Improving photoluminescence, optical and electrical characteristics of PMMA films with gamma irradiation

Polymeric materials are macromolecules, essentially a combination of numerous repeated subunits. Polymers are innovative and advanced materials that currently have a strong impact on our daily lives. In recent years, polymer use has been prominent due to the materials’ distinctive properties; thus, they entered different fields of science, technology and industrial-biomedical applications.The improvement of photoluminescence, optical and electrical characteristics of non-conducting Poly(methyl methacrylate) (PMMA) films was studied. Upon gamma irradiation of various doses, the photophysical and electrical properties of PMMA films were investigated using photoluminescence spectroscopy, ultraviolet–visible (UV-Vis) spectroscopy and the LCR Meter Bridge Circuit technique. The fluorescent response improved the photoluminescence (PL) spectral emission peaks according to gamma values. Strong fluorescence peaks appeared with the highest gamma dose. The UV–Vis results revealed a significant red-shift in the absorption edge as gamma doses increased. This shift exhibits a continuous decrease in the energy band gap values (from 3.50 to 2.60 eV for direct transition and from 3.05 to 1.55 eV for indirect transition). This was due to the formation of carbon clusters, which led to an increase in the electrical conductivity and improved the dielectric parameters of the irradiated PMMA films. Among a variety of measurements presented and discussed in the present study, the electrical measurements showed improved electrical characteristics of gamma-irradiated PMMA films.

«EVERYDAY LIFE» IN THE WORKS BY W. C. WILLIAMS AND J. JARMUSCH: FROM POETRY TO POETICS. INTERMEDIALITY

The article examines William Carlos Williams’ works that focus on the everyday, mundanity, and poetize daily life which was common in modernist literature. In our time, Williams’ poetry inspired director Jim Jarmusch to make a poetic film «Paterson» about everyday life and the poetic potential of ordinary routine life. The director reinterprets Williams’ ideas and makes a complex, postmodern film about everyday life in the small town Paterson, where he depicts the routine life of his main character, a bus driver. This life, despite its external simplicity and triviality, encourages the hero named Paterson to read modernist literature and write his own poems whose themes and images are intertwined with the work of the well-known Paterson resident, William Carlos Williams himself. In particular, we examine the intermedial interaction of Williams’ works («Paterson» and «This Is Just To Say») with the film and the indirect transition of one sign system into another. In addition to the more or less direct and explicit influence of literature on film through allusions or quotations from the work of the American modernist poet, Williams’ poetry becomes a precedent for the stylized poems of the film’s main character, written by a contemporary American poet Ron Padgett («Another One», «The Run», «Love Poem») and Jarmusch himself («Water Falls»). In this article, we also compare Padgett’s and Jarmusch’s poetry with some of Williams’ poems («Blizzard», «To A Poor Old Woman»), to demonstrate the similarity of motifs and imagery. Thedirector’s work can be interpreted as a manifestation of the idea of looking for poetry in the everyday, or that everyday life is already poetry. Jarmusch’s film about everyday life provides a possible answer to the question of literary anthropology «why is literature as a medium important in people’s lives» – creativity is the very meaning of life. This penetration of one art form (poetry) into another (cinema) gives grounds for speaking about the relevance of the themes of modernist poetry in the context of modernity and about the meaning and value of simplicity for creativity in general.

SYNTHESIS OF CARBON DOTS (CDS) AND DETERMINATION OF OPTICAL GAP ENERGY WITH TAUC PLOT METHOD

Carbon Dots (CDs) which have been synthesized using the laser ablation method show the presence of UV-Vis absorption in the wavelength range of 303 nm to 333 nm for absorbance and 495 nm to 503 nm for fluorescence. Changes in the time duration 1, 2, 3 hours of CDs resulted in changes in the optical energy gap. The optical energy gap valuesare distinguished by the type of indirect transition (n=2) is 3.40 eV (1 hour), 3.15 eV (2 hour), 2.85 eV (3 hour) and direct transition (n=1/2) is 2.58 eV (1 hour), 2.31 eV (2 hour), 1.70 eV (1 hour).

