Halogen Lamp Illumination Research Articles

Hyperspectral microscopy imaging based on Fourier ptychographic microscopy

Hyperspectral resolution, high spatial resolution, and a wide field of view (FOV) are the targets of optical spectral microscopy imaging. However, hyperspectral microscopy imaging technology cannot provide a wide FOV and a high spatial resolution at the same time. Fourier ptychographic microscopy (FPM) is a novel microscopy imaging technique that uses LEDs at varying angles to capture a series of low-spatial-resolution images that are used to recover images that have both high spatial resolution and a wide FOV. Since FPM cannot obtain the spectral resolution of the sample, in this paper, an efficient strategy based on the FPM system is proposed for the reconstruction of hyperspectral images. First, the traditional FPM setup is optimized, with a new experimental setup based on halogen lamp illumination and a narrow band-pass filter to capture a series of low-spatial-resolution images at different wavelengths. Second, a new algorithm, combining hyperspectral resolution imaging using interpolation compensation and a phase retrieval algorithm, is proposed to reconstruct high-spatial-resolution, wide FOV, and hyperspectral resolution images. Finally, we verified the feasibility and effectiveness of our experimental setup and algorithm by both simulation and experiment. The results show that our method can not only reconstruct high-spatial-resolution and wide FOV images, but also has a spectral resolution of 5 nm.

Design and Performance of a Near-Infrared Spectroscopy Measurement System for In-Field Alfalfa Moisture Measurement

Near-infrared spectroscopy (NIRS) is widely used in fruit and vegetable quality evaluations, usually after harvesting. In particular, the moisture content is a key parameter for determining product quality; processing phase, e.g., drying process; and economical value. NIRS methods are well-established for laboratory practices where the specimens are properly prepared and measurement conditions are well controlled. On the other hand, it is known that in-field NIRS measurements present several difficulties, as many influencing variables, such as mechanical vibrations, electrical and optical disturbances, and dust or dirt in general, can affect the spectral measurement. In this paper, we propose the design and present the prototype of a NIRS-based measuring system for the rapid determination of the moisture content of bales. The new system uses of a halogen lamp illumination unit to recover water absorption spectral data in the range of 900–1700 nm. The compact stainless steel body makes the instrument portable and easy to transport for rapid in-field MC measurements. The prototype system was characterized and its performance extensively evaluated in a laboratory environment. Finally, a preliminary test was carried out, where the moisture contents of 12 freshly harvested crops samples were measured using the partial least squares (PLSs) regression method. The obtained results show that our prototype system can estimate the alfalfa moisture content information with a coefficient of determination R2 of 0.985 and a root mean square relative error of estimation of 7.1%.

Short-wavelength infrared reflectance spectroscopy of minerals by supercontinuum illumination and speckle reduction

The advent of broadband supercontinuum (SC) light sources offers an opportunity to improve techniques such as reflectance spectroscopy. In this study, a SC laser, providing a broad spectral bandwidth and higher-intensity light than traditional halogen lamps, is used to illuminate mineral samples in the short-wavelength infrared (SWIR; 1.10–2.35 μm) spectrum. To overcome speckle interference originating from the intrinsic coherence of the SC laser illumination, a rotation-based technique is applied to achieve high signal-to-noise interference-free reflectance spectra of the three minerals studied (muscovite, kaolinite and calcite) and these spectra are compared to reference spectra obtained from the United States Geological Survey spectral library. We report a speckle magnitude, σSpk< 2×10−3 (35 times better than without rotation) resulting in a measurement time <1.6 s with a repeatability of >99%. The benefits and limitations of using SC laser illumination over halogen lamp illumination are discussed with regards to the measurement time, speckle, laser operation safety and cost. The technique described could be used for time-efficient (<1.6 s) in-lab mineral assay of minerals having distinct SWIR absorption features or developed for real-time (within few milliseconds) on-conveyor mineral assay of crushed ores.

Donor/Acceptor Heterojunction Organic Solar Cells

The operation and the design of organic solar cells with donor/acceptor heterojunction structure and exciton blocking layer is outlined and results of their initial development and assessment are reported. Under halogen lamp illumination with 100 mW/cm2 incident optical power density, the devices exhibits an open circuit voltage VOC = 0.45 V, a short circuit current density JSC between 2 and 2.5 mA/cm2 with a fill factor FF ≈ 50%, an external quantum efficiency (electrons/s over incident photons/s) EQE ≈ 5% and a power conversion efficiency of about 0.5%. Measurements of the photoelectrical characteristics with time are also reported, confirming that non encapsulated organic solar cells have limited stability in ambient atmosphere.

