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Metal halide perovskite nanocrystals (NCs) have attracted great attention in the fields of light-emitting diodes, lasers, X-ray imaging, solar cells and photoelectric detectors due to their excellent optoelectronic properties. Compared with organic-inorganic hybrid perovskite NCs, all inorganic perovskite CsPbX3 (X = Cl, Br, I) NCs have good photoelectric properties and high stability. To further improve the photoluminescence (PL) quantum yields (QYs) and stability of CsPbX3 NCs, researchers reduced the defects as nonradiative recombination centers in NCs by the following strategies: 1) surface treatment with different ligands; 2) control of synthesis conditions with halide rich compounds; 3) doping of metal ions. Among them, metal doping is considered as a universal and effective way to adjust the optoelectronic properties of semiconductors. It is found that the type and the concentration of metal ions have great influence on the electronic band structure and PL performance of NCs after the metal ions have been doped into CsPbX3 NCs. At the same time, compared with II-VI and III-V semiconductors, the unique structure of all inorganic perovskite NCs makes the doping of metal ions easier. Appropriate doping can not only enhance the intrinsic optical properties of the NCs without affecting their crystal structure, but also introduce new electronic energy levels into the NCs and new luminescent properties of doped metal ions. Based on metal ions doping strategy, the PLQYs of doped CsPbX3 NCs have been enhanced to nearly 100%. In this work, we summarize recent advances in metal doping of the four typical kinds of perovskite NCs, including CsPbCl3, CsPbBr3, CsPbI3, and Mn2+ doped CsPbX3, and discuss the physical mechanisms of the improved properties through doping metal ions. It should be pointed out that the doping of some metal ions such as Ni2+ and Cd2+ into the above four kinds of NC systems can effectively passivate NC defects, thus improving the PL QY and stability of NCs. In addition, we put forward some personal perspectives on the future research subjects of interest and directions of metal doping for enhanced PL of CsPbX3 NCs, which needs to be further explored in order to promote extensive application of perovskite NCs to various optoelectronic devices.

Wurtzite CdS nanoribbons are prepared by using a simple thermal evaporation method. Electron microscopy shows that the ribbons are smooth in surface and uniform in size. Besides the intrinsic emission, the photoluminescence spectrum of a CdS nanoribbon shows a peak at about 580 nm, which may arise from the defect- and the trap- related transitions. The photoresponse of single CdS nanoribbons is researched. When these nanoribbons are exposed to a laser with a wavelength of 400 nm, their conductivity is enhanced greatly. The conductivity of CdS nanoribbons cannot be restored to a value without any illumination even at 5 minutes after the illumination. A model is proposed to explain this phenomenon, which may be due to a slow photoresponse induced by the trap.

We have synthesized core/shell structure ZnO composite nanoparticles by surface chemical modification. This new composite material shows a large optical gap redshift compared with the homogeneous ZnO nanoparticles. The visible photoluminescence ranging from blue to red in color with fast decay time may be assigned to the interfacial bound-exciton-like emission.

The linear and nonlinear optical properties of nanometer-sized In2O3 organosol were investigated by using TEM, ESR, UV-visible absorption spectrum, photoluminescence spectra and Z-scan technique. It was found that the prepared In2O3 organosol showed a series of new optical properties, which can be explained by its special structure. These new optical properties made its application in information optics enlarged.

A double-potential-well model is proposed to describe the core-shell thickness-dependent photoluminescence peaks and energy relaxations in semiconductor quantum dots (QDs). The surface effect plays an important role in the formation of new states - polaronic states around the surface of QDs. The polaronic states formed emit light due to the strong interaction between the core state (confined state) and the surface state with an enhanced participation of the size effect.

Ternary alloy CdS0.65Se0.35 nanoribbons were successfully grown by a one-step thermal evaporation. The nanoribbons obtained have high-quality single-crystalline nature. To understand the whole picture of waveguide behavior in CdS0.65Se0.35 nanoribbons, we quantitatively studied the guided photoluminescence (PL) through individual CdS0.65Se0.35 nanoribbon by using scanning near-field optical microscopy (SNOM) at room temperature. The results show significant sustained red shift of PL spectra of the CdS0.65Se0.35 nanoribbons optical waveguide with the increase of the light propagation distance. According to our analysis, the red shift is attributed to the absorption of band-tail of states in nanoribbons. This finding may be extended to other ternary nanosyotems and be useful for fabricating new subwavelength photonic components.

In this article, nanometer-sized In2O3 organosol capped with a layer of anionic surfactants was prepared using microemulsion method. Its structure and optical properties were investigated through transmission electron microscopy, ultraviolet-visible absorption spectra, photoluminescence spectra and Z-scan technique. It was found that the prepared In2O3 organosol showed a series of new optical properties, which can be explained by its special oxygen vacancy structure. These new optical properties enhance its applications in information optics.

In this paper, nanometer-sized CdO organosol was prepared by using microemulsion methods. Its electronic structure and optical properties are characterized through UV-visible light absorption, photoluminescence, and Z-scan techniques. Some newfeatures were observed. Fluorescence and nonlinear optical responses are mainly related to surface trapped states.