Spectral Response Range Research Articles

Inhibitor effects on molecular beacon-based mercury assays for tuning of detection range

A series of inhibitors were incorporated to modulate the detection range of mercury assay. A single-strand DNA-based mercury probe (ssDNA-Hg) containing 5 thymine (T) bases at both termini, which forms a hairpin structure in the presence of mercuric (Hg2+) ions via the T⋯Hg2+⋯T interaction, was designed. Although many previous studies focused on mercury detection to improve the sensitivity and selectivity, few studies have been reported to tune the detection range to cover a wide range of target concentrations in different environments. In the present study, a new Hg2+ detection scheme was designed to extend, narrow and shift the range of mercury detection using inhibitors. The complementary DNA (ssDNA-C) and cationic conjugated polyelectrolyte (CPE) induced a shift or broadening of the spectral response range by functioning as an allosteric inhibitor. Iodide and cyanide ions worked as efficient depletants, adjusting the binding constant of ssDNA-Hg and Hg2+ (1.1×107M−1) by ∼10 times (up to ∼1.4×106M−1) in the presence of I− or CN− ions, resulting in a large shift in the detection range according to [I−] or [CN−] with a sharp titration curve via a sequestration mechanism. Similar Hg2+ detection range shift was successfully demonstrated using same series of inhibitors in real samples such as Han River and tap water. This study suggests that the binding affinity of probe can be tuned toward a target and the resulting detection response range can be controlled using a range of inhibitors.

The Latest Research Progress of Coupling between BiOX and Semiconductor Photocatalyst

The heterojunction was formed between two kinds of coupling semiconductors , which improved the charge separation efficiency of system, widened the spectral response range of catalysts and improved photocatalytic propertirs of catalysts. The process of preparation of semiconductors coupling was easily affected by preparation methods and reaction temperature and so on, which would cause the changes in crystal structure and surface properties of coupling semiconductors, thus photocatalytic quantum efficiency of coupling semiconductors was increased. In this article, the following three aspects were mainly discussed. (1) About the coupled system of halogen bismuth oxide and oxide, because generaling BiOX with the semiconductor material compound, the efficient heterojunction structure could be formed, photocatalytic performances of the photocatalytic degradation of pollutants were improved. (2) About the coupled system of AgX and BiOX, compared with the pure AgI or BiOI, composite photocatalytic materials of AgI/BiOI had higher photocatalytic reactivity in visible light. (3) About the coupled system of halogen bismuth oxide and other compounds, after Bi2S3 coupled with BiOX, photoproduction electronic migrated in the two kinds of catalysts, the separation efficiency of electrons and holes was improved, and photocatalytic performances of coupling compound were improved. In addition, in recent years, the latest research progress of the preparation method, the influencing factors of the photocatalytic performance and improving the utilization efficiency of visible light of semiconductors coupling at home and abroad was reviewed in this paper. Finally, the main problems and the future striving direction in semiconductors coupling were presented.

CdS/CdSe quantum dots and ZnPc dye co-sensitized solar cells with Au nanoparticles/graphene oxide as efficient modified layer

Co-sensitization by using two or more sensitizers with complementary absorption spectra to expand the spectral response range is an effective approach to enhance device performance of quantum dot sensitized solar cells (QDSSCs). To improve the light-harvesting in the visible/near-infrared (NIR) region, organic dye zinc phthalocyanine (ZnPc) was combined with CdS/CdSe quantum dots (QDs) for co-sensitized solar cells based on ZnO inverse opals (IOs) as photoanode. The resulting co-sensitized device shows an efficient panchromatic spectral response feature to ∼750nm and presents an overall conversion efficiency of 4.01%, which is superior to that of the individual ZnPc-sensitized solar cells and CdS/CdSe-sensitized solar cells. Meanwhile, an Au nanoparticles/graphene oxide (Au NPs/GO) composite layer was successfully prepared to modify Cu2S counter electrode for the co-sensitized solar cells. Reducing the carrier recombination process by GO and catalytic process of Au NPs leads to increased power conversion efficiency(PCE) from 4.01 to 4.60% and sustainable stability remains ∼85% of its original value after 60min light exposure. In this paper, introduction of the organic dyes as co-sensitizer and Au NPs/GO as counter electrode modified layer has been proved to be an effective route to improve the performance of QDSSCs.

