Composite Pt/ZnO porous nanocages with ultrathin porous ZnO shell layers and ultrafine embedded Pt nanoparticles were facilely fabricated by ultrasonic irradiation-assisted two-step etching of Zn/ZnO core/shell nanoparticle colloids. The Pt cluster size can be well adjusted by the applied ultrasonic power. These Pt/ZnO nanocages exhibit excellent photocatalytic performance and can be further improved by the control of the embedded noble metal nanoparticles, which can be attributed to the abundant nanoscale Schottky contacts in the Pt−ZnO metal−semiconductor interfaces as well as to the large specific surface area due to the unique porous structure. The selective etching route used here could be of considerable universality for fabrication of a series of noble metal/oxide porous nanostructures as photocatalysts, such as the (Au, Ag, Pt, Pd)/(ZnO, TiO2) system.

A weak acid selective etching strategy was put forward to fabricate oxide-based hollow nanoparticles (HNPs) using core/shell nanostructures of active metal/oxide nanoparticles as sacrificial templates. ZnO-based HNPs, including pure ZnO, Au/ZnO, Pt/ZnO, and Au/Pt/ZnO HNPs with diameter below 50 nm and shell thickness below 6 nm has been first achieved at low temperature. The diameter, thickness, and even sizes of ZnO and noble metal ultrafine crystals of HNPs can be well adjusted by the etching process. Synchronous with the formation of HNPs, the internal metal−semiconductor interfaces can be controllably eliminated (Zn−ZnO) and reconstructed (noble metal−ZnO). Excitingly, such microstructure manipulation has endued them with giant improvements in related performances, including the very strong blue luminescence with enhancement over 3 orders of magnitude for the pure ZnO HNPs and the greatly improved photocatalytic activity for the noble metal/ZnO HNPs. These give them strong potentials in relevant applications, such as blue light emitting devices, environment remediation, drug delivery and release, energy storage and conversion, and sensors. The designed fabrication procedure is simple, feasible, and universal for a series of oxide and noble metal/oxide HNPs with controlled microstructure and improved performances.

A strong violet photoluminescence (PL) band at 425nm (2.92eV) was observed from the ZnO shell layer of the Zn∕ZnO core-shell nanoparticles prepared by laser ablation in liquid media. Such violet PL decreases with increase of the shell thickness or annealing temperature, showing good controllability. Based on the electron paramagnetic resonance measurements, the violet emission is attributed to the electronic transition from the defect level, corresponding to high-concentration zinc interstitials, to the valence band. This study is in favor to clarify the defect-related emissions and to extend the optical and electronic applications of nanostructured ZnO.

We present composition-controlled synthesis of ZnO−Zn composite nanoparticles by laser ablation of a zinc metal target in pure water or in aqueous solution of sodium dodecyl sulfate (SDS). By SDS concentration, composition and size of the nanoparticles can be controlled in a wide range. Relative amounts of the components Zn and ZnO, the particle size, and the microstructure can evolve with SDS concentration in solution. High SDS concentration corresponds to high relative amount of Zn nanoparticles existing as the core in the core/shell nanostructures, whereas low SDS concentration leads to high ZnO amount. This was explained by a dynamic mechanism on the basis of the competition between aqueous oxidation and SDS capping protection. Correspondingly, optical absorption spectra evolve from the excitonic peak of ZnO (about 350 nm) to the Zn surface plasmon resonance (about 242 nm) with rise of SDS concentration. A blue (about 450 nm) photoluminescence was observed in the obtained ZnO nanoparticles, which was attributed to existence of interstitial zinc in ZnO lattices. This study has revealed that laser ablation of active metal in liquid media is an appropriate method to synthesize a series of metal oxide semiconductor−metal composite nanoparticles with controlled composition and size.

Localized surface plasmon resonance (LSPR) has many applications which require meeting specific wavelength windows. The most prominent examples are photothermal therapy in biology, matched to the biological window (650–1350 nm), and communication relying on photodetection in optoelectronics, matched to the communication window (1260–1675 nm). However, for the classic noble metals (Au, Ag), tuning LSPRs from visible region to these two windows is still a demanding task due to their intrinsic limitations on charge density and dielectric function. Here, the discovery of near‐infrared biological and communication window‐matched plasmonic properties of semimetal TiS2 nanosheets (NSs) is reported for the first time. Developed synthesis procedures allow fine‐tuning width and thickness of single‐crystal TiS2 NSs. During characterization a new and intensive absorption peak in the 1000–1400 nm range is observed from both TiS2 NS colloid solutions and films. This peak is attributed to LSPR due to its dependence on particle shape and on the refractive index of solvents. The superiority of such LSPRs is demonstrated in both, biological and optical applications: excitation at 808 and 980 nm generates a ≈50 °C photothermal temperature rise, while excitation at 1310 nm results in two‐times enhanced photocurrents of PbS photodetectors compared to untreated devices.