Acid Capped Silver Nanoparticles Research Articles

Harnessing photocurrent enhancement in silver-bacterial cellulose nanocomposite for ultra-sensitive Hg2+ electrochemical detection

Global health and ecosystem concerns over mercury pollution require stringent monitoring. Herein, we showcase a novel approach for detecting trace Hg2+ ions in water using cyclic voltammetry (CV). Our approach involves modifying glassy carbon electrode (GCE) and screen printed electrode (SPE) surfaces with a nanocomposite of ascorbic acid-capped silver nanoparticles (AsAgNPs) embedded in nanocrystalline bacterial cellulose (AsAgNP-NBC). Analytical techniques confirmed the nanocomposite’s stability and morphological characteristics, exhibiting high accuracy within a linear range of 10 nM to 1 µM Hg2+ and a low limit of detection (LOD) of 3.531 nM. Additionally, on irradiation with 455 nm light source, AsAgNP-NBC modified SPE displayed a remarkable 9.6 times enhanced photocurrent, achieving an LOD of 3.95 pM, and enhanced photoresponsivity of 55.2 mA W−1, showcasing its potential for ultra-trace level detection. This cost-effective and biocompatible nanocomposite presents a promising alternative to conventional analytical methods for selective detection of trace Hg2+ ions in environmental samples.

Microwave-assisted synthesis of oleic acid-capped silver nanoparticles as lubricant additives

Recently, metal nanoparticles have been studied extensively as lubricant additives. Owning to their nanometer size, the nanoparticles can fill micro defects on contacting surfaces, acting as repairing agents. In this work, we describe a simple and fast method to fabricate monodisperse silver nanoparticles using oleic acid as a capping agent. In particular, silver nitrate was reduced by oleylamine in the oleic acid medium using acetonitrile as a co-solvent, and the reaction was heated by a microwave source. Results showed that the particle size was greatly affected by varying the reductant concentration. The average diameter of synthesized nanoparticles ranges from 3.0 nm to 4.0 nm at optimum conditions. The dispersibility in the oil of the product is attributed to the long-chain alkyl from fatty acid grafted on the surface layer, which constitutes about 21% of the weight of the nanoparticles as determined by thermogravimetric analysis.

Molecular marker identification, antioxidant, antinociceptive, and anti-inflammatory responsiveness of malonic acid capped silver nanoparticle.

Nano-sized silver has drawn a great deal of attention in the field of health sciences owing to its remarkable therapeutic applications. Interestingly, the method applied to synthesize nanoparticles and the choice of reagents considerably influence their therapeutic potential and toxicities. Current research has explored the toxicity, anti-inflammatory, antinociceptive, and antioxidant responses of the malonic acid-capped silver nanoparticles (MA-AgNPs (C) by using sodium borohydride as a reducing agent at low temperatures by employing both in vitro and in vivo approaches. Furthermore, it has highlighted the synergistic effect of these novel compounds with conventional anti-inflammatory therapeutic agents. Acute and sub-acute toxicity analysis performed following OECD guidelines showed that the studied MA-AgNPs (C) are safer, and prominent toxic signs have not been detected at the highest studied dose of 2,000mg/kg. Cytotoxicity evaluation through brine shrimp lethality revealed 20% lethality at the highest concentration of 169.8μg/mL. Significantly, positive anti-inflammatory and analgesic responses alone as well as synergism with the standard were identified through in vitro as well as in vivo methods which were more potent at a lower dose (200mg/kg). Notably synergistic outcomes were more pronounced than individual ones, indicating their prominent effect as a feasible drug delivery system. IL-6 and TNF-α assessment in excised paw tissue through RTPCR technique further supported their anti-inflammatory potential. DPPH assay revealed eminent in vitro antioxidant activity which was further corroborated by in vivo antioxidant assessment through evaluation of SOD in excised paw tissue.

Radical Scavenging, Hemocompatibility, and Antibacterial Activity against MDR Acinetobacter baumannii in Alginate-Based Aerogels Containing Lipoic Acid-Capped Silver Nanoparticles.

