Dispersed Ag Research Articles

Surface Coordination Chemistry of Graphitic Carbon Nitride from Ag Molecular Probes.

Graphitic carbon nitride (g-C3N4) has gained significant attention for its catalytic properties,especiallyin the development of Single Atom Catalysts (SACs).However,the surface chemistry underlying the formation of these isolated metal sites remains poorly understood.In thisstudyweemploy Surface OrganoMetallic Chemistry (SOMC) together with advanced microscopic and spectroscopic techniquesfor an in-depth analysis of functionalizedg-C3N4materials, where tailored organosilver probe molecules are used to monitor surface processes and characterize resulting surface species. Amulti-technique approach-including high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM), X-ray absorption spectroscopy (XAS), and multinuclear solid-state Nuclear Magnetic Resonance spectroscopy (ssNMR),coupled with density functional theory (DFT) calculations- identifies three primary surface speciesin Ag-functionalized g-C3N4:bis-NHC-Ag+, dispersed Ag+sites, andphysisorbed molecular precursor.These findings highlight a dynamic grafting process and provide insights into the surface coordination chemistryof functionalizedg-C3N4materials.

Ag Nanoparticles-Confined Doped within Triazine-Based Covalent Organic Frameworks for Syngas Production from Electrocatalytic Reduction of CO2.

Electrocatalytic CO2 reduction reaction (CO2RR) emerges as a promising avenue to mitigate carbon emissions, enabling the capture and conversion of CO2 into high-value products such as syngas with CO/H2. One of the crucial aspects lies in the tailored development of durable and efficient electrocatalysts for the CO2RR. Covalent organic frameworks (COFs) possess unique characteristics that render them attractive candidates for catalytic applications. However, the relationship between structure and performance still requires further exploration; especially, most COFs with such properties are limited to COFs containing specific groups such as phthalocyanine or porphyrin groups. Here, we custom-synthesize two azine-linked nitrogen-rich COFs constructed from triazine building blocks, which are doped with ultrafine and highly dispersed Ag nanoparticles (Ag@TFPT-HZ and Ag@TPT-HZ). Thus-obtained COFs can serve as electrocatalysts for the CO2RR, and a comprehensive investigation has been conducted to uncover the intricate structure-performance relationship within these materials. Notably, Ag@TFPT-HZ exhibits superior CO selectivity in the electrocatalytic CO2RR, achieving a FECO of 81% and a partial current density of 7.65 mA·cm-2 at the potential of -1.0 V (vs reversible hydrogen electrode (RHE)). In addition, Ag@TPT-HZ as an electrocatalyst can continuously produce syngas with a CO/H2 molar ratio of 1:1, an ideal condition for methanol synthesis. The observed distinct performance between these two COFs is attributed to the presence of O atoms in TFPT-HZ. These O atoms facilitate a higher loading capacity of Ag nanoparticles (11 wt %) and generate a greater number of active sites, thereby enhancing electrochemical activity and promoting faster reaction kinetics. Therefore, two tailor-made two-dimensional (2D) nitrogen-rich COFs with various active sites as electrocatalysts can exhibit different outstanding electrocatalytic performances for CO2RR and possess high cycling stability (>50 h). This work offers valuable insights into the design and synthesis of electrocatalysts, particularly in elucidating the intricate relationship between their structure and performance.

Study on the effect and mechanism of support structure and characteristic on Ag-based catalysts for low-temperature selective catalytic oxidation of ammonia

Herein, the influence of support type and properties on the catalytic activity and selectivity of Ag-based NH3-SCO catalyst was studied through the evaluation of NH3-SCO performance, the physicochemical characterization of H2-TPR, NH3-TPD, N2 isothermal adsorption–desorption, XPR and XPS, and the mechanism study of 1H MAS NMR, In-situ DRIFTS and DFT calculations. Ag/nano-TiO2, Ag/Al2O3, and Ag/MnO2 all showed better NH3-SCO activity because of more abundant Brønsted and Lewis acid sites of Al2O3 and TiO2 and more actual Ag loading amount due to the larger specific surface area and suitable surface chemistry. The N2 selectivity of Ag/nano-TiO2 is significantly better, which may be due to the highly dispersed Ag species and the abundant Brønsted acid sites with higher N2 selectivity. The mechanism study showed that the terminal hydroxyl was the preferred consumption target of Ag species, and this consumption promoted the effective dispersion and stable anchoring of Ag on the TiO2 surface.

