Oxidation State Of Au Research Articles

Improvement on electrochemiluminescence properties of graphite carbon nitride by metal oxidation state regulation

AbstractReasonable design is of great significance for improving the performance of electrochemiluminescence (ECL) co‐reactant accelerators. The different d‐band structure of metal single atoms will produce different oxidation states, which may change the adsorption of reaction intermediates to the catalyst and affect its catalytic activity. In this study, we have demonstrated that the ECL performances of graphite carbon nitride (CN) can be promoted by modulating the metal oxidation states of co‐reaction accelerator for the first time. The oxidation states of Au were modulated by the different electronic metal–support interaction (EMSI) between the co‐reaction accelerator (Au single atoms, Au nanoparticles [Au NPs]) and CN, and the effects of Au oxidation states on the ECL performances of CN were investigated. Comparison to pristine CN and CN nanosheets supported Au nanoparticles (Au NPs/CN), stronger and more stable ECL intensity of CN nanosheets supported Au single‐atoms (AuS/CN) was obtained. The ECL signal of AuS/CN was about 32.2 times that of the original CN, and 2.8 times that of Au NPs/CN in the same Au loading content (0.8%). Detailed mechanism revealed that AuS/CN with higher Au oxidation state has better conductivity and stronger catalytic activity, which promotes the electric reduction of CN and S2O82−, increases the lifetime of the excited state CN*, and significantly improves the ECL performance of CN. In addition, this work provides a detailed understanding of the essence of EMSI for the ECL intensity amplification and established a feasible method for the improvement of ECL capacities of co‐reactant accelerators.

In situ/operando spectroscopic evidence on associative redox mechanism for periodic unsteady-state water–gas shift reaction on Au/CeO2 catalyst

Cyclic and repeatable CO2/H2 formation under periodic CO ↔ H2O feeds, that is unsteady-state water–gas shift reaction (uss-WGS), was found to be catalyzed by a gold nanoparticles-loaded CeO2 (Au/CeO2) catalyst. Kinetics of the CO-reduction of Ce4+ to Ce3+ and Ce3+ reoxidation by H2O in combination with transient CO2/H2 formation over Au/CeO2 were studied by operando ultraviolet–visible (UV–vis) and infrared (IR) spectroscopies at 175 °C. The Ce4+–OH species were reduced by CO to give Ce3+-□-Ce3+ (□: oxygen vacancy) and gas phase products (H2, CO2). The Ce3+-□-Ce3+ species were oxidized by H2O to give H2 and Ce4+–OH species. The reduction and reoxidation rates of Ce4+/Ce3+ redox couple were close to the rates of transient CO2/H2 formation. The X-ray absorption spectroscopy results showed that the oxidation states of Au remained unchanged during the redox reactions. These results indicate that the uss-WGS is primary driven by the Ce4+/Ce3+ redox couple. Combined with the observation of adsorbed carboxylate intermediates as a precursor of H2 and CO2, associative redox mechanism is proposed as the main pathway for the unsteady-state WGS reaction on Au/CeO2 at 175 °C.

Stabilizing Au2+ in a mixed-valence 3D halide perovskite.

Although Cu2+ is ubiquitous, the relativistic destabilization of the 5d orbitals makes the isoelectronic Au2+ exceedingly rare, typically stabilized only through Au-Au bonding or by using redox non-innocent ligands. Here we report the perovskite Cs4AuIIAuIII2Cl12, an extended solid with mononuclear Au2+ sites, which is stable to ambient conditions and characterized by single-crystal X-ray diffraction. The 2+ oxidation state of Au was assigned using 197Au Mössbauer spectroscopy, electron paramagnetic resonance, and magnetic susceptibility measurements, with comparison to paramagnetic and diamagnetic analogues with Cu2+ and Pd2+, respectively, as well as to density functional theory calculations. This gold perovskite offers an opportunity to study the optical and electronic transport of the uncommon Au2+/3+ mixed-valence state and the characteristics of the elusive Au2+ ion coordinated to simple ligands. Compared with the perovskite Cs2AuIAuIIICl6, which has been studied since the 1920s, Cs4AuIIAuIII2Cl12 exhibits a 0.7 eV reduction in optical absorption onset and a 103-fold increase in electronic conductivity.