Effects of changing spectral radiation distribution on the performance of photodiode pyranometers

The effect of changes in the spectral distribution of the incident solar radiation on the direct normal responsivity of the LI-COR photodiode pyranometer is examined using DNI spectral data from a PMOD spectroradiometer and the generic spectral response of a LI-COR pyranometer. The direct normal responsivity is found to vary over the day under all weather conditions at Payerne, Switzerland in a systematic manner that can be modeled as a function of air mass or solar zenith angle. This suggests that scattering of other atmospheric constituents plays as a subsidiary role to Rayleigh scattering that preferentially scatters more blue light as the path through the atmosphere increases. The SMARTS2 model is used to examine the effect on the full spectral response range of the photodiode based pyranometer and to refine the estimated response changes. The use of this information is discussed relative to improving adjustments made to Rotating Shadowband Irradiometers measurements. Similar methodology can be used to estimate the spectral effect on the performance of solar modules.

Designing of long wavelength cut thin film filter for temperature reduction of concentrator photovoltaic

This paper presents a comparison of three-dimensional simulation for concentrator photovoltaic module using two types of multi-junction solar cell. Each had its own range of spectral response and based on that range a thin film filter was developed for each case to reflect the unused spectral of the solar spectrum and allowed the desired spectrum to reach the solar cell. The thin film was deposited on a secondary optical element that was used to homogenize the irradiance distribution on the solar cell. A thermal simulation was conducted to compare the resulted decrease in cell temperature due to the use of the thin film for each case.

Fabrication of TiO2/WO3 Composite Nanofibers by Electrospinning and Photocatalystic Performance of the Resultant Fabrics

By coupling the self-assembly of polystyrene-block-poly(ethylene oxide)-containing titanium-tetraisopropoxide and tungsten hexaphenoxide (the precursors of TiO2 and WO3, respectively) with electrospinning technique, the hierarchically porous TiO2/WO3 composite nanofibers with inner-bicontinuous and outer-shell structures have been synthesized. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were employed to characterize the structure of the fibers. In these nanofibers, the TiO2 acts as the frames, and WO3 fills the gaps. The UV–vis spectroscopy suggests that the spectral response range has been successfully extended into the visible regime. Furthermore, the resulting fabrics show enhanced performance in the photocatalytic degradation of acetaldehyde relative to neat TiO2 and neat WO3. Our results indicate that electrospinning the blend solution of block copolymer and two kinds of precursor of inorganic material is an effective strategy to fabricate composite nanofibers that can improve the photocatalytic activity of TiO2, especially for visible light.

Preparation and photoelectric properties of Ho3+-doped titanium dioxide nanowire downconversion photoanode

Ho3+-doped titanium dioxide (TiO2:Ho3+) downconversion (DC) nanowires were synthesized through a simple hydrothermal method followed by a subsequent calcination process after being immersed in Ho(NO3)3 aqueous solution. Moreover, TiO2:Ho3+ nanowires (HTNWs) were used as the photoanode in dye-sensitized solar cells (DSSCs) to investigate their photoelectric properties. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the morphology and structure of the material, respectively. The photofluorescence and ultraviolet–visible absorption spectra of HTNWs reveal a DC from the near and middle ultraviolet light to visible light which matches the strong absorbed region of the N719 dye. Compared with the pure TNW photoanode, HTNWs DC photoanodes show greater photovoltaic efficiency. The photovoltaic conversion efficiency (η) of the DSSCs with HTNWs photoanode doped with 4% Ho2O3 (mass fraction) is two times that with pure TNW photoanode. This enhancement could be attributed to HTNWs which could extend the spectral response range of DSSCs to the near and middle ultraviolet region and increase the short-circuit current density (Jsc) of DSSCs, thus leading to the enhancement of photovoltaic conversion efficiency.

