Microporous‐Ceria‐Wrapped Gold Nanoparticles for Conductometric and SERS Dual Monitoring of Hazardous Gases at Room Temperature

Abstract

metal NPs have relatively high surface energy, and thus easily agglomerate and oxidize. [10] This can lead to unexpected performance losses in practical applications. In addition, bare metal NPs are limited in complex functions, such as modulated carrier transport, enhanced molecular capture, and strong charge separation. In comparison, functional material-wrapped metal NPs have promising reductions in aggregation and can offer more complex functions. [11][12][13][14][15] Among these wrapped metal NPs, microporous shell-[such as silica, and metal-organic frameworks (MOFs)] coated systems have abundant micropores and a large specific surface area. They have great potential applications in molecular catalysis and gas sensing. [16][17][18][19][20][21][22][23] For example, a recent work reported by He, et al. shows that the MOF-5 wrapped Au NPs have a strong enrichment effect of CO 2 gas, thus enabling the detection of CO 2 gas via surface-enhanced Raman spectroscopy (SERS) effect of the Au core. [22] To date, the microporous materials wrapped on a plasmonic metal NPs mainly include MOFs and microporous silica. Microporous silica has only the value as a carrier, stabilizer (for anti-agglomeration or anti-oxidization), and linking ligand. Therefore, microporous-silica-wrapped metal NPs are difficult to offer complex functions (such as strong gas-solid interaction). In contrast, MOF-wrapped metal NPs can likely achieve more functions due to their relatively high chemical activity and other properties. [18][19][20][21][22] However, most MOFs have wide band gaps and are insulators, thus, it is difficult to achieve applications in carrier transport (such as photoelectric conversion and conductometric gas sensing). In addition, the MOF micropores are easily destroyed by acidic gases and even water vapor due to their relatively low structural stability, thus resulting in dramatic performance declines in practical applications.Microporous metal oxides such as titanium dioxide (TiO 2 ), tin oxide (SnO 2 ), and cerium oxide (CeO 2 ) [24][25][26][27] have good chemical stability, strong interactions with many kinds of gas molecules, and tunable carrier transport properties. Therefore, the microporous metal-oxide-wrapped plasmonic metal NPs are This work proposes a novel and simple synthesis method for microporous-ceria-wrapped gold (Au@mp-CeO 2 ) nanoparticles (NPs) based on linker molecule-induced stacking of ultrafine CeO 2 particles (or beads) on the surface of pre-prepared gold NPs. The resulting NPs have a uniform size and microporous CeO 2 shells with a mean thickness of 28 nm and porosity of 42%. The shell is highly tunable from about 4 to 30 nm thick.

Efficient SERS Response of Porous-ZnO-Covered Gold Nanoarray Chips to Trace Benzene–Volatile Organic Compounds

“…Moreover, the target molecules were only limited to aldehydes. Recently, Bao, et al , used the oxides-wrapped Au nanoparticles’ film and achieved the SERS-based detection of mercaptan-VOCs but with a limit of parts per million (ppm) level. As for the reports on the SERS-based detection of B-VOCs, it is very limited, and both fast and sensitive SERS-based detection is still expected.…”

Challenges and opportunities for SERS in the infrared: materials and methods

“…Rare-earth semiconductors can also be utilized to form shells on plasmonic cores, the most common of which is CeO 2 . Bao et al 188 proposed a method that is easily adaptable to several combinations of metal@mesoporous oxide architectures, by simple variation of the pre-formed metal core or shell precursors. The same protocol also allows a facile modification of the shell thickness from 4 to 30 nm, by varying the Ce 3+ added to the colloidal gold sol.…”

In-situ Surface-Enhanced Raman Spectroscopy Reveals a Mars–van Krevelen-Type Gas Sensing Mechanism in Au@SnO2 Nanoparticle-Based Chemiresistors

“…The SnO 2 shell here should be thin enough (about several nanometers) for ensuring enough SERS activity because of the short-range nature of SERS. , The Au@SnO 2 NPs were prepared through a reported method with minor modifications . The gas sensor was fabricated by coating the preprepared Au@SnO 2 NPs as a sensitive film on a blank sensor substrate, , and the test system was constructed by integrating a self-made gas sensing module and a self-made inverted Raman microscope. , More details about NP preparation, sensor fabrication, and test system construction are presented in the Supporting Information.…”