Retaining the hemocompatibility, supporting cell growth, and exhibiting anti-inflammatory and antioxidant properties, while having antimicrobial activity, particularly against multidrug-resistant bacteria (MDR), remain a challenge when designing aerogels for biomedical applications. Here, we report that our synthesized alginate-based aerogels containing either 7.5 or 11.25 μg of lipoic acid-capped silver nanoparticles (AgNPs) showed improved hemocompatibility properties while retaining their antimicrobial effect against MDR Acinetobacter baumannii and the reference strain Escherichia coli, relative to a commercial dressing and polymyxin B, used as a reference. The differences in terms of the microstructure and nature of the silver, used as the bioactive agent, between our synthesized aerogels and the commercial dressing used as a reference allowed us to improve several biological properties in our aerogels with respect to the reference commercial material. Our aerogels showed significantly higher antioxidant capacity, in terms of nmol of Trolox equivalent antioxidant capacity per mg of aerogel, than the commercial dressing. All our synthesized aerogels showed anti-inflammatory activity, expressed as nmol of indomethacin equivalent anti-inflammatory activity per mg of aerogel, while this property was not found in the commercial dressing material. Finally, our aerogels were highly hemocompatible (less than 1% hemolysis ratio); however, the commercial material showed a 20% hemolysis rate. Therefore, our alginate-based aerogels with lipoic acid-capped AgNPs hold promise for biomedical applications.

Modulation of salt stress through application of citrate capped silver nanoparticles and indole acetic acid in maize

The present study was conducted to determine the effect of indole acetic acid (IAA) and Citrate Capped Silver Nanoparticles (Cit-AgNPs) on various attributes of maize under induced salinity stress. Seeds of the said variety were collected from Cereal Crop Research Institute (CCRI) Pirsabaq, Nowshera, sterilized and sown in earthen pots filled with 2 kg silt and soil (1:2) in triplicates in the green house of the Botany Department, University of Peshawar. Nanoparticles were analyzed by scanning electron microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX), Thermo-gravimetric analysis (TGA) and Differential thermal analysis (DTA). Results of SEM revealed spherical morphology of Cit-AgNPs while EDX showed various elemental composition. TGA showed dominant weight loss up to 300 °C while the DTA showed major exothermic peaks at 420 °C. High Salinity concentration (80 mM) imposed significant detrimental impacts by reducing the agronomic attributes, photosynthetic pigments, osmolytes and antioxidant enzymes, which was remarkably ameliorated by the foliar application of Cit-AgNPs and IAA. Agronomic attributes including leaf, root and shoot fresh and dry weight was improved by 52–74%, 43–69% and 36–79% in individual as well as combined treatments of IAA and NPs. Photosynthetic pigments were amplified by 35–63%, total osmolytes were augmented by 39–68% and antioxidant enzymes including SOD and POD were boosted by 42–57% and 37–62% respectively, in combined as well as individual application. Conclusively, Cit-AgNPs are considered as salt mitigating entities that enhance the tolerance level of crop plants along with IAA, which may be beneficial for the plants growing in saline stressed environment.

Bioinspired 5-caffeoylquinic acid capped silver nanoparticles using Coffee arabica leaf extract for high-sensitive cysteine detection

Selection of plant extracts as bioactive phytochemical source to synthesize nanoparticles is highly demanding due to the biocompatibility, nontoxicity, and cost-effectiveness over other available physical and chemical methods. Here, for the first time, Coffee arabica leaf extracts (CAE) were used to produce highly stable silver nanoparticles (AgNPs) and the corresponding bio reduction, capping and stabilization mechanism mediated by dominant isomer 5-caffeoylquinic acid (5-CQA) is discussed. UV–Vis, FTIR, μRaman spectroscopy, TEM, DLS and Zeta potential analyzer measurements were employed to characterize these green synthesized NPs. The affinity of 5-CQA capped CAE–AgNPs to thiol moiety of amino acid is utilized for the selective as well as sensitive detection of L-cysteine (L-Cys) to a low detection limit of 0.1 nM, as obtained from its μRaman spectra. Hence, the proposed novel, simple, eco-friendly, and economically sustainable method can provide a promising nanoplatform in the field of biosensors compliant with large-scale industrial production of AgNPs without aid of further instrumentation.

