Commercial Silver Research Articles

Biocompatible and antimicrobial chitosan/PVP/PEO/PAA/AgNP composite hydrogels synthesized by e-beam cross-linking

Novel biocompatible composite hydrogels with good elastic and antimicrobial properties have been fabricated by e-beam cross-linking using chitosan and water-soluble polymers mixed with commercial silver nanoparticles (AgNP). Hydrogels having different formulations were characterized by rheological, swelling, FTIR, SEM, and biodegradation measurements. The network structure, biocompatibility, and antimicrobial properties were evaluated as well. The composite hydrogels showed higher stability and absorb large amounts of fluids specific to an infected wound without losing structural integrity. The rheological, SEM, and network structure results demonstrate that at above 0.1 mg/mL AgNP, hydrogels with high cross-linking density are obtained. The in vitro response of fibroblasts proved the high biocompatibility of the hydrogel's composites. The antimicrobial activity is directly influenced by the amount of AgNP and cross-linking degree of the hydrogel. Significant antimicrobial activity was recorded against Gram-negative bacteria, while for the Gram-positive ones, the growth inhibition seems to require a decrease of the cross-linking degree.

Fabrication of a Flexible RFID Antenna by Using the Novel Environmentally Friendly Additive Process

The fabrication of flexible antennas for RFID applications can be divided into subtractive and additive methods. In this study, a low-cost additive method is proposed, which involves printing aluminum paste and utilizing a galvanic replacement reaction. Through a galvanic replacement process, copper sulfate waste effluent was employed to convert the aluminum electrode into a highly conductive copper electrode. The physical characteristics of the Cu electrode, such as surface flatness, thickness, and Al-Cu conversion ratio, were studied. The Cu electrode, produced using an innovative additive technique at a temperature of 75°C for 15 minutes, exhibits the lowest resistivity of 5.89 × 10–8 Ωm. This resistivity is comparable to that of a commercial silver thick film electrode, making it suitable for use in manufacturing RFID antennas for RFID module applications. With an S11 of −40 dB at 1.26 GHz, a maximum gain of 2.87 dBi, a maximum efficiency of 53.63%, and a reading distance of 9 meters, the RFID module demonstrates impressive performance. The reading distance of an RFID module with a copper foil antenna is longer (8.5 meters).

Copper-based dressing: Efficacy in a wound infection of ex vivo human skin

This study aimed to evaluate the wound healing and antibacterial effects of two experimental copper dressings compared to a commercial silver dressing. Burn wounds were created in the ex vivo human skin biopsies, then were infected by Staphylococcus aureus. Tissues were treated with copper dressings, silver dressing, or a dressing without any antibacterial component. An infected wound tissue without treatment was considered as the control group. Three days after treatments, tissues were analyzed by bacterial count and histology staining, while their media was used to assess the expression of cytokines and chemokines. Histology staining confirmed the presence of second-degree burn wounds and colonization of bacteria in the surface and superficial layer of tissues. The results demonstrated a higher antibacterial effect, improved epithelium formation, and decreased wound area in one of the copper dressings compared to other dressings. Markers associated with infection control increased in both the copper and silver-treated groups. The cytokine profiling analysis revealed increased expression of markers related to angiogenesis and anti-inflammatory responses and decreased pro-inflammatory cytokine responses in the infected wound treated with one of the copper dressings. Our results confirmed the efficacy of the experimental copper dressing in reducing bacteria and promoting wound healing.

An amperometric method for the determination of cystine in urine samples and pharmaceutical tablets using screen-printed silver electrodes

Elevated urinary cystine levels are closely associated with the development of cystine stone. Therefore, the ability to rapidly and efficiently determine urinary cystine levels is crucial for physicians to manage patients with cystinuria or those undergoing cystine medication. In this study, an amperometric method employing a commercial screen-printed silver electrode was successfully established. The resulting calibration curve indicated a detection limit of 0.65 mg/dL. Satisfactory recoveries ranging from 89% to 109% were obtained for urine samples. The method was also effective for the quality control analysis of cystine in pharmaceutical tablets. The recovery of cystine from pharmaceutical tablets ranged from 98% to 101% using the developed method. This method enables the rapid and accurate determination of cystine in both urine samples and pharmaceutical tablets and provides valuable information for clinical diagnosis and pharmaceutical quality control.

