Metals Ag Research Articles

Electric field-assisted dissolution of bimetal-dielectric multilayer systems

The electric field-assisted dissolution (EFAD) of Ag and Au metal island films (MIFs) in multilayer structures is investigated. The samples consist of Au and Ag MIFs separated by SiO2 layers deposited on soda-lime glass substrates. The samples were subjected to two types of process: a) thermal annealing at 200°C, and b) application of 500 V dc voltage at 200°C. Spectroscopic ellipsometry and secondary ion mass spectrometry were used to track sample changes. It is shown that thermal annealing induces ion exchange between Ag and Na ions from the glass, leading to partial dissolution of Ag MIFs and Ag being incorporated in the glass and Au MIFs. EFAD process leads to the partial or complete dissolution of Ag films depending on the process duration, while Au dissolution turns out to be more difficult. The optical properties are consistent with the compositional changes and additionally suggest MIF morphology modifications. Numerical simulations of ion drift and diffusion reveal the importance of ion exchange during thermal annealing to enable an efficient MIF dissolution. Overall, the study helps to understand the EFAD of different metals in complex systems and provides insights for the application of this technique in systems containing several metals.

Remarkably enhanced hydrogen evolution of g-C3N4 nanosheet under simulated sunlight via AgPt alloy co-catalyst with low amount of Pt

The development of low-cost co-catalysts matched with proper photocatalysts to enhance the photocatalytic hydrogen evolution performance is highly demanded. Herein, the AgPt bimetallic alloy nanoparticles with small amounts of Pt were decorated on g-C3N4 nanosheets (AP-CN) via the NaBH4 reduction method, which were further used as catalysts towards photocatalytic hydrogen evolution from water under AM1.5 irradiation. Compared to mono-metallic co-catalysts, bimetallic AgPt alloy nanoparticles exhibited excellent co-catalytic performance. The optimum AP-CN photocatalyst with 0.5 wt% Pt exhibited photocatalytic hydrogen evolution rate of 3507.89 μmol g−1·h−1, which even surpassed that of the commonly-used photocatalyst 1.0 wt% Pt in-situ photo-deposited on g-C3N4. Meanwhile, the AP-CN showed excellent photocatalytic activity and durability after four experimental cycles. The enhanced activity and stability could be attributed to the synergistic effect between plasmonic metal Ag and Pt, which promoted the transfer and separation of photoinduced charge carriers. Besides, the theoretical results based on DFT calculation also verified that AgPt alloys have better performance of desorbing hydrogen and adsorbing H atoms. This work provides a feasible idea for the development of inexpensive and efficient bimetallic co-catalysts for photocatalytic hydrogen production through water splitting.

Influence of Noble Metals on the Microstructure and Properties of Biodegradable Mg-Nd-Zr Alloy

In this work, the approach to improve the mechanical properties of a biodegradable Mg-Nd-Zr alloy through modification with noble metals (Ag and Au) was proposed. The separate and combined influence of silver and gold on the macro- and microstructure of the alloy was studied. A qualitative and quantitative assessment of the structural components of the alloy was carried out. It was shown that when modifying the melt, noble metals form the complex intermetallic phases which served as additional crystallization centers. It has been established that adding 0.05 to 0.1 wt.% of noble metals to Mg-based alloy increase the volume fraction of intermetallic compounds by ~1.5 times, shifting them towards smaller size groups with the simultaneous formation of spherical intermetallic compounds. The latter are located in the center of the grain proving them to be the additional nucleation sites. It was shown that complex modification (0.1% Ag + 0.1% Au) of a Mg-based alloy refined its structural components by ~1.5 times, increasing the strength by ~20%, and ductility by ~2 times due to the formation of the intermetallic compounds. The proposed technology for modifying cast biodegradable Mg-based alloys is feasible to be used for the manufacture of implants for osteosynthesis.