Ternary SnS(2-x)Se(x) Alloys Nanosheets and Nanosheet Assemblies with Tunable Chemical Compositions and Band Gaps for Photodetector Applications.

Ternary metal dichalcogenides alloys exhibit compositionally tunable optical properties and electronic structure, and therefore, band gap engineering by controllable doping would provide a powerful approach to promote their physical and chemical properties. Herein we obtained ternary SnS2−xSex alloys with tunable chemical compositions and optical properties via a simple one-step solvothermal process. Raman scattering and UV-vis-NIR absorption spectra reveal the composition-related optical features, and the band gaps can be discretely modulated from 2.23 to 1.29 eV with the increase of Se content. The variation tendency of band gap was also confirmed by first-principles calculations. The change of composition results in the difference of crystal structure as well as morphology for SnS2−xSex solid solution, namely, nanosheets assemblies or nanosheet. The photoelectrochemical measurements indicate that the performance of ternary SnS2−xSex alloys depends on their band structures and morphology characteristics. Furthermore, SnS2−xSex photodetectors present high photoresponsivity with a maximum of 35 mA W−1 and good light stability in a wide range of spectral response from ultraviolet to visible light, which renders them promising candidates for a variety of optoelectronic applications.

Toward facile broadband high photoresponse of fullerene based phototransistor from the ultraviolet to the near-infrared region

Organic phototransistor (OPT) is a promising organic device with substantial attention due to its photodetection combined with lightweight, flexibility, large-scale yields, and low cost of organic materials. In addition, spectral tunability and long photocarrier lifetime for organic materials make them highly attractive for advanced optoelectronic device applications. Here, we report high-performance broadband photodetection devices fabricated using an all-organic heterojunction of fullerene/chloroaluminum phthalocyanine with a high-efficiency exciton-dissociation-interface and complementary spectral absorption. Operating at room temperature, the prepared OPTs offer broadband ultraviolet–visible–near infrared spectral response, exhibiting ultrahigh photoresponsivity of 94.4 A/W, the highest detectivity ∼1.5 × 1013 Jones combined with external quantum efficiency of 26,066%, and the ability to measure high-frequency signals. These parameters are comparable or even superior to commercially available silicon carbide, silicon and indium gallium arsenide photodetectors, indicating the possibility of many applications based on broadband detection utilizing our devices. A semi-quantitative calculation and energy level mechanism reasonably explain the ultrahigh performances above. Our results suggest that organic compounds with mutual complementary spectra can be used for constructing photosensitive active layer, in which optimized interfacial electronic structure and morphology help photoexciton dissociation and extend the spectral response range.

A Fully Transparent and Flexible Ultraviolet–Visible Photodetector Based on Controlled Electrospun ZnO‐CdO Heterojunction Nanofiber Arrays

It is essential for novel photodetectors to show good photoresponses, high stability, and have facile fabrication methods. Herein, an optimized electrospinning method to fabricate a photodetector based on nanowire arrays that has a wide spectral response range is demonstrated. Arrays of ZnO‐CdO hybrid nanowires are carefully fabricated fusing ZnO and CdO portions into the same nanowires and subsequently assembling those nanowires into a regular structure. Compared to pure ZnO or CdO nanowire arrays, the hybrid arrays show comparable photocurrent/dark current ratios and response speeds, but they possess a much wider spectral response range from ultraviolet to visible light. The optoelectronic and electronic properties of the ZnO‐CdO hybrid nanowire arrays are systematically explored. Based on this, a transparent and flexible photodetector made of ZnO‐CdO hybrid nanowire arrays is fabricated. It shows a high transparency of around 95% in the spectral range of 400–800 nm and maintains its properties even after 200 bending cycles. Importantly, the developed, simple method can be directly applied to many types of substrates and a transfer of the nanowires becomes unnecessary, which guarantees a high quality of the devices.

