ABSTRACT
In recent years, N-heterocyclic carbenes (NHCs) have garnered significant attention as promising alternatives to thiols to stabilize metallic nanoparticles and planar surfaces. While most studies thus far have focused on NHC-functionalized gold nanoparticles (AuNPs), as an ideal platform to investigate the role of NHCs in stabilizing such nanoparticles, their ability to protect more unstable coinage metal nanoparticles, such as silver nanoparticles (AgNPs), has been largely overlooked. This is despite the fact that AgNPs possess a much more sensitive optical response that, upon their enhanced stability, can broaden their scope of application in various fields, including nanomedicine and catalysis. In this study, the synthesis and use of monomeric and polymeric mesoionic NHC-Ag(I) complexes as precursors to mono- and multidentate NHC-tethered AgNPs are reported. The polymeric analog was obtained by first synthesizing a polymer, containing 1,2,3-triazole repeat units, employing the copper-catalyzed alkyne-azide cycloaddition click polymerization of monomers containing diazide- and dialkyne functional groups. Subsequent quaternization of the triazole moieties and Ag insertion yielded the target NHC-Ag-containing polymer. Using this polymer as well as its monomeric analog as substrates, AgNPs with either catenated networks of NHCs or monomeric NHCs were fabricated by their reduction using borane-tert-butylamine complex. Our stability studies demonstrate that while monomeric NHCs impart some degree of stability to AgNPs, particularly at elevated temperatures in aqueous as well as organic medium, their polymeric analogs further enhance their stability in acidic environment (pH = 2) and against glutathione (3 mM), as an example of a biologically relevant thiol, in aqueous media. To highlight the application of these NHC-functionalized AgNPs in catalysis, we explore the aqueous phase reduction of methyl orange and 4-nitrophenol.
ABSTRACT
Urbanization induces shifts in surface environmental factors, including impervious surface expansion, green space loss, and temperature increase in which the extreme temperature is supposed to significantly raise total electricity consumption (TEC) in urban areas. Applying remote sensing data and data analysis, this study aims to explore relationships between urbanization, surface environmental factors (SEF), and electricity consumption (EC). The relevance of surface temperature and total electricity consumption was also considered. The research found the disturbance of SEF through changes in vegetation index, urban index, and surface temperature. The vegetation was detected to be narrowed while the impervious surface and land surface temperature had the same trend of rising. These tendencies correspond to the urbanization process in the Bangkok Metropolitan Area (BMA). The urbanization process was also detected by extension of customers and electricity consumption, mainly in industrial sectors and household consumption. The number of users in industrial sectors well explained total consumption. Besides, the surface environmental factors jointly contributed to the consumption in the residential sector. Urban expansion assessed by urban index has more contribution to electricity utilization compared to surface temperature. These findings proved that the total consumption originated from the industrial sectors, especially the medium and large scales. These outcomes can serve the electrical business in order to provide adequate and improve service quality.
