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Schiff base compounds were reported to make a complex with Cu2+ and Ag+ and subsequent reduction produced Cu0 and Ag0 nanoparticles separately via UV irradiation. Here, we synthesized a Schiff base, which initially formed a complexation with Cu2+ and made Cu0 nanoparticles after 8 h aging. In that reaction mixture, addition of Ag+ resulted in Ag0 nanoparticles. Emissive semi-carbazone (a Schiff base synthesized from semicarbazide and salicylaldehyde) was employed for the first time to selectively and sensitively detect Cu2+ (linear range of detection 10–4 to 5 × 10–8 M and limit of detection 13 μM) with the formation of copper oxide nanoparticles via complexation–reduction method. The introduction of Ag+ in it produced Ag0 and Cu0 (CuO via aerial oxidation) nanoparticles with a gigantic increase of fluorescence to obtain selective and sensitive Ag+ detection (linear detection range 10–3–10–7 M, and limit of detection 7. 7 μM). Thus, Cu2+ and Ag+ were detected based on turn-off/on fluorescence in one pot. As the evolution of copper and silver nanoparticles was the fundamental reason for sensing, response time is similar to the stable fluorescence behavior of oxidized SC (capping agent) with in situ generated copper and silver nanoparticles. CuO-induced fluorescence quenching was due to the formation of the trapped plasmon, while Ag+-induced fluorescence enhancement was owing to the lightning rod effect. The synergism of Cu and Ag was also investigated in this paper as a driving force of the lightning rod effect for the first time. Both the metals (Cu and Ag) were estimated in natural water, justifying the utility of the sensing platform for practical applications. Besides, the evolution of brilliant red color with semi-carbazone for Ag+ was employed for the colorimetric sensing of Ag+. [ABSTRACT FROM AUTHOR]

Silver nanoparticles were synthesized using alkaline salicylaldehyde (SL) in the presence of silver nitrate. SL was oxidized to quinone form, while silver(I) was converted to silver (0). The solution was highly fluorescent, (quantum yield 7 %, λex 290 nm, λmax 424 nm), where silver (0) exhibited metal‐enhanced fluorescence and quinone acted as the fluorophore. The fluorescence was selectively quenched with the addition of Fe3+. No other metal shows such drastic fluorescence quenching. Thus, silver‐enhanced fluorescence is used to detect iron selectively and sensitively (limit of detection 2×10−9 M, linear detection ranges from 10−4 M to 8×10−9 M). The detection of iron was also done at various water of natural sources (drinking water tap water, rainwater, and Ganga River water). The iron concentration was quite similar to atomic absorption spectroscopy. The enhancement of fluorescence of the sliver atom is attributed to enhanced photonic mode density, related to the lightning rod effect. The quenching of silver‐enhanced fluorescence was attributed to the destruction of the capping agent due to SL‐iron complexation. The variation of distance between the fluorophore and metalized surface was anticipated for the alteration of fluorescence with and without the Fe3+ion. [ABSTRACT FROM AUTHOR]

The small molecule salicylaldehyde was used to achieve copper-enhanced fluorescence. The fluorescence was investigated under various physicochemical conditions. Such fluorescence was utilized to obtain a selective sensing platform for H2O2 with various limits of detection. Cotton was impregnated with copper nanoparticles and used to remove H2O2 in a prototype application and its efficacy was quantified via copper-enhanced fluorescence. [ABSTRACT FROM AUTHOR]

Kaolin, a natural and inexpensive clay mineral, is ubiquitous in soil, dirt, and airborne particles. Amongst four commonly available clay minerals, kaolin, as a result of its layered structure, is the most efficient natural gaseous Hg adsorbent to date (Langmuir maximum adsorption capacity Qm=574.08 μg g−1 and Freundlich Qm=756.49 μg g−1). The Hg uptake proceeds by homogeneous monolayer and heterogeneous processes. Hg physisorption on kaolin occurs in the dark, yet the adsorption rate is enhanced upon irradiation. The effects of several metal complexes, salts, halides and solvents on the Hg uptake were examined. The addition of CuCl2 particles leads to a significant enhancement of the Hg uptake capacity (>30 times) within second timescales and without irradiation. The physisorption with kaolin is switched to chemisorption upon the addition of CuCl2 to kaolin. This process is entirely reversible upon the addition of Zn/Sn granules at room temperature without any added energy. However, the investment of a small amount of renewable energy can speed up the process. This technology demonstrates the facile and efficient capture and recycling of elemental Hg0 from air. A wide range of metal particles and diverse physicochemical processes, which include the microphysics of nucleation, are herein examined to explore the potential reaction mechanism by using a suite of complementary analytical techniques. These new mechanistic insights open a new era of energy‐neutral environmental remediation based on natural soil/airborne particles. [ABSTRACT FROM AUTHOR]