Absorbed Photon Energy Research Articles

(Digital Presentation) Characterization of Ultrafast Dynamics of Refractory Metal Nanoparticles of Interest as Photocatalysts

Plasmonic noble metal nanoparticles are of interest as photocatalysts for several reasons, including a very large absorption cross section and the creation of a greatly enhanced evanescent electromagnetic field at the surface of the nanoparticles when excited at the plasmon resonance. Furthermore, the plasmon resonance is tunable over a wide wavelength range as a function of the size, shape, and composition of the nanoparticles. When these properties are combined with the known photocatalytic activity of noble metals for technologically important targets such as solar fuels, it is not surprising that these nanoparticle systems are widely studied. Noble metals do, however, possess a weakness in that they can be easily melted upon photoexcitation, due to the fact that noble metals dissipate absorbed photon energy efficiently through ultrafast electron-phonon coupling, in roughly one picosecond, to produce heat. As a result, the study of new classes of plasmonic materials, such as refractory metals, with much higher melting points than noble metals is growing rapidly. While there are still challenges in the size-selective synthesis of refractory metal nanoparticles, characterization efforts on these materials are of strong interest. We report here a study on the time-resolved spectroscopy of electron-phonon coupling in refractory metal nanoparticles. There are very significant variations in the efficiency and time-scales of electron-phonon coupling in refractory metal nanoparticles as compared to noble metal nanoparticles. Furthermore, due to the fact that many refractory metals are oxidized under ambient conditions to create a thin oxide layer on the surface of the nanoparticles, these materials also demonstrate dynamics related to electron injection from the metal to the oxide layer that noble metals do not show. Far from being a negative, the added electron injection dynamics offer new opportunities for photocatalysis that we discuss. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

Tuning of the electronic bandgap of SnSe compound by oxygen and sulphur doping and their optical characteristics for solar cell applications

Based on the ab-initio calculations, we have investigated the electronic, optical, and thermal properties of pristine SnSe and doped with oxygen (O) and sulphur (S) at the Se-site at concentration of 3.125%. The calculated negative formation energy indicates the stability of the pristine SnSe and doped system. We find that pristine SnSe possesses a direct bandgap value of 0.90 eV having good comparable to experimental value. The doping of O and S tunes the bandgap of SnSe, which can be promising for photovoltaic devices. Further, for the technological applications of O-/S-doped SnSe, we have analyzed optical properties in terms of absorption of photon energy and polarization. Strong absorption peaks confirms the direct transition of electrons from valence band to conduction band. Moreover, the thermal properties are calculated in terms of electrical/thermal conductivities, Seebeck coefficient, and figure of merit (ZT). At room temperature the ZT values are calculated round about 0.41 for O- and S-doped SnSe, respectively. We expect that our calculated thermoelectric parameters of the O- and S-doped SnSe could pave a new route for the application in the thermoelectric devices.

Antenna effect of pyridoxal phosphate on the fluorescence of mitoxantrone-silicon nanoparticles and its application in alkaline phosphatase assay.

As a kind of sensing and imaging fluorescent probe with the merit of low toxicity, good stability, and environment-friendly, silicon nanoparticles (SiNPs) are currently attracting extensive research. In this work, we obtained mitoxantrone-SiNPs (MXT-SiNPs) with green emission by one-pot synthesis under mild temperature condition. The antenna based on pyridoxal phosphate (PLP) was designed for light-harvesting to enhance the luminescence of MXT-SiNPs and to establish a novel sensing strategy for alkaline phosphatase (ALP). PLP transfers the absorbed photon energy to MXT-SiNPs by forming Schiff base. When PLP is dephosphorized by ALP, the released free hydroxyl group reacts with aldehyde group to form internal hemiacetal, which leads to the failure of Schiff base formation. Based on the relationship between antenna formation ability and PLP hydrolysis degree, the activity of ALP can be measured. A good linear relationship was obtained from 0.2 to 3.0 U/L, with a limit of detection of 0.06 U/L. Furthermore, the sensing platform was successfully used to detect ALP in human serum with recovery of 97.6-106.2%. The rational design of antenna elements for fluorescent nanomaterials can not only provide a new pathway to manipulate the luminescence, but also provide a new direction for fluorescence sensing strategy.

