Capping Agents Research Articles

Grafting of Ag nanoparticles on SrCrO4 nanostructures: green synthesis, characterization, and photocatalytic study for organic dye degradation

In this research for the first time, SrCrO4 nanoparticles were prepared using sol–gel procedure in which amino acid was used as stabilization agent. Different amino acids were used as capping, stabilizer, or reduction agent. In this regard, the effect of Glycine, Alanine, Valin, and Leucine were evaluated on the morphology and crystalline degree of the SrCrO4 nanoparticles. The amino acid has both roles of reduction and capping agent. The molar ratio for Sr3+: Cr3+: amino acid was 1: 1: 4, respectively. In the next step, photodeposition process was used for preparation of SrCrO4/Ag nanostructures. The prepared products were evaluated by using TGA, XRD, EDS, SEM, TEM, DRS, and BET. XRD result indicated that crystalline degree and purity of the nanostructures prepared in the presence of leucine were more when compared with the other samples. On the other hand, based on the Scherrer equation, the average particle size for the optimum specimen was nearly 9 nm. The SrCrO4/Ag nanocomposite which was obtained using leucine showed a high activity in organic dye degradation. We think that this high catalytic activity can be attributed to the synergistic effect between Ag and SrCrO4 nanoparticles.

Green fabrication, characterization of silver nanoparticles using aqueous leaf extract of Ocimum americanum (Hoary Basil) and investigation of its in vitro antibacterial, antioxidant, anticancer and photocatalytic reduction

Green fabrications of metallic nanoparticles are rapidly developing the research era, due to their broad spectrum of applications in the field of biomedical sciences. In the present study, the green fabrication of silver nanoparticles (AgNPs) has been demonstrated by a highly stable, biocompatible, and environmental friendly aqueous leaf extract of Ocimum americanum for their antibacterial, anticancerous, and photocatalytic dye degradation efficiency. The synthesized AgNPs were confirmed by UV–Visible spectroscopy, which indicates the surface plasmon resonance λmax band at 435 nm. The FE-SEM and HR-TEM micrographs showed spherical shaped AgNPs, and EDX analysis confirmed the crystalline purity of green fabricated AgNPs. Fourier transform infrared (FT-IR) technique indicated the presence of active functional groups such as O‒H, C˭C, C‒H, C‒N involved in the reduction and surface capping agent of green fabricated AgNPs. The XRD analysis of synthesized AgNPs showed the face-centered cubic (fcc) crystalline structure. The DLS measurement showed average particle size of distribution was 48.25 nm and Zeta potential value at −20.2 mV revealed high stability of fabricated AgNPs. Further, the synthesized AgNPs has exhibited potential antibacterial activity against pathogenic Gram +ve and Gram −ve bacteria and in-vitro antioxidant activity assessed by DPPH, H2O2 and reducing power assays. The in-vitro cytotoxic effects of fabricated AgNPs against A549 lung cancer cells displayed apoptotic cell death confirmed by fluorescent staining techniques and the cellular apoptotic induction of G0/G1 cell cycle arrest confirmed with the flow cytometry analysis. On the other hand, the AgNPs exhibited efficient photocatalytic dye degradation of eosin yellow (EY) under sunlight and UV-irradiation method. The AgNPs did not lyse the hemoglobin from human red blood cells and showed its biocompatibility on human cells. Herein, the present study proves an effective, economical, and multifunctional AgNPs for improved therapeutic and catalytic applications.

Effect of pH and Nanoparticle Capping Agents on Cr (III) Monitoring in Water: A Kinetic Way to Control the Parameters of Ultrasensitive Environmental Detectors.

