Ag-O Bond Research Articles

Bio-functionalization of Chitosan@Ag nanoparticles using Terminalia arjuna and their antioxidant, antibacterial and cytotoxic activity.

This study aims to create a novel, multifunctional material with enhanced biological activities. We reported bio-functionalized chitosan-loaded silver nanoparticles (Cs@AgNPs) using aqueous and ethanolic bark extract of Terminalia Arjuna (TA). Synthesized NPs have been characterized by UV-VIS, FTIR, XRD, TEM, and SEM-EDX. The characteristic absorbance at 312nm and 460nm in UV-VIS demonstrated the presence of chitosan and AgNPs, respectively. FTIR analysis showed the characteristic vibration for the AgO bond as well as Cs functional groups. XRD analysis of nanocomposites showed 38.21o, 43.80o, 57.48o, and 77.32o, two theta values correspond to (111), (200), (220) and (311) plane characteristics of the composite. SEM-EDX confirmed the presence of Ag quantitatively and qualitatively in the composite. TEM analysis confirmed the fabrication of composites in the range of 50-90nm. TGA analysis revealed the thermal stability and composition of the composites. Almost 85% trapping of DPPH free radical was pointed out for the composites as their antioxidant potential. The antibacterial activity was studied against B. subtilis MTCC121/ATCC6051, E. coli MTCC448/ATCC9637, P. aeruginosa MTCC1934/ATCC10415, and S. aureus MTCC1430/ATCC12600. The cytotoxicity of composites was studied against A549 lung cancer and the IC50 values of both composites were obtained 400g/mL and 300g/mL respectively.

Integrated induction of silver resistance determinants and production of extracellular polymeric substances in Cupriavidus metallidurans BS1 in response to silver ions and silver nanoparticles

Although the antimicrobial mechanisms of nanomaterials have been extensively investigated, bacterial defense mechanisms associated with AgNPs have not been fully elucidated. We here report that dissolved Ag+ (>0.05 μg mL−1) displayed higher toxicity on cell growth of strain Cupriavidus metallidurans BS1 (GCA_003260185.2) in comparison to 2 and 20 nm AgNPs. The genes necessary for synthesis of distinct abundance and composition of extracellular polymeric substances (EPS) were induced in strain BS1 exposed to Ag stress. This resulted in 20.1% (Ag(I)-EPS) and 24.2% (2 nm AgNPs-EPS) of the CO band integrated intensities being converted into C-OH/C-O-C group vibrations and the Ag-O bond was formed between EPS and 20 nm AgNPs. Meanwhile, the expression of primary resistance genes of the cus, sil and cup operon encoding HME-RND-driven efflux systems as well as a PIB1-type ATPase (CupA) were significantly induced after exposure to Ag(I), 2 and 20 nm AgNPs, respectively. Furthermore, distinct genes involved in biosynthesis pathways responsible for production of EPS were induced to relieve the toxicity of Ag(I), 2 nm and 20 nm AgNPs. This combined action is one potential reason why strain BS1 displayed distinct resistances in response to Ag(I) compared to 2 and 20 nm AgNPs. This work will help in understanding processes important in bacterial defensive mechanisms to AgNPs.

Silk fibroin protein and graphene synergistically boosting the reactive oxygen species generation of PU/AgI photocatalytic membrane for tetracycline sustained removal

Solar-light driven organic pollutants degradation by the recyclable photocatalytic membrane materials emerges as a promising technology for sewage purification. However, low generation of reactive oxygen species severely constraints their photocatalytic activity. Herein, we introduce a novel hydrophilic PU/SF/GO/AgI composite photocatalytic membrane fabricated via adding silk fibroin (SF) and graphene oxide (GO) for TC removal. By visible light irradiation, the PU/SF/GO/AgI membrane with 66.7 wt% SF and 0.05 wt% GO degrades TC with 7-fold increase in comparison with the PU/AgI membrane. The enhance photocatalytic activity is primarily attributed to its efficient generation of reactive oxygen species facilitated by the improved hydrophilicity and boosted charge separation. FTIR and electrochemical results demonstrate that the SF and GO with rich surface oxygen-containing groups contribute to the formation of Ag-O bonds for accelerating charge migration and separation. Significantly, the improved hydrophilicity of PU/SF/GO membrane can not only provide rich binging sites for AgI loading, but also be benefitted to attract small molecules for facilitating to reactive oxygen species generation. As a result, •O2−, •OH and H2O2 concentrations produced in PU/SF/GO/AgI membrane system reaches up to 53.20 μmol g−1 h−1, 7.89 μmol g−1 h−1 and 16.52 μmol, respectively, 6.7, 15.4 and 5.1-times higher than PU/AgI membrane system. Meanwhile, under LED irradiation of 12 h, TC degradation efficiency by the dynamic membrane reactor equipped with PU/SF/GO/AgI can reach up to 53 % and achieve 41 % TOC removal, exceeding the pure PU/AgI and those of reported membrane materials. This work proves that tuning hydrophilicity and charge migration of PU membrane can enhance their photocatalytic activity and recyclability, which offers an effective strategy for constructing sustained solar-light driven photocatalytic membrane system.

