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Electronic transport in MoSe <sub/>2</sub> FETs modified by latent tracks created by swift heavy ion irradiation
摘要： Unique characteristics of transition metal dichalcogenides (TMDCs) such as their tunable band gap and ultra-thin body thickness make them potential candidates for applications in optoelectronic, gas sensing and energy storage devices. In this work, 1.8 GeV Ta ions at different ion fluences ranging from 1 × 109 ions cm?2 to 6 × 1010 ions cm?2 were used to introduce amorphous defective regions, latent tracks, in MoSe2 to study the electronic transport behavior in irradiated TMDC-channel field-effect transistors (FETs). Defects in these materials induced by the swift heavy ion irradiation play a vital role in the device applications. The results show that carrier mobility decreases while resistance of the devices increases abruptly with increasing ion fluences. The impact mechanism of the latent tracks on electronic transport behavior in TMDC-channel FETs was analyzed in detail. It was assumed that the Bloch wave of electrons was strongly localized by the latent tracks induced by the SHI irradiation and the Bloch wave of electrons can be scattered by the latent tracks as well. This study helps to investigate the influence of the latent tracks on electronic transport in other 2D materials as well.
关键词： latent track,field-effect transistor,molybdenum selenide,electronic transportation,swift heavy ion irradiation
更新于2025-11-14 17:03:37
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405 nm and 450 nm photoinactivation of <i>Saccharomyces cerevisiae</i>
摘要： Photoinactivation of bacteria with visible light has been reported in numerous studies. Radiation around 405 nm is absorbed by endogenous porphyrins and generates reactive oxygen species that destroy bacteria from within. Blue light in the spectral range of 450–470 nm also exhibits an antibacterial effect, but it is weaker than 405 nm radiation, and the photosensitizers involved have not been clarified yet, even though flavins and porphyrins are possible candidates. There are significantly fewer photoinactivation studies on fungi. To test if visible light can inactivate fungi and to elucidate the mechanisms involved, the model organism Saccharomyces cerevisiae (DSM no. 70449) was irradiated with violet (405 nm) and blue (450 nm) light. The mean irradiation doses required for a one log reduction of colony forming units for this strain were 182 J/cm2 and 526 J/cm2 for 405 nm and 450 nm irradiation, respectively. To investigate the cell damaging mechanisms, trypan blue staining was performed. However, even strongly irradiated cultures hardly showed any stained S. cerevisiae cells, indicating an intact cell membrane and thus arguing against the previously suspected mechanism of cell membrane damage during photoinactivation with visible light at least for the investigated strain. The results are compatible with photoinactivated Saccharomyces cerevisiae cells being in a viable but nonculturable state. To identify potential fungal photosensitizers, the absorption and fluorescence of Saccharomyces cerevisiae cell lysates were determined. The spectral absorption and fluorescence results are in favor of protoporphyrin IX as the most important photosensitizer at 405 nm radiation. For 450 nm irradiation, riboflavin and other flavins may be the main photosensitizer candidates, since porphyrins do not play a prominent role at this wavelength. No evidence of the involvement of other photosensitizers was found in the spectral data of this strain.
关键词： photoinactivation,porphyrin,450 nm irradiation,flavin,Saccharomyces cerevisiae,disinfection,405 nm irradiation
更新于2025-09-23 15:23:52
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Color-center formation and thermal recovery in X-ray and electron-irradiated magnesium aluminate spinel
摘要： We have studied the formation of color centers in magnesium aluminate spinel (MgAl2O4) by X-ray and electron irradiations near room temperature (RT). For this purpose, Cu Kα radiation and three electron energies (1.0, 1.4, and 2.5 MeV) were used for variable fluences (up to 4.2 × 10^18 cm^?2). Off-line UV-visible absorption spectra were recorded at RT as well as at low temperature down to 27 K after electron irradiation. The dependence of the production rate of F centers (oxygen vacancies) on the electron energy yields a threshold displacement energy of 190 ± 10 eV for oxygen atoms at RT, which is much higher than the determinations by molecular-dynamics simulations. Such a discrepancy is discussed on the basis of available migration data of point defects in spinel. Equipartition of F0 and F+ centers, i.e., the neutral (VO^x) and singly ionized (VO^.) oxygen vacancies, is reached for high electron fluences. Moreover, the evolution of the width of color-center absorption bands versus temperature is interpreted with the classical theory for F centers (neutral halogen vacancies) in alkali halides. The Stokes shifts are deduced from the temperature dependence of the absorption bandwidths of color centers like for alkali halides and alkaline-earth oxides. Finally, isothermal annealing data for long annealing time show a non-zero asymptotic behavior for both F0 and F+ centers. This uncommon behavior is interpreted by charge exchange processes leading to an equilibrium state between those two color centers.
