Ultraviolet-visible-near Infrared Research Articles

Surface Functionalization with Copper Tetraaminophthalocyanine Enables Efficient Charge Transport in Indium Tin Oxide Nanocrystal Thin Films.

Macroscopic superlattices of tin-doped indium oxide (ITO) nanocrystals (NCs) are prepared by self-assembly at the air/liquid interface followed by simultaneous ligand exchange with the organic semiconductor copper 4,4',4″,4‴-tetraaminophthalocyanine (Cu4APc). By using X-ray photoelectron spectroscopy (XPS), grazing-incidence small-angle X-ray scattering (GISAXS), and ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy, we demonstrate that the semiconductor molecules largely replace the native surfactant from the ITO NC surface and act as cross-linkers between neighboring particles. Transport measurements reveal an increase in electrical conductance by 9 orders of magnitude, suggesting that Cu4APc provides efficient electronic coupling for neighboring ITO NCs. This material provides the opportunity to study charge and spin transport through phthalocyanine monolayers.

A novel cool material: ASA (acrylonitrile-styrene-acrylate) matrix composites with solar reflective inorganic particles

Nowadays, the undesirable heat generated from solar energy troubles people a lot in various aspects, including the energy consumption for cooling purposes, the potential safety hazards of the outdoor devices used in high-temperature environment and so on. Therefore, many cool materials emerge as the times require, which can mitigate these serious situation. In this study, a concept of solar reflective ASA (acrylonitrile-styrene-acrylate terpolymer) for cool material was proposed. To achieve this purpose, several inorganic particles with high solar reflectance were chosen to mix with ASA via melt blending to improve the cooling property of ASA. Ultraviolet-visible-near infrared (UV-Vis-NIR) spectral and temperature test were carried out to evaluate the cooling properties of ASA and its hybrid composites. The results of the solar spectral test showed that the addition of only 1% volume fraction of inorganic particles could effectively improve the solar reflectance of ASA. And ASA/barium titanate (BaTiO3) hybrid composite possessed the highest reflectance value of 67.66%, nearly 2 times that of neat ASA. The results of the indoor temperature test were in highly consistent with those of the solar reflectance, which showed that all the hybrid composites presented better cooling effect compared with neat ASA. Also, ASA/BaTiO3 hybrid composite exhibited the best cooling effect, nearly 10 °C lower than neat ASA. Besides, the outdoor temperature test showed the same trend with the indoor temperature test. Furthermore, the results of the mechanic test indicated that the improvement of the cooling properties was based on no sacrifice of the mechanical properties.

Optical and electrical properties of Cu2ZnSnS4 thin films grown using spray pyrolysis technique and annealing in air

ABSTRACTCu2ZnSnS4 (CZTS) thin films were manufactured using spray pyrolysis technique and annealed in air. The characteristics of these films manufactured at annealing temperatures of 350–550°C in increments of 50°C for annealing durations of 1, 2, and 3 min were studied using X-ray diffraction, field-emission scanning electron microscopy (FE-SEM), ultraviolet-visible near-infrared (UV-Vis-NIR) spectrometer, and Hall effect measurements. Experimental results showed that the best CZTS film is a film annealed at 500°C for 1 min, which had moderate properties for manufacturing a solar cell device; its band gap energy, volume carrier concentration, mobility, and resistivity were 1.46 eV, 1.22 × 1019 cm− 3, 1.963 cm−2/Vs, and 0.283 Ωcm, respectively.

A high performance and low-cost hole transporting layer for efficient and stable perovskite solar cells.

