Xe-Hg Lamp Research Articles

Hydrothermally synthesized α-MnS nanostructures for electrochemical water oxidation and photocatalytic hydrogen production

Manganese based nanostructures have been extensively used in different applications such as solar cell, photoelectrochemical and opto-electronics devices. Manganese sulfide nanostructure was prepared employing hydrothermal technique with different concentration of hydrazine hydrate (HZH). In observed XRD pattern, high intensity peak at (200) confirmed cubic structure formation of MnS nanostructures. MnS nanomaterials with high concentration of reducing agent such as hydrazine hydrate exhibited better morphology with maximum conductivity and investigated by using TEM images. MnS@4 ml HZH achieved large 191F/g specific capacitance at 10 mV/s in 1 M KOH. MnS@4 ml HZH sample obviously showed high 191F/g specific capacitance than other two samples. MnS@4 ml HZH exhibited high current density (295 mA/g) with the low overpotential of 184 mV. Strong reducing and complexing agent of hydrazine hydrate controlled nanoparticles size and structure is beneficial to improve its surface area and porous nature of synthesized material resulting to exhibit the excellent OER and HER activity. The obtained surface area, pore volume and pore diameter were found to be 13.95 m2/g, 0.027 cc/g and 3.948 nm respectively. The photocatalytic hydrogen production was also studied for MnS@4 ml HZH sample under light irradiation of 450-watt Xe-Hg lamp, which exhibited the average rate activity of 223.4 mmol.h−1.

Photocatalytic Reduction of Benzophenone on TiO2: Effect of Preparation Method and Reaction Conditions

The photocatalytic reduction of benzophenone was studied focusing on improving the yield to benzhydrol. TiO2 was synthesized by means of a hydrothermal technique. TiO2 (Degussa TiO2-P25) was used as a reference. Catalysts were characterized by XRD and nitrogen physisorption. The photocatalytic reduction was carried out in a batch reactor at 25 °C under nitrogen atmosphere, acetonitrile as solvent and isopropanol as electron donor. A 200 W Xe-Hg lamp (λ= 360 nm) was employed as irradiation source. The chemical composition of the reaction system was determined by HPLC. Structural and textural properties of the synthesized TiO2 depended on the type of acid used during sol formation step. Using HCl, a higher specific surface area and narrower pore size distribution of TiO2 was obtained in comparison with acetic acid. As expected, the photochemical reduction of benzophenone yielded benzopinacol as main product, whereas, benzhydrol is only produced in presence of TiO2 (i.e. photocatalytic route). In general, the hydrothermally synthesized catalysts were less active and with a lower yield to benzhydrol. The optimal reaction conditions to highest values of benzhydrol yield (70-80%) were found at 2 g/L (catalyst loading) and 0.5 mM of initial concentration of benzophenone, using commercial TiO2-P25.

Chiral capillary electrophoresis with UV-excited fluorescence detection for the enantioselective analysis of 9-fluorenylmethoxycarbonyl-derivatized amino acids

The potential of capillary electrophoresis (CE) with ultraviolet (UV)-excited fluorescence detection for sensitive chiral analysis of amino acids (AAs) was investigated. dl-AAs were derivatized with 9-fluorenylmethoxycarbonyl chloride (FMOC)-Cl to allow their fluorescence detection and enhance enantioseparation. Fluorescence detection was achieved employing optical fibers, leading UV excitation light (< 300 nm) from a Xe-Hg lamp to the capillary window, and fluorescence emission to a spectrograph equipped with a charge-coupled device (CCD). Signal averaging over time and emission wavelength intervals was carried out to improve the signal-to-noise ratio of the FMOC-AAs. A background electrolyte (BGE) of 40 mM sodium tetraborate (pH 9.5), containing 15% isopropanol (v/v), 30 mM sodium dodecyl sulfate (SDS), and 30 mM β-cyclodextrin (β-CD), was found optimal for AA chemo- and enantioseparation. Enantioresolutions of 1.0 or higher were achieved for 16 proteinogenic dl-AAs. Limits of detection (LODs) were in the 10–100-nM range (injected concentration) for the d-AA enantiomers, except for FMOC-d-tryptophan (536 nM) which showed intramolecular fluorescence quenching. Linearity (R2 > 0.997) and repeatability for peak height (relative standard deviations (RSDs) < 7.0%; n = 5) and electrophoretic mobility (RSDs < 0.6%; n = 5) of individual AA enantiomers were established for chiral analysis of dl-AA mixtures. The applicability of the method was investigated by the analysis of cerebrospinal fluid (CSF). Next to l-AAs, endogenous levels of d-glutamine and d-aspartic acid could be measured in CSF revealing enantiomeric ratios of 0.35 and 19.6%, respectively. This indicates the method’s potential for the analysis of low concentrations of d-AAs in presence of abundant l-AAs.

