe synthesis of nanomaterials using plant extracts is considered to be a safer, environmentally friendly, and cost‐effective alternative method. In this work, Eysenhardtia polystachya (EP) extract and choline chloride/urea (ChCl/urea)‐based deep eutectic solvent (DES) were used for the synthesis of gold nanoparticles (AuNPs), without an additional stabilizing agent, which is of great interest in the field of biomedicine. The antioxidant capacity of the extract and the phenolic content, involved in the reduction of Au3+ ions of the precursor were evaluated. The AuNPs were characterized by ultraviolet‐visible spectroscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, dynamic light scattering, ζ‐potential, confocal laser scanning microscopy, scanning and transmission electron microscopy. The nanoparticles are mostly quasi‐spherical shape, with a multiply‐twinned structure, an average particle size of 36 nm, and a characteristic absorption peak at 545 nm. The colloidal stability was confirmed with a ζ‐potential value of −32.8 mV. Finally, the AuNPs were tested for their potential in cancer therapy using human prostate adenocarcinoma PC‐3 cells. The anti‐inflammatory activity of the EP extract and AuNPs was also evaluated. The results showed that the synthesized AuNPs could potentially induce cell death and have an anti‐inflammatory effect.

Preparation of gold nanoparticles by photolysis and radiolysis in alcohol solutions of functional hyperbranched polyorganosiloxane/H[AuCl4]: Effect of irradiation mode on nanoparticle size and formation mechanism

Ethanol solutions of functional hyperbranched polyorganosiloxanes (0.2 vol%) with a molar ratio of NH2(CH2)2NH-/H[AuCl4]x3H2O of 8/1 were used as precursors for nanocomposite preparation using UV photolysis and X-ray radiolysis. It was shown that various irradiation modes provide the synthesis of gold nanoparticles (AuNPs) with tunable sizes and narrow size distributions. It was established that size distributions of AuNPs depend on the excitation wavelength. AuNPs with an average size of 3.5 nm were obtained by the direct excitation of gold ions using UV light with λmax = 365 nm. Meanwhile, the action of a higher energy light (λ = 254 nm) on the metal polymer complexes resulted in formation of ultra-small nanoparticles with an average size of 1.5 nm, presumably due to the increased efficiency of their nucleation process. In the case of radiolysis with X-rays, reduction of Au3+ ions occurs due to reactions with radicals produced from ethanol and leads to the formation of AuNPs of 2–3 nm. Thus, the size distribution of the prepared AuNPs may be controlled by the irradiation mode, which critically affects nanomaterial properties. Additionally nanoparticles obtained by photochemical or radiation-chemical methods are free of chemical impurities, which is important for the development of functional materials.

Polydopamine-modulated anisotropic co-growth plasmonic blackbody for efficient ultra-broad-spectrum quenching to establish multicolor fluorescent immunoassay

Fluorescence quenching immunoassays have received increasing attention due to their high signal-to-noise ratio, among which multi-color fluorescence quenching methods have great advantages in detecting multiple targets. Preparing an efficient and broad-spectrum quencher is a prerequisite for establishing high-performance multicolor fluorescence quenching immunoassays. In this study, we propose a polydopamine (PDA) modulated seedless co-growth method to synthesize anisotropic plasmonic blackbody (APB) with highly branched chrysanthemum −like shape for efficient ultra-broad-spectrum quenching and utilize APB to establish a sensitive multicolor fluorescent immunoassay. The key to APB synthesis lies in the reduction of Au3+ by dopamine, which simultaneously undergoes oxidation and self-polymerization in situ to form a PDA film. This film continuously deposits on the Au crystal seeds, creating a robust end-capping effect and inducing continuous anisotropic growth of Au. The dual synergistic effects of PDA and the unique 3D-spatial structure contribute to APB’s robust ultra-broad-spectrum UV absorption (6.86 × 1011 L cm−1 mol−1) from 300 to 800 nm, along with efficient ultra-broad-spectrum fluorescence quenching ability (90.1 %). This quenching ability extends to various types of fluorescence microspheres covering the range of 300–800 nm with different excitation and emission spectra. Subsequently, we applied APB in the development of a multicolor fluorescence quenching immunochromatographic assay, enabling simultaneous detection of chloramphenicol (limit of detection, LOD = 0.0045 ng/mL) and sulfadimidine (LOD = 0.038 ng/mL) in milk. This research not only offers a novel direction for designing efficient broad-spectrum quenchers but also advances the practical application of fluorescence quenching sensors.