Design of Improved Molecular Solar‐Thermal Systems by Mechanochemistry: The Case of Azobenzene

AbstractMolecular solar‐thermal systems (MOST) have emerged in these last years as a novel concept to store solar light. They rely on two state molecular switches that can absorb a photon to convert the initial state A to a higher‐in‐energy state B. The chemical energy stored by B can be then released to reconstitute A. Although simple in its principle, an optimal MOST needs to satisfy several requirements: incoming photon energy in the solar spectrum range, high photoreaction quantum yield, high storage density, no degradation. The first challenge is therefore the search for molecular switches that accomplish all such properties. Until now, trial‐and‐error experiments have been performed, led by physicochemical intuition. The result is that most of the initially proposed switches have been abandoned in favor of the preferred norbornadiene/quadricyclane system, together with its derivatives. Nevertheless, most of the solar spectrum is still out of the MOST absorption region, hence requiring novel approaches. Here, it is shown how mechanochemistry can be applied to improve the principally desired characteristics of a MOST: photon absorption energy, storage energy, and thermal B‐to‐A energy barrier. It is especially shown how azobenzene—a paradigmatic photoswitch still attracting much attention—can be proposed, within certain limits, as a MOST when applying external forces.

Highly efficient photocatalytic oxidation of C[sbnd]H bond based on microchannel reactor

A mild photocatalytic CH bond selective oxidation mediated by metal-free photocatalyst 2-Methylanthraquinone was reported. Glass microchannel reactor can enhance the absorption of photon energy and oxygen by the reaction mixture, so as to greatly improve the reaction efficiency of photocatalytic reaction in glass microchannel reactor. This reaction method can quickly oxidize alkyl aromatics into corresponding oxidation products to obtain aromatic ketones in high yield.

Construction of g-C3N4/Ag/TiO2 Z-scheme photocatalyst and Its improved photocatalytic U(VI) reduction application in water.

The reduction of soluble U(VI) to insoluble U(IV) by photocatalytic technology is considered to be a valid method to remove U(VI) from water. Herein, g-C3N4/Ag/TiO2 Z-scheme heterojunction was synthesized for photocatalytic U(VI) reduction application. The SEM, XRD and XPS characterization results showed that a ternary g-C3N4/Ag/TiO2 composite photocatalyst was synthesized successfully. g-C3N4/Ag/TiO2 exhibited excellent photocatalytic reduction performance for U(VI) under visible light irradiation. After 30 min irradiation, the removal rate of U(VI) was above 99%. XPS indicated that the majority of U(VI) on the surface of g-C3N4/Ag/TiO2 was reduced to U(IV). In addition, the photocatalytic activity of g-C3N4/Ag/TiO2 has been kept significantly after five rounds of experiments, indicating good stability. g-C3N4/Ag/TiO2 exhibited better photocatalytic reduction of U(VI) under visible light irradiation, which is mainly ascribed to Z-scheme photocatalytic mechanism assisted by the LSPR effect (Local Surface Plasmon Resonance). Ag with plasmon resonance effect on the loading has a strong absorption of photon energy. In addition, an intermediate charge transfer channel is formed between Ag and the semiconductor to inhibit the combination of photogenerated electrons and holes, resulting in a significant increase in the photocatalytic activity of the photocatalyst. This idea has some significance in design of other composite photocatalytic systems.