Determining the spectral responsivity from relative measurements by using multicolor light-emitting diodes as probing light sources

We measured the ratio of the photocurrent generating from a detector under test to that from a reference one when they were irradiated by the same light-emitting diodes (LED) in the same configuration. We recorded data for various LEDs with their spectra covering different regions in the spectral response range of the test detector. If the spectral responsivity of the reference detector and LEDs’ lineshape functions had been predetermined, we can use a resolution-enhancement algorithm to reconstruct the spectral responsivity from multiple data measured by using multicolor LEDs as probing light sources. We have also successfully generalized the algorithm to the case with an arbitrary broad-band detector as the reference detector and found an alternative algorithm which leads to the same solution. After a suitable correcting step, the resulting spectral responsivity was found to be free from the broadening effect due to the finite bandwidth of LED and in good agreement with the one directly measured by using spectrally pure light as probing light.

Theoretical insight into photo-induced intramolecular electron transfer in heterodinuclear Ru(II)–Co(III) complexes

Photo-induced intramolecular electron transfer (IET) of a series of heterodinuclear Ru(II)–Co(III) complexes has been theoretically investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT). The Ru(II)–Co(III) complexes display Ru → Co metal-to-metal electron transfer (MMET) in the visible region. The photosensitivity involving spectral response range and absorption intensity, and IET rate, are improved by introducing (Z)-N-(1H-isoindol-1-ylidene)-2H-isoindol-1-amine as donor ligands. The Ru → Co IET rate in the newly designed complexes shows at least one order of magnitude larger than that in [(bpy)2-Ru(pytp)Co(tren)]5+. These superior performances indicate that heterodinuclear Ru(II)–Co(III) complexes could be promising as the effective ligand release carriers for the selective cancer treatment.

Enhancing photoelectrical performance of dye–sensitized solar cell by doping SrTiO3:Sm3+@SiO2 core–shell nanoparticles in the photoanode

SrTiO3:Sm3+@SiO2 (STS@SiO2) core–shell nanoparticles were fabricated by Stöber method after a simple hydrothermal process and then being introduced into the TiO2 photoanode to assemble dye–sensitized solar cells (DSSCs). X–ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM) analysis confirmed the formation of core–shell nanoparticles with cubic structured SrTiO3:Sm3+ (STS) as core, SiO2 as shell. The photo–fluorescence (PL) and ultraviolet–visible (UV–Vis) absorption spectra of photoanodes with different STS@SiO2 content indicate a down–conversion from ultraviolet light to visible light which matched the strong absorbing region of the N719 dye. Compared with the pure TiO2 and STS doped TiO2 photoanode, STS@SiO2 doped TiO2 photoanode showed a greater photovoltaic efficiency. The photoelectric conversion efficiency (η) of 5.07% for 10 wt% STS@SiO2 doped TiO2–based DSSC was higher than that of 3.72% for pure TiO2–based DSSC and 4.29% for 10 wt% STS doped TiO2–based DSSC. This phenomenon could be explained by STS@SiO2 core–shell nanoparticles’ triple ability to extend spectral response range to the ultraviolet region, suppress the recombination of electron–electrolyte and lengthen the light traveling distance in the photoanode by the scattering.

A spectrally splitting photovoltaic-thermal hybrid receiver utilising direct absorption and wave interference light filtering

We have developed a novel spectrally splitting hybrid solar receiver by combining a simple dichroic filter and a liquid channel as a selective absorbing medium. The combination acts as a band pass filter for silicon solar cells. The geometry can be optimised for any linear concentrator; in this paper we have optimised it for a commercially available linear rooftop micro-concentrator. The optics of the concentrator at its focal region has been investigated using ray tracing. A simple 5-layer dichroic filter made of titanium dioxide and silicon dioxide has been designed, optimised, and fabricated with a focus placed on manufacturing simplicity. It has been shown that such a filter directs 54.5% of the concentrated light to the silicon photovoltaic cells; the Si cells considered in this paper can convert 26.1% of this energy into electricity which is significantly higher than their 20.6% efficiency under the full spectrum. This is due to the fact that 73.3% of the incident flux is within the cell's relatively high spectral response range, which can be efficiently converted into electricity. The rest of the spectrum can be collected as high temperature heat. This research shows the possibility of employing low-cost direct absorption-dichroic filtering hybrid receivers in liner concentrators.