Synthesis and characterization of gold nano particles using barleria cristata for antimicrobial and anticancer applications

A nano revolution is necessary for the integration of nanoscience and medicine. Drug delivery, electronics, biological sciences, optics, and catalysis are among the fields in which metal nanoparticles find application. The objective of this work is to extract leaves from Barleria cristata in order to produce ecologically friendly gold nanoparticles (Au NP) for pharmacological studies. Several human pathogens were used to assess the biological mechanism and antibacterial properties of gold nanoparticles (AuNPs) in relation to their potential as a cancer treatment. An aqueous extract with a natural pH of 7.4 was obtained by reacting with 1 mM chloroauric acid (HAuCl4.3H2O), and it was then kept at room temperature. The colour changed from pale yellow to pink right away, indicating the reduction of Au3+ ions to Au 0. Using a UV-Visible spectrophotometer, the synthesised AuNPs were seen. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), field emission transmission electron microscopy (FE-TEM), and particle size distribution and zeta potential analysis are a few examples of analytical techniques. The disc diffusion method was used to confirm the extract's antibacterial properties in vitro on a few human illnesses. The MTT test was used to confirm the extract's anticancer properties on Hela carcinoma cell lines, revealing IC50 values of 50 μg/mL.

Photosynthesis‐Mediated Intracellular Biomineralization of Gold Nanoparticles inside Chlorella Cells towards Hydrogen Boosting under Green Light

AbstractEngineering living microorganisms to enhance green biomanufacturing for the development of sustainable and carbon‐neutral energy strategies has attracted the interest of researchers from a wide range of scientific communities. In this study, we develop a method to achieve photosynthesis‐mediated biomineralization of gold nanoparticles (AuNPs) inside Chlorella cells, where the photosynthesis‐dominated reduction of Au3+ to Au0 allows the formed AuNPs to locate preferentially around the thylakoid membrane domain. In particular, we reveal that the electrons generated by the localized surface plasmon resonance of AuNPs could greatly augment hypoxic photosynthesis, which then promotes the generation and transferring of photoelectrons throughout the photosynthetic chain for augmented hydrogen production under sunlight. We demonstrate that the electrons from AuNPs could be directly transferred to hydrogenase, giving rise to an 8.3‐fold enhancement of Chlorella cells hydrogen production independent of the cellular photosynthetic process under monochromatic 560 nm light irradiation. Overall, the photosynthesis‐mediated intracellular biomineralization of AuNPs could contribute to a novel paradigm for functionalizing Chlorella cells to augment biomanufacturing.

Preparation of phosphorus‐doped cow milk‐derived carbon quantum dots and detection of Au3+