Photoluminescence characterization of ZnS-AgInS2 (ZAIS) nanoparticles adsorbed on plasmonic chip studied with fluorescence microscopy

Quantum dots (QDs) are semiconductor nanoparticles showing many advantages for photoluminescence (PL) applications. Since common QDs contain toxic elements such as Cd, Pb, Se, and Te, ZnS-AgInS2 (ZAIS) has been developed as a quantum nanomaterial with low cytotoxicity. In this study, ZAIS@ZnS core-shell QDs coated with carboxyl groups (ZAIS@ZnS-MPA) were prepared as water-soluble nanoparticles. The PL characteristics of ZAIS@ZnS-MPA were studied on a plasmonic chip, which is a substrate with wavelength-scale periodic structures coated with thin metal films, and the PL enhancement of ZAIS by an electromagnetic field derived from grating-coupled surface plasmon resonance (GC-SPR) was also evaluated. The PL spectroscopic characteristics obtained on the grating patterns with a 480 nm-pitch were enhanced in a wider wavelength range. Furthermore, photobleaching, which occurs in conventional fluorescence molecules, was not observed under halogen lamp illumination. The PL and spectroscopic imaging under a microscope indicated the PL characteristics of the ZAIS@ZnS-MPA nanoparticles on the plasmonic chip under appropriate conditions.

Effect of Temperature and Growth Time on Vertically Aligned ZnO Nanorods by Simplified Hydrothermal Technique for Photoelectrochemical Cells.

Despite its large band gap, ZnO has wide applicability in many fields ranging from gas sensors to solar cells. ZnO was chosen over other materials because of its large exciton binding energy (60 meV) and its stability to high-energy radiation. In this study, ZnO nanorods were deposited on ITO glass via a simple dip coating followed by a hydrothermal growth. The morphological, structural and compositional characteristics of the prepared films were analyzed using X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), and ultraviolet-visible spectroscopy (UV-Vis). Photoelectrochemical conversion efficiencies were evaluated via photocurrent measurements under calibrated halogen lamp illumination. Thin film prepared at 120 °C for 4 h of hydrothermal treatment possessed a hexagonal wurtzite structure with the crystallite size of 19.2 nm. The average diameter of the ZnO nanorods was 37.7 nm and the thickness was found to be 2680.2 nm. According to FESEM images, as the hydrothermal growth temperature increases, the nanorod diameter become smaller. Moreover, the thickness of the nanorods increase with the growth time. Therefore, the sample prepared at 120 °C for 4 h displayed an impressive photoresponse by achieving high current density of 0.1944 mA/cm2.

Long-Term Stability of Aluminum Oxide Based Surface Passivation Schemes Under Illumination at Elevated Temperatures

The stability of passivation layers under the conditions of field application of solar modules is a crucial parameter. We have performed an experiment to test the stability of aluminum oxide based passivation schemes under halogen lamp illumination of 1 sun equivalent intensity at 75 °C. We compare aluminum oxide layers with atomic layer deposition and plasma-enhanced chemical vapor deposition with and without an amorphous silicon nitride capping layer. Different thermal treatments are performed to activate the passivation or simulate solar cell contact firing. All passivation schemes are tested on full four inch 1 Ω·cm p- and n-type float-zone silicon wafers. The quality and stability of the surface passivation are tested by means of repeated charge carrier lifetime measurements. No significant surface passivation degradation due to light-soaking is evident on capped samples for several hundred hours. N-type samples are demonstrated to maintain excellent passivation quality for at least 3700 h and only slight degradation of p-type samples is found.

Micro-rotary ratchets driven by migratory phytoplankton with phototactic stimulus

This study proposes micro-rotary ratchets driven by a migratory phytoplankton–Volvox, exhibiting a positive phototaxis. Two types of micro-discs, i.e., ratchet- and starfish-like ratchets are fabricated using conventional photolithography. The ratchet is floated in the center of a Petri dish filled with Volvox suspension under an optical microscope with halogen lamp illumination and is covered by a mask with a small hole so that the microorganisms are concentrated around the micro-ratchets by the phototaxis. Rotations of the ratchets with the same diameter of 0.567mm were observed through a biological microscope; a rotation speed of 0.86rpm for the micro-ratchet and 2.01rpm for the starfish ratchet were obtained for a Volvox density of 1000–3000/mL under an illumination intensity of 0.18W/cm2. As the driving mechanism of the ratchet is based on the microorganisms adhesion to the ratchets surface rather than collision impacts, a gelatin coating on the ratchet was used to enhance the adhered number of Volvox. Although the drag force was increased owing to the larger ratchet diameter, a rotation speed of 0.16rpm was observed. A particle tracking velocimetry measurement using polystyrene beads was performed to study the fluid flow around the micro-ratchet. A vortex generation by the micro-ratchets was confirmed; this effect may work as a micro-mechanical power booster for microorganisms. This drive system may open the possibility of a solar-power-driven and sustainable micro-mechanism using phytoplankton.

