Farid Ahmed

In this study, we present a direct colorimetric technique for the sensitive and specific detection of Ba²⁺ ions in laboratory tap and river water utilizing functionalized 18β-glycyrrhetinic acid peptide silver nanoparticles (GAP-AgNPs).

Environmental pollution caused by heavy metal ions has become a major health problem across the world. In this study, a selective colorimetric sensor based on starch functionalized silver nanoparticles (St-Ag NPs) for rapid detection of Hg²⁺ in real samples was developed. The environmentally friendly green approach was utilized to synthesize starch functionalized silver nanoparticles (St-AgNPs). A multi-technique approach involving UV-Vis absorption spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscope (SEM) was used for the characterization of St-Ag NPs. These starch functionalized AgNPs were tested for the detection of heavy metals at 25 °C. The screening process revealed clear changes in the AgNPs color and absorption intensity only in the presence of Hg²⁺ due to the redox reaction between Ag⁰ and Hg²⁺. The color and absorption intensity of nanoparticles remain unchanged in the presence of all the other tested metals ion. The proposed method has strong selectivity and sensitivity to Hg²⁺ ions, with a detection limit of 1 ppm revealed by UV-visible spectrophotometry. The proposed procedure was found to be successful for the detection of Hg²⁺ in real samples of tap water.

There has been quite a lot of research focused on their structure, stability, reactivity, selectivity, and so on for chemical manipulation in their biological activity or sensor applications since the exploration of the G-quadruplex structure in recent years. This review summarizes the latest applications of G-quadruplex (as detector of genome wide folding, enantioselective catalysts, the disease’s therapeutics, promising drug targets, and smart fluorescence probe). It described that the advancements for detecting different metal ions (Na+, K+, Ag+, Tl+, Cu+/Cu2+, Hg2+ and Pb2+, etc.) and biomolecules (AMP, ATP, DNA/RNA, microRNA, G-quadruplex, Thrombin, T4 PNK, RNase H, ALP, CEA, Lipocalin 1 and UDG, etc.) in fluorescent sensors based on G-quadruplex modification, such as dye-label, dyes complex, intercalating dyes, artificial nucleobase moiety, and bioconjugated nanomaterials (AgNCs, GO, QDs, CDs and MOF, etc.). To investigate extremely efficiently responsive agents for diagnostic and therapeutic applications in medicine, the fluorescence sensors based on G-quadruplex are also employed as a quantitative visualization technique.

Herein, we report the synthesis and characterization of a plant growth regulator based silver nanoparticles and its application as a sensor for the ultrasensitive detection of toxic metal ions (Hg ²⁺ ) in tapwater.

A new tetra triazole functionalized calix[4]resorcinarene macrocycle (5) is synthesized and utilized for the detection of copper ions in the aqueous medium. The photophysical potential of compound (5) is examined by a range of cations (Ba2+, Ca2+, Co2+, Hg2+, K+, Mg2+, Mn2+, Na+, NH4 + and Pd2+). The triazole based calix[4]resorcinarene macrocycle (5) has interacted with Cu2+ ion in preference of other cations. A significant quenching has been observed after the addition of 15 μM Cu2+ ion solution, which produced 4.2 folds drift in the absorption intensity of compound (5). Tetra triazole functionalized calix[4]resorcinarene macrocycle showed high selectivity towards copper ion chemosensing without any interference in competitive studies. The pH studies of compound (5) with Cu2+ indicated the maximum chelation between 7- 7.5 pH. The compound (5) is capable to recognize Cu2+ at 1 μM detectable limit. Copper ion was detected in tap water with 15 μM concentration. Job’s plot showed 1:2 binding ratio between macrocycle (5) and Cu2+.