Detection Wavelength Range Research Articles

Bismuth sulfide quantum dots-CsPbBr3 perovskite nanocrystals heterojunction for enhanced broadband photodetection

Colloidal semiconductor nanocrystals (NCs) or quantum dots (QDs) have shown great potential for solution-processable photodetector due to their exceptional optical and electronic properties. However, broadband and sensitive photodetection from single QDs- based devices is quite challenging. Nano-heterojunction with proper band alignment based on two different materials offers significant advantages for developing broadband photodetector. Herein, we report ultraviolet–visible (UV–Vis) to near-infrared (NIR) light-responsive photodetector based on solution-processed nano-heterojunction of visible light absorber CsPbBr3 perovskite NCs and wide absorption range, environment-friendly Bi2S3 QDs. Our results demonstrate that the CsPbBr3–Bi2S3 nano-heterojunction-based photodetector has higher responsivity (380 μA/W at a wavelength of 532 nm) and higher specific detectivity (1.02 × 105 Jones), as compared to the individual CsPbBr3 or Bi2S3 QDs based devices. Interestingly, the detection wavelength range of our heterojunction device is further extended to the near-infrared region (1064 nm) due to the broadband absorption range of Bi2S3 QDs, which is not observed in the visible light absorber CsPbBr3 devices. Remarkably, the responsivity of the heterojunction device is 90 μA W−1. The enhanced specific detectivity and the broadband response of hybrid devices are attributed to the improved charge carrier generation, efficient charge separation and transfer at the interface between CsPbBr3 and Bi2S3 QDs.

2D Erucamide Crystal Synthesis and Ultraviolet Photodetection

Abstract2D organic crystals play a unique role in photodetection owing to their tunable detection wavelength, low manufacturing cost, compatibility with lightweight, and controllable synthesis. However, their detection wavelength range mainly encompasses the visible (Vis) and near‐infrared (NIR) spectra. Herein, 2D erucamide crystals are synthesized using nitrogen gas and methanol as raw materials without catalysts at room temperature under atmospheric pressure via laser processing. The synthesized 2D erucamide is demonstrated to be a promising broad bandgap organic semiconductor material. A UV photodetector made of 2D erucamide exhibited a responsivity as high as 145 mA W−1, a millisecond‐level response speed, and an excellent detectivity of 4.96 × 109 Jones. Furthermore, the synthesized erucamide showed an excellent UV–vis suppression ratio (R254 nm/R532 nm) of 59. The synthesis mechanism of erucamide via laser bubbling in liquids is proposed. Thermodynamically, the high temperature of the bubbles is beneficial for nitrogen and methanol decomposition. Kinetically, rapid bubble quenching facilitates final product formation. This accomplishment represented the pioneering utilization of lasers in converting nitrogen gas into organic compounds while introducing 2D erucamide into the realm of organic UV photodetectors.

Comparison of NIR and SWIR thermography for defect detection in Laser Powder Bed Fusion

Since laser powder bed fusion (PBF-LB/M) is prone to the formation of defects during the building process, a fundamental requirement for widespread application is to find ways to assure safety and reliability of the additively manufactured parts. A possible solution for this problem lies in the usage of in-situ thermographic monitoring for defect detection. In this contribution we investigate possibilities and limitations of the VIS/NIR wavelength range for defect detection. A VIS/NIR camera can be based on conventional silicon-based sensors which typically have much higher spatial and temporal resolution in the same price range but are more limited in the detectable temperature range than infrared sensors designed for longer wavelengths. To investigate the influence, we compared the thermographic signatures during the creation of artificially provoked defects by local parameter variations in test specimens made of a nickel alloy (UNS N07208) for two different wavelength ranges (~980 nm and ~1600 nm).

Photoconductivity, pyroconductivity, and pyroelectricity effects in photodetection of layer-structured CuInP2S6/MoS2 heterojunction

Layer-structured ferroelectric material-modulated heterojunctions are promising for use as photodetectors. However, the mechanism behind their photodetection performance, including photoconductivity, pyroconductivity, and pyroelectricity effects, has not yet been fully studied. Herein, we present a CuInP2S6/MoS2 heterojunction with a layered structure, in which the narrow bandgap of MoS2 extends the detection wavelength range with a specific detectivity (D*) of 108–1010 Jones. The pyroelectric effect, dominated by polarization, introduces significant current peaks and valleys when the light is turned on and off. A competitive mechanism is discovered among the photoconductivity, pyroconductivity, and pyroelectricity effects. At low optical power intensities, the pyroconductivity effect is dominant under 405 nm light, while the pyroelectricity effect dominates under 808 nm light. However, at high optical power intensities, both the photoconductivity and pyroconductivity effects become dominant, regardless of the light wavelength. The responsivity (R), external quantum efficiency (EQE), and D* of the CuInP2S6/MoS2 heterojunction are two orders of magnitude for 405 nm light compared to 808 nm light. These results not only demonstrate the coupling effect among the photoconductivity, pyroconductivity, and pyroelectricity effects in the photodetection of layer-structured CuInP2S6/MoS2 heterojunctions but also highlight the potential applications of these heterojunctions in multifunctional devices, provided that these effects can be clearly distinguished.

Growth of κ-([Al,In]xGa1-x)2O3 Quantum Wells and Their Potential for Quantum-Well Infrared Photodetectors.