Studies on optical and electrical properties of SILAR-deposited CuO thin films

CuO thin films prepared by SILAR technique using aqueous solutions of various pH values and their characterization are presented in this report. The pH dependence on structural, morphological, optical and electrical properties of the prepared films is studied. Thickness of films is found to vary in between 0.52 and 0.82 µm. Microstructural parameters such as crystallite size, strain and dislocation density of the film have been evaluated. The crystallographic behaviour of the film has shown that all the coated thin films are in monoclinic structure with (002) preferred orientation. The size of the crystallites is found to increase with the pH values. Surface morphological behaviour of the films prepared using different pH values are analysed. Optical properties of the films were analysed from absorption and transmittance studies of CuO thin films. Band gap energy values of CuO thin films have been found to decrease from 2.12 to 1.91 eV with increasing pH values of the solution. The thin film formed at a solution pH 11 has shown least resistivity and high carrier concentration. The I-V characteristics of n-Si/p-CuO heterojunction under 200-watts halogen lamp illumination show open-circuit voltage of ~ 0.37 V and short-circuit current of ~1.02 × 10−6 A.

High-efficient n-type TiO2/p-type Cu2O nanodiode photocatalyst to detoxify hexavalent chromium under visible light irradiation

n-Type TiO2/p-type Cu2O nanodiode photocatalyst with different Cu2O contents had been successfully synthesized. The nanocomposite also had been well characterized and tested for its photocatalytic activity toward reduction of 10 ppm K2Cr2O7 aqueous solution under visible light illumination. It was found that 30 % Cu2O loading in the nanocomposite had the best photocatalytic activity in detoxifying Cr(VI) without any hole scavenger agents and the solution pH adjustment. As a result, water was simultaneously oxidized by photogenerated holes to evolve oxygen. The 20 mg as-prepared TiO2/Cu2O nanocomposites could reduce almost 100 % of 10 ppm K2Cr2O7 aqueous solution in 90 min under 150 W halogen lamp illumination. From the results, it was concluded that the photocatalytic activities of p–n heterojunction of TiO2/Cu2O nanodiodes had proven to be an efficient photocatalyst under visible light illumination. The photocatalytic performances of TiO2/Cu2O nanocomposites and its photoreaction mechanism were proposed and discussed in this work.

Towards hydrogen detection at room temperature with printed ZnO nanoceramics films activated with halogen light

Though semiconducting properties of ZnO have been extensively investigated under hazardous gases, research is still necessary for low-cost sensors working at room temperature. Study of printed ZnO nanopowders based-sensor has been undertaken for hydrogen detection. A ZnO paste made with commercial nanopowders is deposited on interdigitated Pt electrodes and sintered at 400°C. ZnO layer structure and morphology are first examined by XRD, SEM and emission/excitation spectra prior to the study of the effect of UV-light on the electrical conduction of the semiconductor oxide. Then, the response to hydrogen shows that low UV-light provided by a halogen light enhances gas sensitivity and allows detection at room temperature with sensitivity equivalent to those obtained in dark condition at 150°C. A sensitivity S≈44% is obtained for 300 ppm hydrogen at room temperature under halogen lamp illumination whereas a sensitivity S≈38% is measured at 150°C in the dark. Moreover, it is demonstrated that very low UV-light power (15 μW/mm2) provided by the halogen lamp is sufficient to give sensitivities as high as those obtained with UV LED (7.7 mW/mm2). These results are comparable to those obtained for 1 or 2D ZnO nanostructures working at room temperature or at temperature until 250 °C.

Reflection Microspectroscopic Study of Laser Trapping Assembling of Polystyrene Nanoparticles at Air/Solution Interface

We present the formation of a single nanoparticle assembly with periodic array structure induced by laser trapping of 200 nm polystyrene nanoparticles at air/solution interface of the colloidal heavy water solution. Their trapping and assembling behavior is observed by monitoring transmission and backscattering images and measuring reflection spectra under a microscope. Upon the laser irradiation into the solution surface layer, nanoparticles are gathered at and around the focal spot, and eventually a nanoparticle assembly with the size much larger than the focal volume is formed. The assembly gives structural color in visible range under halogen lamp illumination, indicating that constituent nanoparticles are periodically arrayed. Reflection spectra of the assembly show a reflection band, and its peak position is gradually shifted to short wavelength and the bandwidth becomes narrow with time, depending on the distance from the focal spot. After the laser is switched off, red-shift is observed in the ref...