Mechanochemically activated Au/CeO2 for enhanced CO oxidation and COPrOx reaction

COPrOx reaction is one of the particularly appealing and cost-effective solutions for the selective oxidation of CO in hydrogen-rich gas streams to meet the stringent requirement of the current electrocatalysts employed in low-temperature fuel cells. Herein, we synthesized ultrasmall Au clusters supported on ceria by one-step solvent-free mechanochemical method. These catalysts exhibited higher activity for COPrOx and CO oxidation compared to the sample prepared by conventional incipient wetness impregnation. The unique Au-Ce interaction caused by impact and friction between the ball, vessel, and powders, greatly promotes the generation of positive charged Auδ+ active sites and, at the same time, the reducibility of the catalyst. Interestingly, an aging treatment of the ball-milled samples resulted in a significant superior performance of the catalytic activity. This enhancement has been attributed to a change in the oxidation state of Au between the fresh and the aged catalysts prepared by ball milling.

Selectivity Regulation of Au/Titanate by Biochar Modification for Selective Oxidation of Benzyl Alcohol

In organic synthesis, it is important to control the selectivity target product with high purity and reduce the cost of energy and equipment for separation. This study investigated supported gold catalysts on biochar-modified titanate-based nanofibers in order to regulate the catalytic performances by biochar content and surface properties. The catalysts were characterized by SEM, TEM, XRD, XPS, ICP-OES, UV-Vis to confirm their morphology, particle size distribution of Au NPs, crystal structures, oxidation state of Au and other key elements, real Au loading, and optical properties. In the test of selective oxidation of benzyl alcohol to benzaldehyde, the biochar modification could improve the selectivity toward benzaldehyde. Moreover, the influence of catalyst calcination conditions, reaction time, reaction atmospheres, reaction temperatures and solvent were systematically investigated. These results are useful for peer researchers in rational catalyst design.

Deciphering the synergy between electron localization and alloying for photoelectrochemical nitrogen reduction to ammonia

Photoelectrochemistry that directly takes advantage of solar energy by photoelectrodes is a promising green route for the nitrogen fixation, but is currently far from practical application. It is necessary to understand the structure-reactivity interplay of the photocathodes for rendering rational improvement of the existing challenges. Here, we make efforts to reveal AuCoPd-CoOx/SiO2/Si photocathodes capable of selective photoelectrochemical conversion of nitrogen to ammonia at varied pressures, achieving an ammonia yield rate of 22.2 ± 0.4 μg·h−1·cm−2 and a faradic efficiency of 22.9% at −0.1 V vs. reversible hydrogen electrode under 3-MPa nitrogen. In particular, we focus on the remarkable, but often subtle, roles of the synergy between electron localization and alloying in determining the reactivity of the photocathodes. Specifically, operando XPS and XAS illustrate that the oxidation states of Au and Pd enable the photoinduced electron capture as the reduction sites to produce the *N2 and *H active species, respectively, facilitating the couple of N-H for ammonia synthesis. Although this study is not sufficient to break through bottleneck, there is much insight on the design of efficient and robust photocathodes for photoelectrochemical nitrogen fixation.

Synthesis of nanocubic shape controlled Gold-Prussian blue nanocomposite for enhanced electrocatalytic hydrazine oxidation

• A facile wet chemical method used for the synthesis of nano cubic shape controlled Au-PB-NCs. • Au-PB-NC/GCE shows 13 times higher catalytic current density of hydrazine than pristine PB-NCs. • The sensitivity of Au-PB-NCs/GCE is 111 μA.cm −2 μM −1 with LOD of 0.709 µM for sensing of hydrazine. Herein, we report for the first time, facile chemical synthesis of gold nanoparticles embedded in nano-cubic shaped prussian blue (Au-PB-NCs). To understand the role of gold nanoparticles (AuNPs) present in the Au-PB-NCs, the same chemical method is used without involving gold precursor solution for pristine prussian blue nanocubes (PB-NCs). For the proof-of-concept experiment, both Au-PB-NCs and PB-NCs are modified on glassy carbon electrodes (it is called as Au-PB-NCs/GCE and PB-NCs/GCE respectively) to study the electrocatalytic activity of hydrazine molecules as a model system. The exact size of the PB-NCs and the nature of the distribution of AuNPs into the Au-PB-NCs matrix are confirmed by high-resolution transmission electron microscopy (HR-TEM) and high-angle annular dark-field scanning transmission electron microscopic (HAADF-STEM) analysis. X-ray diffraction (XRD) and X-ray photon electron microscopy (XPS) results reveal that the PB-NCs has high crystalline and the oxidation state of Au is Au 0 and Au + in Au-PB-NCs. Compared with PB-NCs/GCE, the Au-PB-NCs/GCE showed higher redox current density and improved charge transfer kinetics in electrochemical measurements. Remarkably, it exhibits higher electrocatalytic oxidation current and excellent amperometric response with the linear range of 0–40 µM for hydrazine molecule when compared with PB-NCs/GCE. The calculated low detection limit and sensitivity value of Au-PB-NCs/GCE is 0.709 µM and 111 µA. cm −2 . µM −1 , respectively, which are comparable with reported literature. The selectivity and stability of electrooxidation of hydrazine molecule on fabricated Au-PB-NCs/GCE platform is investigated by amperometric method. The obtained results clearly indicate that Au-PB-NCs/GCE has excellent stability and selectivity towards hydrazine sensing without the impact of other interference. Also, the developed Au-PB-NCs/GCE sensor platform is applied to the real water samples analysis and showed the results of good recovery, reproducibility and repeatability, which implies its feasibility for realistic application in hydrazine estimation.