Wurtzite Zn1−y(MgxCd1−x)yO quaternary systems for photodiodes in visible spectral range

We investigated the optical bandgap engineering of ZnO based quaternary alloy films of wurtzite Zn1−y(MgxCd1−x)yO for photodiodes in visible spectral range. Quaternary alloy films were successfully synthesized by remote-plasma enhanced metalorganic chemical vapor deposition (RPE-MOCVD). The wurtzite alloy system has an optical bandgap energy between 2.16eV and 3.25eV, which was controlled by the flow ratio of metalorganic sources. The crystal structure and composition was analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). This revealed that carrier compensation effects by alloying with MgO in Zn1−xCdxO system decreases carrier concentration. Strong compensation effects were observed in the bandgap range of Zn1−y(MgxCd1−x)yO between 3.0eV to 3.25eV and the carrier concentration decreased to 1015–1018cm−3. Schottky diodes of PEDOT: PSS/Zn1−y(MgxCd1−y)yO with optical bandgaps in the visible spectral range were fabricated to confirm the viability of photovoltaic applications. The diodes performed photovoltaic characteristics under a Xe–Hg lamp illumination through Schottky junctions. The photoresponse spectra showed a photosensitivity with cutoff energy of 2.23eV and peak energy of 2.90eV at 0V biasing.

Perovskites as new radical photoinitiators for radical and cationic polymerizations

Four perovskites (LaTiO3, LaCrO3, La0.6Sr0.4MnO3 and MAPbI3) are proposed here as new photoinitiators (e.g., free radical generators) in combination with iodonium salt and optionally another additive (N-vinylcarbazole—NVK) to initiate both radical and cationic photopolymerization reactions. The proposed systems are efficient phenyl radical generators under polychromatic light sources such as a halogen lamp or a Xe–Hg lamp. The interest of this approach is the ability to work with very stable inorganic structures as photoinitiators. To the best of our knowledge, this is the first time that perovskites are incorporated in photoinitiating systems. Photochemical mechanisms will be proposed as sustained by electron spin resonance spin trapping (ESR-ST) experiments.

Iodonium‐polyoxometalate and thianthrenium‐polyoxometalate as new one‐component UV photoinitiators for radical and cationic polymerization

ABSTRACTFour novel onium salts (onium‐polyoxometalate) have been synthesized and characterized. They contain a diphenyliodonium or a thianthrenium (TH) moiety and a polyoxomolybdate or a polyoxotungstate as new counter anions. Outstandingly, these counter anions are photochemically active and can sensitize the decomposition of the iodonium or TH moiety through an intramolecular electron transfer. The phenyl radicals generated upon UV light irradiation (Xe–Hg lamp) are very efficient to initiate the radical polymerization of acrylates. Cations are also generated for the cationic polymerization of epoxides. Remarkably, these novel iodonium and TH salts are characterized by a higher reactivity compared with that of the diphenyliodonium hexafluorophosphate and the commercial TH salt, respectively. Interpenetrating polymer networks can also be obtained under air through a concomitant cationic/radical photopolymerization of an epoxy/acrylate blend (monomer conversions &gt; 65%). The photochemical mechanisms are studied by steady‐state photolysis, cyclic voltammetry, and electron spin resonance techniques. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 981–989

Photochemical preparation of silver nanoparticles supported on zeolite crystals.