Here we report a small molecule oxidant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4TCNQ) doped, low cost 2',7'-bis(bis(4-methoxyphenyl)amino)spiro[cyclopenta[2,1-b:3,4-b']dithiophene-4,9'-fluorene] (FDT) hole transporting layer (HTL) for efficient mixed organic cation based MA0.6FA0.4PbI3 (MA = methyl ammonium, FA = formamidinium) perovskite solar cells (PSCs), fabricated via a highly reproducible controlled nucleation assisted restricted volume solvent annealing method, having full temperature compatibility with flexible substrates. The optimized (1 wt%) F4TCNQ doped FDT HTL based devices (F-FDT devices) demonstrate simultaneous enhancement of photovoltaic performance and device stability as well as significant reduction in photo-current hysteresis, as compared to conventional bis(trifluoromethylsulfonyl)amine lithium (Li-TFSI) additive based FDT HTL devices (L-FDT devices). Adding to the merits, F-FDT PSCs exhibit about 75% higher device stability compared to conventional L-FDT devices during the course of three weeks. Mott-Schottky analysis and in-depth charge transport characterization were carried out using electrochemical impedance spectroscopy (EIS) of the fabricated devices to understand the superior performance of the F-FDT devices. In addition, detailed polaronic intensity characterization of the doped HTL films was performed via ultraviolet-visible near-infrared (UV-vis-NIR) spectroscopy to investigate the underlying mechanism. Mitigated photocurrent hysteresis in the F-FDT devices has also been examined in terms of the inherent electrode polarization phenomenon. Furthermore, the superior device stability of the F-FDT PSCs has been probed in terms of variation in electronic properties, surface wettability, crystallinity, and microstrain dislocation density, and a detailed picture of the underlying mechanism behind stability enhancement is presented.

An electronic portable device design to spectroscopically assess fruit quality

As a rapid and nondestructive sensing technique, reflection spectroscopy is useful in monitoring and managing horticultural production; in other words, the ripening of fruits and vegetables can be evaluated using reflection spectroscopy. Based on laboratory data obtained from an ultraviolet/visible/near-infrared (UV/Vis/NIR) spectrophotometer with a diffuse reflectance accessory, we developed a prototype handheld device. The device operates at a range of 400 nm to 1100 nm (blue, green, red, and NIR). LEDs, photodiodes, a microcontroller, digital-to-analog converters, a graphical LCD display, and a keypad were used for instrumentation. With our user-friendly software interface, measurements can be performed and controlled in real time, and measured data can be transferred to a computer using Bluetooth technology. This method of processing and evaluating data is easily managed.

Synthesis and characterization of lithium niobium borate glasses containing neodymium

AbstractA series of (90–x)Li2B4O7-10Nb2O5-xNd2O3 glass samples (x=0, 5 mol.%, 10 mol.%, 15 mol.%, 20 mol.% and 25 mol.%) were synthesized using melt quenching technique. X-ray diffraction (XRD), differential thermal analyzer (DTA), Fourier transformed infrared (FTIR), ultraviolet-visible-near-infrared (UV-Vis-NIR) spectrometer and photoluminescence (PL) spectroscopic characterizations were made to examine the influence of Nd3+ concentration on the physical, structural and optical properties. Various physical properties such as glasses density, molar volume, thermal stability, ion concentration, polar on radius, inter-nuclear distance, field strength, cut-off wavelength, energy band gap and Urbach energy were calculated. The samples were amorphous in nature and confirmed from XRD pattern. The FTIR spectra revealed the presence of BO3 and BO4 functional groups. UV-Vis-NIR spectra exhibited nine prominent bands centered at 353, 430, 475, 524, 583, 681, 745, 803, 875 nm corresponding to the transitions from the ground state to 4D3/2, 2P1/2, 2G9/2, 4G7/2, 4G5/2, 4F9/2, 4F7/2, 4F5/2, 4F3/2 excited states, respectively. Moreover, the emission spectra at 355 nm excitation displayed three peaks centered at 903 nm (4F3/2→4I9/2), 1059 nm (4F3/2→4I11/2) and 1333 nm (4F3/2→4I13/2), respectively. Fluorescence lifetime was recorded between 53.69 to 28.43 µs. It was found that varying concentration of Nd3+ ions strongly affected the physical, structural and optical properties of the glass samples.