Concentration of Heavy Metals in Pollen and Bees Osmia bicornis L. in Three Different Habitats in the Łowicz District in Central Poland

The aim of our research was to compare the levels of pollution in different habitats based on the concentrations of heavy metals found in pollen and the organisms of Osmia bicornis L. bees in three habitats: orchards, berry plantations, and urban habitats (near by power plant, landfill, residential areas, and heavy vehicle traffic). The concentration of Ag, Cd, Cu, Fe, Mn, Ni, Pb and Zn were determined. Samples were quantified using flame atomic absorption spectrophotometry (AAS), with evaluations being carried out three times for each sample. Bee nests were also analyzed concerning reproduction and the presence of parasites. There were no significant differences in the content of heavy metals Ag, Cd, Cu, Fe, Mn, Ni, Pb and Zn in pollen samples between the three habitat types. Bee samples differed only in their Zn content, which was significantly higher in orchards (2.67 mg/kg) than urban habitats (0.80 mg/kg) and berry plantation (0.94 mg/kg). Habitat type had no effect on most bee reproductive parameters (percentage of occupied nest tubes, population growth). Our results show that bees pollinating crops in, for example orchards or berry plantations are exposed to heavy metals to a similar extent to those urban areas.

Optical and electrical properties of thin films of MnS/metal/MnS for photocatalysis and gas sensing applications

Thin films of manganese sulfide (MnS) with interlayers of silver and copper were prepared using the thermal evaporation technique for applications in photocatalysis and gas sensing. The structure, morphology, optical, and electrical properties of the deposited films were described by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), UV/VIS/NIR spectrophotometer, and two-probe technique. Various parameters such as crystallite size, micro-deformation, dislocation density, optical energy gap, refractive index, extinction coefficient, Urbach energy, dielectric constants, dispersion parameters, activation energy, mobility and, Seebeck coefficient were determined. According to the experimental results, XRD analysis revealed that the MnS powder has a crystalline structure with a cubic phase. While the pure MnS thin films exhibited an amorphous structure, the addition of metals (Ag and Cu) as interlayers resulted in a distinct crystallinity. The pure MnS films had a direct optical energy gap of 3.17 eV, which changed to an indirect transition with energy gaps of 2.43 eV and 2.50 eV when Ag and Cu interlayers were added, respectively. The refractive index values and dispersion of the films depended on the type of interlayer, with all films exhibiting normal dispersion. The temperature dependence of the sheet resistance indicates a semiconducting behavior of the samples, and the addition of the interlayer metal reduced the sheet resistance. Overall, the results suggest that thin films of MnS and MnS/metal/MnS hold promise for organic photocatalysis and gas sensor applications, respectively.

Ecological and Risk Assessment of Heavy Metals in a Diverse Industrial Area of Al-Akrasha, Egypt

This study was conducted in one of a diverse industrial area in Al-Akrasha, Egypt. Concentrations of select metals (Cu, Pb, Cr, Ni, Zn, Mn, Cd, Al, Ag, As, B, and Fe) were evaluated in ambient PM10 and surface soils at nine sites. Random samples of fresh edible tilapia fish were collected from Ismailia Canal at two sites near the Al-Akrasha region. In addition, blood and hair samples were collected from workers and residents living in Al-Akrasha as biomarkers of contamination with these metals. The ecological and health risks of these metals to the workers and residents living in the Al-Akrasha region were assessed. The results showed that heavy metal levels in the ambient air (PM10) of the Al-Akrasha region were higher than the national and international guidelines. There was a very high degree of contamination (CD > 32) of the surface soil in the Al-Akrasha area, which can be attributed to industrial activities emissions, mostly from smelters and the subsequent deposition on the surface soil. Ingestion was the dominant pathway for metals to enter the human body in the Al-Akrasha region. Adults have a higher daily intake and exposure risk than infants and children.

3DOM BiOI/TiO2 composites modified by metal Ag with broad spectrum response for photocatalytic degradation and water splitting