Conversion of glycerol to dihydroxyacetone over Au catalysts on various supports

AbstractBACKGROUNDGlycerol, which is a coproduct of biodiesel production, has been identified as a key platform compound for producing various valuable chemicals. The selective catalytic oxidation of glycerol to dihydroxyacetone is very attractive.RESULTSA series of Au catalysts supported on metallic oxides, i.e. ZnO, CuO, Al2O3, Fe2O3 and NiO, were studied for selective catalytic oxidation of glycerol to dihydroxyacetone under base‐free conditions. Among the catalysts, Au/CuO showed the best catalytic activity (glycerol conversion of 89% and dihydroxyacetone selectivity of 82.6% at 80 °C under 10 bar of O2), followed by Au/ZnO ≫ Au/NiO > Au/Al2O3 ≈ Au/CuO‐SD ≈ Au/Fe2O3. The catalytic behaviors of these supported Au catalysts varied depending on the Au particle size, Au oxidation state, Au–support interactions and lattice oxygen reducibility.CONCLUSIONThe main reasons for the high catalytic activity of Au/CuO are as follows. Firstly, the catalyst has small metallic Au particles, which are more active in cleavage of the secondary CH bond in glycerol molecules. Secondly, the interactions between Au and CuO facilitate lattice oxygen reduction, and this increases oxygen mobility, which may promote regeneration of Au–support perimeter active sites by gaseous oxygen. © 2019 Society of Chemical Industry

Tuning the Electron Localization of Gold Enables the Control of Nitrogen-to-Ammonia Fixation.

The (photo)electrochemical N2 reduction reaction (NRR) provides a favorable avenue for the production of NH3 using renewable energy in mild operating conditions. Understanding and building an efficient catalyst with high NH3 selectivity represents an area of intense interest for the early stages of development for NRR. Herein, we introduce a CoOx layer to tune the local electronic structure of Au nanoparticles with positive valence sites for boosting conversion of N2 to NH3 . The catalysts, possessing high average oxidation states (ca. 40 %), achieve a high NH3 yield rate of 15.1 μg cm-2 h-1 and a good faradic efficiency of 19 % at -0.5 V versus reversible hydrogen electrode. Experimental results and simulations reveal that the ability to tune the oxidation state of Au enables the control of N2 adsorption and the concomitant energy barrier of NRR. Altering the Au oxidation state provides a unique strategy for control of NRR in the production of valuable NH3 .

Tuning the Electron Localization of Gold Enables the Control of Nitrogen‐to‐Ammonia Fixation

AbstractThe (photo)electrochemical N2 reduction reaction (NRR) provides a favorable avenue for the production of NH3 using renewable energy in mild operating conditions. Understanding and building an efficient catalyst with high NH3 selectivity represents an area of intense interest for the early stages of development for NRR. Herein, we introduce a CoOx layer to tune the local electronic structure of Au nanoparticles with positive valence sites for boosting conversion of N2 to NH3. The catalysts, possessing high average oxidation states (ca. 40 %), achieve a high NH3 yield rate of 15.1 μg cm−2 h−1 and a good faradic efficiency of 19 % at −0.5 V versus reversible hydrogen electrode. Experimental results and simulations reveal that the ability to tune the oxidation state of Au enables the control of N2 adsorption and the concomitant energy barrier of NRR. Altering the Au oxidation state provides a unique strategy for control of NRR in the production of valuable NH3.