Synthesis of thiolated chlorogenic acid-capped silver nanoparticles for the effective dual action towards antimicrobial and anticancer therapy

Synthesis of thiolated chlorogenic acid-capped silver nanoparticles for the effective dual action towards antimicrobial and anticancer therapy

Novel Carboxylic Acid-Capped Silver Nanoparticles as Antimicrobial and Colorimetric Sensing Agents.

The present work reports the synthesis, characterization, and antimicrobial activities of adipic acid-capped silver nanoparticles (AgNPs@AA) and their utilization for selective detection of Hg2+ ions in an aqueous solution. The AgNPs were synthesized by the reduction of Ag+ ions with NaBH4 followed by capping with adipic acid. Characterization of as-synthesized AgNPs@AA was carried out by different techniques, including UV–Visible spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Dynamic Light Scattering (DLS), and zeta potential (ZP). In the UV–Vis absorption spectrum, the characteristic absorption band for AgNPs was observed at 404 nm. The hydrodynamic size of as-synthesized AgNPs was found to be 30 ± 5.0 nm. ZP values (−35.5 ± 2.4 mV) showed that NPs possessed a negative charge due to carboxylate ions and were electrostatically stabilized. The AgNPs show potential antimicrobial activity against clinically isolated pathogens. These AgNPs were found to be selectively interacting with Hg2+ in an aqueous solution at various concentrations. A calibration curve was constructed by plotting concentration as abscissa and absorbance ratio (AControl − AHg/AControl) as ordinate. The linear range and limit of detection (LOD) of Hg2+ were 0.6–1.6 μM and 0.12 μM, respectively. A rapid response time of 4 min was found for the detection of Hg2+ by the nano-probe. The effect of pH and temperature on the detection of Hg2+ was also investigated. The nano-probe was successfully applied for the detection of Hg2+ from tap and river water

Rosmarinic Acid-Capped Silver Nanoparticles for Colorimetric Detection of CN- and Redox-Modulated Surface Reaction-Aided Detection of Cr(VI) in Water.

Rosmarinic acid-capped silver nanoparticles (Ro-AgNPs) were prepared and applied as a probe for selective colorimetric detection of cyanide (CN–) and chromium(VI) [Cr(VI)] under different conditions in aqueous media. The carbon atom of CN– interacts with the AgNPs, and the carbon atom donates electrons from the HOMO to the vacant orbitals of the coordinatively unsaturated surface atom (Ag0). After donating electrons, CN– attached onto the surface of the nanoparticles becomes very reactive and interacts with dissolved oxygen and generates reactive oxygen species (ROS) such as superoxide (O2–), singlet oxygen (1O2), and so forth. In this process, Ag0 oxidizes to Ag+ and combines with CN– forming water-insoluble AgCN, and the ROS (O2–) formed reacts with Ag/Ag+ to form Ag2O. The oxidation of Ag0 to Ag+ resulted in dissolution of AgNPs, which causes disappearance of the surface plasmon resonance band and color change from yellow to colorless. For detection of Cr(VI), ascorbic acid and CN– were added first; the ascorbic acid replaced the rosmarinic acid and then reduced the added Cr(VI) to Cr(III), and, in this process, ascorbic acid was oxidized to dehydroascorbic acid, which moved away from the nanoparticles’ surface. CN– then interacted with the surface Ag0 atom, got activated, and interacted with dissolved oxygen forming Ag+ and ROS, which then followed the same process as described for CN– to form AgCN and Ag2O with a color change. The limits of detection were found to be 0.01 and 0.03 μM for CN– and Cr(VI), respectively. The material was also used for sensing CN– and Cr(VI) in real samples, and the results obtained were satisfactory. For field application, agarose-based strips were prepared by immobilizing the nanoparticles onto the agarose film and successfully used for the detection of CN– and Cr(VI) in water.