In order to improve the photocatalytic performance of TiO2 and expand its absorption range in the visible light region, depositing noble metals, constructing the p-n heterojunction and controlling the morphology were used to modify TiO2. First, the TiO2 photocatalyst with a three-dimensional ordered macroporous structure was prepared by vacuum impregnation combined with calcination, and then the 3DOM Ag/BiOI/TiO2 composites were successfully prepared by the in-situ deposition and photoreduction. The characterization results show that the composites present a large number of open and transparent pore structures. The pore wall is formed by stacking TiO2 nanoparticles, with BiOI and Ag nanoparticles evenly distributed on the surface of the pore wall and in the macroporous framework, which expands the specific surface area of 3DOM TiO2 and provides more active sites for the reaction. The introduction of BiOI and Ag expands the visible light response range and improves the light utilization efficiency. Furthermore, the formation of the Schottky barrier and the internal electric field formed by the p–n heterojunction effectively promotes the interfacial electron transfer and suppress the electron–hole recombination, thereby generating more active species during the photocatalytic process. The experimental results of multi-mode photocatalytic degradation of methyl orange (MO) also show that 3DOM Ag/BiOI/TiO2 photocatalyst has the best photocatalytic degradation activity. In addition, different samples were tested for hydrogen production by photolysis of water under simulated sunlight conditions, and the results show that 3DOM Ag/BiOI/TiO2 has the best hydrogen production ability of photolysis of water. The excellent performance of multi-modal photocatalytic degradation of organic pollution and high photohydrogen production activity in 3DOM Ag/BiOI/TiO2 composites is attributed to the synergistic effect between the introduction of metallic Ag, the unique 3DOM structure, and the p–n heterojunction.

Dual improvement in sensitivity and selectivity of SnO2 nanospheres for formaldehyde sensing based on molecular imprinting and Ag doping

In order to develop a gas sensitive material with both high sensitivity and good selectivity, Ag–SnO2 MIPs were designed and synthesized by adopting molecular imprinting technique. Specifically, SnO2 nanospheres synthesized through hydrothermal method were used as substrate. Then, Ag–SnO2 was assembled by decorating nano-sized Ag on the surface of SnO2 nanospheres. Molecular imprinting modification with formaldehyde as template molecules was in next conducted to get Ag–SnO2 MIPs. The morphology, valence and crystal structure of the samples were characterized using SEM, XRD, TEM and XPS. The characterization results showed that uniform SnO2 nanospheres were successfully synthesized with metallic Ag distributed on the surface, and the molecular imprinting process did not change the morphology of the material. According to gas sensing measurement results, it was found that the sensor based on Ag–SnO2 MIPs exhibited superior formaldehyde sensing performance. The molecular imprinting modification effectively improved the sensor's selectivity towards formaldehyde gas. Owning to the catalytic property of Ag, the sensing response of sensor was greatly enhanced. Additionally, Ag–SnO2 MIPs also exhibits high reproducibility and long-term stability.

Transforming a volcanic rock powder waste into an efficient adsorbent to remove dyes (acid green 16 and acid red 97) and metals (Ag+, Co2+, and Cu2+) from water.

This study searched for the best synthesis route for producing an adsorbent from the alkaline fusion of volcanic rock powder waste. The samples synthesized under different conditions of temperature and alkalizing ratio/precursor material, nine in total (NP.F, NP.F1, NP.F2, ...NP.F8 ), were used in the adsorption of acid green 16 (AG 16) and acid red 97 (AR 97) dyes and Ag+, Co2+, and Cu2+ ions. Subsequently, the 22 central composite rotational design (CCRD) was applied, and the effects of the alkalizing ratio (NaOH)/volcanic rock (VR) and temperature (T) on the synthesis process were analyzed in terms of their influence on the physical properties of the materials and in the process of adsorption of contaminants. From the experimental design, it can be seen that the independent variables alkalizing ratio/volcanic rock and temperature greatly influence the characteristic and synthesis of adsorbent materials by alkaline fusion, which in turn reflects on the results achieved in the adsorption of contaminants. Therefore, the temperature of 550 °C and NaOH/VR ratio equal to 1 was the most satisfactory synthesis route to obtain high values of adsorption capacity (q, mg g-1) and removal (R, %) for all studied contaminants, as well as the optimization of the physical characteristics of the material. For example, the adsorption capacity of dye AG 16 was 49.1 mg g-1, and for Ag+ was 66.2 mg g-1, while the removal percentages were 97.6% and 93.4%, respectively. This approach made it possible to transform volcanic rock powder wastes into an efficient adsorbent to treat contaminated waters with dyes and metals.