Micro-Swelling and penetration assisted laser Processing: A doping and laser processing method for polydimethylsiloxane films based on swelling and penetration behavior

Polydimethylsiloxane and its laser processing have significance in broad fields. The problems caused by poor absorption and current doping methods have prevailed in the laser processing of polydimethylsiloxane. Here, a simple and efficient dopant-induced laser processing method based on the swelling and penetration behavior was presented to improve the laser processing of polydimethylsiloxane films: micro-swelling and penetration assisted laser processing. In this method, the dopant benzophenone was introduced into polydimethylsiloxane films through micro-swelling and penetration pretreatment to adjust its physical/chemical properties so as to improve the laser processing. Results showed that micro-swelling and penetration assisted laser processing method performed higher efficiency, capability (Depth: 625.9 ± 38 μm, Width: 13.2 ± 0.9 μm, Aspect Ratio: 47.4 ± 1.7:1) and quality (no debris or micro-crack and less thermal effects) compared to the typical laser processing method (Depth: 140.1 ± 5.7 μm, Width: 28.0 ± 2.0 μm, Aspect Ratio: 5.0 ± 0.4:1). The introduction of benzophenone changed the polydimethylsiloxane films’ optical, photochemical and thermodynamic properties and affected its laser ablation process, in which the more complete and uniform photochemical decomposition of polydimethylsiloxane films was promoted due to that benzophenone molecules absorbed photon energy and decomposed, and transferred energy to polydimethylsiloxane. Moreover, this method hardly influenced the original properties of polymer films due to the removability of dopants.

Exponential optical absorption edge in PbS quantum dot-ligand systems on single crystal rutile-TiO2 revealed by photoacoustic and absorbance spectroscopies

The photovoltaic properties of quantum dot (QD) sensitized solar cells (QDSCs) depend significantly on the surface modification applied to the QDs and on the nanostructured interface between the QDs and the electrode surface. In the development of QDSCs with spatially ordered QD arrays, linking molecular ligands with the QDs (QD-ligands) can lead to the realization of novel QDSCs. The ligand shell around the QDs mediates the electron and energy transfer processes that underpin their use in QDSC applications. The dependence of the photovoltaic properties on the interparticle distance (QD spacing) can also be evaluated by applying different sizes of molecular ligands. The present study focuses on specific attention to the exponential optical absorption edge (often termed Urbach tail) in PbS QD-ligand systems with different QD spacing adsorbed on rutile-TiO2 (R-TiO2) substrates with different crystal orientations. It is essential to accurately characterize QD-ligands on electrode surfaces with different crystal orientations, not only for scientific studies, but to further optimize the growth conditions and processes in order to design and fabricate advanced QDSCs. Photoacoustic (PA) and conventional absorbance (Abs) spectroscopies were applied to determine the optical absorption and nonradiative relaxation properties. There is a discrepancy between the PA and Abs spectra especially in the Urbach tail region. As the Urbach tail states are related to the absorbed photon energy lost in the form of heat generated by nonradiative relaxation, therefore characterization of the Urbach tail is important and essential for QDSC applications. Characterization of the Urbach tail and the heat generated by nonradiative relaxation of PbS QD-ligand systems by combined PA and Abs spectroscopies showed that the characteristics depend strongly on the crystal orientation of the R-TiO2 substrate, the QD spacing, and the free energy change.

Photo-oxidative degradation of polyacids derived ceria nanoparticle modulation for chemical mechanical polishing

The effects of photo-oxidative degradation of polyacids at various concentrations and with different durations of ultraviolet (UV) irradiation on the photo-reduction of ceria nanoparticles were investigated. The effect of UV-treated ceria on the performance of chemical mechanical polishing (CMP) for the dielectric layer was also evaluated. When the polyacids were exposed to UV light, they underwent photo-oxidation with consumption of the dissolved oxygen in slurry. UV-treated ceria particles formed oxygen vacancies by absorbing photon energy, resulting in increased Ce3+ ions concentration on the surface, and when the oxygen level of the solution was lowered by the photo-oxidation of polymers, the formation of Ce3+ ions was promoted from 14.2 to 36.5%. Furthermore, chain scissions of polymers occurred during the oxidation process, and polyacids with lower molecular weights were found to be effective in ceria particle dispersion in terms of the decrease in the mean diameter and size distribution maintaining under 0.1 of polydispersity index. With increasing polyacid concentration and UV irradiation time, the Ce3+ concentration and the dispersity of ceria both increased due to the photo-oxidative degradation of the polymer; this enhanced the CMP performance in terms of 87% improved material removal rate and 48% lowered wafer surface roughness.

