A multi-functional chemosensor for highly selective ratiometric fluorescent detection of silver(I) ion and dual turn-on fluorescent and colorimetric detection of sulfide

Biosynthesis and Multifaceted Characterization of Breynia nivosa-Derived Silver Nanoparticles: An Eco-Friendly Approach for Biomedical Applications

This study presents an environmentally friendly synthesis of stable silver nanoparticles (Ag-NPs) using the methanolic extract of Breynia nivosa. Initial phytochemical analysis of the extract revealed the presence of alkaloids, flavonoids, glycosides, saponins, and tannins. Further characterization through high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) analyses identified a diverse array of bioactive compounds, including hydroquinone, stearic acid, neophytadiene, 9,12-octadecadienoic acid (Z,Z), methyl ester, and others. The addition of B. nivosa methanolic extract to an AgNO3 solution resulted in a color change, confirming the green synthesis of Ag-NPs through the reduction of AgNO3, as made evident by ultraviolet-visible (UV-vis) spectroscopy. X-ray diffraction (XRD) analysis provided valuable insights into the crystal structure, and scanning electron microscopy (SEM) analysis visualized the predominantly spherical shape of the Ag-NPs. However, the zeta (ζ)-potential and dynamic light scattering (DLS) analyses confirmed the stability and nanoscale dimensions of the synthesized Ag-NPs. Meanwhile, Fourier transform infrared (FT-IR) spectra exhibited peaks indicative of various functional groups, including carboxylic acids, phenols, alkanes, and isocyanates. These functional groups played a crucial role in both the reduction and capping processes of the Ag-NPs. The study further explored the antioxidant activity, cytotoxicity, acetylcholinesterase inhibition, and α-amylase inhibition activities of the Ag-NPs of the B. nivosa extract, demonstrating their potential for biomedical and therapeutic applications. In conclusion, this environmentally sustainable synthesis of Ag-NPs from the B. nivosa extract, enriched with bioactive secondary metabolites detected through HPLC and GC-MS analysis, holds promise for diverse applications in the burgeoning field of green nanotechnology.

Anthracene benzene conjugate (ABC): An asymmetric Schiff base for the selective detection of Ag+ ion using fluorimetry and its applications

Anthracene based chemosensor ABC has been synthesized and characterized through ¹H, ¹³C NMR, mass spectral studies. UV absorption and emission studies performed to identify the sensing behavior of chemosensor ABC. The probe ABC, originally bright fluorescent, selectively sense Ag⁺ ion by the quenching the fluorescence intensity through a "Switch On-off" process and quench the fluorescence due to the heavy atom effect interaction with the free chemosensor. The binding constant of the probe ABC with Ag⁺ was calculated as 5.4 × 10⁴ M^-1 and the limit of detection upto 1.4 nM level. The practical utilization of the probe ABC was demonstrated by applying to the real water and soil sample analysis, latent finger print, and the sensor as a fluorescent ink.

Green Synthesis and Characterization of Silver Nanoparticles Using Myrsine africana Leaf Extract for Their Antibacterial, Antioxidant and Phytotoxic Activities

Nanotechnology is the study and control of materials at length scales between 1 and 100 nanometers (nm), where incredible phenomena enable new applications. It affects all aspects of human life and is the most active research topic in modern materials science. Among the various metallic nanoparticles used in biomedical applications, silver nanoparticles (AgNPs) are among the most important and interesting nanomaterials. The aim of this study was to synthesize AgNPs from the leaf extract of Myrsine africana to investigate their antibacterial, antioxidant, and phytotoxic activities. When the leaf extract was treated with AgNO3, the color of the reaction solution changed from light brown to dark brown, indicating the formation of AgNPs. The UV-visible spectrum showed an absorption peak at 438 nm, confirming the synthesis of AgNPs. Scanning electron microscopy (SEM) showed that the AgNPs were spherical and oval with an average size of 28.32 nm. Fourier transform infrared spectroscopy confirms the presence of bio-compound functional groups on the surface of the AgNPs. The crystalline nature of the AgNPs was confirmed by XRD pattern. These biosynthesized AgNPs showed pronounced antibacterial activity against Gram-positive and Gram-negative bacteria, with higher inhibitory activity against Escherichia coli. At 40 µg/mL AgNPs, the highest antioxidant activity was obtained, which was 57.7% and an IC50 value of 77.56 µg/mL. A significant positive effect was observed on all morphological parameters when AgNPs were applied to wheat seedlings under constant external conditions at the different concentrations. The present study provides a cost-effective and environmentally friendly method for the synthesis of AgNPs, which can be effectively used in the field of therapeutics, as antimicrobial and diagnostic agents, and as plant growth promoters.