The study of acidic/basic nature of metallothioneins and other metal-binding biomolecules in the soluble hepatic fraction of the northern pike (Esox lucius)

Since fish metalloproteins are still not thoroughly characterized, the aim of this study was to investigate the acidic/basic nature of biomolecules involved in the sequestration of twelve selected metals in the soluble hepatic fraction of an important aquatic bioindicator organism, namely the fish species northern pike (Esox lucius). For this purpose, the hyphenated system HPLC-ICP-MS was applied, with chromatographic separation based on anion/cation-exchange principle at physiological pH (7.4). The results indicated predominant acidic nature of metal-binding peptides/proteins in the studied hepatic fraction. More than 90 % of Ag, Cd, Co, Cu, Fe, Mo, and Pb were eluted with negatively charged biomolecules, and >70 % of Bi, Mn, and Zn. Thallium was revealed to bind equally to negatively and positively charged biomolecules, and Cs predominantly to positively charged ones. The majority of acidic (negatively charged) metalloproteins/peptides were coeluted within the elution time range of applied standard proteins, having pIs clustered around 4–6. Furthermore, binding of several metals (Ag, Cd, Cu, Zn) to two MT-isoforms was assumed, with Cd and Zn preferentially bound to MT1 and Ag to MT2, and Cu evenly distributed between the two. The results presented here are the first of their kind for the important bioindicator species, the northern pike, as well as one of the rare comprehensive studies on the acidic/basic nature of metal-binding biomolecules in fish, which can contribute significantly to a better understanding of the behaviour and fate of metals in the fish organism, specifically in liver as main metabolic and detoxification organ.

Photocatalytic Degradation of Chlorinated Hydrocarbons: The By-Product of the Petrochemical Industry Using Ag-Cu/Graphite Bimetallic Carbon Nitride

In this study, the author improved and modified g-C3N4 by doping it with the metals Ag and Cu, which changed the photochemical properties of g-C3N4, narrowed the band gap, and improved the photocatalytic performance regarding quantum efficiency. Organic hydrocarbons such as 1,2-dichloroethane (DCE) are very stable prepared materials produced as intermediates to obtain polyvinyl chloride, and the prepared photo-catalyst is an innovative method for extreme decomposition of chlorinated hydrocarbons. However, some significant results were obtained using different analysis techniques. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) showed that the addition of Ag and Cu-NPS partially altered the structure of pure graphitic carbon nitride (g-C3N4-Pure). Scanning electron microscopy (TEM) analysis revealed that the morphological features of Ag-Cu/g-C3N4 contain quantum dots of Ag and Cu nanoparticles in addition to 2d-g-C3N4. The better separation of the photo-generated charge carriers is attributed to better photoactivity in the case of 0.3 g Ag-Cu/g-C3N4 with a reaction time of less than 30 min. Furthermore, the Ag-Cu/g-C3N4 recycling experiment showed that the catalyst remained stable after three stages of the pyrolysis experimental cycle. Another clear indicator of DCE degradation is the measurement using the titration of the Cl ions released by the decomposition.

Critical assessment of a TiO2-Ag-ZnO nanocomposite photocatalyst on improved photocatalytic activity under mixed UV-visible light

In recent years, semiconductor photocatalysts such as zinc oxide (ZnO) and titanium dioxide (TiO2) have been studied to utilize solar light for energy production and environmental remediation. However, their wide band gap energy and fast charge recombination limit their practical applications. So far, various approaches, such as noble metal incorporation, metal oxide coupling, and the design of Z-scheme photocatalyst systems, among others, have been explored to enhance the lifetime of photogenerated charge carriers in ZnO and TiO2. In this study, a novel TiO2-Ag-ZnO nanocomposite photocatalyst has been successfully synthesized by a combination of wet chemistry, photochemistry, and plasma-based processes. Simple spin coating of ZnO thin films was coupled with subsequent photodeposition of metallic Ag nanoparticles (NPs). Afterward, well-uniform TiO2 NPs (roughly 18 nm) were deposited on this unique Ag-ZnO surface via a gas cluster aggregation source (GAS) process. The results showed that the activity of the ZnO photocatalyst under mixed UV-visible light was significantly increased by the TiO2 and Ag contributions. A single mechanism to be responsible for the photocatalytic activity can be excluded. Instead, a critical assessment of the possible mechanisms corresponding to the different interfaces present at the TiO2-Ag-ZnO surface including a Z–scheme is provided.

