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This work proposes a novel and simple synthesis method for microporous‐ceria‐wrapped gold (Au@mp‐CeO2) nanoparticles (NPs) based on linker molecule‐induced stacking of ultrafine CeO2 particles (or beads) on the surface of pre‐prepared gold NPs. The resulting NPs have a uniform size and microporous CeO2 shells with a mean thickness of 28 nm and porosity of 42%. The shell is highly tunable from about 4 to 30 nm thick. This method is universal and suitable for other metal@mp‐oxide nanoarchitectures (such as Au@mp‐CuO NPs, Au@mp‐Cr2O3 NPs, Ag@mp‐CeO2 NPs, and Ag@mp‐CeO2 nanowires) simply via changing the pre‐prepared metal cores or shell precursors. Most significantly, the as‐prepared Au@mp‐CeO2 NPs can be used for accurate monitoring of toluene vapor (10 ppm level) at room temperature based on their conductometric and surface‐enhanced Raman spectroscopy (SERS) dual response. Moreover, these NPs can be also used for other hazardous gases, such as chlorobenzene, hydrogen sulfide, and 1‐dodecanethiol. This excellent performance benefits from the micropore‐enhanced interaction between CeO2 and gas molecules. This work not only provides new and controllable preparation for metal@mp‐oxide nanoarchitectures, but also demonstrates the great potential applications of these materials in real‐time and identifiable monitoring of hazardous gases. [ABSTRACT FROM AUTHOR]

A simple and flexible method of preparing an ultrathin semiconducting oxide layer-wrapped gold nanoparticles (NPs) is presented. The method is a single-step procedure based on laser ablation in a precursor solution. The spherical Au NPs (<20 nm in mean size) wrapped with a SnO 2 layer of approximately 2 nm in thickness are formed after the laser ablation of a gold target in SnCl 4 solutions with concentrations of 0.01–0.1 M. The thickness of such SnO 2 shell is nearly independent of Au particle sizes. Results reveal that the formation of Au@SnO 2 NPs involves a two-step process: the laser ablation-induced formation of Au NPs and subsequent Coulomb effect-based colloidal attachment and self-assembly on the Au NPs. Au@SnO 2 NPs-built film exhibits significantly stronger surface-enhanced Raman scattering effect to organic phosphor molecules (phenylphosphonic acid) and much better gas sensing performance to H 2 S at room temperature compared with the bare Au NPs and pure SnO 2 NPs films, respectively. This work presents a simple route to fabricating noble-metal NPs wrapped with symmetrical and ultrathin semiconducting oxide shells. [ABSTRACT FROM AUTHOR]

Here an alternative preparation route, pulsed laser ablation in liquid (LAL) of FeCl3 solution, is reported to facilely synthesize crystalline iron oxychloride (FeOCl) nanosheets at ambient conditions. Well-dispersed spherical gold (Au) nanoparticles (NPs) are simultaneously decorated on surface of the FeOCl nanosheets, which possess (010) preferred orientations with microsized dimensions in planar and tens of nanometers in thickness. The crystalline size and composition of the Au/FeOCl can be effectively modulated by simply changing FeCl3 concentrations. Technical observations illustrate that the nanocomposites possess good thermal stability and surface of which adsorbs abundant H2O molecularly and oxygen species chemically. The FeOCl nanosheets are formed through chemical side hydrolysis reaction in the localized liquid region with gradient temperature, which is derived from thermal transfer of LAL-induced plasma plume. The Au/FeOCl nanocomposites, as chemiresistors, show exceptionally high sensing response and perfect selectivity to HCl gas at room temperature. The excellent sensing behavior is ascribed to the Au-NP-enhanced surface chemisorption of oxygen species and selective adsorption of HCl for FeOCl nanosheets. The synthesized Au/FeOCl nanocomposites provide a new candidate for exclusive HCl detection. And the proposed LAL-assisted fabrication routes might open new perspectives for formation of other metal oxychloride compounds. [ABSTRACT FROM AUTHOR]

Surface Enhanced Raman Spectroscopy (SERS) could be a powerful technique for detecting trace gaseous sulfur-mustard, but it is still challenging due to the difficulty in efficiently capturing sulfur-mustard molecules by normal SERS substrates. Here, a chemically trapping strategy is presented for such detection via coating an ultrathin metal-oxide sensing layer on a SERS substrate. In the strategy, a SERS substrate Au-wrapped Si nanocone array is designed and fabricated by Si wafer-based organic template-etching and appropriate Au deposition, and coated with an ultrathin CuO for chemically capturing sulfur-mustard molecules. The validity of such strategy has been demonstrated via taking the gaseous 2-chloroethyl ethyl sulfide (a simulant of sulfur-mustard, or 2-CEES for short) as the target molecules. The response of the CuO-coated SERS substrate to the gaseous 2-CEES is detectable within 10 min, and the lowest detectable concentration is 10 ppb or less. Further experiments have shown that there exists an optimal CuO coating thickness which is about 6 nm. The CuO coating-based capture of 2-CEES molecules is attributed to the surface hydroxyl-induced specific adsorption, which is subject to the pseudo-second-order kinetics and Freundlich-typed model. This study presents the practical SERS chips and new route for the trace detection of gaseous sulfur-mustard. [Display omitted] • A chemically trapping strategy is presented based on the CuO-coated SERS substrate. • The CuO coating evidently increases SERS responses to gaseous sulfur-mustard simulant. • The SERS response is detectable within 10 min and obeys pseudo-second-order kinetics. • The detection of the gaseous simulant is quantifiable with a lower limit below 10 ppb. • Such CuO coating-enhanced SERS response comes from the hydroxyl-induced adsorption. [ABSTRACT FROM AUTHOR]

• Au@D-SnO 2 NPs are prepared creatively by alloying and selective-oxidation. • The NPs show strong sunlight harvesting and efficient charge separation. • The NPs show efficient photocatalytic-removal of NH 3. Strong sunlight harvesting and efficient charge separation are of great significances for solar energy utilization of metal oxides, but it is a challenge to realize these two aspects simultaneously. Here, we strategize oxygen-vacancy-rich (or defective)-SnO 2 wrapped gold nanoparticles (Au@D-SnO 2 NPs) for this. The designed NPs are fabricated just by adding precursors into boiling pre-prepared Au colloidal solution and then re-dispersing the reacted NPs in water, based on surface alloying and selective oxidation. Typically, the fabricated Au@D-SnO 2 NPs (with 12 nm thick shell) exhibit strong absorption in full solar spectrum (200–2000 nm) with an energy absorption efficiency as high as 84%. Meanwhile, the photocurrent response of the typical NPs is 2.3 and 13.6 times as high as that of Au@SnO 2 NPs (with poor oxygen vacancies) and commercial SnO 2 NPs, respectively, showing efficient charge separation. Such excellent performance is attributed to the synergistic effect of surface plasmon resonance (SPR) of the Au core and the band gap narrowing induced by the abundant oxygen vacancies. Further, the excellent photocatalytic performance of the Au@D-SnO 2 NP catalyst has been demonstrated via exemplary photocatalytic removal of gaseous ammonia. The catalytic rate is about 4.2 and 25 times as high as that of the Au@SnO 2 NP and the commercial SnO 2 NP catalysts, respectively. It is expected that such excellent photocatalytic performance will also be obtained on other defective oxides wrapped metal structures. This work provides a preparation method for Au@D-SnO 2 NPs, which can be used for efficient solar energy utilization. [ABSTRACT FROM AUTHOR]