Semiconductor-mediated photocatalysis has received tremendous attention as it holds great promise to address the worldwide energy and environmental issues. To overcome the serious drawbacks of fast charge recombination and the limited visible-light absorption of semiconductor photocatalysts, many strategies have been developed in the past few decades and the most widely used one is to develop photocatalytic heterojunctions. This review attempts to summarize the recent progress in the rational design and fabrication of heterojunction photocatalysts, such as the semiconductor-semiconductor heterojunction, the semiconductor-metal heterojunction, the semiconductor-carbon heterojunction and the multicomponent heterojunction. The photocatalytic properties of the four junction systems are also discussed in relation to the environmental and energy applications, such as degradation of pollutants, hydrogen generation and photocatalytic disinfection. This tutorial review ends with a summary and some perspectives on the challenges and new directions in this exciting and still emerging area of research.

Photothermal ablation (PTA) therapy has a great potential to revolutionize conventional therapeutic approaches for cancers, but it has been limited by difficulties in obtaining biocompatible photothermal agents that have low cost, small size (<100 nm), and high photothermal conversion efficiency. Herein, we have developed hydrophilic plate-like Cu(9)S(5) nanocrystals (NCs, a mean size of ∼70 nm × 13 nm) as a new photothermal agent, which are synthesized by combining a thermal decomposition and ligand exchange route. The aqueous dispersion of as-synthesized Cu(9)S(5) NCs exhibits an enhanced absorption (e.g., ∼1.2 × 10(9) M(-1) cm(-1) at 980 nm) with the increase of wavelength in near-infrared (NIR) region, which should be attributed to localized surface plasmon resonances (SPR) arising from p-type carriers. The exposure of the aqueous dispersion of Cu(9)S(5) NCs (40 ppm) to 980 nm laser with a power density of 0.51 W/cm(2) can elevate its temperature by 15.1 °C in 7 min; a 980 nm laser heat conversion efficiency reaches as high as 25.7%, which is higher than that of the as-synthesized Au nanorods (23.7% from 980 nm laser) and the recently reported Cu(2-x)Se NCs (22% from 808 nm laser). Importantly, under the irradiation of 980 nm laser with the conservative and safe power density over a short period (∼10 min), cancer cells in vivo can be efficiently killed by the photothermal effects of the Cu(9)S(5) NCs. The present finding demonstrates the promising application of the Cu(9)S(5) NCs as an ideal photothermal agent in the PTA of in vivo tumor tissues.

The construction of nanoporous membranes is of great technological importance for various applications, including catalyst supports, filters for biomolecule purification, environmental remediation and seawater desalination. A major challenge is the scalable fabrication of membranes with the desirable combination of good thermal stability, high selectivity and excellent recyclability. Here we present a self-assembly method for constructing thermally stable, free-standing nanowire membranes that exhibit controlled wetting behaviour ranging from superhydrophilic to superhydrophobic. These membranes can selectively absorb oils up to 20 times the material's weight in preference to water, through a combination of superhydrophobicity and capillary action. Moreover, the nanowires that form the membrane structure can be re-suspended in solutions and subsequently re-form the original paper-like morphology over many cycles. Our results suggest an innovative material that should find practical applications in the removal of organics, particularly in the field of oil spill cleanup.

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Photothermal nanomaterials have recently attracted significant research interest due to their potential applications in biological imaging and therapeutics. However, the development of small-sized photothermal nanomaterials with high thermal stability remains a formidable challenge. Here, we report the rational design and synthesis of ultrasmall (<10 nm) Fe3O4@Cu2-xS core-shell nanoparticles, which offer both high photothermal stability and superparamagnetic properties. Specifically, these core-shell nanoparticles have proven effective as probes for T2-weighted magnetic resonance imaging and infrared thermal imaging because of their strong absorption at the near-infrared region centered around 960 nm. Importantly, the photothermal effect of the nanoparticles can be precisely controlled by varying the Cu content in the core-shell structure. Furthermore, we demonstrate in vitro and in vivo photothermal ablation of cancer cells using these multifunctional nanoparticles. The results should provide improved understanding of synergistic effect resulting from the integration of magnetism with photothermal phenomenon, important for developing multimode nanoparticle probes for biomedical applications.