AbstractA new fluorescent probe based on phosphorus‐doped cow milk‐derived carbon quantum dots (P‐CMCQDs) for the detection of Au3+ was studied in water samples. P‐CMCQDs were prepared by hydrothermal method with cow milk as carbon source and phosphoric acid as dopant. P‐CMCQDs show green fluorescence under ultraviolet light and can be partially quenched by Au3+. However, the excellent fluorescence characteristics of P‐CMCQDs‐ascorbic acid (AA) were obtained and can be used to detect trace Au3+ by simply mixing the P‐CMCQDs with AA. The sensing mechanism is based on the reduction of Au3+ to AuNPs by P‐CMCQDs and AA, and then AuNPs induce the fluorescence quenching of P‐CMCQDs through synergistic static quenching and internal filtering effect. The fluorescence intensity of P‐CMCQDs‐AA varies with the concentration of Au3+ (10–140 μmol/L), the detection limit is 4.2 nmol/L, indicating that the P‐CMCQDS‐AA probe has excellent sensitivity. In the detection of Au3+ in tap water and lake water, it is found that the recovery is between 99.6% and 100.5%, and the relative standard deviation is between 1.7% and 3.2%. This method is fast, efficient, and sensitive, and can be used to detect Au3+ in actual water samples.Practical ApplicationsAlthough the element gold is chemically inert, soluble gold salts remaining in the environment in the form of ions are toxic and serious damage the peripheral nervous system, causing other health issues. Therefore, it seems necessary to design an efficient and sensitive method to detect Au3+ in environment. Among many detection methods, fluorescence sensing method is more suitable for on‐site, rapid detection. However, the complex system, high limit of detection and environmental pollution caused by metal luminescence limit its application. In this paper, the biomass P‐CMCQDs was synthesized from cow milk by hydrothermal method. By adding AA in the synthesized P‐CMCQDs, the limit of detection (LOD) was greatly improved, and the trace Au3+ detection in tap water and lake water was highly selective and sensitive.

Synthesis and luminescence monitoring of iridium(III) complex-functionalized gold nanoparticles and their application for determination of gold(III) ions.

A new method is presented for the one-step synthesis and real-time monitoring of iridium(III) complex-functionalized AuNPs from the precursor gold(III) chloride (AuCl3). The functionalized AuNPs with an average size of 8 - 20nm were obtained by the reduction of Au3+ ions by the alkyne group of iridium(III) complexes, which was accompanied by the anchoring iridium(III) complexes on the surface of the nanoparticles. Meanwhile, the luminescence of the iridium(III) complexes was effectively quenched due to distance-dependent fluorescence quenching by AuNPs, thereby enabling luminescence monitoring of the formation process of the functionalized AuNPs and obtaining scattering information and spectral information in real time. Moreover, this method was applied to the determination of Au3+ ions in buffer with a limit of detection of 0.38μM at 700nm in luminescence mode, while the detection limit for absorbance was 10.04μM. Importantly, the multimodal detection strategy alleviates interference from other metal ions. Furthermore, the iridium(III) alkyne complexes were capable of imaging mitochondrial Au3+ ions in living cells. Taken together, this work opens a new avenue for convenient synthesis and monitoring formation of functionalized AuNPs, and also provides a tool for selective determination of Au3+ ions in solution and in cellulo.

Synthesis of Au NPs/Quince nanoparticles mediated by Quince extract for the treatment of human cervical cancer: Introducing a novel chemotherapeutic supplement

In this study, we have prepared mono-dispersed gold nanoparticles using the aqueous extract of Quince. The effective phytocompounds in the extract carried out the function as both reducing and stabilizing agents in the synthesis of Au NPs. The reduction of Au3+ ions into Au0 NPs was indicated by a visual transform in color from pale yellow to deep red. UV-Vis studies revealed the characteristic surface plasmon resonance band appeared at around 545 nm. FT-IR, TEM, SEM, EDX, XRD, and UV/Vis analytical methods were employed to characterize the Au NPs/Quince nanocomposite. TEM study revealed globular shaped NPs having particle size around 20–30 nm. Towards its biological implication, MTT method was followed in order to survey the cytotoxicity and inhibition of human cervical cancer against Hela, SiHa, and CCI-PI 19 cell lines and the corresponding IC50 values were evaluated as 465, 712, and 785 μg/mL respectively. The % cell viabilities diminished dose-dependently over the bio-nanomaterial. To survey the antioxidant properties of Au NPs/Quince, DPPH assay was used and here the related IC50 value was determined as 72 μg/mL.