Modified lead titanate thin films for pyroelectric infrared detectors on gold electrodes

Pyroelectric infrared detectors provide the advantage of both a wide spectral response and dynamic range, which also has enabled systems to be developed with reduced size, weight and power consumption. This paper demonstrates the deposition of lead zirconium titanate (PZT) and lead calcium titanate (PCT) thin films for uncooled pyroelectric detectors with the utilization of gold electrodes. The modified lead titanate thin films were deposited by pulsed laser deposition on gold electrodes. The PZT and PCT thins films deposited and annealed at temperatures of 650°C and 550°C respectively demonstrated the best pyroelectric performance in this work. The thin films displayed a pyroelectric effect that increased with temperature. Poling of the thin films was carried out for a fixed time periods and fixed dc bias voltages at elevated temperature in order to increase the pyroelectric coefficient by establishing a spontaneous polarization of the thin films. Poling caused the pyroelectric current to increase one order of magnitude.

Synthesis of novel Zn0.5Mg0.5Fe2O4@TiO2 nanotube arrays with enhanced photoelectrocatalytic properties

Zn0.5Mg0.5Fe2O4 nanoparticles contribute to widening of the spectral response range and reducing the charge recombination of TiO2 nanotube arrays.

Highly sensitive polymer photodetectors with a broad spectral response range from UV light to the near infrared region

Highly sensitive polymer photodetectors with a broad spectral response range from UV light to the near infrared region based on P3HT : PTB7-Th : PC71BM as the active layer are reported.

Double dye cubic-sensitized solar cell based on Förster resonant energy transfer

To extend the spectral response range of dye-sensitized solar cells through Förster resonant energy transfer, eosin Y and rhodamine B were chosen as an donor and a acceptor to cubic-sensitize nanocrystalline ZnO thin film.

Wide spectral response field effect phototransistor based on graphene-quantum dot hybrid

The photoelectrical characteristics of field-effect phototransistors (FEPTs) are investigated experimentally based on a graphene–PbS quantum dot (QD) hybrid. The device presented a wide spectral response range from 300 to 1400 nm because of multiple-exciton generation of PbS QDs. The photoelectrical responsivity reached up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">$2\times 10^{5}\ \hbox{A/W}$</tex-math></inline-formula> at low bias voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">$\sim$</tex-math></inline-formula> 10 mV) and became more sensitive with increasing bias voltage. The transient response of the hybrid FEPTs was also measured with the relaxation times and the decay times around several seconds. Such devices exhibit great competitiveness in wide spectral response, flexible integrated circuits with low cost, large area, low energy consumption, and high responsivity.

Hydrothermal carbonization of carboxymethylcellulose: One-pot preparation of conductive carbon microspheres and water-soluble fluorescent carbon nanodots

Conductive carbon spheres (CSs) and water-soluble fluorescent carbon nano-dots (CNDs) were synthesized by the one-pot hydrothermal carbonization of carboxymethylcellulose (CMC) using urea as the nitrogen source. The CSs have diameters of 2–8μm and abundant nitrogen-containing functional groups. They contain N in two forms: (1) chemical N including amidogen and imido groups (NH2/NH), and (2) structural N including pyridine (N-6), pyrrolic/pyridone (N-5) and quaternary (N-Q) nitrogen. Activation at high temperature contributes to the formation of pyridine (N-6) and quaternary nitrogen (N-Q) with a graphite-like structure and higher stability. They are all conductive and CS0.2-900 was found to exhibit the highest electrical conductivity of 166S/m. CNDs are monodispersed spheres with an average diameter of 32nm and show abundant oxygen-containing groups on their surface. They have excitation- and emission-independent pH-sensitive properties. The use of CNDs as photosensitizer in a CNDs/TiO2 system for methylene blue and phenol degradation under visible light irradiation is attractive. The spectral response range of the system was thus expanded from UV region to include part of the visible light region.