Dynamic Light Scattering Analysis in Biomedical Research and Applications of Nanoparticles and Polymers

Nanomaterials are increasingly used in the development of detection systems for various disease biomarkers as tools for reliable early diagnosis, which is a key factor in reducing mortality and increasing treatment effectiveness. The use of quantum dot–antibody conjugates allows for optical detection of various disease markers in biological fluids, tissues, and individual cells with high sensitivity and specificity. The sensitivity and specificity of detection are determined not only by the outstanding optical properties of fluorescent quantum dots but also by the type of antibodies used for binding target analytes and the methods of their conjugation with quantum dots. This review deals with methods of site-specific and site-nonspecific conjugation of quantum dots with antibodies, including full-length and single-domain antibodies, as well as antibody fragments, with a special focus on their structural features and active moieties used for binding to their targets. The review includes examples of successful applications of quantum dot–conjugated antibodies in diagnosis, environment monitoring, and food safety assessment. We also discuss the prospects of further research in this field, including new conjugation methods and issues related to the stability and specificity of probes. The review provides a comprehensive analysis of the current methods and achievements in antibody conjugation from the viewpoint of subsequent analyte detection, highlighting the importance of further research for improving the existing technologies.

CsPbBr₃ perovskite nanocrystals (PNCs) are the focus of recent basic and applied research, with special emphasis on their use in photovoltaic cells, hybrid light-emitting diodes, single-photon sources, basic elements of optical computers, and other optoelectronic devices. The main problem limiting the use of PNCs is their low stability under normal conditions. Development of composite materials where PNCs are embedded in polymer matrices is an approach to solving the problem of the stability of PNCs contacting the atmosphere. Here, we report the results of experiments on designing composite thin films (TFs) consisting of PNCs and modified polymethyl methacrylate (PMMA). Specifically, samples of durable TFs containing CsPbBr₃ with a high photoluminescence quantum yield have been engineered, optimal parameters (including the spinning time, spinning rate, and concentration) for the spin-coating fabrication of the TFs have been found, and the TFs with a highly homogenous film coating have been obtained. This last factor is an important criterion for the use of PNC–PMMA composite as an active layer in quantum dot light-emitting diodes (QDLEDs). In addition, since PNCs are promising as a basis for the scintillating coating of detectors, whose performance depends on the homogeneity of the luminophore distribution within the scintillator (e.g., a CCD array), the results of this study could be used in developing X-ray detectors for medical applications.

Light–matter interactions in optical microcavities attract much attention due to their potential for controlling properties of materials. Among the various types of optical microcavities, porous silicon microcavities (pSiMCs) are of special interest because of their relatively simple fabrication procedure, tunable porosity, and large specific surface area, which make them highly suitable for a wide range of optoelectronic and sensing applications. However, the fabrication of pSiMCs with precisely controlled parameters, which is crucial for effective light–matter coupling, remains challenging due to the multiple variables involved in the process. In addition, the parameter characterizing the capacity of pSiMCs for confining light inside the cavity (the quality factor, QF) rarely exceeds 100. Here, we present advanced methods and protocols for controlled fabrication of pSiMCs at room temperature, combining theoretical and numerical simulations and experimental validation of microcavity structural parameters for enhancing light–matter interactions. This systemic approach has been used to design and fabricate pSiMCs with an about twofold increased QF and correspondingly improved optical performance; the theoretical modeling shows that its further development is expected to increase the QF even more. In addition, we fabricated hybrid fluorescencent structures with the R6G dye embedded into the optimized pSiMCs. This provided a 5.8-fold narrowing of the R6G fluorescence spectrum caused by light–matter coupling, which indicated enhancement of the fluorescence signal at the eigenmode wavelength due to an increased rate of spontaneous emission in the cavity. The proposed methodology offers precise theoretical simulation of microcavities with the parameters required for specific practical applications, which facilitates optimization of microcavity design. The controllable optical properties of pSiMCs make them promising candidates for a wide range of applications where improved spectral resolution, and increased luminescence efficiency are required. This paves the way for further innovations in photonic systems and optoelectronic devices.