Enhanced sonophoto-catalytic and adsorption capabilities of Fe3O4@MC/MWCNT-CuO/Ag for petrochemical organic pollutants degradation from industrial process streams

To address the problem of petrochemical organic pollutants in water, specifically monoethylene glycol (MEG) present in industrial process streams, in this research, we synthesized and evaluated a multifunctional nanocomposite, Fe3O4@MC/MWCNT-CuO/Ag. The nanocomposite was produced by combining magnetic Fe3O4 nanoparticles, methylcellulose (MC), multi-walled carbon nanotubes (MWCNTs), and CuO/Ag nanoparticles by an integrated synthesis process. A consistent dispersion of nanoparticles, with diameters ranging from 30-40 nm, was discovered by FESEM analysis, showing effective integration without aggregation. Effective synthesis was demonstrated by well-doped and evenly dispersed CuO and Ag nanoparticles. Functional groups that improve electrostatic interactions with contaminants hence enhancing catalytic performance and adsorption efficiency, were validated by FTIR analysis. XRD indicated an unchanged crystal structure with an average crystallite size of 8.67 nm. The anticipated elemental composition was verified by EDS & mapping. A VSM study revealed magnetic characteristics (9.33 emu/g) that simplify nanocomposite separation and reuse. TGA proved thermal stability to be up to 600 °C. A BET study showed a highly specific surface area of 67.661 m2/g, enhancing adsorption. According to DRS and PL studies, the bandgap was lowered by 1.31 eV, which led to better optical absorption. The nanocomposite exhibited notable MEG removal efficiency, with 72 % in adsorption, 65 % in photocatalysis, and 56 % in sonocatalysis. This makes it a promising alternative for the remediation of organic pollutants in water treatment.

Mechanisms of mercury removal from water with highly efficient MXene and silver-modified polyethyleneimine cryogel composite filters

Safeguarding aquatic ecosystems and human health requires effective methods for removing pollutants. Mercury (Hg) is a very toxic pollutant with a global presence and is highly mobile and persistent. Here, innovative materials were prepared for separating Hg(II) from water, and the mechanisms underlying the efficient uptake of Hg species have been investigated. The sorbents include silver (Ag) nanoparticles and multilayered Ti3C2Tx MXene, both incorporated into the structure of a three-dimensional polyethyleneimine porous cryogel (PEI) that acts as a scaffold holding and exposing nano active sites involved in the removal of Hg. Specifically, Ag particles were deposited onto MXene phases, and the resulting composite was embedded in the macroporous PEI polymer (PEI/MXene@Ag cryogel). The composite has beneficial properties regarding Hg removal: 99% of Hg was separated from waste within 24 h in batch studies. The maximum removal capacity of Hg reached 875 mg/g from HgCl2, and 761 mg/g and 1280 mg/g from Hg(OAc)2 and Hg(NO3)2 salts by PEI/MXene@Ag. The Hg uptake stems from the composite’s relatively large specific surface area, layered porous channels, and highly dispersed Ag nanoparticles in the multilayered Ti3C2Tx MXene. The matrix in the water samples that were treated with the composite did not hinder the uptake of Hg by PEI/MXene@Ag. The high effectiveness achieved for the removal of Hg, combined with rapid adsorption kinetics, high efficiency, and selectivity, positions it as an efficient solution. Future work should address upscaling its preparation for increasing readiness towards mitigating Hg in surface water.

Design Strategies for High-Performance NH3-SCO Catalysts: Identifying and Modulating Direct Anchoring Sites for Ag on TiO2.