Waste from Argentometric Determination of Chloride as a Source of Silver in the Synthesis of p‐Hydroxybenzoic Acid Capped Silver Nanoparticles

AbstractThis paper describes the utilization of waste from the argentometric determination of chloride in a chemistry teaching laboratory as a source of silver for the synthesis of p‐hydroxybenzoic acid capped silver nanoparticles (AgNPs). All white and red‐brick precipitates in the waste were first separated from the liquid and converted to silver chloride precipitate by washing the precipitates using hydrochloride acid 0.1 M. The silver chloride precipitate was then converted to diammineargentate complex ion by dissolving it into an ammonia solution. The conversion was successfully conducted by using 50 moles of ammonia for every mole of silver chloride. The formation of AgNPs was optimum by applying diammineargentate complex ion and p‐hydroxybenzoic acid solutions at a molar ratio of 1 : 10. The formed AgNPs showed a yellow color and absorption peak at around 420 nm with an average particle size of 26.4 nm. The as‐synthesized AgNPs were stable at least 16 weeks of storage, indicating that p‐hydroxybenzoic acid did not only act as a reducing agent but also play a role as a capping agent.

A highly selective colorimetric assay for the determination of creatinine in biological samples using gluconic acid capped silver nanoparticles after ionic liquid based dispersive liquid phase microextraction

A dispersive liquid-phase microextraction method combined with UV–vis spectrophotometry was utilized to highly selective determination of creatinine in human serum and urine samples. To overcome the interferences in complex matrices, creatinine reacted with 1,4-naphthoquinone-2- potassium sulfonate reagent to produce a red coloured product that could be extracted into a small volume of 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF6) ionic liquid solvent. To increase the sensitivity of the assay, gluconic acid capped silver nanoparticles (Ag NPs) were used. On addition of Ag NPs to the red coloured extracted product, the solution turned to blue accompanied with a red shift in wavelength around 620 nm that could be detected by the naked eye. The effective variables on the determination of creatinine such as concentration of the reagent, amount of formic and hydrochloric acids, type and volume of the extractant, and concentration of Ag NPs were investigated. Under the optimal conditions, the calibration plot was bimodal with linear ranges from 0.1 to 1.5 µg mL−1 and 1.5 to 105 µg mL−1 creatinine with a limit of detection 0.1 µg mL−1. The relative standard deviation for five measurements at 35 µg mL−1 concentration level was 3.8%. The newly developed assay was used for the determination of creatinine in human serum and urine specimens with satisfactory results.

Preparation of a portable calorimetry kit and one-step spectrophotometric nanomolar level detection of l-Histidine in serum and urine samples using sebacic acid capped silver nanoparticles

Abstract This work describes the synthesis of sebacic acid capped silver nanoparticles (SA-AgNPs) by the wet chemical method for the detection of l -Histidine in blood serum and urine samples. The synthesized SA-AgNPs were characterized by several techniques. The obtained particles were spherical in shape and the average diameter was calculated by HR-TEM images to be 11 nm. Moreover, the synthesized SA-AgNPs were stable for more than 3 months in solution. The synthesized SA-AgNPs showed the surface plasmon resonance (SPR) band at 420 nm. Interestingly, after the addition of 18.1 μM of l -Histidine into the SA-AgNPs solution, the SPR band absorbance decreased and the colour of the solution changed from brown to colourless. Based on the changes in the SPR band, we calculated the lowest detection limit to be 122 nM. The observed colour shift and spectral changes were due to the aggregation of SA-AgNPs induced by l -Histidine via hydrogen bonding interaction. Additionally, a possible mechanism is discussed. Furthermore, a 268-fold excess of common interferences did not interfere with the detection of 18.1 μM of l -Histidine. We successfully applied the SA-AgNPs probe for the detection of l -Histidine in blood serum and urine samples. Further, we validated our system with the HPLC technique. Importantly, we prepared a portable smartphone aided paper-based kit for on-site monitoring of l -Histidine. We strongly hope that this facile synthesis of SA-AgNPs and the portable paper-based kit will represent a step forward in the field of biosensing and materials science.