Highly Inoxidizable Heptamethine Cyanine–Glucose Oxidase Conjugate Nanoagent for Combination of Enhanced Photothermal Therapy and Tumor Starvation

AbstractHeptamethine cyanine dye (Cy7) has been widely applied in cell imaging and tumor phototherapy by virtue of its excellent photophysical properties and biocompatibility. However, in the presence of oxygen, large conjugated skeletons are easily destroyed by photooxidation reaction under light irradiation, which greatly limits its inoxidizability and photothermal therapy (PTT) effect. Accordingly, in this study, a new strategy (Cy‐GOx) is developed by the catalytic reaction of glucose oxidase (GOx) that consumes oxygen to highly improve the antioxidant capacity of Cy7, achieving the combination of enhanced PTT and starvation therapy. During this catalytic reaction, glucose as an important nutrient for cancer cell growth is consumed, achieving GOx‐mediated tumor starvation therapy. The fluorescence and intersystem crossing (ISC) of Cy‐GOx are greatly inhibited, which ensures that the absorbed photon energy is mainly released by means of nonradiative transition, significantly improving its photothermal effect. Of note, this strategy can effectively realize tumor inhibition by both intratumoral injection and intravenous injection. Thus, it is believed that this design concept will provide a new strategy for improving the antioxidant capacity and photothermal effect of Cy7 in combination therapy for enhanced antitumor efficacy.

Low-Energy Protons in Strong-Field Dissociation of H 2 + via Dipole-Transitions at Large Bond Lengths

More than ten years ago, the observation of the low-energy structure in the photoelectron energy spectrum, regarded as an “ionization surprise,” has overthrown our understanding of strong-field physics. However, the similar low-energy nuclear fragment generation from dissociating molecules upon the photon energy absorption, one of the well-observed phenomena in light-molecule interaction, still lacks an unambiguous mechanism and remains mysterious. Here, we introduce a time-energy-resolved manner using a multicycle near-infrared femtosecond laser pulse to identify the physical origin of the light-induced ultrafast dynamics of molecules. By simultaneously measuring the bond-stretching times and photon numbers involved in the dissociation of H 2 + driven by a polarization-skewed laser pulse, we reveal that the low-energy protons (below 0.7 eV) are produced via dipole-transitions at large bond lengths. The observed low-energy protons originate from strong-field dissociation of high vibrational states rather than the low ones of H 2 + cation, which is distinct from the well-accepted bond-softening picture. Further numerical simulation of the time-dependent Schrödinger equation unveils that the electronic states are periodically distorted by the strong laser field, and the energy gap between the field-dressed transient electronic states may favor the one- or three-photon transitions at the internuclear distance larger than 5 a.u. The time-dependent scenario and our time-energy-resolved approach presented here can be extended to other molecules to understand the complex ultrafast dynamics.

Neuromodulation of Chemical Synaptic Transmission Driven by THz Photons.

Postsynaptic currents of chemical synapse are modulated by multitudinous neurotransmitters, such as acetylcholine, dopamine, glutamate, and γ-aminobutyric acid, many of which have been used in the treatment of neurological diseases. Here, based on molecular dynamics simulations and quantum chemical calculation, we propose that 30- to 45-THz photons can resonate with a variety of typical neurotransmitter molecules and make them absorb photon energy to activate the transition to high energy state, which is expected to be a new method of neural regulation. Furthermore, we verified the calculated results through experiments that THz irradiation could substantively change neuronal signal emission and enhance the frequency, amplitude, and dynamic properties of excitatory postsynaptic current and inhibitory postsynaptic current. In addition, we demonstrated the potential of neural information regulation by THz photons through 2-photon imaging in vivo. These findings are expected to improve the understanding of the physical mechanism of biological phenomena and facilitate the application of terahertz technology in neural regulation and the development of new functional materials.