Extraordinary Optical Transmission Performances of Nanosandwiched Grating for Wideband Multi-Function Integration

In this paper, we present a peculiar metal-dielectric-metal (MDM) nanosandwich grating structure that can achieve extraordinary optical transmission performances at normal incidence in the ultraviolet-visible-near infrared (UV-VIS-NIR) regions. The proposed structure shows three obvious spectrum characteristics: it can obtain high transmittance up to 80 % in NUV region and efficiently blocking visible wavelengths for transverse-magnetic (TM) polarized incidence; a broadband NIR polarizer can be inspired in the wavelength range from 950 to 1400 nm; more surprisingly, these performances do not deteriorated until 30° tilting angle. Compared to other grating structures with single metal overlayer, it shows wider band-stop characteristics and higher broadband transmission transmittance and extinction ratio (ER) in the investigated wavebands. We analyze the underlying physical mechanism by using numerical simulation, which is primarily attributed to metal ultraviolet transparency, surface plasmon polariton (SPP) at metal/dielectric interface, Fabry–Perot (FP)-like cavity mode within this dielectric grating, and optical magnetic resonance especially in the dielectric interlayer of the MDM sandwiched structure. This structure is very important for developing high-performance subwavelength multifunctional integrated optical devices.

Rapid and Sensitive Detection of Malachite Green and Melamine with Silver Film over Nanospheres by Surface-Enhanced Raman Scattering

Silver film over nanospheres (AgFON) have been prepared by depositing Ag thin film onto the self-assembled monolayer arrays of polystyrene nanospheres with vacuum magnetron sputtering method. The surface morphologies and optical properties have been characterized by using scanning electron microscope (SEM) and ultraviolet-visible near-infrared (UV-Vis-NIR) spectrophotometer. AgFON was used as substrate to detect the surface-enhanced Raman scattering (SERS) spectra of malachite green (MG) and melamine (MA). It was found that the AgFON substrate presented outstanding performance that the Raman enhancement factor was calculated to be as large as 9.76 × 1012. The minimum limit for MG was down to 10−8 mol/L with a good linear response range from 10−4 to 10−8 mol/L. In addition, this substrate showed excellent ability to recognize MA molecules with a detection limit of 0.1 mg/L. A good linearity (r = 0.9887) was obtained in the concentration range of 2–100 mg/L. Furthermore, the AgFON substrate exhibited good uniformity with a relative standard deviation (RSD) of 9.01 % and good reproducibility with RSD of 8.60 %.

Chip-Based Cytometry Illuminated by a Blade-Shape Continuous Light for Multispectral Detection

A high performance diascopic illumination configuration is presented for the simultaneous detection of cells and particles with different sizes and different fluorescence labels in a microchannel. In the proposed approach, the cells/particles are illuminated by an objective-type dark-field condenser equipped with a low-cost tungsten light source and are then characterized by extracting the side-scatter, absorbance, and fluorescence signals from the spectra obtained by a ultraviolet-visible-near infrared (UV-Vis-NIR) spectrometer. A modified computation model is adopted to improve the capability for discriminating more fluorescence dyes simultaneously. The feasibility of the proposed detection configuration is demonstrated by counting and classifying a mixed sample of green, red, and crimson fluorescent-labeled particles and non-labeled particles with various dimensions. The suitability of the proposed system for real-world cytometry applications is then evaluated by classifying a mixed bio-sample comprising of gastric epithelial (AGS) cells stained with Trypan-blue and Erythrosin-bluish dye, respectively. The results show that the cytometer enables the efficient detection, identification, and classification of mixed bio-samples without the need for spatial filters or delicate optical components. Consequently, the proposed system has significant potential for high-performance micro-flow cytometry applications.

A Flexible Gastric Gas Sensor Based on Functionalized Optical Fiber

We present a gastric gas sensor based on conjoined dual optical fibers functionalized with sensitive optical dyes for sensing gases in both fluidic and gaseous environments. The sensor aims to sense various concentrations of carbon dioxide (CO2) and ammonia (NH3), which are two significant biomarkers of H. pylori infection in the stomach. It is known that CO2 and NH3 are released during the hydrolysis of urea by H. pylori, a bacterium that may cause stomach cancer with relatively high probability. CO2 and NH3 sensitive optical dyes, cresol red ion pair and zinc tetraphenylporphyrin, are embedded in silica beads and then functionalized onto the thin PDMS-coated fiber tip. Each type of dye provides a unique spectral emission response when excited with light ranging from 450 to 700 nm. Two SMA connector legs of the as-functionalized sensor are connected to an external light source for illumination and a ultraviolet-visible-near infrared (UV-Vis-NIR) spectrometer for signal collection/readout. To perform the measurements, one fiber illuminates while the other fiber collects the back-scattered light and feeds it to the UV-Vis-NIR spectrometer to measure the change in light spectrum as a function of CO2 or NH3 concentration. This method is easy and flexible and achieves ppm level sensitivity to targeted gas analytes. The proposed sensor can be integrated into a customized tethered capsule for adjunctive diagnosis of H. pylori infection to improve the accuracy of visual endoscopic inspection.