A facile and rapid photochemical method for preparing supported silver nanoparticles (Ag-NPs) in a suspension of faujasite type (FAU) zeolite nanocrystals is described. Silver cations are introduced by ion exchange into the zeolite and subsequently irradiated with a Xe-Hg lamp (200 W) in the presence of a photoactive reducing agent (2-hydroxy-2-methylpropiophenone). UV-vis characterization indicates that irradiation time and intensity (I0) influence significantly the amount of silver cations reduced. The full reduction of silver cations takes place after 60 s of a polychromatic irradiation, and a plasmon band of Ag-NPs appears at 380 nm. Transmission electron microscopy combined with theoretical calculation of the plasmon absorbance band using Mie theory shows that the Ag-NPs, stabilized in the micropores and on the external surface of the FAU zeolite nanocrystals, have an almost spheroidal shape with diameters of 0.75 and 1.12 nm, respectively. Ag-NPs, with a homogeneous distribution of size and morphology, embedded in a suspension of FAU zeolites are very stable (∼8 months), even without stabilizers or capping agents.

Acridinediones: Effect of Substituents on Their Photoinitiating Abilities in Radical and Cationic Photopolymerization

Ten acridinediones (ADs) with different substituents are prepared and investigated for their abilities to initiate a ring‐opening cationic photopolymerization in combination with an iodonium salt and N‐vinylcarbazole upon UV–vis light (Xe–Hg lamp; &gt;330 nm) or visible light (halogen lamp) exposure. The structural effects in the ADs are outlined. The cationic and radical photopolymerization of an epoxide/acrylate blend in a one‐step hybrid cure very efficiently leads to the formation of an interpenetrated polymer network under UV–vis light or visible light irradiation (30 s for tack‐free coatings). The photochemical mechanisms are studied by molecular orbital calculations, steady‐state photolysis, electron spin resonance–spin trapping, cyclic voltammetry, fluorescence, and laser flash photolysis techniques. image

Difunctional acridinediones as photoinitiators of polymerization under UV and visible lights: Structural effects

Seven difunctional acridinediones DAD were prepared and investigated for their abilities to initiate a ring-opening cationic photopolymerization in combination with an iodonium salt (and optionally N-vinylcarbazole) upon UV/visible light (Xe–Hg lamp; >330 nm) or visible light (halogen lamp) exposure. The structural effects in the DADs and the role of the radical cation are outlined. The cationic and radical photopolymerization of an epoxide/acrylate blend in a one-step hybrid cure leads to the formation of an interpenetrated polymer network. The photochemical mechanisms are studied by fluorescence, steady state photolysis, cyclic voltammetry, electron spin resonance spin trapping, and laser flash photolysis techniques.

New functionalized aromatic ketones as photoinitiating systems for near visible and visible light induced polymerizations

Novel functionalized ketones (K_PY) incorporating one/two pyrene moieties or a pyridinium chromophore for radical and/or cationic polymerization under soft irradiation conditions (Xe–Hg lamp, halogen lamp) are proposed. These compounds exhibit red-shifted absorptions and enhanced molar extinction coefficients (e.g. for near visible lights (395 nm), the absorption can be increased by a factor of 20). The ability of the various K_PY/amine couple in the radical polymerization of an acrylate (up to 75% conversion) and the different K_PY/diphenyliodonium salt system in the cationic polymerization of an epoxide (up to 70% conversion) is often better than that of reference compounds. These structures are also very efficient to overcome the oxygen inhibition. Molecular orbital calculations, ESR experiments and laser flash photolysis allow an investigation of the absorption properties, the excited state processes and the involved initiation mechanisms.