A comparative analysis of fiber-based surface plasmonic resonance sensors utilizing various fluoride glass cores and the influence of different oxide layers on the sensor performance in near-infrared

In a fiber-based surface plasmon resonance (SPR) sensor, with multiple layers, including fluoride glass core, cladding, metal (Ag), graphene and alcohols as the analyte, we focused on comparing the effects of 12 different types of fluoride glass cores from three main groups of fluorozirconate (ZrF4-based), fluoroaluminate (AlF3-based) and fluoroindate (InF3-based). The comparison was conducted to evaluate the sensor’s sensitivity and figure of merit (FOM) at specific near infrared (NIR) wavelengths (785 nm, 852 nm, 895 nm and 980 nm) while keeping other parameters constant. The highest FOM was consistently observed at the wavelength of 980 nm for all three categories of fluoride glass cores. Among them, the fluoride glass core IZBSC (40 InF3-20 ZnF2-15 BaF2-20 SrF2-5 CaF2) from InF3-based group presented the largest FOM = 1459.15 RIU−1. Furthermore, we observed that the FOM of the fiber types belonging to the ZrF4-based and InF3-based categories increased with the wavelength. However, the fluoroaluminate fibers showed different trend and they also exhibited the smallest FOM values at 852 nm, 895 nm and 980 nm wavelengths. To enhance the sensor’s performance, we explored the incorporation of an oxide layer into the to the SPR sensor with a ZBLAN (55.8 ZrF4-14.4 BaF2-5.8 LaF3-3.8 AlF3-20.2 NaF) core. We analyzed the effects of various oxide coatings (Sc2O3, Lu2O3, Al2O3, GeO2, TeO2, Ta2O5, MgO, TiO2, and ZnO) on the Ag layer, which has not previously studied, to the best of our knowledge. Among the different oxide coatings, the Ta2O5 layer, with optimized thickness, exhibited a significant enhancement, achieving FOM of 1631.43 RIU−1.

Green Synthesis of Silver Nanoparticle Using Aqueous Leaf Extract of Barleria noctiflora and its Bioactive Efficacy

For millennia, silver has been known to have powerful antibacterial effects. Topical silver dressings are now commonly used to treat infections in burns, open wounds, and persistent ulcers. Because pathogenic organisms evolve on a daily basis as a result of mutation and antibiotic resistance, the manufacture and investigation of nanoparticles for use in antibacterial garments, burn ointments, and medical device coatings is an important industrial topic of nanoscience. This is the first study on the synthesis of silver nanoparticles from leaf extract of the medicinal plant Barleria noctiflora. Through the use of FT-IR, UV-visible spectrum analysis, XRD analysis, SEM EDAX, and antimicrobial potential, the bioreduced nanoparticles were discovered and verified. The greatest absorption peak in the UV-visible spectrum examination was seen at 480 nm for the silver nanoparticles. Twelve distinct peaks were identified in the FTIR spectra of biogenic AgNPs, located at 3127.21, 1624.74, 1400.35, 1155.96, 1021.11, 906.70, 825.31, 718.73, 669.69, 538.93, 457.21, and 417.49 cm-1. Peaks at 2θ values of 10.545, 19.000, 21.137, 22.033, 23.370, 26.691, 31.507, and 33.747, corresponding heights of 23.40, 235.26, 750.78, 357.58, 335.93, 171.19, 186.87, and 115.38cts, respectively, indicated by XRD analysis that the silver particles generated in our experiments were nanocrystals. The silver nanoparticles were tested with "d" spacing values of 8.38940, 4.67087, 4.20328, 4.03422, 3.80651, 3.33986, 2.83949, and 2.65601. SEM spectral analysis revealed oval AgNPs with a size range of 20 m. Metallic nanoparticles generated from Barleria noctiflora were tested for antibacterial activity against gram-positive and gram-negative pathogens such as E. Coli, Staphylococcus aureus, and the fungi Aspergillus niger and Candida albicans using the disc diffusion method. Surprisingly, metallic Ag nanoparticles had strong inhibitory zones against the selected illnesses.

Round-the-clock photocatalysis of plasmonic Ag-enhanced Z-scheme heterojunction material Sr2MgSi2O7:(Eu, Dy)/g‑C3N4@Ag under visible-light irradiation

Self-luminous plasmonic photocatalysts Sr2MgSi2O7:(Eu, Dy)/g-C3N4@Ag were prepared using high-temperature sintering and photodeposition. Compared with pristine g-C3N4, the energy storage property of the long-afterglow luminescent material Sr2MgSi2O7:(Eu, Dy) and the noble metal Ag with localized surface plasmon resonance effect enable the composites to perform more excellent in round-the-clock photocatalytic degradation. The improved photocatalytic performance is attributed to the formation of Z-scheme heterojunction by Sr2MgSi2O7:(Eu, Dy) and g-C3N4, and to the fact that the loaded Ag nanoparticles broaden their visible-light absorption range and enable faster carrier transfer and more productive separation of electron-hole (e−-h+) pairs. According to various characterization outcomes and density functional theory calculations, possible pathways for electrons transfer during the photocatalytic reaction and possible mechanisms for the increasing of photocatalytic performance of Sr2MgSi2O7:(Eu, Dy)/g-C3N4@Ag composites are proposed. This work provides a targeted way for the optimization of round-the-clock heterojunction photocatalysts.