Synthesis and Characterisation of Zinc-doped Antimony Selenide

Antimony selenide substituted with Sb0.4Se0.6 and doped with zinc at three doping ratios (x=0, 0.01 and 0.03) was prepared via the solid state reaction method. The three prepared compositions were reacted thermally at 400 °C for 3 h. The structure of specimens was characterised via X-ray powder diffractometer to obtain the type of crystalline structure and lattice parameters of the prepared specimens, which showed a polycrystalline, orthorhombic structure. Optical characterisation was then achieved via UV-visible spectroscopy to exhibit the transmittance and reflectance spectra and estimate the band gap values of the prepared compositions. The samples showed high absorption spectra at low wavelengths (from 60% to 90%) and low reflectance values (from nearly zero to 17%). The band gap measurement showed an indirect transition, with values ranging from 1.2 eV to 1.23 eV. The electrical characteristics were represented by DC resistivity measurement at low temperature and AC conductivity measurement against frequency. The compositions showed a semiconducting behaviour in DC resistivity and compatible results in AC conductivity.

Tunning the Physical Properties of PVDF/PVC/ Zinc Ferrite Nanocomposites Films for More Efficient Adsorption of Cd (II)

This work studies the enhancement of the physical properties PVDF/PVC blend by adding ZnFe2O4 with different weight percent (from 0% up to 10%) as a nanofiller. The effect of ZnFe2O4 on behavior of PVDF/PVC was studied through XRD, FTIR, FESEM and UV-Visible spectroscopy. The PVDF/PVC/ 10% ZnFe2O4 nanocomposite film was represented the optimum sample. As it shows maximum crystallinity, roughness average (414 nm) and root mean square roughness (113nm) on another hand this sample has also the lowest value of energy band gap for direct and indirect transition. The removal efficiency of Cd(II) by using PVDF/PVC/ 10% ZnFe2O4 reached to about 50 % at pH 6 after 60min. the absorption mechanism as well as kinetics isotherm have been studied.

Synthesis and Study of the Optical Properties of PMMA Microspheres and Opals

Polymethylmethacrylate (PMMA) microspheres were synthesized by surfactant-free emulsion polymerization. These microspheres were used to obtain opals by the self-assembly method. Monomer and initiator quantities were varied systematically to monitor the size of PMMA microspheres. From SEM and DLS measurements, a trend was observed showing as the monomer and initiator amounts increased the average diameter of PMMA microspheres increased except when a minimum monomer amount was reached, for which the size of the microspheres remained practically constant. Diffuse reflectance spectra were processed by the Kubelka–Munk treatment to estimate the energy band gap (Eg) of the PMMA microspheres. It was found that PMMA microspheres present an indirect transition. From SEM micrographs, it is seen that PMMA opals photonic crystals are formed by microspheres in a uniform periodic face-centered cubic (fcc) array. Variable-angle specular reflectance spectra show that the opals possess a pseudo photonic band gap (PBG) in the visible and near-IR regions. Furthermore, it was found that PBGs shift towards larger wavelengths as the average diameter of the PMMA microspheres increases.

A comprehensive assessment of statin discontinuation among patients who concurrently initiate statins and CYP3A4-inhibitor drugs; a multistate transition model