Syntheses and antimicrobial activities of two coordination polymers assembled with Ag[sbnd]N and Ag[sbnd]O bonds

Two new coordination polymers ({[Ag(p-phda)2](BF4)} n (1) and {[Ag2(1,5-nds)(DMSO)2] DMSO}n (2) (p-phda: p-phenyldiacetonitrile, 1,5-nds: 1,5-naphthalene disulfonic acid, DMSO: dimethyl sulfoxide) were synthesized and characterized by IR, EA,TG and X-ray single crystal diffraction. 1 was revealed as a 2D “fishing net” assembled by AgN bonds with BF4− as equilibrium charge. IR and PXRD analysis showed the BF4− can be irreversibly exchanged by six anions varied in atomic numbers, sizes, configurations and coordination abilities. 2 is constructed by AgO bonds where DMSO function both as guest and bridging ligand. Further diffusion of NO into the solution of 1 and 2 generated two new compounds (1′ and 2′). All four compounds showed excellent broad-spectrum antimicrobial activities against gram-negative bacteria, gram-positive bacteria and yeast. The stronger antibacterial abilities of 1 against S. aureus and P. aeruginosa than those of 2 were evidenced by the smaller minimum inhibitory concentrations of silver ions (AgMICs) and the higher silver ion release rate in aqueous solution. It was concluded that the looser packing of 1 facilitate the silver ions releasing and play a more crucial role than binding mode and ligand-exchangeability. The enhanced P. aeruginosa inhibitions of 1′ and 2′ were elementarily ascribed to NO incorporation, supporting by their increased diameter of inhibition zones and decreased AgMICs.

A Study the Addition of Silver Dioxide on Some Optical Properties of Phosphate Bioactive Glass

This study investigates the influence of silver oxide (Ag2O) concentration on the optical characteristics of phosphate bioactive glasses (PBGs). PBGs have emerged as promising alternatives to conventional silicate glasses in the medical field due to their excellent bioactivity and chemical resistance. Samples with varying Ag2O concentrations (0, 0.25, 0.5, and 0.75g) were sintered at 780°C for 2 hrs in an electric furnace. The samples were subjected to Fourier transfer infrared spectroscopy (FTIR), ultraviolet-visible (UV-Vis) spectroscopy, and photoluminescence (PL) tests to assess their functional groups and optical properties. By analyzing the FTIR spectrum of phosphate bioactive glass containing different amounts of Ag2O, it is possible to identify changes in the vibrational modes associated with Ag-O bonds and to gain insights into the structure and composition of the material. Because Ag-O bonds exhibit infrared vibrational modes, introducing Ag2O changed the FTIR spectrum. As Ag2O concentration increased, Ag-O vibrational modes strengthened, indicating more Ag-O bonds. UV-Vis spectroscopy, with increasing Ag2O concentration, the peak location shifted towards shorter wavelengths. Optical spectra show distinct UV absorption in the prepared glass spectrum, extending to near visible with increasing Ag2O content. The PL spectra peaks and band gap energies revealed that Ag2O altered the glass's electrical structure and optical activity. These discoveries help optimize metal-phosphate bi-active glass for biomedical implants and UV-blocking coatings. The melting-annealing technique prepared glasses based on the base host Na2O-CaF2-P2O5 system with increasing Ag2O as additives or loading (0.2 to 1 wt%).