New Cleavable Photoinitiator Architecture with Huge Molar Extinction Coefficients for Polymerization in the 340–450 nm Range.

A new Type I photoinitiator Tr_DMPA is described. It consists in three 2,2′-dimethoxy 2-phenyl acetophenone (DMPA) units grafted onto a truxene (Tr) scaffold. Compared to DMPA itself, the lowest electronic transition exhibits a ππ* character and the corresponding molar extinction coefficients ε are increased from about 400 M–1 cm–1 (at about 332 nm for DMPA) to 63 000 M–1 cm–1 (at 338 nm for Tr_DMPA); such huge values are exceptional in Type I photoinitiators at this wavelength. Tr_DMPA undergoes a fast cleavage and efficiently initiate an acrylate polymerization upon a Xe–Hg lamp, a halogen lamp or a laser diode exposure at 405 nm (upon very low light intensities: 2–12 mW/cm2) in the 300–450 nm range. The polymerization of epoxides or divinylethers is also feasible in the presence of an iodonium salt at 405 nm where reference photoinitiators cannot efficiently operate. The chemical mechanisms analyzed by ESR, fluorescence, steady state photolysis, and laser flash photolysis experiments are discussed.

New insights into radical and cationic polymerizations upon visible light exposure: role of novel photoinitiator systems based on the pyrene chromophore

New aromatic derivatives PyD based on a pyrene moiety are proposed here as new photoinitiators (PIs) in multi-component systems (with an iodonium salt, a sulfonium salt and optionally a silane) for the radical polymerization of acrylates and the cationic polymerization of epoxy, epoxy-silicone and vinyl ethers. These new photoinitiators allow the use of a long wavelength excitation (using visible light delivered by a halogen lamp, a laser diode at 457 nm or a Xe–Hg lamp). Excellent polymerization profiles are obtained. For polymerization processes using pyrene, very low conversions are reached in agreement with the lack of absorption of this compound for λ > 380 nm i.e.PyDs are attractive compounds for visible light. Acrylate–epoxide, acrylate–vinyl ether and vinyl ether–epoxide blends are also easily polymerized i.e. for the synthesis of interpenetrating or crosslinked polymer networks. The initiation step mechanisms analyzed by ESR, fluorescence, steady state photolysis and laser flash photolysis experiments are discussed.

Design of new Type I and Type II photoinitiators possessing highly coupled pyrene–ketone moieties

New Type I and Type II photoinitiators based on 2,2-dimethoxy-2-phenylacetophenone (DMPA), benzophenone (BP) and thioxanthone (TX) linked to a pyrene (Py) moiety (Py_DMPA, Py_BP, Py_TX) are proposed here for the free radical polymerization of acrylates and the cationic polymerization of epoxides and vinylethers under a Xe–Hg lamp, laser diode at 405 nm or a halogen lamp. Excellent polymerization profiles using Py_DMPA and Py_BP are obtained, i.e. better than those recorded with the reference compounds (DMPA and BP). Specifically, Py_DMPA and Py_BP absorb in the near UV-visible range (360–420 nm range; absorption red-shift ∼15 nm), exhibit huge e values (up to a 90 fold increase) and high photochemical reactivity. The mechanisms analyzed by electron spin resonance, steady state photolysis, fluorescence and laser flash photolysis experiments are discussed for the different initiating systems.

Trifunctional Photoinitiators Based on a Triazine Skeleton for Visible Light Source and UV LED Induced Polymerizations

Trifunctional photoinitiators (tPIs) based on benzophenone, anthracene, and pyrene chromophores linked to a triazine moiety are proposed as new initiating systems. In combination with an iodonium salt and a silane, these structures are able to initiate the radical polymerization RP of acrylates and the cationic polymerization CP of epoxides and vinylethers under Xe–Hg lamp, LED and very soft irradiation (i.e., halogen lamp). Upon addition of an amine, these new photoinitiators were also able to start the radical polymerization of acrylates. Excellent RP and CP polymerization profiles are obtained i.e. better than those recorded using the reference compounds (benzophenone, anthracence and pyrene). In CP, some of these compounds combined with thianthrenium salts can also be used. The mechanisms involved in the different multicomponent initiating systems were analyzed by ESR, fluorescence, steady state photolysis, and laser flash photolysis experiments.