Facet-controlled synthesis of silver microsheets for printed flexible conductive film based on SO42- and Ce4+ ions: An experimental and DFT study

It is widely accepted that polymeric surfactants adsorbed on the surface of silver sheets will affect their conductivity. Here a novel seed-mediated growth method without using polymeric surfactants is proposed to synthesize uniform microsheets in aqueous solution. The roles of SO42- and Ce4+ are discussed in detail. The possible formation mechanism of microsheets is presented. The results of density functional theory (DFT) calculation demonstrate that the binding energies of SO42- on Ag(111), Ag(110), and Ag(100) facets are − 4.56, − 4.34, and − 4.10 eV respectively, indicating that SO42- are preferentially adsorbed on the Ag(111) facet. The analyses of charge density difference and density of states (DOS) indicate that the adsorption of SO42- on Ag surfaces is chemical adsorption, in agreement with the results of XPS and FT-IR spectrum. The flexible conductive film using as-synthesized silver microsheets as the conductive filler shows lower bulk resistivity (1.2 ×10−5 Ω·cm) than that using the commercial ball-milled silver microsheets as the conductive filler (8.0 ×10−5 Ω·cm) under the same silver content conditions (80 wt%), which demonstrates good application prospects in printed electronics.

Oxygen reduction reaction on AgPd nanocatalysts prepared by galvanic exchange

In this work galvanic exchange was employed as bimetallic catalyst preparation method to obtain AgPd nanocatalysts. Ag nanoparticles synthesized by the citrate method and commercial silver nanowires (AgNWs) were used for Pd spontaneous deposition. From transmission electron microscopy images, the particle sizes were determined between 10 and 20 nm and AgPd particles with the Ag/Pd molar ratio of 18:82 obtained using MP-AES were larger compared to those of 89:11 ratio. The galvanic exchange process resulted in porous and half-moon shaped particles. Pd distribution for AgPd/C_1 (18:82) and AgPd/C_2 (56:44) catalysts was rather uniform. Decreasing the amount of Pd salt in the galvanic exchange bath led to only surface decoration of Ag particles as can be seen in the case of AgPd/C_3 (79:21) and AgPd/C_4 (89:11). AgPd120NW and AgPd80NW samples showed the Ag/Pd ratio of 82:18 and 94:6, respectively. The electrocatalysts were studied for oxygen reduction reaction (ORR) in alkaline media using the rotating disk electrode technique. Higher specific activity values for ORR were obtained on larger particles, however galvanic exchange process was not limited to surface layers, thus increasing Pd content resulted in lower mass activities. For all the AgPd catalysts a typical Tafel slope value of ∼−60 mV was observed.

Direct visualization of nanoparticle morphology in thermally sintered nanoparticle ink traces and the relationship among nanoparticle morphology, incomplete polymer removal, and trace conductivity

A key challenge encountered by printed electronics is that the conductivity of sintered metal nanoparticle (NP) traces is always several times smaller than the bulk metal conductivity. Identifying the relative roles of the voids and the residual polymers on NP surfaces in sintered NP traces, in determining such reduced conductivity, is essential. In this paper, we employ a combination of electron microscopy imaging and detailed simulations to quantify the relative roles of such voids and residual polymers in the conductivity of sintered traces of a commercial (Novacentrix) silver nanoparticle-based ink. High resolution transmission electron microscopy imaging revealed details of the morphology of the inks before and after being sintered at 150 °C. Prior to sintering, NPs were randomly close packed into aggregates with nanometer thick polymer layers in the interstices. The 2D porosity in the aggregates prior to sintering was near 20%. After heating at 150 °C, NPs sintered together into dense aggregates (nanoaggregates or NAgs) with sizes ranging from 100 to 500 nm and the 2D porosity decreased to near 10%. Within the NAgs, the NPs were mostly connected via sintered metal bridges, while the outer surfaces of the NAgs were coated with a nanometer thick layer of polymer. Motivated by these experimental results, we developed a computational model for calculating the effective conductivity of the ink deposit represented by a prototypical NAg consisting of NPs connected by metallic bonds and having a polymer layer on its outer surface placed in a surrounding medium. The calculations reveal that a NAg that is 35%–40% covered by a nanometer thick polymeric layer has a similar conductivity compared to prior experimental measurements. The findings also demonstrate that the conductivity is less influenced by the polymer layer thickness or the absolute value of the NAg dimensions. Most importantly, we are able to infer that the reduced value of the conductivity of the sintered traces is less dependent on the void fraction and is primarily attributed to the incomplete removal of the polymeric material even after sintering.