Ammonia (NH3) slip from diesel vehicle aftertreatment systems and internal combustion engines fueled by NH3 or NH3/H2 poses serious environmental problems. Ag-based catalysts are widely used for the selective catalytic oxidation of NH3 to N2 (NH3-SCO), and their performance is greatly dependent on the state of Ag, which is influenced by the anchoring sites on the support. Despite efforts to identify the direct anchoring sites of metal atoms on TiO2, conflicting views persist. Here, we compared the correlation between Ag dispersion and the content of hydroxyl (OH) groups or defects on TiO2 and conducted density functional theory (DFT) calculations, and the results confirmed that the surface OH groups of TiO2 serve as the direct anchoring sites for Ag. By modulating the OH group content through thermal induction, the optimal OH group content on TiO2-800 resulted in more metallic Ag nanoparticles (Ag0 NPs) in larger sizes, leading to the development of an excellent NH3-SCO catalyst. Moreover, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), kinetic studies, and DFT calculations suggested that more Ag0 NPs in larger sizes on 10Ag/TiO2-800 were conducive to O2 activation and NH3 dissociation. Our findings provide new insights for designing efficient NH3-SCO catalysts, and OH groups as direct anchoring sites could be extended to other metals and supports for the rational design of catalysts.

Modulating the Electrocatalytic CO2-CO Performance by Ag Morphology

Highly selective conversion of CO2 into CO molecules remains a major challenge in electrocatalytic CO2 reduction reactions, and metallic silver-based materials have great potential. However, the selectivity and activity of traditional silver (Ag)-based materials cannot reach the desired level, and the development of new Ag-based materials has become a hot research topic. Here, novel ag-glomerated spore-shaped Ag nanomaterials are reported for the efficient reduction of CO2 to CO. The unique nanostructures endowed with larger specific surface area, and the spore-like dispersed Ag nanoparticles (NPs) have more unsaturated Ag sites, which endowed the catalysts with higher intrinsic activity. Electrochemical tests show that spore-like Ag can obtain a Faraday efficiency (FE) of 95.6% at −1 V vs RHE, which is much higher than that of Ag nanowires (NWs) (73%) and ordinary Ag NPs (83%) synthesized in the same period. By using the three different morphologies of Ag synthesized as a research platform and statistically comparing the FE in the corresponding voltage interval, we obtained the influence of morphology effect on the selectivity of CO product production by electrocatalytic CO2 production over Ag-based catalysts, which can be further used as a guideline for catalyst development.

Highly dispersed Ag quantum dots anchored on palmitic acid/ graphitic carbon nitride composite phase change materials for enhanced photo-thermal storage

Phase change materials (PCM) have attracted much attention in the field of thermal energy storage because of exceptional heat storage capacity, stable operating temperature, and recyclability. However, organic phase change materials, represented by palmitic acid (PA), are limited by inherent leakage problem, unsatisfactory thermal responsiveness and inefficient photo-thermal storage capacity, which severely hamper the development of PCMs technology. As a means of addressing these challenges, we developed one novel support material with 2D/0D structure for palmitic acid via thermal polymerization, specifically, in which highly dispersed Ag quantum dots (Ag QDs) was firmly anchored on graphitic carbon nitride (g-C3N4). PA was further infiltrated into the layered structure of nanoporous g-C3N4/Ag QDs to successfully synthesize novel shape-stabilized PA/g-C3N4/Ag QDs composite phase change materials (CPCM). On the one hand, benefiting from the tightly stacked porous structure of g-C3N4/Ag QDs, PA is effectively encapsulated to avoid leakage problem during the solid-liquid transition with a superior adsorption capacity up to 65 %. On the other hand, the combination of g-C3N4 and Ag QDs in PA/g-C3N4/Ag QDs CPCM demonstrated a synergistic effect resulting in faster heat transfer capability and more efficient solar energy capture capability compared to pure PA, which is capable of dual utilization of heat and solar energy. The newly developed PA/g-C3N4/Ag QDs CPCM features a high melting latent heat and an appropriate phase change temperature, which are 128.35 J/g and 61.92 °C, respectively. The corresponding solidification enthalpy and temperature are 121.70 J/g and 60.02 °C. The photo-thermal conversion efficiency of the material is improved to 78.6 %, facilitating a rapid capture and storage of solar energy. Furthermore, through the optimization of the preparation process, Ag QDs are densely anchored on the surface of g-C3N4, which retains the excellent properties of metallic silver while eliminates the metal agglomeration phenomenon after repeated utilization of CPCMs. PA/g-C3N4/Ag QDs CPCM is proved to be extremely recyclable and thermally stable after massive thermal cycles. This innovative and operational encapsulation modified method significantly optimizes the practicality of phase change materials. The obtained shape-stabilized PA/g-C3N4/Ag QDs CPCM is more versatile, and its unique comprehensive properties can provide high-quality materials for photo-thermal storage systems.