CO2 Conversion into Methanol Using Granular Silicon Carbide (α6H-SiC): A Comparative Evaluation of 355 nm Laser and Xenon Mercury Broad Band Radiation Sources

Granular silicon carbide (α6H-SiC) was investigated as a photo-reduction catalyst for CO2 conversion into methanol using a 355 nm laser from the third harmonic of pulsed Nd:YAG laser and 500 W collimated xenon mercury (XeHg) broad band lamp. The reaction cell was filled with distilled water, α6H-SiC granules and pressurized with CO2 gas at 50 psi. Maximum molar concentration of methanol achieved was 1.25 and 0.375 mmol/l and the photonic efficiencies of CO2 conversion into methanol achieved were 1.95 and 1.16 % using the laser and the XeHg lamp respectively. The selectivity of methanol produced using the laser irradiation was 100 % as compared to about 50 % with the XeHg lamp irradiation. The band gap energy of silicon carbide was estimated to be 3.17 eV and XRD demonstrated that it is a highly crystalline material. This study demonstrated that commercially available granular silicon carbide is a promising photo-reduction catalyst for CO2 into methanol. Gas Chromatograms of reaction products collected at 30–120 min irradiation in the presence of 355 nm laser having 40 mJ/pulse energy. The inset shows the comparison of retention time of GC peaks with the methanol standard and it is at 2.46 min.

Application of a pyrolysis-GC/MS system incorporating with micro-UV irradiation to rapid evaluation of the weatherability of acrylic coating paints for house exterior walls

A pyrolysis-GC/MS system incorporating with micro-UV irradiator (Xe–Hg lamp) was applied to the evaluation of the weatherability of the acrylic coating paints for house exterior walls. The deterioration of the materials during UV irradiation under thermal, and oxidative atmosphere was evaluated within a relatively short period of time with evolved gas analysis-mass spectrometry (EGA-MS) using a sub-milligram polymer sample. The EGA-MS thermograms indicated that both micro-UV irradiator with Xe–Hg lamp and weather meter with metal halide lamp caused similar photo, thermal, and oxidative degradation to the coating paint samples. Strong correlations between the results obtained by the UV/Py-GC/MS and that obtained by conventional weathering test using metal halide lamp was observed. It was suggested that UV/Py-GC/MS method could be used for compensating the conventional method by reducing the test period.

Lamp‐based wavelength‐resolved fluorescence detection for protein capillary electrophoresis: Setup and detector performance

A lamp-based fluorescence detection (Flu) system for CE was extended with a wavelength-resolved (WR) detector to allow recording of full protein emission spectra. WRFlu was achieved using a fluorescence cell that employs optical fibres to lead excitation light from a Xe-Hg lamp to the capillary window and protein fluorescence emission to a spectrograph equipped with a CCD. A 280 nm band pass filter etc. together with a 300 nm short pass cut-off filter was used for excitation. A capillary cartridge was modified to hold the detection cell in a commercial CE instrument enabling WRFlu in routine CE. The performance of the WRFlu detection was evaluated and optimised using lysozyme as model protein. Based on reference spectral data, a signal-intensity adjustment was introduced to correct for transmission losses in the detector optics that occurred for lower protein emission wavelengths. CE-WRFlu of lysozyme was performed using BGEs of 50 mM sodium phosphate (pH 6.5 or 3.0) and a charged-polymer coated capillary. Using the 3-D data set, signal averaging over time and emission-wavelength intervals was carried out to improve the S/N of emission spectra and electropherograms. The detection limit for lysozyme was 21 nM, providing sufficient sensitivity to obtain spectral information on protein impurities.