Tinospora cordifolia-assisted synthesis of silver ferrite nanoparticles: a multifunctional approach to photocatalytic degradation of reactive blue-13 dye, anti-bacterial efficacy, and antioxidant properties

Tinospora cordifolia-assisted synthesis of silver ferrite nanoparticles: a multifunctional approach to photocatalytic degradation of reactive blue-13 dye, anti-bacterial efficacy, and antioxidant properties

Green Pesticide High Activity Based on TiO2 Nanosuspension Incorporated Silver Microspheres Against Phytophthora palmivora.

Cocoa pod production has experienced a significant decline due to attacks by the Phytophthora palmivora (P. palmivora) fungus, which is the main cause of cocoa pod rot. To overcome this problem, Titanium dioxide (TiO2) was chosen because of its potential as an antifungal, and its activity can be increased by adding silver nanoparticles (AgNPs). This research aims to determine the antifungal properties of TiO2-Ag nanosuspension on the growth of P. palmivora under exposure to UV, Visible and without irradiation. The sol-gel process was used to synthesize TiO2, and ultrasonics was used to integrate silver nanoparticles into TiO2. Characterization of UV-Vis diffuse reflectance spectroscopy (UV-DRS) shows a change in the energy gap from 3.24 to 2.82eV. The Fourier confirmed the crystal structure of the TiO2-Ag anatase transform infrared spectroscopy (FTIR) spectrum, which showed the stretching vibration peak of the Ti-O and Ag-O bonds (463.88cm-1). Particle size analysis (PSA) characterization revealed that the nanoscale of TiO2-Ag was 92.4nm. The disc diffusion method was used to test the antifungal inhibitory of 0.1%, 0.3%, and 0.5% TiO2-Ag against P. palmivora. The antifungal activity of the TiO2-Ag showed strong resistance under exposure to visible light, and the optimum concentration of TiO2-Ag was 0.5%.

Study on the adsorption of 2,4-dichlorophenoxyacetic acid on silver doped carbon nanotube using tight-binding quantum chemical method

The GFN2-xTB tight-binding quantum chemical method was utilized to investigate the adsorption ability of 2,4-dichlorophenoxylacetic acid (2,4-D) on pristine single-walled carbon nanotube (CNT) and silver-doped carbon nanotube (Ag-CNT). The effects of solvents (water, methanol, and acetonitrile) on the adsorption process were evaluated via the linear Poisson-Boltzmann analysis algorithm. The analysis of ionization energy, electron affinity, and global electrophilic indexes indicates that Ag doping alters the electronic properties of CNT through the formation of Ag-C chemical bonds. While the adsorption process of 2,4-D on pristine CNT is primarily of a physical nature, the adsorption on Ag-CNT involves chemical adsorption facilitated by the formation of Ag-Cl and Ag-O bonds. Contributions from non-covalent interactions (such as π-π stacking, van der Waals interactions, etc.) were analysed and clarified through the computation of the reduced density gradient. Our findings suggest that Ag-CNT has significant potential as a material for the adsorption and remediation of 2,4-D.

Synergistic effect of V and Ag diffusion favored the temperature-adaptive tribological behavior of VAlN/Ag multi-layer coating

Surface coating technology offers several benefits (excellent wear resistance, low coefficient of friction-COF, better corrosion durability etc.) for key components used in harsh aero-engines. However, the development of temperature-adaptive lubricant coating is still the crucial issue. In this study, VAlN/Ag multi-layer coatings with various thickness ratios were fabricated by a hybrid deposition system composing of DCMS and HiPIMS techniques. Results showed that all coatings presented Ag layers with growth twins, and fcc-VAlN layers with columnar structure. Increasing the temperature from 25 to 650 ℃ led to a decrease of COF from 0.47 to 0.22 in coatings, where the lowest COF and wear rate was particularly achieved at 0.08 and 4.3 × 10−5 mm3N−1m−1 under higher rotation speed, respectively. Based on the microstructural characterizations on wear track of coating and wear scar of counter ball, the synergistic diffusion of V and Ag elements at elevating temperature stimulated the in-situ formation of distinctive Al2O3/AgVO3-Ag3VO4/Ag microstructure, which encompass lubricant phases for lower COF and high wear resistance. The reason behind of this phenomena could be attributed to the easily broken of Ag-O bonds in lamellar silver vanadium oxides at high temperature, accompanying the remarkable lubrication of Ag on top layer.