关键词： thermal recovery,X-ray irradiation,color centers,threshold displacement energy,F centers,electron irradiation,absorption spectroscopy,magnesium aluminate spinel
更新于2025-09-23 15:23:52
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Phototransformations of some 3-cyclohexenyloxychromenones: Synthesis of Spirocyclic compounds
摘要： The phototransformation of the 3-cyclohexenyloxychromenones by irradiation with a pyrex-filtered light from a 125 W Hg vapor lamp under an inert atmosphere into the spirocyclic fused xanthenones was described. The efficacy of the protocol depended upon the position (o-, m-, or p-) of the cyclohexenyloxy group appended to the 2-aryl moiety on the chromenone nucleus, which was further invoked by steric, electronic, and proximity considerations. The structure(s) of the substrates and photoproducts were established using the spectroscopic (IR and NMR) data.
关键词： spirocyclics,irradiation,1,4-biradical,cyclohexenyloxychromenones
更新于2025-09-23 15:23:52
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Straw Degradation Behaviors under Different Conditions of Relative Air Humidity and Ultraviolet-A Irradiation
摘要： In this study, straw was degraded continuously for 150 days under one of three levels of relative air humidity (RH) (90%, 60%, or 30%) to estimate the effect of humidity on straw biodegradation. Moreover, straw was treated with ultraviolet (UV)-A irradiation + 90% RH for 180 days to evaluate the interaction between photodegradation and biodegradation. The effects of 30% and 60% RH on straw degradation was inconspicuous. Straw mass losses at 90% RH and UV-A + 90% RH were 18.5% and 39.1%, respectively. BIOLOG analysis showed that filamentous fungi played a major role in straw biodegradation. Thermogravimetric analysis showed that treatment with UV-A + 90% RH tended to increase the maximum pyrolysis rate and decreased the initial pyrolysis temperature. Compared with 90% RH, infrared spectra analysis showed that functional groups of UV-A + 90% RH treatment, e.g., –CH, –C=O, and the benzene ring structure, clearly decreased. Straw-degrading bacteria were observed by scanning electron microscopy at the beginning and end of UV-A + 90% RH treatment. Results highlight the role of humidity in the degree of straw biodegradation by filamentous fungi. Straw degradation is accelerated by the combined action of photodegradation and biodegradation under high UV-A irradiation and high humidity.
关键词： Relative air humidity,Biodegradation,TGA,Photodegradation,Ultraviolet-A irradiation,BIOLOG,SEM,ATR-FTIR
更新于2025-09-23 15:23:52
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Activated carbons with adsorbed cations as photocatalysts for pollutants degradation in aqueous medium
摘要： Oxidized activated carbon (AC) based on commercial coconut-shell carbon Aquacarb 607C has been prepared. This AC has micro-mesoporous structure and contains surface carboxyl and phenol/enol groups. Cu- and Co-containing ACs have been synthesized via ion-exchange in acid medium. According to potentiometric titration and XPS data, cation-exchanged forms of AC contain about 0.5% of metal ions. Such cation-containing ACs possess narrowed band gap compared oxidized AC as it is observed for doped oxides. Oxidized and cation-containing ACs have been tested as catalysts in photodegradation of dyes and phenol under UV- and visible irradiation. Initial oxidized AC is photoactive toward rhodamine B and methyl orange under UV illumination but inactive under visible light. For the first time it is shown that cation-exchanged forms of AC have enhanced activity towards rhodamine B, methyl orange and phenol in both UV and visible region. Therefore, the principal possibility of improving the photocatalytic properties of AC by introducing a minimal amount of copper and cobalt cations is shown.
关键词： Cation-exchanged forms,Decolourisation and mineralization,UV and visible irradiation,Activated carbon,Photocatalytic degradation
更新于2025-09-23 15:23:52
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The Influence of Ceramic Far-Infrared Ray (cFIR) Irradiation on Water Hydrogen Bonding and its Related Chemo-physical Properties
摘要： The property of water is highly related to the earth's environment and climate change. The fundamental dynamical process of water is include formation and breaking of hydrogen bonds. This dynamic process, so far, is still poorly understood. We investigated weakening of the hydrogen bonds of water after ceramic Far-Infrared Ray (cFIR) irradiation and the resulting effects on physical and chemical properties of water. In this study, the Fourier transform infrared spectroscopy (FT-IR) was used to explore hydrogen bonding change of cFIR-irradiated water; in addition, capillary viscometers, Gas Chromatographs (GC), Differential Scanning Calorimetry (DSC), contact angles, Franz cells, High-Performance Liquid Chromatography (HPLC), and capillary electrophoresis analysis were used to evaluate its physical characteristics, such as viscosity, volatility, temperatures of water crystallization, surface tension, diffusion, hydrogen peroxide dissociation, solubility of solid particles, and changes in pH of acetic acid. The cFIR treated water decreased in viscosity and surface tension (contact angles), but increased in the solubility of solid particles, hydrogen peroxide dissociation, temperatures of water crystallization, and acidity of acetic acid. The weakening of water hydrogen bonds caused by cFIR irradiation is correspondent with our previous medical-biological studies on cFIR.