Investigation of thermal performance of semi-transparent PV technologies

In order to reduce the building heat gains through windows, among different glazing cooling technologies being under intensive research and development are the addition of semi-transparent photovoltaics (STPV). However, the implementation of a particular technology requires its extensive environmental and thermal characterization in buildings. In this work, small samples of c-Si and a-Si PV glazings were initially characterized by ultraviolet–visible–near infrared (UV/VIS/NIR) spectrophotometry and solar simulator irradiation in a benchtop wind tunnel of controllable environmental conditions. The obtained data were used to perform extensive simulations based on a reference building using a package of specific software tools to take proper account of the STPV peculiarities. From validated model, both glazings were found by the simulation to reduce cooling loads compared to the reference glass and providing energy efficiency dependable on the PV covering ratio. However the reduction of indoors daylighting points out to the need of further characterization and optimization of their environmental performance.

Fabrication of Pt/Ti/TiO₂ Photoelectrodes by RF-Magnetron Sputtering for Separate Hydrogen and Oxygen Production.

Evolution of pure hydrogen and oxygen by photocatalytic water splitting was attained from the opposite sides of a composite Pt/Ti/TiO2 photoelectrode. The TiO2 films were prepared by radio frequency (RF)-Magnetron Sputtering at different deposition time ranging from 1 up to 8 h and then characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible-near infrared (UV-vis-NIR) diffuse reflectance spectroscopy. The photocatalytic activity was evaluated by incident photon to current efficiency (IPCE) measurements and by photocatalytic water splitting measurements in a two-compartment cell. The highest H2 production rate was attained with the photoelectrode prepared by 6 h-long TiO2 deposition thanks to its high content in the rutile polymorph, which is active under visible light. By contrast, the photoactivity dropped for longer deposition time, because of the increased probability of electron-hole recombination due to the longer electron transfer path.

Damp Heat Aging Behavior of a Polyamide-Based Backsheet for Photovoltaic Modules

This paper describes and evaluates accelerated aging of a titanium dioxide (TiO2) filled polyamide (PA) based backsheet film for photovoltaic (PV) modules. Damp heat exposure (85%RH, 85 °C) was carried out up to 2000 hrs. The backsheet was characterized using microscopic, spectroscopic, thermoanalytic, chromatographic, and mechanical methods. While Raman microscopy, infrared spectroscopy in attenuated total reflection mode (IR-ATR), scanning calorimetry (DSC), and thermal gravimetric analysis did not reveal aging-induced changes, significant yellowing was detected by ultraviolet visible near infrared (UV/VIS/NIR) spectroscopy. Depending on the stabilizer type (UV-absorbers, hindered amine light stabilizers (HALSs), and antioxidants), rather different consumption rates were ascertained by high-performance liquid chromatography (HPLC) and gas chromatography (GC). Although the ultimate mechanical properties decreased significantly, no full embrittlement was obtained after damp heat exposure of up to 2000 hrs. The observed physical and chemical aging mechanisms were classified as within the induction period without premature failure.