Enhanced Tribological Performance of Micro-Beam Plasma-Cladded Ni60 Coatings with Addition of Mo and Ag Lubricants in a Wide Temperature Range

In recent years, there has been significant attention on the application potential of medium and high-temperature self-lubricating composites as sliding parts in extreme environments. This study examines the effects of different Mo and Ag content on the composition and wear resistance of Ni60-cladded coatings at room temperature, 300 °C and 600 °C, while also analyzing their wear mechanism by studying the tribofilm. The results indicate that with an appropriate weight addition of Mo and Ag, one typical lubricant called Ag2MoO4 emerges. At room temperature, the cladding layer containing 5 wt.% Mo and 5 wt.% Ag exhibits a wear rate of 2.08 × 10−6 mm3/Nm, and an average coefficient of friction (COF) of 0.3410. These two are 85% and 11% lower than those of the Ni60 cladding layer, respectively. At 300 °C, MoO3 and Cr2MoO6 act as solid lubricants. Furthermore, at 600 °C, a MoSi2 and SiO2 film forms on the worn surface to prevent further oxidation of MoSi2 and enhance oxidation resistance. The main wear mechanism is adhesion wear. Under higher temperatures, the newly formed Ag2MoO4 in the composite cladding layer adopts a layered cubic spinel structure where low-energy Ag-O bonds preferentially break during friction processes, demonstrating excellent lubrication performance.

Formulation of a modern anti-human breast cancer drug from silver nanoparticles green-synthesized using Allium saralicum

Nanotechnology has immense potential for the development of novel and necessary products that benefit human health, the environment, and industries. Silver nanoparticles and their nanocomposites have gained tremendous importance in the field of nanotechnology owing to their widespread usage in various realms of science and technology, including electronics, biomedical, environmental protection, textile industry, cosmetics, therapeutics, photonics, agriculture, and so on. As the characteristic properties of silver nanostructures, like excellent SERS/SPR, surface properties, diversity in shape, surface charge, dissolution rate, controlled silver ion release for mediating the antimicrobial toxicity and cytotoxicity towards cancer cells, and efficient biocompatibility, which render them to be potential antimicrobial, anticancer and diagnostic agents. Recently, Allium saralicum extract has been used for green-synthesizing the silver nanoparticles and investigation of its biomedical effects. In the present research, we formulated a modern chemotherapeutic drug by silver nanoparticles (AgNPs) containing Allium saralicum‎ aqueous extract for the treatment of breast cancer. Characterization of AgNPs was done by UV-Vis, FT‐IR, TEM, and FE‐SEM. The bands at 488 and 539 cm−1 (belonging to the Ag-O bond) approves the production of silver nanoparticles. The spherical morphology with a range size of 13.9–55.2 nm is obtained for synthesized nanoparticles. The band at 434 nm approves the AgNPs formation. To survey the cytotoxicity and anti-human breast cancer effects of AgNO3, Allium saralicum‎, and AgNPs, MTT assay was used on the SK-BR-3, MDA-MB-231, AU565 [AU-565], and Hs 281. T cell lines. Silver nanoparticles had very low cell viability and anticancer properties dose-dependently against cancer cell lines without any cytotoxicity on the normal cell line. The best result of anticancer properties of AgNPs against the above cell lines was seen in the case of the MDA-MB-231 cell line. The IC50 of nanoparticles were 208, 250, 200, and 188 µg/ml against SK-BR-3, MDA-MB-231, AU565 [AU-565], and Hs 281. T cell lines, ‎respectively. ‎

Synergistic effects of heterointerface and surface Br vacancies in ultrathin 2D/2D H2WO4/Cs2AgBiBr6 for efficient CO2 photoreduction to CH4