In-situ exploration of divergent methane coupling pathways in dry and aqueous environments on silver and palladium heteropolyacid-titania photocatalysts

Methane, abundant but inert, contributes significantly to greenhouse gases, primarily through combustion, which emits vast amounts of CO2. Photocatalytic methane coupling at ambient temperature offers a method to convert it into ethane, a more versatile hydrocarbon. This study examines selective methane-to-ethane coupling using heterogeneous photocatalysts comprising silver and palladium salts dispersed on titania. Through a combination of ex-situ and in-situ techniques along with DFT simulations, distinct mechanisms and active phases in these catalysts are revealed. In silver catalysts, dispersed cationic Ag+ species are crucial for methane activation, while in palladium catalysts, palladium primarily exists in metallic form during coupling. Water strongly enhances coupling rates with both catalysts. DFT modeling identified methane adsorption sites, suggesting methane activation via •OH radicals, experimentally supported by EPR under in-situ conditions.

Coordination Confined Silver-Organic Framework for High Performance Electrochemical Deionization.

Silver (Ag) is deemed a promising anode material for capacitive deionization (CDI) due to its high theoretical capacity and efficient selectivity to Cl-. However, the strong volume change during the conversion reaction significantly undermines the cycling performance of the Ag electrode. Additionally, achieving well-dispersed Ag in the active matrix is challenging, as Ag electrodes prepared by conventional thermal reduction tend to agglomerate. Herein, the organic linker confinement strategy is proposed, applying metal-organic framework (MOF) chemistry between Ag nodes and organic ligands to construct Ag-based MOF. The uniform dispersion of Ag at the molecular level, confined in the organic matrix, efficiently enhances the utilization of active sites, and strengthens the interfacial stability of Ag. Consequently, the Ag-MOF for the CDI anode exhibits an excellent Cl- removal capacity of 121.52mg g-1 at 20mA g-1 in 500mg L-1 NaCl solution, and a high Ag utilization rate of 60.54%. After 100 cycles, a capacity retention of 96.93% is achieved. Furthermore, the Cl- capture mechanism of Ag-MOF is elucidated through density functional theory (DFT) calculations, ex situ XRD, ex situ Raman and XPS. This ingenious electrode design can offer valuable insights for the development of high-performance conversion electrodes for CDI applications.

The Development of the Regenerable Catalytic System in Selective Catalytic Oxidation of Ammonia with High N2 Selectivity.

Supported particulate noble-metal catalysts are widely used in industrial catalytic reactions. However, these metal species, whether in the form of nanoparticles or highly dispersed entities, tend to aggregate during reactions, leading to a reduced activity or selectivity. Addressing the frequent necessity for the replacement of industrial catalysts remains a significant challenge. Herein, we demonstrate the feasibility of the 'regenerable catalytic system' exemplified by selective catalytic oxidation of ammonia (NH3-SCO) employing Ag/Al2O3 catalysts. Results demonstrate that our highly dispersed Ag catalyst (Ag HD) maintains >90% N2 selectivity at 80% NH3 conversion and >80% N2 selectivity at 100% NH3 conversion after enduring 5 cycles of reducible aggregation and oxidative dispersion. Moreover, it consistently upholds over 98% N2 selectivity at 100% NH3 conversion after 10 cycles of Ar treatment. During the aggregation-dispersion process, the Ag HD catalyst intentionally aggregated into Ag nanoparticles (Ag NP) after H2 reduction and exhibited remarkable regenerable capabilities, returning to the Ag HD state after calcination in the air. This structural evolution was characterized through in situ transmission electron microscopy, atomically resolved high-angle annular dark-field scanning transmission electron microscopy, and X-ray absorption spectroscopy, revealing the on-site oxidative dispersion of Ag NP. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy provided insights into the exceptional N2 selectivity on Ag HD catalysts, elucidating the critical role of NO+ intermediates. Our findings suggest a sustainable and cost-effective solution for various industry applications.