Development of Thin Film Amorphous Silicon Tandem Junction Based Photocathodes Providing High Open-Circuit Voltages for Hydrogen Production

Hydrogenated amorphous silicon thin film tandem solar cells (a-Si:H/a-Si:H) have been developed with focus on high open-circuit voltages for the direct application as photocathodes in photoelectrochemical water splitting devices. By temperature variation during deposition of the intrinsic a-Si:H absorber layers the band gap energy of a-Si:H absorber layers, correlating with the hydrogen content of the material, can be adjusted and combined in a way that a-Si:H/a-Si:H tandem solar cells provide open-circuit voltages up to 1.87 V. The applicability of the tandem solar cells as photocathodes was investigated in a photoelectrochemical cell (PEC) measurement set-up. With platinum as a catalyst, the a-Si:H/a-Si:H based photocathodes exhibit a high photocurrent onset potential of 1.76 V versus the reversible hydrogen electrode (RHE) and a photocurrent of 5.3 mA/cm2at 0 V versus RHE (under halogen lamp illumination). Our results provide evidence that a direct application of thin film silicon based photocathodes fulfills the main thermodynamic requirements to generate hydrogen. Furthermore, the presented approach may provide an efficient and low-cost route to solar hydrogen production.

Photocatalytic degradation of some endocrine disrupting compounds by modified TiO2 under UV or halogen lamp illumination

For the first time, data on the effect of TiO2 modification by N-doping or by carbon nanotubes on the photocatalytic destruction of endocrine disrupting compounds 17α-ethynylestradiol (EE2) and 17β-estradiol (E2) in aqueous solutions are reported. A possibility to accomplish photocatalytic process under halogen lamp irradiation is shown. The catalyst is prepared by a sol–gel method. During the synthesis process, it is modified by N-doping (1.8 % nitrogen) or by carbon nanotube addition (5 % of the TiO2 mass). X-ray diffractometry, SEM, TEM, N2 adsorption–desorption, X-ray photoelectron and UV–Vis diffuse reflectance spectroscopy are applied for characterization. The crystal structure, phase composition, crystallites size, specific surface area, pores average diameter, pore area and volume distribution, morphology, UV–Vis and X-ray photoelectron spectra of the materials are reported and discussed. An HPLC technique is used for estrogen analysis. The sorption ability and photocatalytic activity (measured by degradation rate constant and percentage of the pollutant conversion) of the catalysts under UV (150 W, emission maximum at 365 nm) or 150 W halogen lamp illumination are determined. Full destruction of E2 and >99.7 % of EE2 is reached after 2 h irradiation with halogen lamp.

Paper modified with ZnO nanorods – antimicrobial studies

Paper with antimicrobial properties was developed through in situ growth of ZnO nanorods. The targeted application for this type of paper is in health centers as wallpaper, writing paper, facemasks, tissue paper, etc. The paper was tested on three model microbes, Gram-positive bacteria Staphylococcus aureus, Gram-negative bacteria Escherichia coli and common airborne fungus Aspergillus niger. No viable bacterial colonies or fungal spores could be detected in the areas surrounding test samples of the antimicrobial paper. Gram-negative bacteria Escherichia coli were found to be inhibited in an area that is 239% and 163% the area of the paper sample under different room lighting conditions, i.e., halogen and fluorescent lamp illumination, respectively. For Gram-positive bacteria Staphylococcus aureus the zones of inhibition surrounding the paper samples are 102% and 70%, and for Aspergillus niger, 224% and 183% of the sample area, under similar lighting conditions.

