Undoped ZnO, Ce-doped ZnO, and (Li, Ce)-codoped ZnO nanophosphors were prepared by a sol-gel process. The effects of the additional doping with Li ions on the crystal structure, particle morphology, and luminescence properties of Ce-doped ZnO were investigated by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy and photoluminescence spectroscopy. The results indicate that the obtained samples are single phase, and a nanorod shaped morphology is observed for (Li, Ce)-codoping. Under excitation with 325 nm light, Ce-doped ZnO phosphors show an ultraviolet emission, a green emission, and a blue emission caused by Zn interstitials. The spectrum of the sample codoped with a proper Li concentration features two additional emissions that can be attributed to the Ce3+ ions. With the increase of the Li doping concentration, the Ce3+ blue luminescence of (Li, Ce)-codoped ZnO is obviously enhanced, which results not only from the increase of the Ce3+ ion concentration itself but also from the energy transfer from the ZnO host material to the Ce3+ ions. This enhancement reaches a maximum at a Li content of 0.02, and then decreases sharply due to the concentration quench. These nanophosphors may promise for application to the visible-light-emitting devices.

Lanthanide materials have great applications in optical communication, biological fluorescence imaging, laser, and so on, due to their narrow emission bandwidths, large Stokes’ shifts, long emission lifetimes, and excellent photo-stability. However, the photon absorption cross-section of lanthanide ions is generally small, and the luminescence efficiency is relatively low. The effective improvement of the lanthanide-doped materials has been a challenge in the implementation of many applications. The local surface plasmon resonance (LSPR) effect of plasmonic nanoparticles (NPs) can improve the luminescence in different aspects: excitation enhancement induced by enhanced local field, emission enhancement induced by increased radiative decay, and quenching induced by increased non-radiative decay. In addition, plasmonic NPs can also regulate the energy transfer between two close lanthanide ions. In this review, the properties of the nanocomposite systems of lanthanide material and plasmonic NPs are presented, respectively. The mechanism of lanthanide materials regulated by plasmonic NPs and the scientific and technological discoveries of the luminescence technology are elaborated. Due to the large gap between the reported enhancement and the theoretical enhancement, some new strategies applied in lanthanide materials and related development in the plasmonic enhancing luminescence are presented.

Plasmonic nanostructures have great potential for improving the radiation properties of emitters. Here, the plasmonic Au nanorods-PVA nanocomposite films are used to uniformly improve the photoluminescence of Tb/Eu co-doped PMMA film within the local micro-region. Under the excitation of 292 nm, the maximum enhancement factor is 37.2-fold for emission at 612 nm and 21.6-fold for emission at 545 nm. Moreover, the finite different time domain simulations are developed to further explain the experimental results. It is indicated that the modulation of luminescence can be attributed to the increase of the local density of optical states through the Purcell effect and the improvement of the energy transfer efficiency between Tb and Eu. Under the excitation of 360 nm, the maximum enhancement factor is about 71.5-fold. In this case, the Au nanorods are mainly used for modulating the emission process at 612 nm, which deduced a greater enhancement factor at 612 nm. This study provides a deep understanding of the interactions between rare earth ions co-doped materials and plasmonic nanostructures, building a bridge to fabricate a useful platform for several applications, such as thin film-based detectors and sensors.

The hydrothermal approach has been used to fabricate a heterojunction of n-aluminum-doped ZnO nanorods/p-B-doped diamond (n-Al:ZnO NRs/p-BDD). It exhibits a significant increase in photoluminescence (PL) intensity and a blue shift of the UV emission peak when compared to the n-ZnO NRs/p-BDD heterojunction. The current voltage (I-V) characteristics exhibit excellent rectifying behavior with a high rectification ratio of 838 at 5 V. The n-Al:ZnO NRs/p-BDD heterojunction shows a minimum turn-on voltage (0.27 V) and reverse leakage current (0.077 μA). The forward current of the n-Al:ZnO NRs/p-BDD heterojunction is more than 1300 times than that of the n-ZnO NRs/p-BDD heterojunction at 5 V. The ideality factor and the barrier height of the Al-doped device were found to decrease. The electrical transport behavior and carrier injection process of the n-Al:ZnO NRs/p-BDD heterojunction were analyzed through the equilibrium energy band diagrams and semiconductor theoretical models.

Accurate and efficient determination of malachite green (MG) in aquaculture is crucial for ensuring environment and food safety. Herein, we present a dual-response fluorescence probe based on an Ag/PMMA/Eu nanocomposite for the sensitive detection of MG with low concentration and single droplet. The luminescence properties of the Ag/PMMA/Eu nanocomposite and the fluorescence resonance energy transfer (FRET) effect between Eu and MG are significantly improved due to the localized surface plasmon resonance (LSPR) effect. The dual-response system enables the detection of MG through both luminescence intensity and energy transfer efficiency using the Ag/PMMA/Eu nanocomposite as a detection platform in the range of 0-10.78 µmol/L. The detection limit reaches as low as 0.5 nmol/L, a significant improvement over the 0.11 µmol/L limit achievable by pure Eu film alone, demonstrating superior sensitivity compared to traditional fluorescence detection techniques. The results indicate that the nanocomposite significantly boosts the sensitivity of the dual-mode sensors. In addition, the sensor successfully detects MG residues in lake water, highlighting the Ag/PMMA/Eu nanocomposite’s potential to advance high sensitivity, selectivity, stability, and accurate detection in food security and biological analysis.