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Optical Nanoprobes for Diagnosis
Published in D. Sakthi Kumar, Aswathy Ravindran Girija, Bionanotechnology in Cancer, 2023
R. G. Aswathy, D. Sakthi Kumar
These unique properties lead to QDs of different-size emitting lights of different wavelengths from ultraviolet to infrared spectrum. For example, the bulk bandgap of semiconductor cadmium selenide (CdSe) is 1.7 eV corresponding to 730 nm light emission. By changing the nanocrystal diameter of CdSe from 2 nm to 7 nm, it can be tuned to emit light with wavelength between 450 nm and 650 nm. The material composition can also be used as another factor for the modification of band gap of the semiconductor. By changing the composition of the alloy CdSexTe1–x of 5 nm size can be tuned to emit light in 610–800 nm. The size and shape of semiconductor QDs can be specifically controlled by factors such as experimental duration, temperature, and concentration of precursor molecules in the synthesis.
Solid-State Dose Measuring Devices
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
The atomic structure of diamond results in few free charge carriers and hence, very low leakage currents. Indeed, the resistivity of intrinsic (pure) diamond is very high (around 1014 Ωcm), making it an insulator, although it is often referred to as a semiconductor because of the presence of a small amount of impurities. It is then theoretically possible to obtain a device with extremely low leakage currents in the presence of an external electric field. Diamond is also a wide-band-gap semiconductor, resulting in low noise at room temperature and non-response to visible light (it carries very low current even under high voltages). The low capacitance of the material results in very low noise.
Radiation Detection and Measurement
Published in Shaheen A. Dewji, Nolan E. Hertel, Advanced Radiation Protection Dosimetry, 2019
When a TLD is irradiated, the deposited energy can provide electrons that are in the valence band with enough energy to transition to the conduction band. This transition leaves behind a positive charge in the valence band known as a hole. The electron transitioning to the conduction band may lose some energy and drop into an energy level in the band gap that is present because of the added dopants of Mg and Ti. This energy level is known as an electron trap. A corresponding energy level near the valence band is known as a hole trap. Either electron traps or hole traps may be luminescence centers. When an electron or hole recombines at such a center, luminescence is produced. Heating of the TLD provides energy to trapped electrons causing them to enter the conduction band. As the temperature of the TLD is increased, electrons or holes recombine at a luminescence center, visible light is emitted as a function of time, and the resulting signal, detected by a photomultiplier, is known as a glow curve. It can be shown that the peak height, or the area under the glow curve, is proportional to dose. The application of heat for emptying traps is a relatively inefficient process. The probability of an electron migrating from a trap can be given as a function of time by an equation that is similar to the Arrhenius equation governing chemical reactions (Galwey and Brown 2002):
Anti-microbial and anti-cancer activities of Mn0.5Zn0.5DyxFe2-xO4 (x ≤ 0.1) nanoparticles
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2021
Suhailah S. Al-Jameel, Suriya Rehman, Munirah A. Almessiere, Firdos A. Khan, Yassine Slimani, Najat S. Al-Saleh, Ayyar Manikandan, Ebtesam A. Al-Suhaimi, Abdulhadi Baykal
The structural and morphological characterizations of Mn0.5Zn0.5DyxFe2-xO4 NPs (x ≤ 0.1) were analysed by an XRD, TEM and SEM methods which has been previously published study by Almessiere et al. [33]. As per XRD, the average size of the MNPs was in the range from 11 to 18 nm. Direct optical energy band gaps were in a small band range of 1.61–1.67 eV. All products displayed super-paramagnetic properties at room temperature [33]. The SEM analysis showed that NPs revealed a regular size and uniform distribution of cubic particles with aggregation and the average particles size was less than 20 nm and was found to increase in size with increasing the Dy content. Similarly, the TEM analysis showed that NPs were agglomeration of cubic nanoparticles because of the magnetic interaction among nanoparticles [33].
Topical delivery of growth factors and metal/metal oxide nanoparticles to infected wounds by polymeric nanoparticles: an overview
Published in Expert Review of Anti-infective Therapy, 2020
To sum up, several factors should be considered for the application of GFs as a remedy for chronic wounds. In this context, finding carriers with properties of suitable biocompatibility, biodegradability, and controlled release of growth factors is important. Wound type and wound-healing phase are other determinant factors in selection of appropriate GFs for capsulation. Moreover, in infected wounds such as DFU, removal of pathogenic microorganisms particularly bacteria and fungi can be a complicated issue. In this review, we have compared wound healing and antimicrobial capacities of encapsulated MNPs/MONPs with growth factors in micro- and nanocarrier systems. In the case of bacterial infection, the release of metal ion forms MNPs particularly AgNPs followed by ROS production can form a pit in cell wall and damage biological macromolecules involving enzymes and nucleic acids. The major drawback in using AgNPs is higher cytotoxicity of these NPs against human cells. ZnO and TiO2NPs as two common MONPs have more antibacterial activities under a specific wavelength of light irradiation. This ability is associated to the amount of band gap energy
Green synthesis of zinc oxide nanoparticles using different plant extracts and their antibacterial activity against Xanthomonas oryzae pv. oryzae
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Solabomi Olaitan Ogunyemi, Yasmine Abdallah, Muchen Zhang, Hatem Fouad, Xianxian Hong, Ezzeldin Ibrahim, Md. Mahidul Islam Masum, Afsana Hossain, Jianchu Mo, Bin Li
The synthesis of zinc oxide by chamomile flower (Matricaria chamomilla L.), olive leaves (Olea europaea), and red tomato fruit (Lycopersicon esculentum M.) gave an end product of pale white and light brown precipitate respectively (Figure 1). The precipitates were freeze-dried to yield zinc oxide nanopowder which was used for further characterization. The UV – vis spectra of zinc oxide nanoparticles showed a strong absorption band at 384, 380, and 386 nm for chamomile flower (Matricaria chamomilla L.), olive leaves (Olea europaea), and red tomato fruit (Lycopersicon esculentum M.) respectively (Figure 2). The synthesized zinc oxide nanoparticles confirmed in this study by the UV – vis absorption spectra at the wavelength range of 380 to 386 nm which is the characteristic wavelength range of zinc oxide nanoparticles is consistent with the studies of [45]. The synthesized zinc oxide nanoparticles exhibited surface plasmon resonance (SPR) peak at 320 nm which is a blue shift. The band gap energy of SPR was calculated using the formula E = hc/λ, where “h” is the Plank’s constant, “c” is the velocity of light and “λ” the wavelength. The band gap was found to be 3.88 eV as earlier reported [46].