Red fluorescent carbon dots for sensitive and selective detection and reduction of Au3+

Simultaneous detection and reduction of Au3+ in contaminated water is extremely desirable. Herein, we synthesized red fluorescent carbon dots (CDs) for Au3+ detection with dual colorimetric and fluorescent spectral response within 2 min. The CDs showed high sensitivity and selectivity towards Au3+ with a low detection limit of 29 nM. Further, CDs selectively reduce Au3+ to Au0 via redox reaction between the thioether group on the surface of CDs and Au3+. Accordingly, CDs were effectively utilized to detect and extract Au3+ without interference from other metal ions.

Gold nanoparticles supported on ionic‐liquid‐functionalized cellulose (Au@CIL): A heterogeneous catalyst for the selective reduction of aromatic nitro compounds

In response to the increasing need for green and cost‐effective catalysts, a novel biomass‐derived heterogeneous catalyst that is effective in a number of environmentally friendly applications has been synthesized. The heterogeneous catalyst (Au@CIL), composed of ionic‐liquid‐functionalized cellulose embedded with Au nanoparticles (NPs), was developed for the selective reduction of the nitro group. The Au NPs are formed by the reduction of Au3+ to Au0 with ascorbic acid while embedded in the solid support system. The presence of embedded Au NPs was confirmed using infrared spectroscopy, powder X‐ray diffraction, scanning electron microscopy, zeta‐potential measurements, energy‐dispersive X‐ray analysis, elemental dot mapping, and atomic force microscopy. In water at 30 °C, the heterogeneous catalyst Au@CIL selectively transforms aromatic nitro compounds into the corresponding amines in the presence of other functional groups, such as hydroxy, amino, aldehyde, carboxylic acid, and amide.

Fabrication of gold-immobilized quantum dots/silica core–shell nanoparticles and their multimodal imaging properties

This work describes the fabrication of quantum dot (QD)/silica (SiO2) core–shell particles immobilized with Au nanoparticles and the evaluation of their abilities in fluorescence and x-ray computed tomography (CT) imaging. The QD nanoparticles were coated with silica shells by a sol-gel method using tetraethyl orthosilicate (QD/SiO2). Reduction of Au3+ in a citrate aqueous solution gave an Au nanoparticle colloidal solution. (3-Mercaptopropyl)trimethoxysilane thiolated the QD/SiO2 particle surface (QD/SiO2/SH). Immobilization of the Au nanoparticles on the QD/SiO2/SH particle surface was performed with the addition of the Au nanoparticle colloidal solution to the QD/SiO2/SH nanoparticle colloidal solution (QD/SiO2/SH/Au). Surface-PEGylated QD/SiO2/SH/Au particles were fabricated using thiol-terminated polyethylene glycol (PEG) (QD/SiO2/SH/Au/PEG). The QD/SiO2/SH/Au/PEG nanoparticle colloidal solution was imaged by fluorescence and x-ray CT imaging techniques. The CT value per unit concentration of Au (M) for the QD/SiO2/SH/Au/PEG nanoparticle colloidal solution was 1.5 × 104 HU/M. The QD/SiO2/SH/Au/PEG nanoparticle colloidal solution was injected into the tail vein of a mouse and circulated in the blood, although some QD/SiO2/SH/Au/PEG nanoparticles were trapped and remained in the liver and spleen.

Design and One-Pot Synthesis of Capsid-like Gold Colloids with Tunable Surface Roughness and Their Enhanced Sensing and Catalytic Performances.