Direct Optical Observation of Band-Edge Excitons, Band Gap, and Fermi Level in Degenerate Semiconducting Oxide Nanowires In2O3

Direct optical evidence of Burstein–Moss shift (BMS) in conduction band of cubic c-In2O3 nanowires is reported herein. The optical property of degenerate semiconducting oxide c-In2O3 has been investigated by thermoreflectance (TR) spectroscopy. Low-temperature TR spectra clearly show a series of band-edge excitons for c-In2O3. The threshold energy for the exciton series was determined. One transition feature of direct gap caused by BMS was detected in all TR spectra from 20 to 300 K. The Femi-level (EF) energy above conduction-band edge (EC) is determined to be EF – EC ≈ 92 meV. The energy value causes a calculated electron density of ∼2.1 × 1019 cm–3. The direct gap of c-In2O3 with BMS is 3.43 eV at 300 K. Free exciton, bound exciton complexes, donor–acceptor pair transition, and defect emissions have been evaluated by photoluminescence (PL) measurements from 10 to 300 K. Photoresistivity change (i.e., 5.71 × 10–2 → 4.85 × 10–2 Ω-cm) under the illumination of halogen lamp (5 mW·cm–2) for c-In2O3 thin-film nanorods was detected. The experimental results show In2O3 nanocrystals an appropriate candidate applied not only for light-emitting devices but also for photoelectric-conversion cells.

Crystalline Silicon Solar Cells with Two Different Metals

We propose crystalline silicon solar cells with Al and Au metals. P-type substrates were coated with 100-nm-thick thermally grown SiO2 layers. The top SiO2 layer was thinned to about 1.5 nm. Stripes of Al and Au were formed with a gap of 0.29 mm on the top surface in order to cause an internal built-in potential in silicon because of the difference between their work functions. Solar cell characteristics were observed by halogen lamp illumination at 21.7 mW/cm2. The short-circuit current density, open-circuit voltage, and fill factor were 5.8 mA/cm2, 0.49 V, and 0.57. The conversion efficiency was 7.5%. Photo-induced holes and electrons flowed into Au and Al electrodes, respectively, by the tunneling effect.

18.1: Invited Paper: Oxide TFT Driving Transparent AMOLED

AbstractWe have fabricated 3.2″ QVGA transparent AMOLED by integrating photostable top gate IGZO TFT array and highly transparent OLED. The photostability of oxide TFT was investigated under constant gate bias and constant current CC stress to explore the possibility of OLED application. After 40 hours CC stress of 10 μA with halogen lamp illumination, the ΔVth was just − 0.22 V while that obtained under dark was + 0.1 V. with newly designed OLED cathode and transparent getter we increase OLED transmittance up to 80% with keeping resistance of cathode at 6 Ω;/□. Outdoor stability of OLED and oxide TFT make transparent AMOLED viable in the real market.

Effect of illumination on the space charge limited current in organic bulk heterojunction diodes

Current–voltage (J–V) characteristics of organic bulk heterojunction diodes based on an interpenetrating network of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl esters (PCBM) have been studied in the dark and under halogen lamp illumination. The diodes contained 1:1 and 1:0.6 weight ratios of P3HT and PCBM. For both diodes the currents measured in dark (J d , commonly known as the dark current) in forward bias are found to agree with the space charge limited current (SCLC). The illuminated current consists of a current due to applied voltage (J da ) and the light generated current (J L ). J da extracted from the illuminated current agrees well with Shockley’s diffusion and recombination current. This observation shows that illumination changes the SCLC into Shockley’s diffusion and recombination current. The forward current under illumination has been observed to be greater than the dark current, which is contrary to the photo–voltaic (PV) theory. This result is well explained by the change of SCLC into Shockley’s diffusion and recombination current.

Radiation damage of variscite in historic crafts: Solarization, decolouration, structural changes and spectra from ionoluminescence

X-ray diffraction measurements, during halogen lamp illumination to simulate sunlight, (TXRD) show a phase transition from variscite (AlPO 4·H 2O) Messbach to variscite Lucin and a loss of the dark green colour. The differential-thermal and thermo-gravimetric (DTA-TG) analyses and thermoluminescence (TL) peaks all depict this first-order phase transition which takes place under sunlight. From the water vaporization temperature up to circa 650 °C, a second-order phase transition progressively occurs from variscite to berlinite (AlPO 4) by loss of a second unit of water with hydrogen bonded to the lattice. The ion beam luminescence (IBL) spectra of the Zamora variscite display a spectral band from 500 to 570 nm attributed to [UO 2] 2+ in phosphates, and another spectral band from 670 to 740 nm is linked with Cr(VI) 3+ defects situated in octahedral Al(VI) 3+ positions. In the hydrous variscite lattice, the Al–O and P–O chemical bonds are mainly covalent; with the degree of covalency of the P–O chemical bond significantly larger than of Al–O. This open structure of variscite, which has a crystal field of reduced strength, involves small shifts of the absorption bands which intensify the blue–green transmission producing the characteristic emerald colour of the dark green variscite of Zamora. These data provide a valuable basis for detection of solarization damage in historic crafts with inlaid variscite in the Museo del Prado (Madrid, Spain).