Atomically dispersed Ag implanted zeolitic imidazolate Frameworks-8 for Visible-Light enhanced plasmonic opto-chemical sensor

A reliable and highly sensitive gas sensor is regarded as an indispensable approach for monitoring and ensuring human health and safety. Herein, a wet-chemical synthesis strategy is developed to fabricate a Agx/ZIF-8 heterostructure, in which Ag is encapsulated in porous zeolitic imidazolate frameworks-8 (ZIF-8). The size of Ag is highly tunable and precisely controllable in the range of single atom to 50 nm. Agx/ZIF-8 samples are found to be particularly useful in gas sensors for triethylamine (TEA) detection, and their sensing performance can be further enhanced via downsizing the Ag nanoparticle (NPs) into the atomical level, thus realizing the maximum utilization of Ag element as well as achieving the most outstanding sensing performance. As a result, the optimal sample Ag(SAs-1mL)/ZIF-8 with the atomic Ag, shows relatively lower operating temperature (290 °C), high response (142), superior detection limits (0.41 ppm), and ultra-fast response/recovery time (4/15 s), which are significantly better than the sample Ag(0.5nm-0.25mL)/ZIF-8 with Ag nanoclusters (ca. 0.5–1 nm in size) and other Agx/ZIF-8 samples with larger Ag nanoparticles (range from ca. 2 nm to 50 nm in diameter). Moreover, benefiting from the localized surface plasmon resonance (LSPR) effect, the response of Ag(SAs-1mL)/ZIF-8 sensor is greatly increased by as much as 440 % when it illuminated with the 405 nm LED, where the light wavelength resonates with the plasmon frequency of Ag. This work highlights the crucial role of size effect of noble metal, proves the LSPR effect of atomic level Ag, and offering an attractive strategy to improve sensitivity and stability of gas sensors based on single atoms.

Atomic level dispersed nickel coupled with silver nanoparticle to boost the efficiency of CO2 conversion to CO via spin electrons regulation

Modulating the electronic configuration by coupling multi-scale active sites for electrocatalytic conversion of CO2 to CO is extremely challenging in terms of structural analysis and mechanism elucidation. Herein, a catalyst NiAD/AgNPs@CN with both atomic-level dispersed Ni and Ag nanoparticles on N-doped carbon substrate has been designed to reveal the true active sites and catalytic mechanism in complex materials. NiAD/AgNPs@CN exhibits CO Faraday efficiency (FECO) of 99.97% at −0.88 V (vs. RHE) in H-type cell and 91.77% FECO with a high current density of 79.70 mA/cm2 in flow cell. DFT calculations show that the tiny change in the energy level of spin electrons at atomic sites has a significant impact on the CO2 activation. The regulation of atomic Ni on Ag sites is the main reason for improving CO2RR performance. This work gives a new understanding on the catalytic mechanism of composite materials structured by atomic-level dispersed metal and nanoparticles.

In Situ Growth of MOF from Wood Aerogel toward Bromide Ion Adsorption in Simulated Saline Water.

Utilizing metal-organic framework (MOF) materials for the extraction of bromide ions (Br-) from aqueous solutions, as an alternative to chlorine gas oxidation technology, holds promising potential for future applications. However, the limitations of powdered MOFs, such as low utilization efficiency, ease of aggregation in water, and challenging recovery processes, have hindered their practical application. Shaping MOF materials into application-oriented forms represents an effective but challenging approach to address these drawbacks. In this work, a novel Ag-UiO-66-(OH)2@delignified wood cellulose aerogel (CA) adsorbent is synthesized using an oil bath impregnation method, involving the deposition of UiO-66-(OH)2 nanoparticles onto CA and the uniform dispersion of Ag0 nanoparticles across its surface. CA, characterized by the intertwined cellulose nanofiber structure and a highly hydrophilic surface, serves as an ideal substrate for the uniform growth of UiO-66-(OH)2 nanoparticles, which, in turn, spontaneously reduce Ag+ to form distributed Ag0 nanoparticles due to the abundant hydroxyl groups provided. Leveraging the well-defined biological structure of CA, which offers excellent mass transfer channels, and the highly dispersed Ag adsorption sites, Ag-UiO-(OH)2/CA exhibits remarkable adsorption capacity (642 mg/gAg) under optimized conditions. Furthermore, an integrated device is constructed by interconnecting Ag-UiO-(OH)2/CA adsorbents in series, affirming its potential application in the continuous recovery of Br-. This study not only presents an efficient Ag-UiO-(OH)2/CA adsorbent for Br- recovery but also sheds light on the extraction of other valuable elements from various liquid ores.