In this work, we apply surface-enhanced Raman spectroscopy (SERS) to study the kinetics of chromium Cr (III) detection in solution using EDTA and silver nanoparticles (AgNPs). We examine for the first time the effect of pH and nanoparticles’ capping agent on the kinetic mechanism of Cr (III) detection using SERS temporal variations. The full width at half maximum (FWHM) and Raman shift variations show that the mechanism of detection is composed of two steps: a first one consisting of chemical coordination between Cr (III) and AgNPs that leads to exalted chemical and electromagnetic enhancement and the second one is an aggregation process with an important optical enhancement. The obtained results showed that the first step in the detection at lower pH was five times faster than in a basic medium using citrate capped silver nanoparticles (Cit-AgNPs). On the other hand, using a capping agent with dicarboxylate groups such as oxalate (Oxa-AgNPs) led to an important enhancement in SERS detection signal (more than 30 times) compared with Cit-AgNPs, although the detection kinetic’s mechanism was slower.

A rapid microwave-assisted synthesis of silver nanoparticles using Ziziphus jujuba Mill fruit extract and their catalytic and antimicrobial properties

An eco-friendly and sustainable approach was developed for the synthesis of silver nanoparticles (AgNPs) of Ziziphus jujuba Mill (ZJM) fruit extract by a microwave-assisted technique. The developed method was simple, economically viable, sustainable, and eco-friendly. Concentrations of AgNO3 and ZJM fruit extract and reaction time were optimized for the final properties of synthesized AgNPs. The prepared AgNPs were characterized by UV-visible and FTIR spectrophotometers, powder XRD, TEM, and DLS. XRD results showed a face-centered cubic structure for the prepared AgNPs. The obtained size of AgNPs was 8 ± 1 nm with spherical shape. The FTIR spectrum indicates that ZJM is a good capping agent to stabilize AgNPs. A negative zeta potentials value of − 21.2 mV indicates the stability of AgNPs. The AgNPs has good stability over a wide range of pH and ionic strength. The role and efficacy of AgNPs in the catalytic degradation of methylene blue (MB) and Congo red (CR) dye were studied, and the reduction reaction rate constants were found to be 0.033 s−1 (180 s) and 0.025 s−1 (200 s) respectively. The synthesized AgNPs showed rapid and excellent catalytic reduction of MB and CR dyes. The rapid catalytic reduction reactions followed pseudo-order kinetics. The ZJM fruit extract-capped AgNPs showed good antimicrobial activity against tested bacterial and fungal cultures.

Capping agent-induced variation of physicochemical and biological properties of α-Fe2O3 nanoparticles

Capping agents play a vital role in controlling the size, morphology, and monodispersity of nanoparticles. To understand a comprehensive overview of the influence of capping on the structure and properties of hematite nanoparticles (HNPs), we have synthesized hematite nanoparticles (HNPs) with narrow size distribution by an economic co-precipitation method using capping agents like sodium citrate, Polyvinyl Pyrrolidone (PVP) and starch. A comparative in-depth study of structure, morphology, and surface analysis along with thermal, optical, magnetic and electrochemical properties of synthesized capped and uncapped HNPs has been performed. The effect of capping agents on photocatalytic and antioxidant activities along with cytotoxicity of all fabricated nanoparticles was studied against MDA-MB-231 cell line causing breast cancer along with flow cytometry. Results revealed a definite improvement in grain size, crystallinity, optical, thermal and magnetic properties of HNPs is due to efficient capping. PVP has reduced the maximum of crystalline size up to 23% of HNPs and removed 98.80% of dye from wastewater among all capping agents. Our findings also suggest that PVP capped HNPs proved to be cytotoxic to the cancer cell line. Taken together, our studies will be helpful to understand the role of capping agents in determining properties of HNPs that can further help in designing engineer HNPs.

Dentists’ Preference of Pulp Capping Agent for Indirect Pulp Capping in Primary and Permanent Molars - An Observational Study

One of the major challenges associated with indirect pulp capping is to prevent the exposure of the pulp andmaintain its vitality. It is based on the rationale that pulpal mesenchymal cells induce dentin bridge formation.The common pulp capping agents used are calcium hydroxide and mineral trioxide aggregate both of whichact based on their high pH. The aim of the study is to infer the most preferred pulp capping agent by dentistsin a private dental college so as to achieve a good prognosis after indirect pulp capping of primary andpermanent molars.A total of 297 restorative procedures were obtained after reviewing patient case sheetsand were analysed using descriptive statistics on SPSS Software. Among 139 treatment procedures, themost common pulp capping agent used was calcium hydroxide (69.1%) in primary molars and mandibularpermanent molars and MTA (30.9%) mostly in maxillary permanent molars. Within the limits of the study,calcium hydroxide was the preferred pulp capping agent for indirect pulp capping by dentists in a privatedental college in both primary and permanent molars. However, with its clinical advantages, mineral trioxideaggregate shows a promising candidate as an indirect pulp capping agent in primary and permanent teeth.