Highly sensitive ethanol sensor based on Ag NP-modified SnO2–In2Sn2O7-x ternary composite enhanced by synergistic catalysis

In this paper, the noble metal Ag-modified SnO2–In2Sn2O7-x ternary nanocomposites were designed to detect ethanol efficiently. Firstly, the SnO2–In2Sn2O7-x nanocomposites were synthesized by a simple hydrothermal method, and the microstructure of the SnO2 nanomaterials were adjusted by controlling the content of In2Sn2O7-x. With the increase of In2Sn2O7-x content, the morphology of the synthesized SnO2–In2Sn2O7-x composites gradually tends to be regular with porous spherical morphology. In the same synthesis conditions, the porous spherical morphology of SnO2–In2Sn2O7-x composites was more uniform at 0.5 at% of In element content, and the distribution in the material was more homogeneous and dispersed, which was conducive to the diffusion and adsorption of gases on the surface of the material, as well as to the loading of Ag nanoparticles. On this basis, the Ag nanoparticles were successfully modified through the chemical reduction route, and the Ag nanoparticles modified SnO2–In2Sn2O7-x with 0.5 at% In elemental content ternary nanocomposites were prepared. X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive Spectrometer (EDS) were used to characterize the structure and morphology of the prepared gas-sensitive materials. The gas-sensing performance of SnO2, In2Sn2O7-x, SnO2–In2Sn2O7-x, and Ag-modified SnO2–In2Sn2O7-x sensors were tested systematically. The results showed that the 1.5 wt% Ag-modified SnO2–In2Sn2O7-x nanocomposites with 0.5 at% In elemental content have good gas-sensing properties. The response of the sensor to 100 ppm ethanol vapor can reach 666 at the optimal operating temperature of 250 °C, and the response time is shortened to 45 s. It has good sensitivity for ethanol gas, and the minimum detectable gas concentration is reduced to 500 ppb. The improved performance of the sensor is primarily due to the construction of the heterogeneous interface of the SnO2 and In2Sn2O7-x and the catalytic synergism of the noble metal Ag.

Simultaneous Extraction of Valuable Metals from Iron-Containing Residues by Selective Chlorination and Evaporation

In different nonferrous metal-producing industry sectors, the impurity element iron has to be removed from the process solution. Examples for the arising residues are jarosite or goethite precipitates from nickel or zinc production but also red mud from aluminum production. Regardless of environmental concerns, the material is landfilled in almost any case, although valuables such as indium, silver, nickel, or zinc are present in considerable amounts. Within the presented research, a low carbon dioxide emitting multi-metal recovery from such iron-containing residues by means of a selective chlorination extraction has been fundamentally evaluated by experiments but also by comprehensive thermodynamic calculations. The paper summarizes the thermodynamic fundamental concept exploited to separate the dominating iron matrix from the valuable elements and shows verification experiments in a lab size of several grams. Through thermodynamic calculations and small-scale experiments with pure metal oxides and sulfates, it has been proven that the metal chlorides AlCl3∙6H2O, FeCl3∙6H2O, and MgCl2∙6H2O are viable and effective reactants for chlorination. In trials with actual industrial iron precipitation residues from the zinc industry, especially, the use of MgCl2∙6H2O and FeCl3∙6H2O leads to high extraction rates for the investigated valuable metals Ag, Au, Bi, Cu, In, Pb, Sn, and Zn.