Controlling cisplatin release by synergistic action of silver-cisplatin on monodispersed spherical silica for targeted anticancer and antibacterial activities

Recently, metal-based nanoformulations have been explored for targeted cancer therapeutics. In this study, synergistic therapeutic action of silver (Ag)-cisplatin nanoparticles loaded on monodispersed spherical silica (MSS) was investigated to evaluate anti-cancer (HCT-116 and HeLa cells) and antibacterial activity (P.aeruginosa, and S.aureus). Four different wt% of Ag (1, 2, 4 and 6 wt%) was loaded on MSS using a wet impregnation method. Characterization using XRD revealed the cubic phase of Ag nanoparticles with (111), (200) and (220) plane on MSS. The chemical state, dispersion of Ag and synergistic cohabitation with cisplatin (Cpt) was identified using diffuse reflectance UV–visible spectroscopy (DR-UV Vis), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM-EDS) and High-resolution transmission electron microscopy (HR-TEM). Zeta potential analysis indicated an increase in hydrodynamic diameter with high colloidal stability (–23.3 to −28.5 mV). The percentage cumulative Cpt release was studied using automated Franz cell and dialysis membrane technique. The effect of Cpt release on 4 wt%Ag impregnated on different shaped supports was investigated using cubic SBA-16 (Santa Barbara Amorphous), MFI type Ti-ZSM-5 (Zeolite Socony Mobil #5), hexagonal mesosilicalite, nanotube halloysite, and Ag-silicalite, respectively. Drug release study indicates that Ag loading controls the Cpt release. The kinetics of drug release for the different formulations was examined using Korsmeyers-Peppas model. Release constant (k) and release exponent (n) were utilized for the rate of drug release and diffusion mechanisms, respectively. The in vitro study revealed an efficient interaction of nanoformulations promoting both antibacterial and anticancer activities.

Identification of Direct Anchoring Sites for Monoatomic Dispersion of Precious Metals (Pt, Pd, Ag) on CeO2 Support.

Monoatomic dispersion of precious metals on the surface of CeO2 nanocrystals is a highly practical approach for dramatically reducing the usage of precious metals while exploiting the unique properties of single-atom catalysts. However, the specific atomic sites for anchoring precious metal atoms on the CeO2 support and underlying chemical mechanism remain partially unknown. Herein, we show that the terminal hydroxyls on the (100) surface are the most stable sites for anchoring Ag atoms on CeO2 , indicating that CeO2 nanocubes are the most efficient substrates to achieve monoatomic dispersion of Ag. Importantly, the newly identified chemical mechanism for single-metal-atom dispersion on CeO2 nanocubes appears to be generic and can thus be extended to other precious metals (Pt and Pd). In fact, our experiments also show that atomically dispersed Pt/Pd species exhibit morphology- and temperature-dependent CO selectivity in the catalytic CO2 hydrogenation reaction.

Identification of Direct Anchoring Sites for Monoatomic Dispersion of Precious Metals (Pt, Pd, Ag) on CeO2 Support

AbstractMonoatomic dispersion of precious metals on the surface of CeO2 nanocrystals is a highly practical approach for dramatically reducing the usage of precious metals while exploiting the unique properties of single‐atom catalysts. However, the specific atomic sites for anchoring precious metal atoms on the CeO2 support and underlying chemical mechanism remain partially unknown. Herein, we show that the terminal hydroxyls on the (100) surface are the most stable sites for anchoring Ag atoms on CeO2, indicating that CeO2 nanocubes are the most efficient substrates to achieve monoatomic dispersion of Ag. Importantly, the newly identified chemical mechanism for single‐metal‐atom dispersion on CeO2 nanocubes appears to be generic and can thus be extended to other precious metals (Pt and Pd). In fact, our experiments also show that atomically dispersed Pt/Pd species exhibit morphology‐ and temperature‐dependent CO selectivity in the catalytic CO2 hydrogenation reaction.

