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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]

Salicylaldehyde (SD) and its derivatives are effective precursors for generating coinage metal (gold, silver, and copper) nanoparticles (NPs). These NPs have a variety of potential environmental applications, such as in water purification and sensing, and those arising from their antibacterial activity. The use of SD and its derivatives for synthesizing coinage NPs is attractive due to several factors. First, SD is a relatively inexpensive and readily available starting material. Second, the synthetic procedures are typically simple and can be carried out under mild conditions. Finally, the resulting NPs can be tailored to have specific properties, such as size, shape, and surface functionality, by varying the reaction conditions. In an alkaline solution, the phenolate form of SD was converted to its quinone form, while ionic coinage metal salts were converted to zero-valent nanoparticles. The capping in situ produced quinone of coinage metal nanoparticles generated metal-enhanced fluorescence under suitable experimental conditions. The formation of iminic bonds during the formation of Schiff bases altered the properties (especially metal-enhanced fluorescence) and applications., Competing Interests: The authors declare that they have no competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (This journal is © The Royal Society of Chemistry.)

Silver metal, being a 3d transition metal in group 11 in the periodic table, is widely used in material science for its distinguished plasmonic properties. Nanoparticles (NPs) and nanoclusters (NCs) are widely used in sensing applications having a surface plasmon band and emissive properties, respectively. Mercury is one of the detrimental toxins and threats to various ecosystems. The distinction between nanoparticles and nanoclusters, the utility and toxicity of heavy metal mercury, fluorometric and colorimetric approaches to the recognition of mercury ions with NPs and NCs, the mechanism of detection, spot detection, and natural water sample analyses were illustrated in detail in this review article. Moreover, the sensing platform and analyte (Hg 2+ ) fate were described for substantiating the mechanism. It was observed that NCs are mostly utilized for fluorometric approaches, while NPs are mostly employed for colorimetric approaches. Fluorometric detection is mainly quenching-based. However, sensing with enhancement was found in a few reports. Adulteration of other metals with silver particles often modifies the sensing platform., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A condensation polymer (urea-formaldehyde resin) passivated ZnO nanoparticles were used as an efficient photocatalyst for methyl blue degradation in the presence of H 2 O 2 involving a Fenton-like reaction. The formation of OH˙ radicals were attributed to the pivotal factor for the degradation process. The method was easy and recyclable. The dose of photocatalyst, initial dye concentration, pH variation, variations of the composition of the photocatalyst, and the effect of scavengers were gauged. The degraded product was highly fluorescent and fluorometric detection of H 2 O 2 was achieved along with a colorimetric recognition pathway. No other dye could be degraded under similar experimental conditions, implying the novel utility of methyl blue for environmental remediation., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)