Synthesis and characterization of SnO2 crystalline nanoparticles: A new approach for enhancing the catalytic ozonation of acetaminophen

A novel sol-gel method was employed in this study to efficiently synthesize SnO2 nanoparticles to catalyze the ozonation of acetaminophen (ACT) from aqueous solutions. The influence of various parameters including Sn source, type of capping and alkaline agents, and calcination temperature on the catalytic activity of the SnO2 preparations was investigated. The SnO2 nanoparticles prepared by tin tetrachloride as Sn source, NaOH as gelatin agent, CTAB as capping agent and at calcination temperature of 550 °C (SnNaC-550) exhibited the maximum performance in the catalysis of ACT. The optimized catalyst (SnNaC-550) had spherical-homogeneous and cubic-shaped nanocrystalline particles with 5.5 nm mean particle size and a BET surface area of 81 m2/g, which resulted in 98% degradation and 84% mineralization of 50 mg/L ACT at 20 and 30 min reaction time, respectively when combined with ozonation (COP). Based on the radical scavenger experiments, •OH was the major oxidizing agent involved in the removal of ACT. LC/MS analysis showed that short-chain carboxylic acids were the main intermediates. Furthermore, the SnNaC-550 catalytic activity was preserved after four successive cycles. Collectively, the new method has the potential to efficiently synthesize stable and reusable SnO2 nanoparticles to catalyze the ozonation of ACT from aquatic environments.

A Retrospective Analysis of The Correlation Between the Type of Pulp Exposure and The Choice of Pulp Capping Agents

The aim was mainly to determine the correlation between the type of pulp capping method and the material of choice in this study. Pulp capping in the carious teeth has been considered as unpredictable and they mainly have a lesser success rate. The pulp capping can be mainly done in two methods; they are direct and indirect pulp capping which can be mainly done with the help of different materials of choice like calcium hydroxide,MTA etc. The study was conducted in Saveetha Dental College . The data collection has been done from the department of Conservative dentistry and Endodontics for patients undergoing pulp capping treatment. A total sample data of 140 patients were obtained for a period of nine months ( June 2019 – April 2020.). Statistical analysis was done by using chi-square test with SPSS software version 23. The results were obtained and tabulated, the type of pulp capping method were 67% of indirect pulp capping and 33% of direct pulp capping method in which 81% of calcium hydroxide, 8% of MTA and 11% of RMGIC was used as the materials of choice. Among which indirect pulp capping method was most commonly used than the direct pulp capping method with calcium hydroxide as the material of choice for the treatment (p < 0.05 which is statistically significant). The pulpal exposure was mainly due to the dental caries and mechanical preparation of the tooth. Within the limits of the present study, the most common type of the pulp exposure was due to the dental caries and mechanical exposure during the cavity preparation of the tooth and the most common method of pulp capping was the indirect method with calcium hydroxide (CaOH) as the most common material of choice.

Role of Capping Agents in the Synthesis of Salicylate-Capped Zinc Oxide Nanoparticles

Capping agents are often used for controlling the size, aggregation, and properties of nanoparticles. To guide the design of improved nanomaterials for targeted performance, one can use mechanistic...