Aims: To describe the 1-year direct and indirect transition probabilities to premature discontinuation of statin therapy after concurrently initiating statins and CYP3A4-inhibitor drugs. Methods and Results: A retrospective new-user cohort study design was used to identify (N=160828) patients who concurrently initiated CYP3A4-inhibitors (diltiazem, ketoconazole, clarithromycin, others) and CYP3A4-metabolized statins (statin DDI exposed, n = 104774) vs. other statins (unexposed, n = 56054) from the MarketScan Commercial claims database (2012 to 2017). These groups were matched (2:1) through propensity score-matching techniques. We applied a multistate transition model to compare the 1-year transition probabilities involving four distinct states (start, adverse drug events [ADEs], discontinuation of CYP3A4-inhibitor drugs, and discontinuation of statin therapy) between those exposed to statin DDIs, vs. unexposed. Statistically significant differences were assessed by comparing the 95% confidence intervals (CIs) of probabilities. Patients exposed to statin DDIs, vs. unexposed, were significantly less likely to discontinue statin therapy (71.4 [95% CI: 71.1, 71.6] vs. 73.3 [95% CI: 72.9, 73.6]) but more likely to experience an ADE (3.4 [95% CI: 3.3, 3.5] vs. 3.2 [95% CI: 3.1, 3.3]) and discontinue with CYP3A4-inhibitor therapy (21.0 [95% CI: 20.8, 21.3] vs. 19.5 [95% CI: 19.2, 19.8]) directly after concurrently starting stains and CYP3A. Subsequent to experiencing an ADE, those exposed to statin DDIs were still less likely to discontinue statin therapy but were significantly more likely to discontinue CYP3A4-inhibitor therapy. Conclusion: While statin DDI exposure was associated with higher likelihood of ADEs, this did not increase the risk of premature statin discontinuation among patients exposed to statin DDIs, versus unexposed.

Effect of Samarium Ions on Physical and Optical Properties of Zinc Borotellurite Glass System

Modifying the physical and optical properties of zinc borotellurite glasses by controlling rare earth (RE) doping is important in order to obtain high quality glass. In this study, Samarium (Sm3+) doped zinc borotellurite glasses were successfully fabricated by using conventional melt-quenching technique with chemical composition (where x = 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%). The physical properties by mean of their density as well as molar volume were measured while the optical properties have been studied through UV-Vis spectroscopy in order to determine the optical band gap (Eopt) and Urbach energy (ΔΕ) of the glass system. Optical absorption spectra of the glass samples were recorded in the range 350 nm - 750 nm at room temperature. The amorphous nature of the glass was confirmed from X-ray diffraction techniques. The density and molar volume of the glass samples were found to vary with respect to Sm3+ ions content. The value of optical band gap, Eopt lies between 2.605 eV to 2.982 eV for the direct transition and 2.768 eV to 3.198 eV for the indirect transition respectively. Meanwhile, the Urbach energy, ΔE was observed in the range of 0.112 eV to 0.694 eV respectively. The physical and optical properties were found to be strongly affected by the varying concentration of Sm3+ ions. Some other results will be analysed and discussed in detail.

Experimental and DFT studies on the structural and optical properties of chitosan/polyvinyle pyrrolidone/ZnS nano composites

Chitosan/ Polyvinyl pyrrolidone (CS/PVP) semi-natural polymeric blend involving gradient concentrations of ZnS nanoparticles (ZnS-NPS) was prepared via a simple casting method. In conjunction with computational density functional theory approaches (DFT), prepared samples were characterized by UV/Vis spectrophotometric studies and Fourier transform infrared measurements (FTIR) to take into account a detailed description of the different reaction mechanisms within the polymeric matrices. To conduct all calculations, the Becke three-parameter hybrid functional (B3LYP) correlation function used with the electron core potential basis set LANL2DZ was used. A detailed study for different reaction regimes was studied and reaction via Oxygen was observed to be preferred and compatible with that of the experimental data. UV/vis. Absorption experimental data were used to calculate the optical energy gap using the Mott-Davis equation and observed data was found to follow an indirect transition route.

Electronic Properties and Scanning Tunneling Microscopy Simulation of MoS2 Nanosheets by Using Density Functional Theory

The ab-initio Density Functional Theory (DFT) approach is used to study the electronic properties of bulk and layered MoS2 nanosheets. For the layered structures mono, bi, tri, tetra and penta layered structure is used. The direct to indirect transition of bandgap is observed as the number of layers is increasing. This transition of bandgap is attributed to the van der Waals interlayer interaction between two layers of MoS2 nanosheets. The indirect bandgap in the bulk MoS2 is found to be 0.94 eV, whereas for a single layered nanosheet is found to be direct bandgap with the value of 1.83 eV. To confirm the surface termination and understand the surface morphology of MoS2 the scanning tunneling microscopy (STM) simulation is performed in constant height mode. It is found that the detection of surface atoms via STM depends on the tip atom of the STM. Dhaka Univ. J. Sci. 69(1): 53-57, 2021 (January)