Ionic liquid dopant induced 3D hierarchical CuO nanostructures with doped heteroatoms and highly dispersed Ag for electrochemical upgrading of 5-hydroxymethylfurfural

The electrocatalytic 5-hydroxymethylfurfural oxidation reaction (HMFOR) has received increasing attention due to its carbon–neutral and value-added chemical properties, and the development of electrocatalyst with highly active and selective is crucial. Highly dispersing metal atoms throughout the catalyst can maximize the catalytic efficiency. Here, we synthesized a 3D hierarchical CuO nanostructure induced by ionic liquid with heteroatoms doping and Ag dispersing (Ag-CuO@IL), and this self-supported catalyst can reach 10 mA cm−2 at only 1.33 V vs RHE and achieved HMF conversion of 98.5 %, FDCA yield of 97.1 % and Faraday efficiency of 92.2 %. The excellent catalytic performance of Ag-CuO@IL for HMFOR is attributed to the doped heteroatoms derived from ILs to promote electron redistribution and the generated oxygen vacancies induced by IL anions to highly disperse Ag. Also, the catalyst was the nanosheet-assembled spherical clusters with 3D nanostructure, which exposed a large number of active sites. Density functional theory calculations showed that Ag-CuO@IL possessed moderate adsorption strengths of HMF and OH–, thus facilitating the desorption of the products in the reaction process. The design that induced by ionic liquid dopant not only provides an effective and green mean for HMFOR, but also has the large potential to guide the synthesis of other catalysts with improved performances in various applications.

Simple method for optical characterization of surface agents on conjugated silver nanoparticles

In this study, a simple formula has been proposed to calculate the refractive index of surface agents of silver nanoparticles (Ag NPs) by using the plasmonic peak of the absorption spectra of dispersed Ag nano-colloids. The basis of the study is the shift in the localized surface plasmon resonance (LSPR) of Ag NPs upon alteration of surface agents. The color changes in a typical metal nano-colloid are mainly due to the shift in the LSPR, which is caused because of electrical interactions of surface agents on the particles. There are some theoretical models to simulate the absorption spectrum, but using these methods to evaluate the plasmonic peak is not facile for a wide range of users. Here, the required simulations were performed for different values of the refractive index of surface agents and particle sizes, and the absorption spectrum and dispersive curves were accordingly plotted. A simple formula was obtained between the wavelength of the plasmonic peak, the refractive index of the shell of surface agents, and the ratio of the hydrodynamic diameter to Feret size of the particles (R0). The refractive index of the surface agents can be calculated by n2=λmax−(202.3R02−748.6R0+947.4)−152.2R02+561.3R0−405.1, where λmax (in nanometer) is the wavelength of the absorption peak due to LSPR. This method can pave the way for experimenters to obtain the refractive index and consequently the type of surface agents around Ag NPs without the need for numerical or mathematical operations. It can also be useful in analyzing the spectral diagnosis of biological agents such as viral antibodies and antigens.

Conductive cotton fabric fabricated using stable Ag/MXene colloidal solution and PDMS for heating and electromagnetic shielding

Cracking of conductive coatings is a primary cause of the poor durability of conductive fabrics. To address this, an Ag/MXene colloidal solution was prepared, which was stable owing to the evenly dispersed Ag particles on the MXene sheet structure. A cotton fabric sample was then coated with Ag/MXene using a dipping method, which resulted in excellent electrical conductivity. Finally, the Ag/MXene conductive coating on the polydimethylsiloxane (PDMS)-covered fabric significantly improved the conductive durability of the fabric. The finished cotton fabric exhibited excellent conductive properties, with a surface resistance of 13.9 ± 0.3 Ω/sq. In addition, the finished cotton fabric exhibited excellent mechanical durability against bending, folding, and strain. Therefore, finished cotton fabrics with excellent electrical conductivity and durability have great potential for application in wearable textiles and flexible sensors.