Sulfur Moiety as a Double-Edged Sword for Realizing Ultrafine Supported Metal Nanoclusters with a Cationic Nature

Heterogeneously and uniformly dispersed metal nanoclusters with high thermal stability and stable nonmetallic nature show outstanding catalytic performance. In this work, we report on the role of sulfur moieties in hydrochlorination catalysis over carbon-supported gold (Au/C). A combination of experimental and theoretical analyses shows that the -SO3H and derived -SO2H sulfur species in high oxidation states at the interface between Au and -SO3H at ≥180 °C give rise to high thermal stability and catalytic activity. By contrast, the grafted thiol group (-SH) and the derived low-valence sulfur species on carbon markedly destabilize the Au nanoclusters, promoting their rapid sintering into large Au nanoparticles and leading to the loss of their cationic nature. Theoretical calculations suggest that -SO3H favorably adsorbs and stabilizes cationic Au species. Compared to Au/C and Au-SH/C with the Auα+/Au0 atomic ratios of 1.02 and 0.24, respectively (α = 1 or 3), the activity and durability of acetylene hydrochlorination are remarkably enhanced by the interaction between the -SO3H moieties and cationic Au species that enables the high oxidation state of Au to be effectively retained (Auα+/Au0 = 3.82). These results clearly demonstrate the double-edged sword effect of sulfur moieties on the catalytic Au component in acetylene hydrochlorination. The double-edged sword effect of sulfur species in the stabilization/destabilization of metal nanoclusters is also applicable to other metals such as Ru, Pd, Pt, and Cu. Overall, this study enriches the general understanding of the stabilization of metal clusters and provides insight into a wet chemistry strategy for stabilizing supported ligand-free nanoclusters.

Protein-mediated disproportionation of Au(i): insights from the structures of adducts of Au(iii) compounds bearing N,N-pyridylbenzimidazole derivatives with lysozyme.

Au(iii) compounds bearing N,N-pyridylbenzimidazole derivatives with the ethyl (1) or propyl sulfonate (2) appendage react with the model protein hen egg white lysozyme (HEWL), forming adducts with different gold-containing fragments. The conformation of the enzyme, the exact gold binding sites and the oxidation state of Au in the adducts are unknown. Here we report a structural study on the reaction of 1 and 2 with HEWL in solution and solid state. In agreement with previously reported electrospray ionization mass spectra, the compounds degrade in their interaction with the protein. In the structure derived from HEWL crystals exposed to 1 for less than one day, three Au binding sites were identified: Au(i) ions are bound to the side chain of His15 and to the side chains of His15 and Asn93. The third gold centre is buried in the hydrophobic pocket of the protein via the binding to the side chain of Met105 and the trapping between the side chains of Trp28, Trp108 and Trp111. In a second crystal fished three hours later from the same drop, only one Au ion, probably in the +1 oxidation state, is observed; it binds the protein close to the side chains of Asn93 and His15. After three days of soaking, the colour of HEWL crystals obtained in the presence of 1 turned violet. In these crystals, anomalous signals attributable to Au are found on the protein surface; gold atoms are not directly coordinated to residue side chains. Longer exposure of HEWL crystals to 1 produces gold-free crystals. In the adduct of HEWL exposed to 2 for one day, three Au(i) ions are detected close to the side chains of both Asn93 and His15, the side chain of His15 and that of Met105. Longer exposure of HEWL crystals to 2 affords gold-free crystals. These structural data and those of the other protein/gold adducts available at the Protein Data Bank suggest that the reduction of Au(iii) into Au(i) is the basis of the mechanism of action of the biologically active gold(iii) compounds. Besides, Au(i) ions can undergo disproportionation into Au(iii) and Au(0) that can diffuse away from the protein crystals.

Oxidation or Reduction State of Au Stabilized by an MOF: Active Site Identification for the Three‐Component Coupling Reaction

AbstractAs one of the most efficient catalysts for the three‐component coupling reaction of aldehyde, amine, and alkyne (A3 coupling), Au has attracted extensive attention, but there is a debating issue on whether Auδ+ (δ > 0, representing the oxidation state of Au species) or Au0 is the better active site. According to previous reports, both Auδ+ and Au0 can catalyze the A3 coupling reaction. Therefore, the establishment of a suitable comparison model to identify the better active site is highly desired. In this work, an ideal model to identify the efficient active sites for the A3 coupling reaction based on a metal–organic framework (MOF) platform is rationally fabricated. The Auδ+ in oxidation state can be well bound to the MOF, MIL‐101‐NH2, via postsynthetic modification, and the Au0 catalyst with retained MOF skeleton can be formed via a subsequent one‐step reduction, which provide ideal comparison models with the only difference in the Au oxidation state. Strikingly, the two catalysts exhibit significant activity difference in the A3 coupling reaction. The activity of Auδ+ catalyst is 11‐fold higher than that of Au0, which reveals that Auδ+ serves as a much more effective active site in the A3 coupling reaction.