Facile fabrication of malonic acid capped silver nanoparticles and their antibacterial activity

The successful management of infections caused by human pathogenic bacteria is becoming a challenge for clinicians. Therefore, new strategies to circumvent the growth of pathogens need to be developed. The current study was therefore aimed to synthesize silver nanoparticles (AgNPs) through chemical reduction process of silver nitrate by tri sodium citrate or sodium borohydride and evaluated their antibacterial activity. During the synthesis process, AgNPs were capped by malonic acid (a dicarboxylic acid). We have exploited two approaches of cold (reduction by NaBH4) and hot (reduction by trisodium citrate) process for the synthesis of AgNPs which revealed maximum absorbance of AgNPs at 412 nm and 397 nm respectively. The malonic acid (MA) functionalized AgNPs (AgNPs/MA) were systematically characterized for their size, surface changes and morphology. These colloidal AgNPs were stable and polydisperse in nature with an average diameter of 20 nm. The zeta potential (ZP) analysis showed stable AgNPs. The AgNPs synthesis was optimized in a set of different reactions where concentration of metal precursor, concentration of capping agent, temperature, time of stirring and duration of reaction were variable. The AgNPs/MA were found poly-dispersed in nature with predominantly spherical shape. The antibacterial potential of AgNPs was then assessed against both Gram positive (Staphylococcus aureus) and Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and Klebsiella pneumoniae) by antimicrobial disc susceptibility assay with three replicates per treatment which showed promising antibacterial activity of AgNPs. The AgNPs/MA possessing remarkably smaller size exhibited encouraging antibacterial activity against human bacterial pathogens suggesting their potential application in controlling bacterial infections in clinical settings and can be utilized in further biomedical applications.

Synthesis and Comparative Antibacterial Activity of Fatty Acid Capped Silver Nanoparticles

In the present work, the chemical reduction method has been used to synthesize silver nanoparticles using stearic acid capping agents in different concentrations. These nanoparticles are characterized by ultraviolet-visible spectroscopy and dynamic light scattering (DLS). The size of the synthesized silver nanoparticles found between 80-100 nm and stable up to 5 months. These nanoparticles show a very good bactericidal influence on E. coli and S. aureus. In this method silver nanoparticles have synthesized at room temperature without using any inert atmosphere, this is the advantage of this method over others.

Reductive degradation of toxic six dyes in industrial wastewater using diaminobenzoic acid capped silver nanoparticles

Abstract The present work describes the reductive degradation of Phloxine B, Methyl Orange, Rhodamine B, Acriflavine, Auramine O, and Thymol Blue using silver nanoparticles as a catalyst. 3,4-diaminobenzoic acid capped silver nanoparticles (DAB-AgNPs) was synthesized by wet-chemical method. The obtained particles are spherical in shape, and their average diameter was calculated to be 9.2 ± 0.19 nm by high-resolution transmission electron microscopy (HR-TEM) images. We have successfully applied DAB-AgNPs as a catalyst for the degradation of six different dyes and monitored their catalytic efficiency by UV–vis spectrophotometer. Interestingly, DAB-AgNPs shows the higher catalytic efficiency for the degradation of Phloxine B, Methyl Orange, Rhodamine B, Acriflavine, Auramine O, and Thymol Blue dyes. Further, we have performed the degradation of six dyes mixture using DAB-AgNPs. Finally, this system was applied for the degradation of the dyes in wastewater. Moreover, we have performed the total organic carbon (TOC) studies, before and after the degradation of dyes. The degradation mechanism also was discussed.

Colorimetric speciation analysis of chromium using 2-thiobarbituric acid capped silver nanoparticles

In the present work, 2-thiobarbituric acid (TBA)-capped silver nanoparticles (AgNPs) have been introduced as a novel nanoprobe in the construction of a sensitive and selective colorimetric sensor for Cr(iii) and Cr(vi) ions. Cr(iii) can be linked to TBA on the AgNP surface via -N or -OH groups and form a bridge between two or more AgNPs causing their aggregation. This phenomenon leads to a dramatic color change in TBA-AgNPs from yellow to pinkish red. UV-Vis spectrophotometry, FT-IR and transmission electron microscopy (TEM) were utilized for quantitative analyses, characterization of modified AgNPs and determination of the interaction mechanism of TBA-AgNPs - Cr(iii). The color change depended on the concentration of Cr(iii) and the ratio of UV-Vis absorption intensity at 520 nm to that at 418 nm (A520/A418) was linearly proportional to the concentration of Cr(iii) from 0.012 to 3.25 mg L-1 (LOD = 8.4 µg L-1). To eliminate or reduce the interference of other cations in Cr(iii) determination, EDTA was used as a masking agent at pH 6.5. Moreover, the developed method was used for the determination of Cr(vi) in the presence of ascorbic acid (AA) (as a reducing agent) in the concentration range of 0.20 to 1.40 mg L-1. The proposed probe was successfully applied for the determination of Cr(iii) and Cr(vi) in cement factory wastewater.