Comparative study between Au/Pd/Cu and Au/Pd(P)/Cu films in soldering applications

Abstract A comparative study between Au/Pd/Cu and Au/Pd(2–5 wt% P)/Cu films in soldering applications was carried out by means of field-emission scanning electron microscopy (FE-SEM), field-emission electron probe X-ray microanalysis (FE-EPMA), ultraviolet/visible/near infrared (UV/VIS/NIR) spectrophotometry, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and high-speed ball shear (HSBS) test. We investigated the interfacial microstructure via FE-SEM and FE-EPMA, the mechanical properties of solder joints via HSBS test, and the light properties and the microstructure of the exterior surfaces of solder bumps via UV/VIS/NIR spectrophotometry, XPS, and TEM. The interfacial microstructures/mechanical properties (with Cu pads) were approximately independent of the P content in the Pd(P) films. However, the discoloration in the solder bumps resulting from the formation of a SnO2 nanolayer (or Au/Pd/Cu) could be greatly improved by replacing it with a Sn-O-P phase through a minor addition of P into the Pd film. This suggested that the Au/Pd(P)/Cu pads enabled an appropriate solderability. The results of the above investigations indicated that the dissolved P from the Pd(P) film during soldering played a significant role in determining the light properties of solder joints, even though the Pd(P) film was less than one micron thick and its P content was quite limited (2–5 wt%).

Effect of Two Interacting Rings in Metalloporphyrin Dimers upon Stepwise Oxidations.

The interaction between two porphyrin macrocycles, connected covalently through either a rigid ethylene or a flexible ethane bridge, in the metalloporphyrin dimers (M: 2H, Zn(2+)) have been investigated upon stepwise oxidations. Upon 1e-oxidation, two porphyrin macrocycles come closer and cofacial to each other while 2e-oxidation forces them to be separated as far as possible. This has resulted in the conversion of the cis isomer to trans for the ethylene bridged porphyrin dimer with the stabilization of an unusual "U" form, which has unique spectral and geometrical features. Detailed ultraviolet-visible-near-infrared (UV-vis-NIR), infrared (IR), electron paramagnetic resonance (EPR), and nuclear magnetic resonance (NMR) spectroscopic investigations, along with X-ray structure determination of the 2e-oxidized complexes, have demonstrated strong electronic communications between two porphyrin π-cation radicals through the bridging ethylene group. Such extensive π-conjugation also results in strong antiferromagnetic coupling between the radical spins of both of the macrocycles, which generates a diamagnetic compound. The experimental observations are also strongly supported by density functional theory (DFT) calculations.

Assessment of Transition Element Speciation in Glasses Using a Portable Transmission Ultraviolet-Visible-Near-Infrared (UV-Vis-NIR) Spectrometer.

A new low-cost experimental setup based on two compact dispersive optical spectrometers has been developed to measure optical absorption transmission spectra over the 350-2500 nm energy range. We demonstrate how near-infrared (NIR) data are essential to identify the coloring species in addition to ultraviolet visible data. After calibration with reference glasses, the use of an original sample stage that maintains the window panel in the vertical position enables the comparison of ancient and modern glasses embedded in a panel from the Sainte-Chapelle of Paris, without any sampling. The spectral resolution enables to observe fine resonances arising in the absorption bands of Cr(3+), and the complementary information obtained in the NIR enables to determine the contribution of Fe(2+), a key indicator of glassmaking conditions.

SAMARIUM ACTIVATED ABSORPTION AND EMISSION OF ZINC TELLURITE GLASS

Enhanced absorption and emission cross-sections of rare earth doped binary glasses are highly demanding for various photonic applications. Determining the right glass compositions with appropriate rare earth dopants remain challenging. Different microscopic mechanisms responsible for optical enhancement and quenching are not fully understood. In this view, we prepare a series of glasses with composition (80-x)TeO2-20ZnO-(x)Sm2O3, where 0 ≤ x ≤ 1.5 mol% using melt quenching technique. X-ray diffraction (XRD), Photoluminescence (PL) and Ultraviolet Visible Near-Infrared (UV-Vis-NIR) spectroscopic measurements are carried out to inspect the samarium concentration dependent absorption and emission features of the prepared glasses. Physical properties such as glass density and molar volume are found to be in the range 5.57-5.61 g cm-3 and 25.84-26.15 cm3 mol-1, respectively. XRD pattern verifies the amorphous nature of the prepared samples. The UV-Vis-NIR absorption spectra reveal nine peaks centered at 470, 548, 947, 1085, 1238, 1385, 1492, 1550 and 1589 nm. These bands arise due to 6H5/2→4I11/2, 4G5/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2, and 6F1/2 transitions, respectively. PL spectra under the excitation of 452 nm display four emission bands centered at 563, 600, 644 and 705 nm corresponding to 4G5/2→6H5/2, 6H7/2, 6H9/2 and 6H11/2 transitions of samarium ions. The mechanism of photoluminescence enhancement is identified, analyzed, and understood. A correlation between samarium concentration and optical response is established. This composition may be useful for fabricating various optical devices

Analysis of Redox Series of Unsymmetrical 1,4-Diamido-9,10-anthraquinone-Bridged Diruthenium Compounds.