An ESIPT-based fluorescent turn-on probe with isothiocyanate for detecting hydrogen sulfide in environmental and biological systems

A probe with an isothiocyanate group was synthesized and evaluated for its H₂S sensing ability. Upon addition of H₂S, the probe exhibited ratiometric properties during absorption with a red-shift. The probe exhibited fluorescent off-on responses towards H₂S via the ESIPT process, due to the conversion of isocyanate into amine. UV-vis, fluorescence, and ¹H NMR spectroscopic analyses were performed to investigate the sensing mechanism. The probe has a large Stokes shift, short response time, and low detection limit. It can be used to estimate H₂S levels within the range of 0-36 nM. The practical applicability of the probe was demonstrated using water samples and living cells.

Colorimetric cadmium ion detection in aqueous solutions by newly synthesized Schiff bases

Two newly synthesized Schiff bases DMCA and DMBA were used for selective detection of Cd²⁺ over a wide range of other metal ions in acetonitrile (ACN)/ Tris-HCl buffer (10 mM, pH 7.32, v/v 2:1). The sensors can detect Cd²⁺ ions by colour changes from colourless to orange for DMBA and yellow to reddish for DMCA. Response of the probes towards metal ions was investigated by using UV-vis spectroscopy. The complex stoichiometry between the sensors, DMBA and DMCA, and Cd²⁺ was found to be 2:1 and the binding constants were calculated to be 2.65 ×10¹² M^-2 and 4.95 ×10¹² M^-2, respectively. The absorbance-based detection limits of DMBA and DMCA were calculated as 0.438 μM and 0.102 μM, respectively. The sensors were also successfully applied to real samples.

Design and synthesis of new functionalized 8-(thiophen-2-yl)-1,2,3,4-tetrahydroquinolines as turn-off chemosensors for selective recognition of Pd2+ ions

Functionalized 8-thienyl-1,2,3,4-tetrahydroquinoline was synthesized as a fluorescent turn-off chemosensor for selective recognition of Pd²⁺ ions with a low detection limit.

Triazole-Coupled Benzimidazole-Based Fluorescent Sensor for Silver, Bromide, and Chloride Ions in Aqueous Media

A triazole-coupled benzimidazole-based fluorescent probe S1 with nitrogen and oxygen binding sites was synthesized and its properties as a probe for cations were investigated. Probe S1 was found to be highly selective toward Ag⁺ ions in aqueous media. The fluorescence intensity of S1 was quenched as a function of the concentration of Ag⁺ ions in the presence of potential interfering cations with a detection limit of 2.70 μM. The resulting S1-Ag⁺ complex was subsequently studied for its anion recognition abilities and found to recognize Br^- and Cl^- ions, revealing the concentration-dependent fluorescence enhancement with detection limits of 22.2 and 23.0 μM, respectively. Revival of the fluorescence profile of probe S1 indicated that Ag⁺ ion was released from the S1-Ag⁺ complex. Probe S1 is a sensor that can be single-handedly utilized for the qualitative and quantitative determination of Ag⁺, Br^-, and Cl^- ions in aqueous media.

A Fluorescence Strategy for Silver Ion Assay via Cation Exchange Reaction and Formation of Poly(thymine)-templated Copper Nanoclusters

The detection of Ag⁺ ions in the environment and biological systems is important to both environmental monitoring and modern medicine. Herein, a novel and label-free method was developed for Ag⁺ detection, which utilizes a florescence strategy combining DNA-templated copper nanoclusters (Cu NCs) with cation exchange reactions. The method is primarily based on the effective detection of an Ag⁺-triggered cation exchange reaction and the release of free Cu²⁺ from CuS nanoparticles (CuS NPs), while the probe T30 serves as an effective template for the formation of fluorescence-inducing Cu NCs. Under optimal conditions, this sensing system displays high sensitivity with a 50 nM limit of detection and a range from 0 - 100 μM. In addition, the proposed method exhibits high selectivity and, therefore, was successfully applied to the analysis of real samples. Overall, these results demonstrate that our established method has advantages of design and operation simplicity, as well as cost-effectiveness.