Green synthesis of photocatalytic TiO2/Ag nanoparticles for an efficient water remediation

This work reports a green method to produce efficient photocatalytic nanopowders. Titanium dioxide nanoparticles were easily synthetized by an extract of Thymus vulgaris, and then decorated with commercial silver nanoparticles. A detailed morphological, structural, and chemical characterization was performed by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) adsorption–desorption of N2, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), Raman spectroscopy, transmission electron microscopy (TEM), and UV–Vis spectroscopy. The synthetized TiO2 nanoparticles showed a mean size of 10–15 nm, and had the anatase crystallographic phase. The photocatalytic efficiency of the TiO2 nanoparticles was demonstrated by the photo-degradation under UV-light irradiation of different pollutants in aqueous solution (methylene blue, diclofenac, and sodium dodecyl sulfate). TiO2 was coupled to Ag nanoparticles with different percentage in weight (from 0.25 to 3%), to investigate an eventual improvement of its photocatalytic efficiency. The best photocatalytic composite among the tested compositions was the one with the lowest Ag percentage (0.25%). Zebrafish embryo toxicity tests ruled out the toxicity of the synthetized nanoparticles. The present results offer a new, green, and easy method to prepare TiO2/Ag nanoparticles with high photocatalytic efficiency. The proposed materials are therefore promising for applications in photocatalysis, especially for wastewater remediation and reuse.

A Processing Model toward Printing High-Flatness Layers for Direct-Ink-Writing Printed Self-Leveling Inks

The direct-ink-writing (DIW) has been widely used to print various functional devices using different self-leveling inks. Due to the complicated rheological behavior and multiple processing parameters, how to rapidly determine the crucial parameter for high-precision printing is still challenging. Here we adapt a widely used commercial silver paste and identify the critical parameter for dominating the flatness through observation of the microstructure evolution for the line-to-layer forming process. An analytical model for flatness with printing parameters was established. Using the proposed model, the printing process parameters for achieving high flatness can be directly determined, avoiding the high cost of extensive experimental exploration.

DEVELOPMENT OF A TOPICAL GEL CONTAINING A DIPEPTIDYL PEPTIDASE-4 INHIBITOR FOR WOUND HEALING APPLICATIONS

Chronic wounds are challenging for healthcare because they are difficult to treat and cannot heal by themselves. Active compounds that can accelerate wound healing are, therefore, necessary. Dipeptidyl peptidase (DPP)-4 inhibitors are antihyperglycemic drugs widely used in patients with type 2 diabetes that not only maintain the homeostasis of blood sugar levels but have also been shown to promote chronic wound healing. In this study, we formulated a topical gel containing, sitagliptin, a commonly used DPP-4 inhibitor drug to treat diabetes, using Carbopol 940 as a base due to its high viscosity and biocompatibility. The characteristics of the sitagliptin gel, including its physical appearance, viscoelastic properties, swelling and degradation, and stability, were investigated. The gel appeared to be transparent with a uniform distribution of drug molecules and was stable at 4 °C for more than 1 month. Moreover, the gel was shown to exhibit shear thinning pseudoplastic behavior, which is desirable for topical gels. The gel could absorb up to 250% of liquid within 2 days but later degraded in aqueous solution following zeroth-order kinetics. In the in vitro release study, the cumulative release data were best fitted with the first order kinetic model, in which the release rate depended on the concentration. To further demonstrate the use of the DPP-4 inhibitor gel, the gel was applied directly onto subcutaneous wounds on experimental pigs. The topical gel was shown to exhibit the desired spread ability without causing any inflammation around the wound area which was comparable to IntraSite® gel and commercial silver nanoparticle cream.

