Plasmon–exciton coupling is of great importance to many optical devices and applications. One of the coupling manifestations is plasmon-enhanced fluorescence. Although this effect is demonstrated in numerous experimental and theoretical works, there are different particle shapes for which this effect is not fully investigated. In this work electrostatic complexes of gold nanorods and CdSe/CdZnS quantum dots were studied. Double-resonant gold nanorods have an advantage of the simultaneous enhancement of the absorption and emission when the plasmon bands match the excitation and fluorescence wavelengths of an emitter. A relationship between the concentration of quantum dots in the complexes and the enhancement factor was established. It was demonstrated that the enhancement factor is inversely proportional to the concentration of quantum dots. The maximal fluorescence enhancement by 10.8 times was observed in the complex with the smallest relative concentration of 2.5 quantum dots per rod and approximately 5 nm distance between them. Moreover, the influence of quantum dot location on the gold nanorod surface plays an important role. Theoretical study and experimental data indicate that only the position near the nanorod ends provides the enhancement. At the same time, the localization of quantum dots on the sides of the nanorods leads to the fluorescence quenching.

The work reports on the use of laser ablation and post-ablation irradiation techniques for the preparation Nd³⁺ doped ZnO nanoparticles (NPs). The focus has been made on photoluminescence of Nd-doped ZnO NPs in the second near infrared (NIR-II) spectral window (1000–1700 nm) of the biological transparency. Morphology, phase composition and optical properties of the synthesized NPs were studied by absorption and photoluminescence spectroscopy, X-Ray diffraction (XRD) and transmission (TEM) electron microscopy. Near-infrared luminescence of Nd³⁺ doped ZnO nanocrystals in the region of 1000–1400 nm was detected both upon excitation from the ground state (800 nm) and upon UV excitation. The latter proves the incorporation of the Nd³⁺ into ZnO lattice as photoluminescence occurs through the transfer of excitation energy from the ZnO matrix to the Nd³⁺ ion. The possibility of control over the luminescence properties by a variation of solvent composition and by additional laser irradiation was demonstrated.

We report the spark discharge synthesis of aerosol germanium nanoparticles followed by sintering in a tube furnace at different temperatures varying from 25 to 800 °C. The size, structure, chemical composition and optical properties were studied. We have demonstrated a melting mechanism of nanoparticles agglomerates, the growth of the mean primary particle size from 7 to 51 nm and the reduction of the size of agglomerates with a temperature increase. According to transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) data, primary nanoparticles sintered at temperatures from 25 to 475 °C basically have a structure of Ge crystals embedded in a GeOx amorphous matrix, as well as visible photoluminescence (PL) with the maximum at 550 nm. Pure germanium nanoparticles are prepared at temperatures above 625 °C and distinguished by their absence of visible PL. The shape of the experimental UV-vis-NIR extinction spectra significantly depends on the size distribution of the germanium crystals. This fact was confirmed by simulations according to Mie theory for obtained ensembles of germanium nanoparticles.

A model immunoassay test system is proposed based on metal enhanced photoluminescence to analyze low concentrations of alpha-fetoprotein, a tumor marker. Antigen-antibody reaction was performed on polystyrene plates coated with silver nanoparticles to increase sensitivity of fluorescent immunoassay and signal-to-noise ratio as compared to silver-free system. The proposed test system model uses layer-by-layer assembly approach, LED excitation and nanowatt photodetection set-up, so it is characterized by smaller probe volume, fast analysis and simplicity. The proposed model system offers alpha-fetoprotein detection at concentrations used in clinical practice. Photostability and photoluminescence enhancement for labeled alpha-fetoprotein antibodies on a silver substrate were found to depend on antibodies concentration. Labeled antibodies photostability on substrates was found to deviate within 20% as compared to silver-free samples whereas photoluminescence intensity enhancement is typically in the range of 6-8 times.