Recent applications of coinage metal nanoparticles passivated with salicylaldehyde and salicylaldehyde-based Schiff bases

Abstract

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.

Fig. 1. (a) Synthesis protocol of 4-extended SD derivatives 1a–d, 2a–b, and 3a–b. (b) Compounds of SD that exhibit intense fluorescence in multiple environments in solution and solid state. (c) 4-Extended SD derivatives. (d) SD's emission spectra in aerated solutions of toluene at room temperature are as follows: 1a (plain blue), 1b (dotted blue), 1c (dashed blue), 1d (dotted dashed blue), 2a (plain red), 2b (dotted red), 3a (plain green), and 3b (dotted green). Reproduced with permission from ref. , copyright 2024, Eur. J. Org. Chem.

Fig. 2. Synthesis protocol of salicylaldehyde.

Fig. 3. Energy diagram for fluorescence in the presence and absence of a metal surface. Reproduced with permission from ref. , copyright 2024, Nanoscale.

Fig. 4. Effect of metal ions on (OSD-AgNPs-MB); (a) fluorescence spectra and (b) bar diagram; (c) fluorescence spectra of OSD-AgNPs-MB at different [Pb²⁺] and (d) plot of I/I₀vs. [Pb²⁺] and linear detection range of Pb²⁺ detection. Reproduced with permission from ref. , copyright 2024, Spectrochim. Acta, Part A.

Fig. 5. H₂O₂ removal using OSD-CuNP-modified cotton wool. Reproduced with permission from ref. , copyright 2024, New J. Chem.

Fig. 6. Displayed imine brings selectivity for silver-enhanced fluorescence (A) without imminic bond, (B) with imminic bonds. Reproduced with permission from ref. , copyright 2024, Dalton Trans.

Fig. 7. TEM and HRTEM digital images of CuNPs. Reproduced with permission from ref. , copyright 2024, New J. Chem.

Fig. 8. Schematic representation for the synthesis of SD-derived Schiff bases.

Fig. 9. Mono-iminic Schiff base capping on coinage metal nanoparticle synthesis mechanism.

Fig. 10. Synergism of Cu and Ag to generate strong metal-enhanced fluorescence. Reproduced with permission from ref. , copyright 2024, Appl. Nanosci.

Fig. 11. Schiff base capped AgNPs displayed antibacterial activity against S. aureus, P. aeruginosa, K. pneumoniae, and E. coli. Reproduced with permission from ref. , copyright 2024, Egypt. J. Chem.

Fig. 12. Distinct diamines and salicylaldehyde-derived synthetic DSBs and the mechanism of the formation of metal nanoparticles.

Fig. 13. Fluorescence spectra (A–F) showing enhancement/quenching of exposed DSBs in the presence of photoproduced CuNPs. The bar diagram represents different degrees of enhancement from the exposed DSBs in the presence of photoproduced CuNPs (I = fluorescence intensity of exposed C₂ in the presence of photogenerated CuNPs; I₀ = fluorescence intensity of exposed C2 solution without copper). Reproduced with permission from ref. , copyright 2024, Chem.–Eur. J.

Fig. 14. An illustration of the permeation experiment showing how easily the alkaline CP passed through the egg membrane. Reproduced with permission from ref. , copyright 2024, Dalton Trans.

Fig. 15. (A) Powder XRD pattern, (B) lattice fringe, and (C) XPS spectra for the element Ag of DSB capped AgNPs. Reproduced with permission from ref. , copyright 2024, Langmuir.

Mamta Sahu

Mainak Ganguly

Priyanka Sharma