Development of a Topical Gel Containing a Dipeptidyl Peptidase-4 Inhibitor for Wound Healing Applications

Chronic wounds are challenging for healthcare because they are difficult to treat and cannot heal by themselves. Active compounds that can accelerate wound healing are, therefore, necessary. Dipeptidyl peptidase (DPP)-4 inhibitors are antihyperglycemic drugs widely used in patients with type 2 diabetes that not only maintain the homeostasis of blood sugar levels but have also been shown to promote chronic wound healing. In this study, we formulated a topical gel containing, sitagliptin, a commonly used DPP-4 inhibitor drug to treat diabetes, using Carbopol 940 as a base due to its high viscosity and biocompatibility. The characteristics of the sitagliptin gel, including its physical appearance, viscoelastic properties, swelling and degradation, and stability, were investigated. The gel appeared to be transparent with a uniform distribution of drug molecules and was stable at 4 °C for more than 1 month. Moreover, the gel was shown to exhibit shear thinning pseudoplastic behavior, which is desirable for topical gels. The gel could absorb up to 250% of liquid within 2 days but later degraded in aqueous solution following zeroth-order kinetics. In the in vitro release study, the cumulative release data were best fitted with the first order kinetic model, in which the release rate depended on the concentration. To further demonstrate the use of the DPP-4 inhibitor gel, the gel was applied directly onto subcutaneous wounds on experimental pigs. The topical gel was shown to exhibit the desired spread ability without causing any inflammation around the wound area which was comparable to IntraSite® gel and commercial silver nanoparticle cream.

Pluronic® F127 Hydrogel Containing Silver Nanoparticles in Skin Burn Regeneration: An Experimental Approach from Fundamental to Translational Research.

Presently, skin burns are considered one of the main public health problems and lack therapeutic options. In recent years, silver nanoparticles (AgNPs) have been widely studied, playing an increasingly important role in wound healing due to their antibacterial activity. This work is focused on the production and characterization of AgNPs loaded in a Pluronic® F127 hydrogel, as well as assessing its antimicrobial and wound-healing potential. Pluronic® F127 has been extensively explored for therapeutic applications mainly due to its appealing properties. The developed AgNPs had an average size of 48.04 ± 14.87 nm (when prepared by method C) and a negative surface charge. Macroscopically, the AgNPs solution presented a translucent yellow coloration with a characteristic absorption peak at 407 nm. Microscopically, the AgNPs presented a multiform morphology with small sizes (~50 nm). Skin permeation studies revealed that no AgNPs permeated the skin after 24 h. AgNPs further demonstrated antimicrobial activity against different bacterial species predominant in burns. A chemical burn model was developed to perform preliminary in vivo assays and the results showed that the performance of the developed AgNPs loaded in hydrogel, with smaller silver dose, was comparable with a commercial silver cream using higher doses. In conclusion, hydrogel-loaded AgNPs is potentially an important resource in the treatment of skin burns due to their proven efficacy by topical administration.

Comparison of Cariostatic and Remineralizing Potential of Two Commercial Silver Diamine Fluoride Preparations using Confocal Laser Microscopy and EDX-SEM Spectroscopy: An In Vitro study.