Efficient photocatalytic conversion of CO2 to CH4 is challenging due to the complex eight-electron coupled proton transfer process. Herein, a 2D/2D H2WO4/Cs2AgBiBr6 (HWO/CABB) heterojunction was fabricated specifically through the “top-down” acid cleavage of layered Bi2WO6 (Bi2O2-WO4) into 2D HWO nanosheet, followed by the in-situ “bottom-up” epitaxial growth of 2D CABB on HWO nanosheet. Detailed characterizations revealed that HWO/CABB possessed abundant surface Br-vacancies (VBr) with an ultrathin 2D/2D heterointerface involving Bi-O and Ag-O bonds, facilitating charge transfer via an S-scheme. Density functional theory (DFT) calculations demonstrated that VBr could promote the adsorption/activation of CO2 and reduce the formation energy barrier of CHO* significantly. Therefore, HWO/CABB exhibited an enhanced CH4 production rate of 22.6 µmol·g−1·h−1 (the electron selectivity of 86.1%), approximately 30 times higher than that of pristine CABB. Furthermore, a plausible mechanism of photocatalytic CO2 to CH4 was proposed based on in-situ diffuse reflectance infrared spectroscopy and DFT calculations. This work demonstrates the potential of heterointerface and surface defects in synergistically tailoring CO2 selective reduction on halide perovskite photocatalysts.

Ligand Size and Carbon-Chain Length Study of Silver Carboxylates in Focused Electron-Beam-Induced Deposition.

Gas-assisted focused electron-beam-induced deposition is a versatile tool for the direct writing of complex-shaped nanostructures with unprecedented shape fidelity and resolution. While the technique is well-established for various materials, the direct electron beam writing of silver is still in its infancy. Here, we examine and compare five different silver carboxylates, three perfluorinated: [Ag2(µ-O2CCF3)2], [Ag2(µ-O2CC2F5)2], and [Ag2(µ-O2CC3F7)2], and two containing branched substituents: [Ag2(µ-O2CCMe2Et)2] and [Ag2(µ-O2CtBu)2], as potential precursors for focused electron-beam-induced deposition. All of the compounds show high sensitivity to electron dissociation and efficient dissociation of Ag-O bonds. The as-deposited materials have silver contents from 42 at.% to above 70 at.% and are composed of silver nano-crystals with impurities of carbon and fluorine between them. Precursors with the shortest carbon-fluorine chain ligands yield the highest silver contents. In addition, the deposited silver content depends on the balance of electron-induced ligand co-deposition and ligand desorption. For all of the tested compounds, low electron flux was related to high silver content. Our findings demonstrate that silver carboxylates constitute a promising group of precursors for gas-assisted focused electron beam writing of high silver content materials.

Tuning the interface adhesion of Ag/ZnO composites by metallic dopants: A DFT study

Ag/ZnO composites have been widely applied in various fields, whilst their poor interface adhesion limits the integrative performance of these composites. Recently, metallic doping has been considered as a versatile strategy to tune the interface adhesion of metal/ceramic interfaces. However, the relationship between interface adhesion and electronic structure induced by doping at the Ag/ZnO interface needs to be further clarified. In this work, we investigated the work of separation (Wsep, value to estimate of interface adhesion), effective bond order and charge movement of Ag/ZnO interfaces with various dopants under four typical configurations by DFT calculations. It demonstrated that the dopants with lower electronegativity could enhance the interface adhesion of Ag/ZnO due to the interfacial Ag-O bonds with higher covalency level and shorter bond-lengths induced by larger charge transfer (Δq) and a higher degree of the p-d hybridization between the interfacial Ag and O atoms, while the dopants with higher electronegativity could weaken the interface adhesion. Moreover, we found that three atomic parameters (bond-lengths, <AEBO>-the average of effective bond order, Δq) were able to quantitatively rationalize the Wsep. This work advances the understanding of doping effect on the interface adhesion of Ag/ZnO interfaces that can be extended to other metal/ceramic interfaces.

Evolution of the microstructure and lubrication mechanism of AgTaO3 films at high temperatures: A MD simulation study

Ternary oxides are widely used as solid lubricants in aerospace industry due to their ability to reduce friction at high temperatures. Here, we studied sliding friction behavior of films of the ternary oxide silver tantalate (AgTaO3) at different temperatures by molecular dynamics simulations (MD). The results indicate that the friction on the AgTaO3 film decreased with increasing the temperature, and at a temperature of 750 °C the frictional force decreased to 70% of its value at room temperature. The excellent lubrication property of the investigated AgTaO3 film is mainly attributed to the fact that the number of silver clusters formed on the friction surface increases with increasing the temperature, which is related to the thermal and shear-induced breaking of Ag-O bonds. The effects of normal load and shear speed on the generation of silver clusters are also discussed. The Pearson correlation analysis showed that the normal load plays a key role in the observed low friction on AgTaO3 film.