Viral capsid-like particles tiled with mosaic patches have attracted great attention as they imitate nature's design to achieve advanced material properties and functions. Here, we develop a facile one-pot soft-template method to synthesize biomimetic gold capsid-like colloids with tunable particle size and surface roughness. Uniform submicron-to-micron-sized hollow gold colloidal particles are successfully achieved by using tannic acids as soft templates and reducing agents, which first self-assemble into spherical complex templates before the reduction of Au3+ ions via their surface hydroxyl groups. The surface roughness, the size, and the total number of the patches of the prepared gold particles are further tuned, utilizing a mechanism that offers morphology control by varying the number of surface hydroxyl groups participating in the reduction reactions. Among different capsid-like gold colloids, those possessing a rough surface display superior catalytic properties and show promising results as surface-enhanced Raman spectroscopy (SERS) solid substrates for detecting small organic molecules and biomimetic enzymes in a liquid phase for sensing biomolecules in real samples. These capsid-like gold colloids are also expected to find practical applications in delivery systems, electronics, and optics. We believe that our strategy of imitating nature's design of capsid-like structures should also be used in the design and fabrication of other functional colloidal particles.

Colorimetric sensing of imidacloprid in cucumber fruits using a graphene quantum dot/Au (III) chemosensor

The current research presents a very simple method for the colorimetric detection of imidacloprid using a graphene quantum dot/Au (III) chemosensor. The results demonstrated that there is an interaction between Au3+ ions and the imidazole group of the pesticide toward reduction of Au3+ to Au0 in the presence of graphene quantum dots. This phenomenon changes the color of gold nanoparticles from yellow to grey or red, and causes a shift in the peak of localized surface plasmon resonance (LSPR) as gold nanoparticles are formed or aggregated based on the concentration of imidacloprid. Imidacloprid was determined by the developed sensor in a linear area of 0.01–1 ppm with a detection limit of 0.007 ppm. Therefore, a simple, quick, and sustainable sensor has been developed for the determination of the investigated analyte. Moreover, the sensor was applied to determine imidacloprid in the real cucumber samples fairly successful.

Facile preparation of fluorescent carbon quantum dots from denatured sour milk and its multifunctional applications in the fluorometric determination of gold ions, in vitro bioimaging and fluorescent polymer film

In the present study, the multifunctional applications of food waste derived carbon quantum dots (CQD) have been demonstrated. The results obtained from the absorption and fluorescence spectroscopic analysis affirmed the superior photophysical property of the prepared CQD. X-ray diffraction (XRD), Fourier transformed infra-red spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) studies further confirmed the crystallographic phase and surface functional groups present in the CQD. The ultrafine size of the CQD is established from the high-resolution transmission electron microscope (HR-TEM) micrographs with the grain size of 2−4 nm. The excellent fluorescence property of the CQD is utilised to detect trace levels of Au3+ ions by simply mixing aqueous dispersion of CQD with ascorbic acid (AA). The sensing mechanism is based on the reduction of Au3+ to gold nanoparticles (AuNPs) by AA and the subsequent AuNPs induced fluorescence quenching of CQD by synergistic static quenching and inner filter effect. The CQD/AA probe could selectively detect Au3+ ion as low as 0.95 μM. The cytotoxicity of the CQD toward U-251 MG glioblastoma cell revealed that the CQD did not possess any significant cytotoxicity. The application of CQD in bioimaging of cells is ascertained by fluorescence microscopic analysis. Furthermore, fluorescent polymer films were prepared by incorporating CQD within the polymer matrix (poly-vinyl-alcohol).

Green method for synthesis and characterization of gold nanoparticles using Lawsonia inermis seed extract and their photocatalytic activity

In this study, we have prepared polydispersed gold nanoparticles using the aqueous fraction of Lawsonia inermis seed extract by the ultrasound-assisted method. The effective phytocompounds in the aqueous fraction act as both reducing and stabilizing agents in the production of AuNPs. The colour change from pale yellow to purple which indicates the reduction of Au3+ ions to Au0 and the gold surface plasmon resonance band appeared at 546 nm. The shape and size of the synthesized nanoparticles were explored by HR-TEM. The green synthesized AuNPs act as a good nanocatalyst in the methyl orange degradation reaction under visible light in the presence of sodium borohydride.