To investigate the cariostatic and remineralizing effect of two commercial silver diamine fluoride (SDF) preparations on enamel and dentinal caries using a bacterial plaque model. A total of 32 extracted primary molars were divided into two groups (n = 16), group I (FAgamin), and group II (SDF). Plaque bacterial model was used to induce caries on enamel and dentin. Preoperative evaluation of samples was done using confocal laser microscopy (CLSM) and energy-dispersive X-ray spectroscopy-scanning electron microscope (EDX-SEM). All samples were treated with test materials and evaluated for postoperative remineralization quantification. Energy-dispersive X-ray spectroscopy (EDX) revealed that mean preoperative levels (in weight %) of silver (Ag) and fluoride (F2) in carious enamel lesions were 0.0 and 0.0, which increased postoperatively to 11.40 and 31.05 for FAgamin and 13.61 and 31.87 for SDF, respectively. For dentinal caries, EDX revealed mean preoperative levels (in weight %) of Ag and F2 were 0.0 and 0.0, which increased to 11.47 and 48.71 for FAgamin and 10.16 and 47.82 for SDF, respectively postoperatively. Both the groups showed evident demineralization with exposed collagen under SEM. The mean value of enamel lesion depth for the group I and II were 38.64 and 39.30 µm, that reduced to 28.02 and 28.70 µm while for dentinal caries, the mean depth from 38.05 and 38.29 µm that reduced significantly to 28.96 and 30.10 µm, respectively (p < 0.001). Caries depth declined significantly after the application of both FAgamin and SDF (p < 0.001). FAgamin and SDF show similar cariostatic and remineralization potential for dental caries. The bacterial plaque model used in this study is an efficient method to induce artificial carious lesions in teeth. A comparative evaluation of these two cariostatic and remineralizing agents will aid in identifying the efficacy of both commercial products in treating initial caries lesions in an effective noninvasive and child-friendly manner. Kale YJ, Misal S, Dadpe MV, et al. Comparison of Cariostatic and Remineralizing Potential of Two Commercial Silver Diamine Fluoride Preparations using Confocal Laser Microscopy and EDX-SEM Spectroscopy: An In Vitro study. Int J Clin Pediatr Dent 2022;15(6):643-651.

Controlling the Inkjet Printing Process for Electrochemical (Bio)Sensors

AbstractInkjet printing is a popular technique for depositing high‐precision ink lines. This study reports the printing parameters’ influence on the electrical properties of the sensing devices. The electrochemical sensors are fabricated with a commercial piezoelectric printer and silver ink. Different substrates are evaluated in the printing process, including paper, polyimide, and polyvinyl chloride (PVC) tapes. Ink depositions’ temperature, ink drop spacing, length, and the number of the ink layer are also evaluated in this study. Higher temperatures (40 °C) make the substrate surface smoother, improving the printing quality. Controlling the ink drop spacing produces narrow continuous ink lines. The number of ink layers changes the film thickness, altering their electroactive surface area. The best printing parameters are PVC tape at 40 °C, 17 µm drop spacing, one layer, and 13 mm length. Under optimized conditions, three‐electrode electrochemical systems are fully printed with silver ink, showing batch‐to‐batch reproducibility (RSD = 3%). Their analytical performance is evaluated for picric acid, hydrogen peroxide, and glucose quantification. The sensors are modified with glucose oxidase to quantify glucose in artificial saliva, confirming their analytical applicability. Therefore, this work reports fundamental aspects of inkjet printing, bringing valuable findings to guide new research involving inkjet‐printed electrochemical biosensors/sensors ((bio)sensors).

One-step synthesis of micro-sized flake silver particles as electrically conductive adhesive fillers in printed electronics

A novel one-step liquid phase reduction method was proposed to synthesize uniform micro-sized flake silver particles at room temperature. The La(OH)3 was used to replace other expensive agent (H2PtCl6 or H2PdCl4) as structure-directing agent. The role of the reagents and possible formation mechanism of micro-sized flake silver particles were investigated in detail. The effect of each synthesis parameter on morphology and particle size of micro-sized flake silver particles was also explored. It is found that La(OH)3 could control the reduction rate of Ag+ and its oriented growth by adsorbing on the (111) crystal plane of silver particles. The uniform micro-sized flake silver particles with a length of 4-55 μm and thickness of 0.2-5 μm could be synthesized by tuning the synthesis parameters. The synthesized micro-sized flake silver particles presented a smoother and straighter surface compared with commercial micro-sized flake silver particles prepared by ball milling. What is more important, the electrically conductive adhesive (ECA) filled by as-prepared micro-sized flake silver particles printed on polyethylene terephthalate film (PET) exhibited lower bulk resistivity (about 4.4×10-5 Ω·cm) than that filled by the commercial ball-milled micro-sized flake silver particles with the same Ag content of 80 wt. % (about 1.2×10-4 Ω·cm).