关键词： Hydrogen bonds,Fourier transform infrared spectroscopy (FT-IR),Contact angle,Ceramic far infrared ray (cFIR),Irradiation water,Solubility,Volatility
更新于2025-09-23 15:23:52
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Variation in Structural, Electrical and Optical Properties of Selenium Nanowires After Irradiation with Ni6+ Ions
摘要： The effect of Ni ion irradiation on selenium nanowires of 80 nm diameter is studied in the present work. Se nanowires were prepared by using electrodeposition technique in polycarbonate membrane. Changes in the structural, optical and electrical properties are studied using XRD, UV/Vis spectroscopy and current–voltage characteristics, of the pristine and irradiated samples. X-ray diffraction study confirms the variation in peak intensity without any shifting in peak position. Variation in texture coefficient and grain size was clearly observed which is a consequence of changing plane orientation, irradiation induced grain growth and grain fragmentation. A decrease in the optical band gap takes place due to interstitial energy band states in the vicinity of conduction and valence band. IVC also shows variation in the conductivity which is due to the generation of current carriers with the passage of energetic ions.
关键词： Ion irradiation,Optical analysis,Selenium nanowires,Impedance,Electrical properties,Structural analysis
更新于2025-09-23 15:23:52
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Enhanced sensor life using UV treatment of sulphur poisoned Pt-PtOx
摘要： In this work, we report a novel method for recovery of sulphur poisoned platinum/platinum oxide (Pt-PtOx) core-shell nanowire sensor using UV irradiation. The optimum core to shell thickness ratio and the operating conditions are the key factors to achieve a high-performance H2S sensor, described in this report. The fabricated core-shell nanowire sensor demonstrated response of 6.4% at 1 ppm H2S with detection limit of 10 ppb at 150°C operating temperature. The sensor undergoes prominent time-dependent poisoning at H2S exposure of 3 ppm when operated at 150°C due to sensor surface contamination by sulphur, later confirmed by XPS analysis. Ultraviolet light at two wavelengths, 365 nm, and 248 nm is investigated to recover the poisoned Pt-PtOx surface. UV irradiation at 248 nm for 5 minutes results in sensor recovery, confirmed by further H2S sensing characterization and XPS studies on the recovered sensor. To the best of our knowledge, this is one of the first reports on UV irradiation for recovery of sulphur poisoned metal-oxide surfaces.
关键词： sulphidation,recovery,plasma oxidation,UV irradiation,core-shell nanowire
更新于2025-09-23 15:23:52
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UV photolysis of tetrachloro-p-benzoquinone (TCBQ) in aqueous solution: Mechanistic insight from quantum chemical calculations
摘要： In this work, a systematical investigation on the transformation of tetrachloro-p-benzoquinone (TCBQ) under UV irradiation (at 253.7 nm) in aqueous solution has been conducted through quantum chemical calculations. The UV irradiation at 253.7 nm could induce the excitation of TCBQ to its first excited singlet state, followed by the intersystem crossing to its first triplet state. In aqueous solution, the first triplet state of TCBQ was thermodynamically and kinetically feasible to react with H2O via 1,4-addition, where the addition of OH- to the α–β conjugated system was the dominant step. Interestingly, with the addition of hydroxyl to TCBQ, the dechlorination of TCBQ occurred with the formation of the monohydroxylated product of TCBQ (OH-TriCBQ). The UV photolysis pathway of OH-TriCBQ was similar to that of TCBQ, and the 1,4-addition of OH- to the ortho-position of the hydroxyl was the most efficient pathway. The dechlorination by 1,4-addition of OH- was also observed for OH-TriCBQ. With much larger forward energy barriers, the nucleophilic addition of carbonyl by OH- (i.e., 1,2-addition) might be less important for the UV photolysis of TCBQ and OH-TriCBQ. The findings in the present study may help to understand the transformation of TCBQ in aqueous solution.
关键词： UV irradiation,Quantum chemical calculations,Dechlorination,Tetrachloro-p-benzoquinone
更新于2025-09-23 15:23:52