Room-temperature synthesis of nanometric and luminescent silver-MOFs.

Three silver-MOFs were prepared using an optimized, room-temperature methodology starting from AgNO₃ and dicarboxylate ligands in water/ethanol yielding Ag 2 BDC, Ag 2 NDC (UAM-1), and Ag 2 TDC (UAM-2) at 38%-48% (BDC, benzenedicarboxylate; NDC, 1,8-naphthalene-dicarboxylate; TDC, p-terphenyl-4,4″-dicarboxylate). They were characterized by PXRD/FT-IR/TGA/photoluminescence spectroscopy, and the former two by SEM. These materials started decomposing at 330°C, while showing stability. The crystal structure of UAM-1 was determined by PXRD, DFT calculations, and Rietveld refinement. In general, the structure was 3D, with the largest Ag-O bond interlinking 2D layers. The FT-IR spectra revealed 1450 and 1680 bands (cm-1) of asymmetrically stretching aniso-/iso-bidentate -COO in coordination with 2/3-Ag atoms, accompanied by Ag-O bands at 780-740 cm-1, all demonstrating the network formation. XRD and SEM showed nanometric-scale crystals in Ag₂BDC, and UAM-1 developed micrometric single-stranded/agglomerated fibrillar particles of varying nanometric widths. Luminescence spectroscopy showed emission by Ag₂BDC, which was attributed to ligand-to-metal or ligand-to-metal-metal transitions, suggesting energy transfer due to the short distance between adjacent BDC molecules. UAM-1 and UAM-2 did not show luminescence emission attributable to ligand-to-metal transition; rather, they presented only UV emission. The stabilities of Ag₂BDC and UAM-1 were evaluated in PBS/DMEM/DMEM+FBS media by XRD, which showed that they lost their crystallinity, resulting in AgCl due to soft-soft (Pearson's principle) affinity.

Synthesis of Silver Nanoparticle-Based Chitosan Nanocomposites Using Neowestiellopsis persica Strain A1387 and Characterization of Their Potential Antimicrobial Activity Against Oral Pathogen

Today, overuse and unregulated application of antibiotics and antimicrobial agents have resulted in a substantial increase in drug-resistant pathogens. Therefore, there is a great need for innovative therapeutic methods that can replace ineffective antibiotics. Cyanobacteria are one of the most useful natural candidates in the biosynthesis of nanoparticles to face antibiotic resistance in pathogens. In this study, the antimicrobial effect of different concentrations of silver (AgNPs) nanoparticles based chitosan nanocomposites biosynthesized by &lt;i&gt;Neowestiellopsis persica &lt;/i&gt;against oral pathogens was investigated. The NPs biosynthesis were characterized through UV-visible spectroscopy, scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR) and X-ray diffraction analysis (XRD). Results of UV-visible Spectroscopy showed that the amount of absorption increased significantly with increasing time. The SEM and TEM images depict the size of the nanocomposite to be 78.74 to 74.29 and 100 nm respectively and spherical in shape. According to the results of the FT-IR spectrum, the peaks located at a wave number less than 800 cm&lt;sup&gt;-1&lt;/sup&gt; are related to the stretching vibration of metal-oxygen bonds in a crystal structure, where due to the presence of silver nanoparticles, these peaks can be related to the symmetric and asymmetric stretching vibration of Ag-O bonds. The results of XRD crystallography confirmed the success of the synthesis of microcoated silver nanoparticles by chitosan. The average crystal size of silver nanoparticles covered by chitosan was 17.6 nm. The antimicrobial efficacy of the biosynthesized AgNP nanocomposite showed that with the increase in the concentration of nanoparticles and nanoparticles coated with chitosan, the diameter of the growth halo increased significantly (&lt;i&gt;p&lt;/i&gt; &amp;#60; 0.05). Totally the results of this study confirmed that nanoparticle-based chitosan nanocomposites biosynthesized by cyanobacteria species can be converted into nanomedicine to meet future biomedical needs.