Antimicrobial activity of different wound dressing products treated with silver

The main goal of this work was to optimize the method of processing wound dressing products (like gauzes, sanitary pads, cotton wool, compresses, and bandages) with a commercial silver colloidal solution (Koloid doo, Belgrade, Serbia) and then to examine the antimicrobial properties of the obtained items in order to potentially reach the market with new improved wound dressing products. The influence of different silver concentrations used for treatment on antimicrobial activity was investigated only against Escherichia coli. The antimicrobial activity of different types of materials treated with silver solutions of 30 ppm was investigated against Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, Gram-positive bacteria Staphylococcus aureus, Bacillus subtilis, and Enterococcus faecalis, as well as the fungus Candida albicans. The microbial reduction of the tested materials loaded with a silver solution of 30 ppm (15-20 ?g of Ag on 1 g of fabric) against the Gram-negative bacteria E. coli and P. aeruginosa was almost maximal after 2 h of contact (i.e. 95 and 99 %, respectively). In the case of Gram-positive bacteria S. aureus, B. subtilis, and E. faecalis, a longer time is needed to completely eradicate bacteria (over 99 %). Antifungal activity testing against the fungus C. albicans gave moderate antifungal activity results.

Comparative Evaluation of Cariostatic and Remineralizing Potential of Two Commercial Silver Diamine Fluoride Preparations Using Confocal Laser Microscopy and EDX-SEM Spectroscopy: An In Vitro Study.

To investigate the cariostatic and remineralizing effect of two commercial silver diamine fluoride (SDF) preparations on enamel and dentinal caries using a plaque bacterial model. Thirty-two extracted primary molars were divided into two groups (n = 16) as group I (Advantage Arrest) and group II (e-SDF). Plaque bacterial model was used to induce caries on enamel and dentin. Preoperative evaluation of samples was done using confocal laser scanning microscopy (CLSM) and energy-dispersive X-ray spectroscopy-scanning electron microscope (EDX-SEM). All samples were treated with test materials and evaluated for postoperative remineralization quantification. EDX revealed that mean preoperative levels (in weight%) of silver (Ag) and fluoride (F) in enamel carious lesions were 0.0 and 0.0, which increased postoperatively to 11.40 and 31.05 for Advantage Arrest and 13.61 and 31.87 for e-SDF, respectively. For dentinal caries, EDX revealed mean preoperative levels (in weight%) of Ag and F were 0.0 and 0.0, which increased to 11.47 and 48.71 for Advantage Arrest and 10.16 and 47.82 for e-SDF, respectively postoperatively. Both groups showed evident demineralization with exposed collagen under SEM. The mean values of enamel lesion depth for the group I and II were 38.64 and 39.30 µm, that reduced to 28.02 and 28.70 µm, while for dentinal caries, the mean depth from 38.05 to 38.29 µm that reduced significantly to 28.96 and 30.10 µm, respectively (p < 0.001). Caries depth declined significantly after the application of both Advantage Arrest and e-SDF (p < 0.001). Advantage arrest and e-SDF show similar cariostatic and remineralization potential for dental caries. The plaque bacterial model used in this study is an efficient method to induce artificial carious lesions in teeth. Kale YJ, Misal S, Dadpe M, et al. Comparative Evaluation of Cariostatic and Remineralizing Potential of Two Commercial Silver Diamine Fluoride Preparations Using Confocal Laser Microscopy and EDX-SEM Spectroscopy: An In Vitro Study. Int J Clin Pediatr Dent 2022;15(4):442-449.

