Western Kentucky University
Department of Physics and Astronomy


MS HSS Students

Department of Physics and Astronomy
Western Kentucky University

"MS HSS Graduate Students Presentations"

April 22, 2019 @ 4:00 pm in EST 260


Ermek Belekov

Bacterial deactivation by using graphene quantum dot as an effective photodynamic therapy agent

Bacterial infections are a major cause of chronic infections. Antibiotics are commonly used in bacterial infection. However, the widespread use of antibiotics has resulted in the emergence of multidrug-resistant or pathogenic bacterial strains. Consequently, the need for developing new bactericidal materials and techniques arose. Photodynamic therapy (PDT) is proposed as an alternative approach. In PDT, light interacts with certain materials and chemicals to induce damage to bacteria. Graphene quantum dots (GQD) are one of the most promising antimicrobial agents since they possess high germicidal activity against a broad range of microbes. In our project, we aim to investigate an effective, inexpensive and available compound which will hold even higher antimicrobial activity and lower toxicity toward human blood. For this purposes, we used GQD and methylene blue (MB), another chemical commonly used in PDT. GQDs were grown by focusing nanosecond laser pulses into benzene and then were later combined with methylene blue (MB) and used to eradicate the Gram-negative bacteria, Escherichia coli, and Gram-positive bacteria, Micrococcus luteus. Theoretical calculation of pressure evolution was calculated using the standard finite difference method. Detailed characterization was performed with transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fouriertransform infrared (FTIR), UV-Visible (UV-Vis), and photoluminescence (PL) spectra. The (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) (MTT) assay was used to determine if GQDs in dark conditions caused human cellular side effects and affected cancer and noncancer cellular viability.

Bektur Abdisatarov
Nanosecond pulsed laser deposition of Pb thin film on Si (111)

Pb thin film was deposited onto a Si (111) substrate by pulsed laser deposition (PLD). The Pb target was ablated with a Q-switched 1064 Nd: YAG pulsed laser with 5 nanosecond pulse width, 10 Hz repetition rate, and 1 mm beam diameter. Laser energy density, temperature wavelength and the number of pulses were changed. Different thicknesses of the film ranging from 5 to 70 nm were obtained. Morphological structures of the films were measured using scanning electron microscopy and atomic force microscopy. X-ray diffraction (XRD) is used to characterize the phases, preferred crystal orientation and crystallinity. Our results show that laser energy density, wavelength, and temperature play an important role in morphology. In addition, quantum size effects (QSE) were observed on the ultra-thin films and coarsening effects were observed on the films that underwent high-temperature deposition. Experimental observation is supported by theoretical simulations.

Alex Larin

A novel approach to analysis of complex gaseous mixtures is presented. The approach is based on utilization of a compact gas chromatograph in combination with an array of highly integrated and selective metal oxide (MOX) sensors. Thanks to the implementation of a multisensory detector, the device is collecting multiple chromatograms in a single run. The sensors in the integrated MEMS platform are very distinct in their catalytic properties. Hence, the time separation by chromatographic column is complemented by catalytic separation by a multisensory detector. Also, the device can perform the analysis in a broad range of concentrations from ppb to hundreds of ppm. Low ppb and even sub-ppb level of detection for some VOCs was achieved. As a part of this effort, nanocomposite gas sensors were synthesized for selective detection of hydrogen sulfide, mercaptans, alcohols, ketones and heavy hydrocarbons.