Facile, controllable, chemical reduction synthesis of copper nanostructures utilizing different capping agents

This investigation reports a simple, controllable, chemical reduction method for the formation of copper nanoparticles by reducing copper sulfate with sodium hypophosphite in ethylene glycol using different capping agents: sodium dodecyl sulfate (SDS), polyethylene glycol 2000 (PEG2000), and polyethylene glycol 4000 (PEG4000). The synthetic parameters influencing the purity, size, and morphology of the copper nanoparticles such as reaction time, reaction temperature, reaction solvent, initial copper sulfate concentration, and capping agent were investigated. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The results revealed that pure copper nanoparticles with an average crystallite size of 28 nm were successfully prepared in the presence of PEG4000 capping agent, at 70 °C, and in 45 min. The formation mechanism of the as-prepared Cu nanoparticles was also proposed.

Ultrasound-assisted microwave synthesis of CdS/MWCNTs QDs: A material for photocatalytic and corrosion inhibition activity

Semiconductor CdS/Multiwalled carbon nanotube quantum dots with crystallite size of 2–3 nm have been successfully synthesized by an ultrasound-assisted microwave method. The sap of opunica ficus-indica fruit is used as natural capping agent to enhance the quantum dot’s stability. The synthesized CdS/MWCNTs QDs were characterized by XRD, UV–Visible, FT-IR, HR-TEM, DLS, TGA, DTA and XRF. The photocatalytic activity of the QDs was tested for the degradation of dye, pararosaniline under simulated Ultra-violet radiation. The degradation rate was found up to 99.19% within 150 Min. The influence of QDs as corrosion inhibition on zinc plate in three aerated electrolytes solutions namely NaCl, HCl and KOH was studied by Tafel polarization technique. The result showed that corrosion resistance succeeded due to CdS/MWCNTs QDs coating over Zn surface.

Biosynthesis of Copper Nanoparticle using Nerium oleander

Nerium oleander leaves were collected from Sipcot IT Park. Nerium oleander leaf extract was prepared in deionized water and used for the synthesis of copper nanoparticles. The change in the colour of the solution from yellowish green to dark brown, confirmed the formation of copper nanoparticles. CuNPs were characterized by UV-Vis spectroscopy from which absorbance peak was found at 320 nm-620 nm. CuNPs confirmed natural bio compounds found in the leaf extract by FTIR peaks that are responsible for reducing and stabilizing agent. SEM micrographs of the synthesized by the reduction of copper sulphate revealed spherical and crystalline NPs average size of 20 nm. The biological method found to be eco-friendly, cost-effective method, which provided natural capping agents.

Nanoparticles and their Biomedical Applications

Over the years, due to the remarkable functional properties, the nanoparticles have been widely used and being tested in the treatment and diagnosis of diseases such as cancer, diabetes, etc. The green synthesis of these nanoparticles can be achieved by physical, chemical, and biological methods. Nanoparticles biosynthesis is put forth to be advantageous over chemical and physical methods because it is non or minimally toxic, environmentally friendly, and cost-effective. A green biosynthesis is an approach that connects nanotechnology with plants, microorganisms, waste materials, and biomolecules. The biological methods help to eliminate destructive processing situations, via letting the synthesis at biological pH, room temperature, and simultaneously, affordable price. Among various biological alternatives, medicinal plants and plant extracts seem to be the best options. Plants are the chemical factories of nature, the plant extracts contain various secondary metabolites, and it functions as reducing and stabilizing (capping) agent in bio-reduction reaction to synthesize new nanoparticles. Keeping these points in view, the present article reviews the various synthesis methodologies, key factors, characterizations, usages, and foretold antimicrobial approach in a systematic manner, concentrating on several green pathways for nanoparticles synthesis.

Green Synthesized ZnO Nanoparticles Mediated by Mentha Spicata Extract Induce Plant Systemic Resistance against Tobacco Mosaic Virus