The unsymmetrical diruthenium complexes [(bpy)2Ru(II)(μ-H2L(2-))Ru(III)(acac)2]ClO4 ([3]ClO4), [(pap)2RuII(μ-H2L(2-))Ru(III)(acac)2]ClO4 ([4]ClO4), and [(bpy)2Ru(II)(μ-H2L(2-))Ru(II)(pap)2](ClO4)2 ([5](ClO4)2) have been obtained by way of the mononuclear precursors [(bpy)2Ru(II)(H3L(-))]ClO4 ([1]ClO4) and [(pap)2Ru(II)(H3L(-))]ClO4 ([2]ClO4) (where bpy = 2,2′-bipyridine, pap = 2-phenylazopyridine, acac(-) = 2,4-pentanedionate, and H4L = 1,4-diamino-9,10-anthraquinone). Structural characterization by single-crystal X-ray diffraction and magnetic resonance (nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR)) were used to establish the oxidation state situation in each of the isolated materials. Cyclic voltammetry, EPR, and ultraviolet-visible-near-infrared (UV-vis-NIR) spectroelectrochemistry were used to analyze the multielectron transfer series of the potentially class I mixed-valent dinuclear compounds, considering the redox activities of differently coordinated metals, of the noninnocent bridge and of the terminal ligands. Comparison with symmetrical analogues [L2′Ru(μ-H2L)RuL2′](n) (where L′ = bpy, pap, or acac(-)) shows that the redox processes in the unsymmetrical dinuclear compounds are not averaged, with respect to the corresponding symmetrical systems, because of intramolecular charge rearrangements involving the metals, the noninnocent bridge, and the ancillary ligands.

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties.

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step process that finishes with Negishi coupling. Negishi coupling is a cross-coupling process in which a chemical precursor is first lithiated, followed by transmetallation with ZnCl2. The resultant organozinc compound can be coupled to a dibrominated aromatic precursor to give the conjugated monomer. Polymer films can be prepared via electropolymerization of the monomer and characterized using cyclic voltammetry and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. Nanoparticles (NPs) are prepared via emulsion polymerization of the monomer using a two-surfactant system to yield an aqueous dispersion of the polymer NPs. The NPs are characterized using dynamic light scattering, electron microscopy, and UV-Vis-NIR-spectroscopy. Cytocompatibility of NPs is investigated using the cell viability assay. Finally, the NP suspensions are irradiated with a NIR laser to determine their effectiveness as potential materials for photothermal therapy (PTT).

Photoluminescence Properties of CaO-BaO-P<sub>2</sub>O<sub>5</sub> Glass Systems Doped with Sm<sup>3+</sup>

This paper reports on physical, optical and photoluminescence properties of Sm3+doped calcium barium phosphate (CaO: BaO: P2O5: Sm2O3) glass systems. The glass samples have been prepared by the melt-quenching technique at 1200°C. It was found that the density of glasses tended to increase with increasing of Sm2O3 concentration. While, the molar volume of glasses tended to decrease with increasing of Sm2O3 concentration higher than 0.1 mol%. The absorption spectra of glasses were recorded in the ultraviolet visible near infrared (UV-Vis-NIR) region. The absorption bands centered at 374, 402, 416, 438, 473, 527, 946, 1083, 1236, 1382, 1483, 1531 and 1977 nm, respectively have been observed. The emission spectra of glass samples centered at 561, 597, 643 and 704 nm corresponding to the energy levels from 4G5/2 to 6H5/2, 6H7/2, 6H9/2 and 6H11/2, respectively have been observed with 402 nm excitation wavelength.