Recent Advances in the Preparation and Application of DNA-Encoded Metal Nanoclusters

DNA as an intriguing organic ligand has been widely employed for synthesizing metal nanoclusters and engineering their properties. This review aims to present recent progress on DNA-encoded metal (Ag, Cu, Au, Ag/Pt, Cu/Ag, etc.) nanoclusters (DNA-MNCs), focusing on their applications in the fields of analysis, logic operation, and therapy based on properties including fluorescence, electrochemiluminescence (ECL), and antibacterial and catalytic activity, and summarizes the attractive features of the latest research. The key points are briefly described as follows. (1) Analytical systems have been constructed based on fluorescence regulation, and nuclease-assisted and enzyme-free amplification strategies have been extensively adopted with fluorescent DNA-MNCs for amplified analysis. (2) DNA-MNCs may play more than one role (emitter, quencher, or catalyst) in ECL-based analytical systems. (3) Apart from antibacterial activity, DNA-MNCs also possess apparent catalytic capability, such as enzyme-like activity (i.e., nanozymes), which has been applied in colorimetric systems. (4) Reversibly regulating the catalytic activity of DNA-MNCs has been attained with DNA systems. It is believed that through in-depth investigation of the relationship between atomic structure and property, more novel DNA-MNCs will be explored and applied in the future.

Cyclic Voltammetry and Photoluminescence Studies of Ag-doped ZnO Nanoparticles

Introduction: Herein, we prepared Zinc oxide (ZnO) and silver (Ag) doped ZnO nanoparticles (NPs) using a simple, fast, effective and economic coprecipitation method. The superior characteristics in the nanoscale range of ZnO encourage us to work on the ZnO NPs. Also, Ag has long been employed for its antibacterial qualities. X-ray diffraction (XRD) results indicate a hexagonal wurtzite structure of ZnO NPs and an additional peak corresponding to the metallic Ag phase in the Ag-ZnO sample. The EDAX elemental mapping confirms the uniform distribution of Ag in ZnO NPs. Photoluminescence (PL) spectroscopy investigates electronic structure and defects in NPs.ic co-precipitation method and study of Cyclic Voltammetry and Photoluminescence characteristics. Method: According to the PL study, the strong photoluminescence NBE observed at 393 nm, indicating the high crystalline quality of the material and broad blue-green emission at 467 nm and green-yellow emission at 560 nm were attributed to the Zn interstitial and oxygen vacancy defects present in ZnO NPs. Measurements from cyclic voltammetry (CV) demonstrate approximately symmetric peaks related to anodic and cathodic behaviours of the NPs based electrode. Result: For ZnO sample, the anodic peak was found at 0.49 V and cathodic at 0.29 V, whereas, for Ag-ZnO sample, the anodic peak was at 0.59 V, and the cathodic peak was present at 0.19 V, respectively. The separation between cathodic and anodic peaks enhanced with Ag-doping in ZnO, which could be associated with the variations in the transfer of electrons at the interface between the working electrode and the solution, confirming an increase in the reaction activity of Ag-ZnO NPs. Conclusion: The results indicate that Ag-doped ZnO NPs may be an efficient catalyst for waste water treatment and photocatalytic applications.

Insight into catalytic cracking pathways of n‐pentane over bifunctional catalysts to produce light olefins

AbstractRevealing the reaction mechanism to guide the industrial production of targeted products still remains a grand challenge for catalytic cracking of light alkanes to olefins over metal‐acid bifunctional catalyst. Herein, we systematically investigated the reaction mechanism of n‐pentane cracking on the Ag/ZSM‐5 bifunctional catalyst featuring both dehydrogenation and cracking capabilities. Specifically, overall cracking network of n‐pentane was comprehensively constructed to show the roles of metal dehydrogenation sites and acid sites respectively, in which metal Ag could substitute the H of the Brønsted acid site to form the Al–O–Ag linkage with enhanced adsorption and activation of n‐pentane, while Brønsted acid site with weak acid strength relay to promote cracking reaction. Thanks to this synergy of the two active sites, the apparent activation energy of n‐pentane cracking to light olefins was decreased from 82.77 KJ/mol to 68.26 KJ/mol and the proportion of specific path (C5H12 → H2 + C5H10) in n‐pentane monomolecular cracking reaction increased from 14.62% to 69.24%. In addition, 0.57Ag/ZSM‐5 catalyst exhibited the conversion of n‐pentane up to 67.55 wt%, which improved the performance of the parent ZSM‐5 by 13.42 wt%. These analysis results of reaction mechanism may provide some insights for the rational design of catalysts and the full utilization of petrochemical resources.