Deactivation of a Single-Site Gold-on-Carbon Acetylene Hydrochlorination Catalyst: An X-ray Absorption and Inelastic Neutron Scattering Study

Single-site Au species supported on carbon have been shown to be the active sites for acetylene hydrochlorination. The evolution of these single-site species has been monitored by Au L3 X-ray Absorption Spectroscopy (XAS). Alternating between a standard reaction mixture of HCl/C2H2 and the single reactants, has provided insights into the reaction mechanism and catalyst deactivation processes. We demonstrate that oxidative addition of HCl across an Au(I) chloride species requires concerted addition with C2H2, in accordance with both the XAS measurements of Au oxidation state and the reaction kinetics being 1st order with respect to each reactant. The addition of excess C2H2 changes the Au speciation and results in the formation of oligomeric acetylene species which were detected by inelastic neutron scattering. Catalyst deactivation at extended reaction times can be correlated with the formation of metallic Au particles. The presence of this Au(0) species generated during the sequential gas experiments or after prolonged reaction times, results in the analysis of the normalised near edge white line intensity of the Au L3 X-ray absorption spectrum alone becoming an unsuitable guide for identifying the active Au species, affecting the strong correlation between normalized white line height and VCM productivity usually observed in the active catalyst. Thus, a combination of scanning transmission electron microscopy and detailed modelling of whole XAS spectrum was required to distinguish active Au(I) and Au(III) species from the spectator Au(0) component.

Gold with +4 and +6 Oxidation States in AuF4 and AuF6.

An important goal in chemistry is to prepare compounds with unusual oxidation states showing exciting properties. For gold (Au), the relativistic expansion of its 5d orbitals makes it form high oxidation state compounds. Thus far, the highest oxidation state of Au known is +5. Here, we propose high pressure as a controllable method for preparing +4 and +6 oxidation states in Au via its reaction with fluorine. First-principles swarm-intelligence structure search identifies two hitherto unknown stoichiometric compounds, AuF4 and AuF6, exhibiting typical molecular crystal character. The high-pressure phase diagram of Au fluorides is rather different from Cu or Ag fluorides, which is indicated by stable chemical compositions and the pressures needed for the synthesis of these compounds. This difference can be associated with the stronger relativistic effects in Au relative to Cu or Ag. Our work represents a significant step forward in a more complete understanding of the oxidation states of Au.

Dye‐containing wastewater treatment by photo‐assisted wet peroxidation using Au nanosized catalysts

AbstractBackgroundThe aim of this study is to test different supports on which to deposit Au nanoparticles and to determine the most suitable for Orange II (OII) dye degradation by a photo‐assisted wet peroxidation (PWPO) process. The catalysts used (Au‐Fe2O3, Au‐TiO2, Au‐ZnO and Au‐Al2O3) were prepared by the deposition–precipitation method; a reference catalyst from the World Gold Council, hereafter denoted as Au‐Fe2O3*, was also used for comparison. The catalysts were characterized in terms of surface area (SBET), gold nanoparticles size, Au loading and Au oxidation state using several techniques (namely, nitrogen adsorption at −196°C, X‐ray photoelectron spectroscopy – XPS, and high resolution transmission electron microscopy – HR‐TEM). Several runs were carried out for each material, to evaluate its efficiency in OII dye degradation by the PWPO process.ResultsAll catalysts reached OII dye removals of >96% and considerable total organic carbon (TOC) degradation – between 58.4% and 80.5%. The materials had negligible Au leaching, showing very good stability. For the catalyst with best performance (Au/Al2O3), a parametric study was carried out to assess the effect of different variables on dye and TOC removals. Under the best conditions, excellent efficiency of the advanced oxidation process was obtained. A simulated industrial acrylic dyeing effluent was also treated by PWPO and very good performance was reached, with removals up to 100%, 72.4% and 70.0% for color, TOC and COD, respectively, with only 2 h of reaction. Moreover, there was an improvement in biodegradability and a non‐toxic effluent was generated.ConclusionsPWPO using nano‐sized gold‐based catalysts proved to be a promising technique for the degradation of pollutants in water. The used gold supports have an important role in the efficiency of the process. The best catalyst was obtained using large surface area Al2O3 as support, although no leaching of gold was found for any of the catalysts. The mineralization degree improved under radiation due the formation of hydroxyl radicals, being reached total dye removal and a decrease of the TOC values greater than 90%. © 2018 Society of Chemical Industry