Synthesis of Hydroxylatopillar[6]arene-Controlled Gold Nanoparticles-Cellulose Nanocrystals and Their Applications.

In this work, two macrocyclic hosts, named hydroxylatopillar[6]arene and dihydroxylatopillar[6]arene (HP6, 2HP6), are proposed. We found that the reduction of Au3+ to Au0 can success by using HP6 or 2HP6 as a reductant and stabilizing agent. At the end of HP6/2HP6, hydroxyl (-OH) groups were used as a reductant to reduce Au3+ to Au0. At the same time, -OH on HP6/2HP6 was oxidized to -COOH, and then the formed -COOH can be used as the stabilizer to prevent the infinite growth of AuNPs. The cellulose nanocrystals (CNCs) prepared by a clean and nonpolluting method were used as carriers to load AuNPs on them. The CNCs were applied for the adsorption of methylene blue (MB), and then the MB was catalytically degraded by HP6/2HP6-AuNPs-CNC. Besides, the HP6/2HP6-AuNPs-CNC showed remarkable catalytic performance for reducing nitro to the amino group in 4-nitrophenol. The advantages of clean and green synthesis make the HP6/2HP6-AuNPs-CNC a hybrid material and its application sustainable.

Exploring the Gelation Mechanisms and Cytocompatibility of Gold (III)-Mediated Regenerated and Thiolated Silk Fibroin Hydrogels.

Accelerating the gelation of silk fibroin (SF) solution from several days or weeks to minutes or few hours is critical for several applications (e.g., cell encapsulation, bio-ink for 3D printing, and injectable controlled release). In this study, the rapid gelation of SF induced by a gold salt (Au3+) as well as the cytocompatibility of Au3+-mediated SF hydrogels are reported. The gelation behaviors and mechanisms of regenerated SF and thiolated SF (tSF) were compared. Hydrogels can be obtained immediately after mixing or within three days depending on the types of silk proteins used and amount of Au3+. Au3+-mediated SF and tSF hydrogels showed different color appearances. The color of Au-SF hydrogels was purple-red, whereas the Au-tSF hydrogels maintained their initial solution color, indicating different gelation mechanisms. The reduction of Au3+ by amino groups and further reduction to Au by tyrosine present in SF, resulting in a dityrosine bonding and Au nanoparticles (NPs) production, are proposed as underlying mechanisms of Au-SF gel formation. Thiol groups of the tSF reduced Au3+ to Au+ and formed a disulfide bond, before a formation of Au+-S bonds. Protons generated during the reactions between Au3+ and SF or tSF led to a decrease of the local pH, which affected the chain aggregation of the SF, and induced the conformational transition of SF protein to beta sheet. The cytocompatibility of the Au-SF and tSF hydrogels was demonstrated by culturing with a L929 cell line, indicating that the developed hydrogels can be promising 3D matrices for different biomedical applications.

Interface-mediated noble metal deposition on transition metal dichalcogenide nanostructures.

Functionalizing the surfaces of transition metal dichalcogenide (TMD) nanosheets with noble metals is important for electrically contacting them to devices, as well as improving their catalytic and sensing capabilities. Solution-phase deposition provides a scalable approach to the creation of metal-TMD hybrid systems, but controlling such processes remains challenging. Here we elucidate the different pathways by which gold and silver deposit at room temperature onto colloidal 1T-WS2, 2H-WS2, 2H-MoSe2, 2H-WSe2, 1T'-MoTe2 and Td-WTe2 few-layer nanostructures to produce several distinct classes of 0D-2D and 2D-2D metal-TMD hybrids. Uniform gold nanoparticles form on all of the TMDs. By contrast, silver deposits as nanoparticles with a bimodal size distribution on the disulfides and diselenides, and as atomically thin layers on the ditellurides. The various sizes and morphologies of these surface-bound metal species arise from the relative strengths of the interfacial metal-chalcogen bonds during the reduction of Au3+ or Ag+ by the TMDs.