Enriching Surface-Accessible CO2 in the Zero-Gap Anion-Exchange-Membrane-Based CO2 Electrolyzer.

Zero-gap anion exchange membrane (AEM)-based CO2 electrolysis is a promising technology for CO production, however, their performance at elevated current densities still suffers from the low local CO2 concentration due to heavy CO2 neutralization. Herein, via modulating the CO2 feed mode and quantitative analyzing CO2 utilization with the aid of mass transport modeling, we develop a descriptor denoted as the surface-accessible CO2 concentration ([CO2 ]SA ), which enables us to indicate the transient state of the local [CO2 ]/[OH- ] ratio and helps define the limits of CO2 -to-CO conversion. To enrich the [CO2 ]SA , we developed three general strategies: (1) increasing catalyst layer thickness, (2) elevating CO2 pressure, and (3) applying a pulsed electrochemical (PE) method. Notably, an optimized PE method allows to keep the [CO2 ]SA at a high level by utilizing the dynamic balance period of CO2 neutralization. A maximum jCO of 368±28 mA cmgeo -2 was achieved using a commercial silver catalyst.

Enriching Surface‐Accessible CO2 in the Zero‐Gap Anion‐Exchange‐Membrane‐Based CO2 Electrolyzer

AbstractZero‐gap anion exchange membrane (AEM)‐based CO2 electrolysis is a promising technology for CO production, however, their performance at elevated current densities still suffers from the low local CO2 concentration due to heavy CO2 neutralization. Herein, via modulating the CO2 feed mode and quantitative analyzing CO2 utilization with the aid of mass transport modeling, we develop a descriptor denoted as the surface‐accessible CO2 concentration ([CO2]SA), which enables us to indicate the transient state of the local [CO2]/[OH−] ratio and helps define the limits of CO2‐to‐CO conversion. To enrich the [CO2]SA, we developed three general strategies: (1) increasing catalyst layer thickness, (2) elevating CO2 pressure, and (3) applying a pulsed electrochemical (PE) method. Notably, an optimized PE method allows to keep the [CO2]SA at a high level by utilizing the dynamic balance period of CO2 neutralization. A maximum jCO of 368±28 mA cmgeo−2 was achieved using a commercial silver catalyst.

Eco-Friendly Green Synthesis of Rubropunctatin Functionalized Silver Nanoparticles and Evaluation of Antibacterial Activity.

In order to solve the problems of rubropunctatin insoluble in water and its low bioavailability, and explore the synthesis method of green silver nanoparticles, rubropunctatin was used as reducing agent and blocking agent, rubropunctatin-functionalized silver nanoparticles (R-AgNPs) were successfully synthesized. The distinctive absorption peak at 410 nm confirmed the formation of R-AgNPs. Zeta potential measurement showed excellent stability of R-AgNPs with negative values of -29.81 ± 0.37 mV. The results of TEM and XRD showed that the prepared R-AgNPs were round, well dispersed and crystallized with average particle size of 13.54 ± 0.42 nm. FT-IR and XPS studies show that functional groups are involved in R-AgNPs synthesis. The antibacterial activity of R-AgNPs was compared with commercial silver nanoparticles (AgNPs) by microdilution method. The results showed that R-AgNPs (MIC 7.81 μg/mL) has stronger antibacterial activity than commercial AgNPs. The bacteria morphology was observed by the live and dead (SYTO 9/PI) staining assay and SEM showed that the antibacterial effect of R-AgNPs was caused by the destruction of the bacterial cell membrane. Cytotoxicity of rubropunctatin-functionalized silver nanoparticles and commercial silver nanoparticles on mouse fibroblast 3T3 cells was assessed by CCK-8 assay. The results showed that the toxicity of rubropunctatin-functionalized silver nanoparticles to 3T3 cells was lower than that of commercial silver nanoparticles. In summary, synthesis of silver nanoparticles using rubropunctatin is a green synthesis method, and R-AgNPs is a potential antibacterial agent.