Microwave-Assisted Formation of Gold Nanoclusters Capped in Bovine Serum Albumin and Exhibiting Red or Blue Emission

In this study, a microwave-assisted method for preparing fluorescent gold nanoclusters capped in bovine serum albumin (AuNCs@BSA) was developed. Through fluorescence spectrometry, transmission electron microscopy, and X-ray photoelectron spectroscopy (XPS), the effect of reaction temperature on the size and oxidation state of AuNCs@BSA samples was determined. Blue-emitting AuNCs@BSA (B-AuNCs@BSA), with weak bonds between AuNCs and BSA, were prepared at 135 °C. Red-emitting AuNCs@BSA (R-AuNCs@BSA) were also formed, and their formation was followed by an aggregation of polydispersed AuNCs@BSA. Through infrared spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, it was confirmed that the R-AuNCs@BSA, consisting of 18 Au atoms, was successfully embedded in BSA. In addition, XPS measurements revealed that Au+ ions were present only in the R-AuNCs@BSA. Steady-state and lifetime results revealed the importance of the size and oxidation state of Au+ in the stabilization ...

Direct observation of the nanoscale Kirkendall effect during galvanic replacement reactions

Galvanic replacement (GR) is a simple and widely used approach to synthesize hollow nanostructures for applications in catalysis, plasmonics, and biomedical research. The reaction is driven by the difference in electrochemical potential between two metals in a solution. However, transient stages of this reaction are not fully understood. Here, we show using liquid cell transmission electron microscopy that silver (Ag) nanocubes become hollow via the nucleation, growth, and coalescence of voids inside the nanocubes, as they undergo GR with gold (Au) ions at different temperatures. These direct in situ observations indicate that void formation due to the nanoscale Kirkendall effect occurs in conjunction with GR. Although this mechanism has been suggested before, it has not been verified experimentally until now. These experiments can inform future strategies for deriving such nanostructures by providing insights into the structural transformations as a function of Au ion concentration, oxidation state of Au, and temperature.

Active Au Species During the Low-Temperature Water Gas Shift Reaction on Au/CeO2: A Time-Resolved Operando XAS and DRIFTS Study

Operando XAS measurements in the near (XANES) and the extended (EXAFS) Au LIII edge as well as in situ diffuse reflectance FTIR (DRIFTS) spectroscopy were employed in combination with kinetic measurements in a further attempt to identify the nature of the active Au species responsible for the high activity of Au/CeO2 catalyst in the low-temperature water gas shift (LT-WGS) reaction. The changes in the reaction behavior during the LT-WGS were followed at 180 °C for different initial states of the catalyst, prepared by either reducing or oxidizing pretreatments at different temperatures. Findings from kinetic and deactivation measurements were correlated with experimental data on the Au particle size, the Au oxidation state, and the CO-Au adsorption properties directly after different pretreatments and during the subsequent LT-WGS reaction obtained by operando/in situ spectroscopy measurements. The combined experimental results show that the use of different pretreatments can significantly influence the ele...

Green Synthesis of Pectin-Gold-PLA-PEG-PLA Nanoconjugates: In Vitro Cytotoxicity and Anti-Inflammatory Activity

The gold nanoparticles (AuNPs) have been synthesized by a green chemical approach using the biopolymer pectin which is isolated from the orange peel. The pectin-AuNPs nanoconjugates are attached on the PLA-PEG-PLA triblock copolymer matrix by the ultra-sonication induced water-in-oil (W/O) emulsion method. The pectin-AuNPs-PLA-PEG-PLA nanoconjugates are characterized by UV-Visible absorption spectroscopy, X-Ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive X-Ray spectroscopy (EDS) and X-Ray photo electron spectroscopy (XPS). The XPS results confirm the zero oxidation state of Au, while the TEM images confirm the spherical shape of 7–13 nm of AuNPs. The XRD analysis reveals that the AuNPs exhibit fcc crystal structure with an average crystallite size of 12 nm. The biocompatibility of the pectin-AuNPs-PLA-PEG-PLA nanoconjugates has been investigated by the In Vitro cell line study on South African green monkey’s kidney cells. The anti-inflammatory activity of the nanoconjugates has been established by the membrane stabilization and inhibition of protein denaturation methods. The pectin-AuNPs-PLA-PEG-PLA nanoconjugates exhibit better anti-inflammatory activity than pectin and pectin-AuNPs.