Combating Drug-Resistant Bacteria Using Photothermally Active Nanomaterials: A Perspective Review.

Injudicious use of antibiotics has been the main driver of severe bacterial non-susceptibility to commonly available antibiotics (known as drug resistance or antimicrobial resistance), a global threat to human health and healthcare. There is an increase in the incidence and levels of resistance to antibacterial drugs not only in nosocomial settings but also in community ones. The drying pipeline of new and effective antibiotics has further worsened the situation and is leading to a potentially “post-antibiotic era.” This requires novel and effective therapies and therapeutic agents for combating drug-resistant pathogenic microbes. Nanomaterials are emerging as potent antimicrobial agents with both bactericidal and potentiating effects reported against drug-resistant microbes. Among them, the photothermally active nanomaterials (PANs) are gaining attention for their broad-spectrum antibacterial potencies driven mainly by the photothermal effect, which is characterized by the conversion of absorbed photon energy into heat energy by the PANs. The current review capitalizes on the importance of using PANs as an effective approach for overcoming bacterial resistance to drugs. Various PANs leveraging broad-spectrum therapeutic antibacterial (both bactericidal and synergistic) potentials against drug-resistant pathogens have been discussed. The review also provides deeper mechanistic insights into the mechanisms of the action of PANs against a variety of drug-resistant pathogens with a critical evaluation of efflux pumps, cell membrane permeability, biofilm, and quorum sensing inhibition. We also discuss the use of PANs as drug carriers. This review also discusses possible cytotoxicities related to the therapeutic use of PANs and effective strategies to overcome this. Recent developments, success stories, challenges, and prospects are also presented.

Analysis of ternary AlGaX2(X = As, Sb) compounds for opto-electronic and renewable energy devices using density functional theory

Based on the First-principles calculations, we have investigated the opto-electronic properties of AlGaX2(X = As, Sb). We find that the AlGaX2(X = As, Sb) is energetically stable due to lower formation enthalpy. Additionally, the dynamical stability is also confirmed by phonon calculation and found no-imaginary frequencies in the phonon-spectra. Interestingly, both AlGaAs2 and AlGaSb2 compounds possesses semiconductor nature with a direct bandgap of 1.40 eV and 0.70 eV, respectively. For the technological applications of AlGaX2(X = As, Sb), we have analyzed optical properties in terms of absorption of photon energy and polarization. A strong absorption peaks are observed in the visible region. Moreover, the thermoelectric properties are calculated in terms of electrical/thermal conductivities, Seebeck coefficient, and figure of merit (ZT). Thermal parameters are critical for determining a material’ thermal stability across the wide range of temperatures. We expect that our calculated properties of AlGaAs2 and AlGaSb2 compounds could pave a new route for the applications in the optoelectronics and thermoelectric devices.

Insight into photoelectrocatalytic mechanisms of bifunctional cobaltite hollow-nanofibers towards oxygen evolution and oxygen reduction reactions for high-energy zinc-air batteries

