Radioluminescence properties of the CdSe/ZnS Quantum Dot nanocrystals with analysis of long-memory trends

Inorganic Nanoparticles as Radiosensitizers for Cancer Treatment

Nanotechnology has expanded what can be achieved in our approach to cancer treatment. The ability to produce and engineer functional nanoparticle formulations to elicit higher incidences of tumor cell radiolysis has resulted in substantial improvements in cancer cell eradication while also permitting multi-modal biomedical functionalities. These radiosensitive nanomaterials utilize material characteristics, such as radio-blocking/absorbing high-Z atomic number elements, to mediate localized effects from therapeutic irradiation. These materials thereby allow subsequent scattered or emitted radiation to produce direct (e.g., damage to genetic materials) or indirect (e.g., protein oxidation, reactive oxygen species formation) damage to tumor cells. Using nanomaterials that activate under certain physiologic conditions, such as the tumor microenvironment, can selectively target tumor cells. These characteristics, combined with biological interactions that can target the tumor environment, allow for localized radio-sensitization while mitigating damage to healthy cells. This review explores the various nanomaterial formulations utilized in cancer radiosensitivity research. Emphasis on inorganic nanomaterials showcases the specific material characteristics that enable higher incidences of radiation while ensuring localized cancer targeting based on tumor microenvironment activation. The aim of this review is to guide future research in cancer radiosensitization using nanomaterial formulations and to detail common approaches to its treatment, as well as their relations to commonly implemented radiotherapy techniques.

Recent advances, challenges, and opportunities of inorganic nanoscintillators

This review article highlights the exploration of inorganic nanoscintillators for various scientific and technological applications in the fields of radiation detection, bioimaging, and medical theranostics. Various aspects of nanoscintillators pertaining to their fundamental principles, mechanism, structure, applications are briefly discussed. The mechanisms of inorganic nanoscintillators are explained based on the fundamental principles, instrumentation involved, and associated physical and chemical phenomena, etc. Subsequently, the promise of nanoscintillators over the existing single-crystal scintillators and other types of scintillators is presented, enabling their development for multifunctional applications. The processes governing the scintillation mechanisms in nanodomains, such as surface, structure, quantum, and dielectric confinement, are explained to reveal the underlying nanoscale scintillation phenomena. Additionally, suitable examples are provided to explain these processes based on the published data. Furthermore, we attempt to explain the different types of inorganic nanoscintillators in terms of the powder nanoparticles, thin films, nanoceramics, and glasses to ensure that the effect of nanoscience in different nanoscintillator domains can be appreciated. The limitations of nanoscintillators are also highlighted in this review article. The advantages of nanostructured scintillators, including their property-driven applications, are also explained. This review article presents the considerable application potential of nanostructured scintillators with respect to important aspects as well as their physical and application significance in a concise manner.

Fabrication and Luminescent Properties of Zn–Cu–In–S/ZnS Quantum Dot Films under UV Excitation

Quantum dots (QDs) are quite interesting materials due to their unique chemical and physical properties. ZnCuInS/ZnS QDs can be produced either in hydrophobic or hydrophilic form, are non-toxic, and thus favorable for studies in the area of biology. Poly(methyl methacrylate) (PMMA) is a well-known biocompatible resin which is widely used in dentistry, ophthalmology, and orthopedic surgery. Four composite PMMA films of ZnCuInS/ZnS nanocrystals with maximum emission at 530 nm and concentrations of 1.0, 4.0, 6.0, and 10.0 %w/v, were prepared. X-ray irradiation was used to evaluate the volume homogeneity of the final samples, as a measure of QD dispersion. The luminescent efficiency was evaluated, under ultraviolet (UV) irradiation. The process of UV irradiation involved the experimental measurement of the forward luminescent light, as well as the backward luminescent light, in order to accurately calculate the energy quantum efficiency (EQE) of ZnCuInS/ZnS QDs. Reflected UV radiation was also measured, and results showed that it ranges from 2% to 6% approximately as the QD concentration rises from 1.0 %w/v to 10.0 %w/v. Beyond 6.0 %w/v, the reflected UV radiation remains essentially unchanged. Additionally, the reflected UV radiation remained unaffected as the power of the incident UV increased. Approximately 9% of incident UV radiation passed through the 1.0 %w/v sample, whereas for the samples with higher ZnCuInS/ZnS concentration, 0% UV radiation passed through. The EQE reached a maximum of about 45% with the 10.0 %w/v sample, while it remained practically unaffected relative to the increase of the emitted UV power. The homogeneity measurements revealed that the coefficient of variation (CV) increased with increasing concentration, for the 1.0, 4.0, and 6.0 %w/v samples. The minimum CV was obtained for the sample of 10.0 %w/v due to the incorporation of sonication in the final product, during the fabrication process.

Fractal and Long-Memory Traces in PM10 Time Series in Athens, Greece

This work examines if chaos and long memory exist in PM10 concentrations recorded in Athens, Greece. The algorithms of Katz, Higuchi, and Sevcik were employed for the calculation of fractal dimensions and Rescaled Range (R/S) analysis for the calculation of the Hurst exponent. Windows of approximately two months’ duration were employed, sliding one sample forward until the end of each utilized signal. Analysis was applied to three long PM10 time series recorded by three different stations located around Athens. Analysis identified numerous dynamical complex fractal time-series segments with patterns of long memory. All these windows exhibited Hurst exponents above 0.8 and fractal dimensions below 1.5 for the Katz and Higuchi algorithms, and 1.2 for the Sevcik algorithm. The paper discusses the importance of threshold values for the postanalysis of the discrimination of fractal and long-memory windows. After setting thresholds, computational calculations were performed on all possible combinations of two or more techniques for the data of all or two stations under study. When all techniques were combined, several common dates were found for the data of the two combinations of two stations. When the three techniques were combined, more common dates were found if the Katz algorithm was not included in the meta-analysis. Excluding Katz’s algorithm, 12 common dates were found for the data from all stations. This is the first time that the results from sliding-window chaos and long-memory techniques in PM10 time series were combined in this manner.

Radioluminescence in biomedicine: physics, applications, and models

The electromagnetic spectrum contains different frequency bands useful for medical imaging and therapy. Short wavelengths (ionizing radiation) are commonly used for radiological and radionuclide imaging and for cancer radiation therapy. Intermediate wavelengths (optical radiation) are useful for more localized imaging and for photodynamic therapy (PDT). Finally, longer wavelengths are the basis for magnetic resonance imaging and for hyperthermia treatments. Recently, there has been a surge of interest for new biomedical methods that synergize optical and ionizing radiation by exploiting the ability of ionizing radiation to stimulate optical emissions. These physical phenomena, together known as radioluminescence, are being used for applications as diverse as radionuclide imaging, radiation therapy monitoring, phototherapy, and nanoparticle-based molecular imaging. This review provides a comprehensive treatment of the physics of radioluminescence and includes simple analytical models to estimate the luminescence yield of scintillators and nanoscintillators, Cherenkov radiation, air fluorescence, and biologically endogenous radioluminescence. Examples of methods that use radioluminescence for diagnostic or therapeutic applications are reviewed and analyzed in light of these quantitative physical models of radioluminescence.