Globally, plant viral infection is one of the most difficult challenges of food security, where considerable losses in crop production occur. Nanoparticles are an effective control agent against numerous plant pathogens. However, there is limited knowledge concerning their effects against viral infection. In the present study, the green synthesis of zinc oxide nanoparticles (ZnO NPs) using aqueous leaf extract of Mentha spicata was achieved. X-ray diffraction patterns confirmed the crystalline nature of the prepared ZnO NPs. Dynamic light scattering and scanning electron microscopy analyses revealed that the resultant ZnO NPs were spherical in shape with a particle size ranged from 11 to 88 nm. Fourier transmission infrared spectroscopy detected different functional groups, capping and stability agents, and showed Zn-O bond within wavenumber of 487 cm−1. Under greenhouse conditions, the antiviral activity of biological synthesized ZnO NPs (100 µg/mL) against Tobacco mosaic virus (TMV) was evaluated. The double foliar application of the prepared ZnO NPs, 24 h before and 24 h after TMV-inoculation, was the most effective treatment that showed a 90.21% reduction of viral accumulation level and disease severity. Additionally, the transcriptional levels of PAL, PR-1 (salicylic acid marker gene), CHS, and POD genes were induced and up-regulated in all ZnO NPs treated plants. Notably, the results exhibited that aqueous extract of Mentha spicata was an effective reducing agent for the green synthesis of ZnO NPs, which showed significant antiviral activity. Finally, the detected protective and curative activity of ZnO NPs against TMV can encourage us to recommend its application for plant viral disease management. To our knowledge, this is the first study describing the antiviral activity of the green synthesized ZnO NPs.

Study of a renewable capping agent addition in lignin base catalyzed depolymerization process

The aim of this work was to study the influence of a renewable capping agent (CA) in the production of monomeric compounds from the depolymerization of an organosolv lignin (Pinus radiata) by a base catalyzed depolymerization (BCD) process. After the delignification process of the Pinus radiata sawdust, the lignin contained in the black liquor was subjected to a first mild depolymerization process, without using any catalyst, in order to obtain two different products: a lignin which was the feed in the subsequent BCD process and a phenolic oil which was used as CA in the same BCD process. This process was carried out at 230 °C in three consecutive cycles of 20 min using different amounts of capping agent dissolved in a 4% wt. NaOH solution with a lignin:solvent ratio of 1:20. The use of a renewable capping agent derived from lignin was effective not only in terms of phenolic oil production increasing but also in maximizing the monomeric phenolic compounds concentration. The use of CA: lignin ratio of 1:1 resulted the most effective with 10.64% of oil yield and almost 44% of monomeric phenolic compounds concentration while minimizing de undesired by-products yield.

Activation Matters: Hysteresis Effects during Electrochemical Looping of Colloidal Ag Nanowire Catalysts

Colloidal electrocatalysts are commonly synthesized using organic capping agents (surfactants), which control the size distribution and shape of the resulting nano-objects and prevent them from agg...

The remarkable role of emulsifier and chitosan, dextran and PEG as capping agents in the enhanced delivery of curcumin by nanoparticles in breast cancer cells

Curcumin has been found to be a powerful anti-cancer agent. However, its efficacy is limited by its poor solubility in aqueous medium. The bioavailability of curcumin was increased by poly (lactic-co-glycolic) acid [PLGA (60/40)] nanoparticles with different capping agents such as Chitosan, Dextran and PEG and emulsifier (Tocopherol Poly (Ethylene Glycol)1000 Succinate: TPGS) with good drug loading and delivery performance. The preparation of nanoparticles derived from PLGA was achieved by emulsion solvent evaporation method and the resultant nanoparticles were characterized. The encapsulation efficiency of curcumin by PLGA NPs with different capping agents such as Chitosan, PEG and Dextran and emulsifier lies in the range of 82% to 89% and the anti-oxidant activity is 80%. The in vitro anticancer activity of PLGA nanoparticles embedded with curcumin and different capping agents on MCF-7 indicates that they are more effective in arresting cell growth. The cellular uptake of TPGS emulsified dextran capped curcumin encapsulated PLGA NPs is much higher when compared to that of PLGA NPs with other capping agents, emulsifier and free curcumin.

