Hybrid nanoparticles combine two or more disparate materials on the same nanosystem and represent a powerful approach for achieving advanced materials with multiple functionalities stemming from the unusual materials combinations. This review focuses on recent advances in the area of semiconductor−metal hybrid nanoparticles. Synthesis approaches offering high degree of control over the number of components, their compositions, shapes, and interfacial characteristics are discussed, including examples of advanced architectures. Progress in hybrid nanoscale inorganic cage structures prepared by a selective edge growth mechanism of the metal onto the semiconductor nanocrystal is also presented. The combined and often synergistic properties of the hybrid nanoparticles are described with emphasis on optical properties, electronic structure, electrical characteristics, and light induced charge separation effects. Progress toward the application of hybrid nanoparticles in photocatalysis is overviewed. We conclude with a summary and point out some challenges for further development and understanding of semiconductor−metal hybrid nanoparticles. This progress shows promise for application of hybrid nanoparticles in photocatalysis, catalysis, optical components, and electronic devices.

A new approach for doping of Cu2S nanocrystal arrays using thermal treatment at moderate temperatures (T < 400 K) is presented. This thermal doping process yields conductance enhancement by 6 orders of magnitude. Local probe measurements prove this doping is an intraparticle effect and, moreover, tunneling spectroscopy data signify p-type doping. The doping mechanism is attributed to Cu vacancy formation, resulting in free holes. Thermal-doping temperature dependence exhibits an Arrhenius-like behavior, providing the vacancy formation energy of 1.6 eV. The moderate temperature conditions for thermal doping unique to these nanocrystals allow patterned doping of nanocrystal films through local heating by a focused laser beam, toward fabrication of nanocrystal-based electronic devices.

Combining metal and semiconductor segments with well-defined morphologies on a single hybrid nanoparticle provides functionality benefiting from the joint and possibly also synergetic properties of the disparate components. We have recently reported the synthesis of a novel family of Ru nano-inorganic caged (NICed) copper(I) sulfide hybrid nanoparticles, which were grown through a mechanism of selective edge growth of the Ru on the copper(I) sulfide seeds. In this work we investigate the effect of reaction conditions on the Ru–Cu2S products. There is an extraordinary sensitivity to reaction temperature in which four product structures were discovered upon varying the reaction temperature from 190 to 220 °C. The products changed from homogeneous nuclei of Ru along with the free Cu2S seed at lower temperature, to Ru nano-inorganic caged copper(I) sulfide, to long thin Ru structures protruding from the seed surface at the higher temperature range. The resulting materials were imaged and characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), high-angle annular dark field-scanning TEM (HAADF-STEM), and powder Xray diffraction. Differential scanning calorimetric (DSC) analysis of the Cu2S template nanoparticles revealed an endothermic peak at the specific temperature for selective edge growth of Ru, and was assigned to a surface change on the seed particle. Competition between homogeneous nucleation of the secondary material Ru and heterogeneous nucleation on the seed Cu2S nanoparticle leading to a rich reaction landscape is discussed.

The level structure of copper sulfide nanocrystals of different sizes was investigated by correlating scanning tunneling spectroscopy and cyclic voltammetry data in relation to sensing applications. Upon oxidation of Cu2 S nanocrystals in the low-chalcocite phase, correlated changes are detected by both methods. The cyclic voltammetry oxidation peak of Cu(1+) down shifts, while in-gap states, adjacent to the valence-band edge, appeared in the tunneling spectra. These changes are attributed to Cu vacancy formation leading to a Cu depleted phase of the nanocrystals. The relevance of the oxidation to the use of copper sulfide nanocrystals in hydrogen peroxide sensing was also addressed, showing that upon oxidation the sensitivity vanishes. These findings bare significance to the use of copper sulfide nanocrystals in glucose sensing applications.

Edge growth of rhodium and ruthenium–rhodium metals on highly faceted Cu2S semiconductor seeds yields a family of nano-inorganic caged hybrid nanoparticles.