• Synthesis of high-efficient hollow nanofibers of bifunctional photoelectrocatalyst. • Photoelectrocatalytic activity depends on band structures of catalysts. • Photogenerated electron and hole (NiCo 2 O 4 *) in the conduction band and valence band play very important role. • NiCo 2 O 4 exhibit the highest photoelectrocatalytic activity towards OER and ORR for high-performance Zinc-air batteries. • In situ XAS reveals that light can enhance both Ni and Co catalytic activities but Ni is found to be the main active species for OER. Using the photoelectrocatalyst to facilitate the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) for the charge storage enhancement of Zn-air batteries (ZABs) has not yet been widely investigated. This work presents bimetal cobaltite hollow nanofiber electrocatalysts as the photocathodes in the ZABs. Among all catalysts, the NiCo 2 O 4 hollow nanofiber exhibits superior performances towards OER and ORR. Under light irradiation (AM1.5), the NiCo 2 O 4 can absorb photon energy and generate free electrons and photogenerated carriers or holes, reducing the energy barrier enhancing the kinetic activity of OER/ORR. The NiCo 2 O 4 hollow nanofiber decreases the OER and ORR overpotentials for 14.3% and 8.1%, respectively and improves the OER and ORR kinetics for 19.3% and 20.8%, respectively compared with those under dark condition. The in situ electrochemical X-ray absorption spectroscopy results reveal that light can enhance both Ni and Co catalytic activities but Ni is found to be the main active species for the OER. The as-fabricated ZAB cell with the NiCo 2 O 4 photocathode exhibits the decreasing voltage gap from 0.85 V (Dark) to 0.64 V (Light) due to the highly active hole and the excited electron increasing the specific capacity up to 11.4% as compared to that under dark condition.

Negative Bias Instability of InZnO-Based Thin-Film Transistors Under Illumination Stress.

In this study, we investigated the threshold voltage (Vth) instability of solution-processed indium zinc oxide (IZO) thin film transistors (TFTs) prior to and after negative bias illumination stress (NBIS) with varying carrier suppressors (Ga, Al, Hf, and Zr). Variations in electrical properties of the IZO-based TFTs as a function of carrier suppressors were attributed to the differences in metal-oxygen bonding energy of the materials, which was numerically verified by calculating the relative oxygen deficient ratio from the X-ray photoelectron spectroscopy analysis. Furthermore, the values of Vth shift (ΔVth) of the devices subjected to negative gate bias stress under 635 nm (red), 530 nm (green), and 480 nm (blue) wavelength light irradiation increased as the incident photon energy increased. IZO TFTs doped with Ga atoms demonstrated weaker metal-oxygen bonding energy compared to the others and exhibited the largest ΔVth. This result was attributed to the suppressor-dependent distribution of neutral oxygen vacancies which determine the degrees of photon energy absorption in the IZO films. Then, the ΔVth instability of IZO-based TFTs under NBIS correlated well with a stretched exponential function.

Effect of Photobiomodulation Therapy on Oxidative Stress Markers in Healing Dynamics of Diabetic Neuropathic Wounds in Wistar Rats

BackgroundProlonged and overlapping phases of wound healing in diabetes are mainly due to the redox imbalance resulting in the chronicity of the wound. Photobiomodulation therapy works on the principle of absorption of photon energy and its transduction into a biological response in the living tissue. It alleviates the cellular responses, thereby improving the mechanism of wound healing in diabetes.ObjectiveTo find out the effect of photobiomodulation therapy of dosage 4 J/cm2 in the healing dynamics of diabetic neuropathic wounds in Wistar rats and its relation with oxidative stress markers.MethodologyDiabetes was induced using Streptozotocin of 60 mg/kg of body weight to eighteen female Wistar rats. Neuropathy was induced by the sciatic nerve crush injury followed by an excisional wound of 2 cm2 on the back of the animal. Experimental group animals were treated with dosage 4 J/cm2 of wavelength 655 and 808 nm, and control group animals were kept unirradiated. The biomechanical, histopathological, and biochemical changes were analysed in both groups.ResultsThere was a reduction in mean wound healing time and an increased rate of wound contraction in the experimental group animals compared to its control group. The experimental group showed improved redox status, and histopathological findings revealed better proliferative cells, keratinisation, and epithelialization than un-irradiated controls.ConclusionsPhotobiomodulation therapy of dosage 4 J/cm2 enhanced the overall wound healing dynamics of the diabetes-induced neuropathic wound and optimised the oxidative status of the wound, thereby facilitating a faster healing process.