Development of a new transfer standard for high UV irradiances

Source-based radiometry requires reliable transfer standards which are easy to handle. For low irradiances in the UV spectral range, 30 W deuterium lamps are commonly used. However, for the growing field of high UV irradiance applications, new high power standards are required. Here we report on a Xe-Hg lamp system which has been characterised and improved to match the high requirements of a working standard. For this purpose, several parameters of the system such as lamp stability, re-ignition reproducibility, irradiance uniformity and usability have been investigated. Components for the customised light guide-based output optics have been selected with the help of extensive characterisations. The resulting lamp system can be used for a high-grade instrument calibration at high UV irradiance levels.

Dye-sensitized solar cells based on TiO 2 nanotubes and a solid-state electrolyte

Anatase TiO 2 nanotubes were employed with success as photoanode in dye-sensitized solar cells (DSSC) using a plasticized polymer electrolyte based on a poly(ethylene oxide) derivative. The plasticized electrolyte, poly(ethylene oxide-co-epychlorohydrin) containing NaI–I 2 had their conductivity and thermal behavior characterized as a function of the salt content. The highest ionic conductivity (5.5 × 10 −4 S cm −1) was obtained with 12.5 wt% NaI and 50 wt% of the plasticizer poly(ethyleneglycol)dibenzoate. The TiO 2 nanotubes were prepared by a simple sol–gel route and were characterized by FEG-SEM, TEM, XRD and BET. For the same film thickness, the DSSC assembled with the titania nanotubes had much higher efficiency in comparison with the device using TiO 2 nanoparticles. Although the one-dimensional properties exhibited by these materials can improve the electronic transport, in this study we demonstrated that the increase in the DSSC performance may be much more closely related to the high surface area of the titania films. This more open structure allows much more dye to be chemically absorbed and also facilitates the penetration of the polymer electrolyte, improving the iodide diffusion inside the film. We also observed that it was necessary to introduce a film of nanoparticulated TiO 2 prior deposition of the nanotubes in order to improve electrical contact with the conducting glass. Devices with efficiency of 4.03% at 100 mW cm −2 (Xe(Hg) lamp) can be obtained using a combination of TiO 2 nanotubes and this plasticized polymer electrolyte.

Synthesis and Properties of Water-Soluble Core–Shell–Shell Silica–CdSe/CdS–Silica Nanoparticles

This paper describes the synthesis of highly water-soluble and fluorescent core-shell-shell silica-CdSe/CdS-silica nanoparticles (CSS silica-QDs-silica NPs). We used cadmium nitrate and 1,1-dimethyl-2-selenourea precursors to synthesize CdSe quantum dots (QDs) in aqueous solution under simultaneous illumination with a diode-pumped solid state green laser and a Xe-Hg lamp. After passivation of the CdSe QDs with CdS, the CdSe/CdS QDs were then conjugated covalently to (3-mercaptopropyl)trimethoxysilane (MPS); we call these nanoparticles "MPS-QDs". We mixed the MPS-QDs with tetraethoxysilane (TEOS), ethanol, and NH3. By controlling the concentrations of the reagents, the stirring speed, and the reaction time, we synthesized CSS silica-QDs-silica NPs having sizes ranging from 75 to 190 nm. The incubation time for preparing the MPS-QDs and their concentrations are important parameters in determining the morphologies of the CSS silica-QDs-silica NPs. When we mixed 50 nM MPS-QDs, 1.1 mM TEOS, and 78 mM NH3 and reacted them at a stirring speed of 750 rpm, we obtained 85-nm-diameter CSS silica-QDs-silica NPs having a QD shell thickness of about 20 nm. The CSS silica-QDs-silica NPs provide a strong photoluminescence intensity (quantum yield 88%) and exhibit enhanced stability both photochemically and in high-conductivity media (e.g., 1.0 M NaCl).