Lipoic acid capped silver nanoparticles: a facile route to covalent protein capping and oxidative stability within biological systems

Covalent attachment of human serum albumin protein to the surface of spherical lipoic acid capped silver nanoparticles results in the generation of stable nanoparticle–protein hybrids with well defined surface composition. Enhanced stability towards oxidation and in the presence of complex media with high ionic strength, holds promise towards the use of these conjugates as therapeutics in biomedical applications and sensing.

Nanoformulation of C-18 long fatty acid-capped silver nanoparticles with exploration of photocatalytic and antibacterial activities

C-18 fatty acid-coated silver nanoparticles are synthesized using a facile and worthwhile chemical method.

Efficacy and safety of alpha lipoic acid-capped silver nanoparticles for oral applications.

Silver nanoparticles (AgNPs) are widely studied for their broad-spectrum antimicrobial effects, and can be utilised readily in biomaterials, however the cellular safety of specific AgNP formulations should be profiled prior to clinical usage. This study determined the cytotoxic effect of small sized (6 nm) alpha lipoic acid capped-AgNPs on human gingival fibroblasts (HGF), as compared to ionic silver and clinical antiseptics. The metabolic pathway was investigated to determine the cellular effects on HGF cells. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) was established for a range of oral related bacteria. Results showed that cell viability decreased with increasing AgNP concentration, whereas lower concentrations of AgNPs, (≤5 μg ml−1) caused a significant increase in cell proliferation at 24 and 72 hour time points. The cytotoxicity profile of AgNPs exhibited significantly lower concentrations, relative to the dose of clinical efficacy, when compared to clinical antiseptics. Caspase 3/7 was not significantly altered when HGF cells were treated with 0.225 μg ml−1 AgNPs, indicating cell necrosis rather than apoptosis. Quantitative RT2-PCR detected an upregulation of genes associated with oxidative stress and the G2M cell cycle checkpoint at ≤4 hours, but expression levels returned to levels consistent with control cells at 24–96 hours. An MIC range of 2.5–12.5 μg ml−1 (min. Escherichia coli, Streptococcus mutans, S. mitis; max. Staphylococcus aureus) was determined across the bacterial species tested and an MBC range of 5–100 μg ml−1 (min. E. coli, max. S. mutans). The antimicrobial profile was similar to that of AgNO3 which suggested that the antimicrobial effect may be influenced by free Ag+ release. It was concluded that alpha lipoic acid capped AgNPs possess limited cytotoxic activity to HGF cells when compared to clinically utilised oral antiseptics, observed via the cellular recovery after initial AgNP treatment and a lack of cumulative cytotoxic effect, whilst maintaining a broad range antimicrobial effect of the AgNPs.

Synthesis and characterization of stearic acid capped silver nanoparticles: pH dependent stabilization and colorimetric detection of Hg(II) in water

This work reports, synthesis of Ag nanoparticles in aqueous medium, under ambient reaction conditions using stearic acid as capping agent. Ag nanoparticles have been used for colorimetric detection of Hg 2+ in water. Effect of pH of the medium on size and stabilization of silver nanoparticles has been studied. Synthesized by chemical reduction of AgNO3 using NaBH4, Ag nanoparticles were characterised by UV-visible spectroscopy, transmission electron microscopy (TEM), FTIR spectroscopy and TGA techniques. Quenching of intensity along with blue shift of SPR band of Ag nanoparticles is observed due to deposition of Hg layer over Ag nanoparticles. Change in colour of Ag nanoparticles from dark yellow to colourless led to naked eye detection of Hg 2+ in water. The detection limit of Hg 2+ in water was found up to 1ppm monitored by colorimetric response of Ag nanoparticles by UV-visible spectrophotometer. A simple and cost-effective process allows quick determination of Hg 2+ in water.