Evaluation of the physical, structural, thermal, and advanced radiation absorption characteristics of SiO2–Na2O–K2O–P2O5–CaO bioactive glasses

We report herein an evaluation of the physical, structural, thermal, advanced photon energy absorption, and fast neutron removal characteristics of a series of bioactive glasses having the compositions 20SiO2-7.5Na2O-7.5K2O-(65–x)P2O5-xCaO, where x = 2.5, 5.0, 7.5, and 10.0 mol.%. X-ray diffraction (XRD) patterns confirmed the amorphous nature of these phosphosilicate glass systems fabricated by the melt-quench technique. To confirm the in vitro bioactivity of the prepared glasses, powdered samples of each composition were compressed into pellets and then soaked in simulated body fluid (SBF) at 37 ± 0.5 °C for 28 days. Soaked samples were investigated by means of XRD, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS/EDX). Thermo-gravimetric and differential thermal analysis (TG-DTA) was applied to determine the glass transition temperature (Tg) and crystallization temperature (Tc) for each glass sample. Fourier-transform infrared (FTIR) measurements were performed in the range 4000–400 cm−1, and showed the bending and stretching motions of different groups and the presence of CO2 and OH− groups in the glasses. Radiation absorption properties, such as mass energy absorption coefficient (μen/ρ), kinetic energy released per unit mass (KERMA) relative to air (ҠR), and mean free path values have been obtained for the bioactive glasses and compared with those of registered 45S5 Bioglass®. The simultaneous variation of mass energy absorption and mass attenuation values with photon energy has been explored to visualize the difference between absorption and attenuation. Linear attenuation coefficients for the present glass samples have been measured at photon energies of 511, 662, 1173, and 1332 keV in narrow-beam transmission geometry, and were in good agreement with theoretical results (error < 2 %). Further, detailed comparative analysis of energy absorption build-up factor (EABF) values for the glass samples has been conducted using two software tools, namely Photon Shielding and Dosimetry (PSD) and EXABCal, as well as on the basis of equivalent atomic number (Zeq) and effective atomic number (Zeff). We also attempted to calculate effective removal cross-sections (∑R) in order to evaluate the neutron absorption performances of these glass samples. The present detailed analysis shows that glass sample S4 with 10 mol.% CaO exhibits the most promising radiation absorption properties, resembling those of 45S5 Bioglass®.

Photo-characterization of Organic Dye-Sensitized Tin Oxide Films

Objectives: To develop organic dye sensitized film electrodes from highly porous tin oxide (SnO2) thin films prepared at room temperature using the SILAR technique. Methods/Analysis: SnO2 films were fabricated by the successive ionic layer adsorption and reaction (SILAR) technique at room temperature and its sensitization was done using the organic dye Rose Bengal (RB). The effect of sensitization on the as-grown and annealed film electrodes was investigated. Findings : Crystalline films with cauliflower-like morphology exhibit a large inherent adsorptive surface area and exhibit steady transmittance of 60-80% in the visible region. As-grown SnO2 films possess higher porosity and lower refractive index than that of the annealed films. SnO2 films have a resistivity in the range of 10-2-10-3 ΩcmΩcm. The dye adsorbed SnO2 film electrodes have much higher absorbance and cover a broad visible region compared to the bare SnO2 film electrodes. RB sensitization leads to an accelerated improvement in absorbed photon energy through the visible region of the spectrum extending from 2 to 3.75 eV. Novelty: Contrary to the sophisticated methods of preparation in the reported literature, highly porous crystalline SnO2 thin films were prepared at room temperature, using glacial acetic acid and hydrogen peroxide by a cost-effective simple wet chemical method. Work demonstrates that SnO2 films sensitized with RB act as an excellent dye-sensitized electrode, which can absorb almost half the visible spectrum (400-600 nm) of solar radiations. We believe that this is the unique report of surface modification of wet chemically prepared SnO2 electrodes by the photo-sensitizer RB. Keywords Photo­characterization, rose bengal, sensitization, thin films, tin oxide electrodes

Numerical investigation on photon energy absorption parameters for some Bi–Sn–Zn alloys in wide energy region

Numerical investigation on photon energy absorption parameters for some Bi–Sn–Zn alloys in wide energy region