Chitosan/PVA hydrogels incorporated with green synthesized cerium oxide nanoparticles for wound healing applications

In this paper, we report the synthesis and evaluation of a polyvinyl alcohol/chitosan (PVA/chitosan) hydrogel incorporated with green synthesized cerium oxide nanoparticles (CeO2-NPs) using a Zingiber officinale extract as the reducing, capping and stabilizer agent for wound healing applications. The PVA/chitosan/CeO2-NPs hydrogel was synthesized via the freeze-thaw technique with 0 to 1% (wt) 5 nm CeO2-NPs. Results revealed that the hydrogels containing 0.5% of CeO2-NPs showed better antibacterial activities after just 12 hr (with MRSA but not E. coli) and healthy human dermal fibroblast viabilities up to 5 days (more than 90%) compared to the control group. Therefore, these chitosan/PVA hydrogels incorporated with Ce-NPs could be a potential candidate as a robust wound dressing agent that impressively may decrease wound infections without resorting to the use of antibiotics.

Green Synthesis of Silver Nanoparticles from Aqueous Leaf Extract of 'Selaginella bryopteris' and Elucidation of its Antimicrobial Activity

Background: Biosynthesis of nanoparticles from aqueous leaf extract of ‘Selaginella bryopteris’ is a green chemistry approach and is considered to be one of the most efficient methods as it is devoid of toxic chemicals as well as provides natural capping agents for the stabilization of synthesized nanoparticles. ‘S.bryopteris’ also known as ‘Sanjeevani’ (in India), is thought to be prospective natural resource that possesses extraordinary pharmaceutical potential. Objective: S. bryopteris is exclusively native to India and has already been known for its expression of stress-associated genes and high levels of protective metabolites of sugars, phenolic compounds, and polyols. Its potential as an antibacterial agent is being elucidated. Methods: Different leaf extract volumes, silver nitrate (AgNO3) concentrations, and reaction time were investigated separately and the optimal conditions for the synthesis of AgNPs were suggested. The resulting AgNPs were characterized by various techniques like Ultraviolet-Visible (UV-Vis) Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and XRay Diffraction (XRD). Antibacterial assays were carried out by using both agar disk and well diffusion method. Results: The AgNPs synthesized in this process were found to have efficient antimicrobial activity against both Gram-positive as well as Gram-negative bacteria. The antibacterial efficacy of S. bryopteris was consciously tried on uropathogenic Escherichia coli (Gram-negative bacteria) and Bacillus megaterium (Gram-positive bacteria) which have the self-limiting food poisoning potential along with opportunistic uropathogenic bacterial strains namely Proteus mirabilis (Gram-negative bacteria) and a non-pathogenic Micrococcus luteus (Gram-positive bacteria) for comparison. Conclusion: S. bryopteris mediated silver nanoparticles’ synthesis is attempted for being cost-effective, eco-friendly and safe for human therapeutics.

Ultrasensitive Monitoring of Museum Airborne Pollutants Using a Silver Nanoparticle Sensor Array.

The preservation of cultural heritage materials requires extremely low concentration limits for indoor pollutants. This poses an unmet challenge for monitoring the artwork in museums and on exhibit, especially to do so in a cost-effective manner for a large number of locations. A novel type of colorimetric sensor array based on printed inks of 10 nm silver nanoparticles (AgNPs) with several different capping agents has been developed as an alternative to metal coupons or other passive sampling indicators traditionally used by conservators. The AgNP colorimetric sensor array, combined with digital imaging, offers ultrasensitive dosimetric identification of acidic and oxidizing gases and other air pollutants commonly found in a museum; the limits of detection are sub-ppb for 1 h exposures. For an array of AgNP inks with various capping agents, a unique and distinguishable color response pattern is observed for each specific analyte. Excellent discrimination among 11 gas pollutants over a wide range of concentrations was demonstrated using standard chemometric methods. The observed changes in color during pollutant exposure originate from the sintering of solid-state nanoparticles that leads to changes in the localized surface plasmon resonance. Such chemically induced sintering mechanism of nanoparticles paves the way for a new class of field-deployable solid-state optical sensor arrays. As an example, we have demonstrated the use of AgNP sensor arrays for the nondestructive analysis of acidic volatile emission from five types of printing paper, relevant for the conservation of cultural heritage objects, including ancient manuscripts and books.