There is a growing demand for materials for detecting ionizing radiation, which has led to the expansion of research and development of new scintillators. Typically, scintillators are synthesized by crystallizing materials at high temperatures, and their photoluminescence (PL) is difficult to tune in the visible spectral range. Therefore, composite materials based on CsPbBr₃ perovskite nanocrystals (PNCs), which have a high average atomic number and a long charge-carrier diffusion length, are of particular interest and may be used for detecting ionizing radiation. Unlike bulk scintillators, PNCs are synthesized in solution at relatively low temperatures, with the PL tunable throughout the visible spectrum. The main problem limiting the widespread use of PNCs is their low stability upon contact with the environment. This study presents the results of experiments on the encapsulation of PNCs in a polystyrene matrix, the evaluation of the changes in the luminescence quantum yield (QY) over time, and the development of a technique for studying the amplitude characteristics of signals recorded during the interaction of α-particles with composite materials based on CsPbBr₃ PNCs and polystyrene. The study has shown that composite samples based on PNCs and polystyrene retain a stable luminescence QY for two weeks. Using a ²⁴¹Am source with a characteristic α-particle energy of about 4.6 MeV and γ-ray energy of 60 keV, the light output values were calculated for the samples studied. The maximum light output was 20% of that of the standard “fast” plastic scintillator (POPOP) at a volume fraction of PNCs in the composite of less than 1%, which indicates the prospect of PNCs as a basis for composite scintillators and their further use in X-ray diagnosis.

BACKGROUND: The development of new scintillation materials based on fluorescent nanocrystals with a perovskite structure of CsPbBr3 composition and CdSe/ZnS quantum dots is a pressing topic that is being pursued by numerous scientific groups [1–4]. Both of these materials have a high potential for application in this role due to their excellent fluorophore properties, with a quantum yield of luminescence of approximately 100%. Additionally, they possess high values of the effective atomic Zeff number. The photoelectric cross section is dependent on Zeff as (Zeff)5, while the magnitude of X-ray absorption is dependent on Zeff as (Zeff)4/(AE3), where A is the atomic mass of the substance absorbing the γ-quantum and E is the energy of the X-ray photon [5]. AIM: The aim of the study was to develop a technique for fabricating scintillators based on quantum dots and polymer matrices with a high degree of transparency, high temporal stability of luminescence quantum yield, and short luminescence decay times (time of illumination or average lifetime of the substance in the excited state) for gamma-ray registration. MATERIALS AND METHODS: A HAMAMAMATSU R7400U-6 photomultiplier tube was employed to register scintillation signals. A 137Cs source with a γ-quantum energy of 661.7 keV was used as a source of ionizing radiation. RESULTS: At irradiation with γ-quanta of 137Cs isotope samples based on poly(para-methylstyrene) matrix cross-linked with divinylbenzene molecules (10% wt%), activated with naphthalene (10%, primary acceptor), anthracene (1%) and quantum dots/perovskite nanocrystals (0, 1–1.0%, re-emitter), the energy spectrum showed effective Compton scattering of gamma-quanta in matter on atoms included in quantum dots/perovskite nanocrystals. The study revealed that samples devoid of inorganic elements, including quantum dots and perovskite nanocrystals, do not exhibit the Compton effect for gamma-quanta. Furthermore, the paramethylstyrene matrix serves to safeguard perovskite nanocrystals from external influences. The photoluminescence quantum yield of bulk composite materials based on perovskite nanocrystals of the CsPbBr3 composition and poly(paramethylstyrene) remains constant over an extended period, with minimal fluctuations within the margin of error. CONCLUSIONS: Experimental evidence has demonstrated that quantum dots and perovskite nanocrystals encapsulated in various polymer matrices exhibit scintillator properties when subjected to ionizing radiation. The fabricated samples of perovskite nanocrystals/quantum dots and various polymers have been identified as the most promising candidates for use as scintillation material for the registration of X-ray and gamma radiation.