The effect of Ag content on the electronic structure and optical property of α-Fe2O3

The electronic structure and optical properties of Ag-doped α-Fe2O3 with different Ag contents (1.67 mol%, 3.33 mol%, 5.00 mol% and 6.67 mol%) were studied by density-functional theory (DFT). α-Fe2O3 has the characteristics of semimetal after Ag doping, and the semimetal property increases with increasing Ag contents. Doped Ag loses less electrons for Ag-doped α-Fe2O3 than corresponding Fe (replaced iron) for pure α-Fe2O3, which led the weaker Ag-O bond than Fe-O bond before Ag doping. However, the number of losing electrons for Ag increases gradually with the increase of Ag content. For optical properties, it is found that the peaks of imaginary parts of dielectric function and extinction coefficient for Ag-doped α-Fe2O3 shift to low energy (red shift) relative to those of pure α-Fe2O3. In the ultraviolet range (200 nm-380 nm), Ag doping reduces the optical absorption intensity. However, the optical absorption is enhanced steeply with the increase of Ag contents in the wavelength of 420 nm to 1400 nm. The optical absorption intensity of 3Ag-doped and 4Ag-doped α-Fe2O3 is similar in the visible range, suggesting that excessive Ag concentration (over 3 Ag) has little effect on the optical absorption property.

Synthesis of a New Dinuclear Ag(I) Complex with Asymmetric Azine Type Ligand: X-ray Structure and Biological Studies

Aspects of the molecular and supramolecular structure of the new dinuclear [Ag(L)(NO3)]2 complex, where L is 2-((E)-(((E)-1-(thiazol-2-yl)ethylidene)hydrazono)methyl)phenol, were discussed. The complex was crystallized in the monoclinic crystal system and P21/n space group. The unit cell parameters are a = 10.3274(2) Å, b = 11.4504(3) Å, c = 12.7137(3) Å and β = 108.2560(10)°. The asymmetric unit comprised one [Ag(L)(NO3)] formula in which the azine and nitrate ligand groups act as NN- and OO-bidentate chelates, respectively. The coordination environment of the Ag(I) is completed by one weak Ag-O bond with another [Ag(L)(NO3)] unit, leading to the dinuclear formula [Ag(L)(NO3)]2. This was clearly revealed by Hirshfeld analysis. Additionally, the Ag…C, O…H and C…C intermolecular interactions played an important role in the molecular packing of the studied complex. The antimicrobial, antioxidant and cytotoxic activities of the [Ag(L)(NO3)]2 complex and the free ligand (L) were discussed. While the [Ag(L)(NO3)]2 complex showed very weak antioxidant activity, the results of the antifungal and cytotoxic activities were promising. The inhibition zone diameters (IZD) and the minimum inhibitory concentration (MIC) values were determined to be 31 mm and 20 μg/mL, respectively, against A. fumigatus, which is compared to 17 mm and 156 μg/mL, respectively, for the positive control Ketoconazole. Generally, the Ag(I) complex has better antimicrobial activities than the free ligand against all microbes except for S. aureus, where the free ligand has higher activity. Additionally, the IC50 value against colon carcinoma (HCT-116 cell line) was determined to be 12.53 ± 0.69 µg/mL, which is compared to 5.35 ± 0.49 µg/mL for cis-platin. Additionally, the Ag(I) complex displays better cytotoxicity than the free ligand (L) (242.92 ± 8.12 µg/mL).

An accurate computational model to study the Ag-doping effect on SrTiO3

Computational simulations via Density Functional Theory were carried out to study the effect of Ag-doping on SrTiO3 and its properties. For accurate results, the coefficients of the Ag basis set were optimized, and the Hartree-Fock exchange parameter of the PBE0 functional was modified. It was found that the doping reduces the Egap by 0.15 eV, modifying the indirect band gap to direct and transforming it from an n-type to a p-type semiconductor. The Crystal Orbital Hamilton Population (COHP) analysis revealed that the Ag-O bond was stronger for the anti-ligand states. The vibrational results showed that doping with Ag promoted a short-range structural disorder in the STO with the appearance of active Raman modes (Ag, B1g, B2g, and B3g). Therefore, Ag is an appropriate metal for the doping of SrTiO3 since it improves its optical absorption properties, thus opening up new possibilities for technology.