Shape and size selective separation of gold nanoclusters by competitive complexation with octadecylamine monolayers at the air–water interface

Ruthenium complex based nanocomposite film with enhanced and selective electrochemical sensing of bifenthrin pesticide

Bifenthrin (BF), a widely used pyrethroid pesticide in farming, lacks highly sensitive and selective sensors despite its extensive application. Ruthenium complexes are very effective for selective sensing applications but suffer from structural instability at elevated conditions, electrochemical activity, and the use of costly electrolytes. This work improves their electrochemical activity and mechanical strength by incorporating silver nanowires and replacing the costly electrolyte with abundant KCl + PBS, resulting in enhanced signal performance. Herein, a ruthenium complex containing composite film was immobilized on a platinum (Pt) electrode using Langmuir Blodgett technique. The fabricated sensor has been characterized by differential pulse voltammetry (DPV) based electrochemical technique. The BF pesticide sensing parameters, including the limit of detection (LOD), linear range (LR), and sensitivity, were evaluated using SWV, DPV, and CV techniques. Among these, the DPV technique demonstrated the best performance, achieving a sensitivity of 0.648 μA cm-2 μM-1, a LR of 1-10 μM, and a LOD of 1 μM. The relative standard deviation (RSD) values using DPV are found to be 6.3% (repeatability study), 3% (reproducibility study), 8% (metal ion interference), 5% (organic species interference), and 2% (real sample study), which are much lesser than the World Health Organization (WHO) recommendation of RSD value on the pesticide (i.e. 20%). The BF sensor demonstrated a selectivity of 2× difference of peak height response compared to similar pesticides. The reported pesticide sensor will open new options for sensor research using metal complex-based LB film nanocomposite.

Green synthesis and spectral characterization of silver nanoparticles from Lakshmi tulasi (Ocimum sanctum) leaf extract

A simple method for the green synthesis of silver nanoparticles (AgNPs) using aqueous extract of Lakshmi tulasi (Ocimum sanctum) leaf as a reducing and stabilizing agent. AgNPs were rapidly synthesized using aqueous extract of tulasi leaf with AgNO(3) solution within 15 min. The green synthesized AgNPs were characterized using physic-chemical techniques viz., UV-Vis, X-ray diffraction (XRD), scanning electron microscope (SEM) coupled with X-ray energy dispersive spectroscopy (EDX) and Fourier transform-infrared spectroscopy (FT-IR). Characterization data reveals that the particles were crystalline in nature and triangle shaped with an average size of 42 nm. The zeta potential of AgNPs were found to be -55.0 mV. This large negative zeta potential value indicates repulsion among AgNPs and their dispersion stability.

One pot synthesis of gold nanoparticles and application in chemotherapy of wild and resistant type visceral leishmaniasis

Gold nanoparticles (Aunp) through biogenetic processes have induced enormous interest for lower toxicity and precise applications. A rapid, one pot synthesis for uniformly sized gold nanoparticles was developed using polyphenolic compound quercetin. Reduction process was followed at low temperatures in a simple bath type sonicator. Nanoparticle plasmon response was recorded at 540 nm and the average size in TEM was observed at 15.07 nm. Detailed X-ray diffraction (XRD) observations proved fcc crystalline structure of metallic gold and the Fourier transform infrared (FTIR) analysis has confirmed nanoparticles conjugation with quercetin. Leishmaniasis, is a neglected tropical disease (NTD) classified by the World Health Organization (WHO). The leishmanial parasite multiply in host macrophages and most strains have developed drug resistance to available chemotherapeutics. Drug delivery is therefore a major problem in macrophage specific leishmanial parasite infections. New quercetin conjugated gold nanoparticles (QAunp) were successfully evaluated for the first time against leishmanial macrophage infections. Antileishmanial efficiency of QAunp was established against wild type (IC50 15±3), sodium stibogluconate resistant strain (IC50 40±8) and the paramomycin resistant (IC50 30±6) strains. Macrophage uptake of QAunp was complete within an hour as observed in TEM experiments.

A Simple, Rapid, and Green Synthesis of Capped Gold Nanospheres and Nanorods Using Aqueous Extract of Azolla

In the last few decades, an increasing commercial demand for metal nanoparticles is found due to their numerous applications in various fields such as electronics, catalysis in organic synthesis, material chemistry, energy, and medicine. Metallic nanoparticles are traditionally synthesized by wet chemical techniques, wherein the chemicals used are quite harmful and flammable. Herein, we reported a cheap and environment-friendly procedure for the synthesis of capped gold nanoparticles of different shapes from aqueous solution of tetrachloroauric acid (HAuCl4) using aqueous extract of Azolla pinnata, blue-green algae used as a reducing as well as capping agent. The so-prepared gold nanoparticles were well characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), and quasi-elastic light scattering (QELS) techniques. The TEM showed nearly uniform distribution of the particles in water, which is again confirmed by QELS. This is for the first time that aqueous extract of A. pinnata was used for the synthesis of gold nanoparticles.

Murraya Koenigii leaf-assisted rapid green synthesis of silver and gold nanoparticles

A facile bottom-up 'green' and rapid synthetic route using Murraya Koenigii leaf extract as reducing and stabilizing agent produced silver nanoparticles at ambient conditions and gold nanoparticles at 373 K. The nanoparticles were characterized using UV-vis, transmission electron microscopy (TEM), X-ray diffraction (XRD) and FTIR analysis. This method allows the synthesis of well-dispersed silver and gold nanoparticles having size ∼10 nm and ∼20 nm, respectively. Silver nanoparticles with size ∼10 nm having symmetric SPR band centered at 411 nm is obtained within 5 min of addition of the extract to the solution of AgNO3 at room temperature. Nearly spherical gold nanoparticles having size ∼20 nm with SPR at 532 nm is obtained on adding the leaf extract to the boiling solution of HAuCl4. Crystallinity of the nanoparticles is confirmed from the high-resolution TEM images, selected area electron diffraction (SAED) and XRD patterns. From the FTIR spectra it is found that the biomolecules responsible for capping are different in gold and silver nanoparticles. A comparison of the present work with the author's earlier reports on biosynthesis is also included.

Aminopyrazole-based ligand induces gold nanoparticle formation and remains available for heavy metal ions sensing. A simple "mix and detect" approach

A novel way to synthesize gold nanoparticles based on the use of N-alkylaminopyrazole is shown. This ligand has a triple functionality: induces AuNPs formation, stabilizes the formed nanoparticles, and even remains available for an external coordination with heavy metal ions. The availability of N-alkylaminopyrazole ligands onto the AuNPs surface is studied using UV-vis and NMR techniques. The mechanism of formation of AuNPs along with the synthesis optimization and characterization are studied using voltammetry and UV-vis, and the results are discussed in detail. The application of N-alkylaminopyrazole-derived gold nanoparticles in the heavy metal ions sensing is also tested showing a high sensitivity for mercury detection at low concentration level. The functionalization of metal nanoparticles with these receptors followed by heavy metal ions detection represents a simple "mix and detect" approach with interest for several other sensing applications.