The wide band gap semiconductor κ-Ga2O3 and its aluminum and indium alloys have been proposed as promising materials for many applications. One of them is the use of inter-sub-band transitions in quantum-well (QW) systems for infrared detectors. Our simulations show that the detection wavelength range of nowadays state of the art GaAs/AlxGa1-xAs quantum-well infrared photodetectors (QWIPs) could be substantially excelled with about 1-100 μm using κ-([Al,In]xGa1-x)2O3, while at the same time being transparent to visible light and therefore insensitive to photon noise due to its wide band gap, demonstrating the application potential of this material system. Our simulations further show that the QWIPs efficiency critically depends on the QW thickness, making a precise control over the thickness during growth and a reliable thickness determination essential. We demonstrate that pulsed laser deposition yields the needed accuracy, by analyzing a series of (InxGa1-x)2O3 QWs with (AlyGa1-y)2O3 barriers with high-resolution X-ray diffraction, X-ray photoelectron spectroscopy (XPS) depth profiling, and transmission electron microscopy (TEM). While the superlattice fringes of high-resolution X-ray diffraction only yield an average combined thickness of the QWs and the barrier and X-ray spectroscopy depth profiling requires elaborated modeling of the XPS signal to accurately determine the thickness of such QWs, TEM is the method of choice when it comes to the determination of QW thicknesses.

Self-powered In2Se3/PtSe2 photodetector with broadband and fast response

The emerging van der Waals semiconductor In2Se3 has recently gained great attention in the field of optoelectronics, due to its high optical absorption and direct bandgap. Different types of In2Se3 photodetectors have been demonstrated with high responsivity, though the detection speed and wavelength range are limited by the device geometry and its absorption edge. In this paper, we have fabricated an α-In2Se3/PtSe2 heterojunction photodetector. Taking advantage of the high mobility and narrow bandgap of PtSe2, a wide wavelength response from 405 to 1550 nm and fast repose speed of ∼ 127 µs has been achieved in the heterojunction photodetector. Also, benefiting from the strong built-in electric field between In2Se3 and PtSe2, the photodetector can work without any external bias with a responsivity highly at 80 mA/W. This fast self-powered In2Se3/PtSe2 photodetector presents an avenue for future low-energy-consumption optoelectronics.

High-speed and low dark current silicon-waveguide-coupled III-V photodetectors selectively grown on SOI

Seamlessly integrating III-V active devices with Si passive components in a monolithic manner is the key for fully integrated Si photonics. In this article, we demonstrate high-performance III-V photodetectors directly grown on industry-standard (001)-oriented silicon-on-insulator (SOI) wafers and intimately coupled with Si waveguides. The Si-waveguide-coupled III-V photodetectors feature a low dark current of 60 pA corresponding to a current density of 0.002 A / c m 2 , a large photocurrent exceeding 1 mA, responsivities of 0.4 A/W at 1.3 µm and 0.2 A/W at 1.5 µm, and a large detection wavelength range over the entire telecom band. High-speed measurements reveal a 3 dB bandwidth over 52 GHz and a data communication rate of 112 Gb/s with four-level pulse-amplitude modulation and 100 Gb/s with on–off keying. The monolithic integration scheme demonstrated for III-V photodetectors in this work is also applicable to future seamless integration of III-V lasers on the Si-photonics platform.

Single‐Crystalline Ge1−xSnx/Si p–n Heterojunction Photodiodes with Sn Compositions up to 10%

AbstractGeSn/Si heterojunction photodiodes are attractive because they can extend light detection wavelength range. However, the development of such photodiodes via epitaxial growth faces great challenges due to unavoidable issues such as lattice and thermal mismatches between Si and GeSn. Here, print Si nanomembranes are transferred on GeSn/Ge/Si substrates to form the GeSn/Si heterojunction photodiodes. The p‐Ge0.977Sn0.023/n‐Si heterojunction photodiodes exhibit a good rectifying behavior with a low dark current density of 40 mA cm−2and responsivity of 0.41 A W−1at 1550 nm under a reverse bias of −2 V. In addition, the detection wavelength range of p‐Ge0.9Sn0.1/n‐Si is extended to 2100 nm because of the increased Sn composition. The bandgap calculation of as‐grown GeSn with various Sn compositions is carried out. It confirms that the enhanced responsivity and extended detection wavelength ranges are attributed to the reduced bandgap from 750 to 601 meV when the Sn composition is increased from 2.3% to 10%. The result shows that the transfer printing of a freestanding single‐crystalline Si nanomembrane to a bulk GeSn/Ge/Si substrate can provide an excellent alternative route for realizing GeSn/Si heterojunction photodiodes.

Probing nanoplastics derived from polypropylene face masks with hyperspectral dark-field microscopy

The high worldwide consumption of cheap plastic goods has already resulted in a serious environmental plastic pollution, exacerbated by piling of disposed personal protective equipment because of the recent outbreak of COVID-19. The aim of this study was to assess the feasibility of dark-field hyperspectral microscopy in the 400–1000 wavelength range for detection of nanoplastics derived from weathered polypropylene masks. A surgical mask was separated to layers and exposed to UV radiation (254 nm) for 192 h. Oxidative degradation of the polypropylene was evidenced by ATR FT-IR analysis. UV treatment for 192 h resulted in generation of differently shaped micro- and nano-sized particles, visualized by dark-field microscopy. The presence of nanoparticles was confirmed by AFM studies. The hyperspectral profiles (400–1000 nm) were collected after every 48 h of the UV treatment. The distinct hyperspectral features faded after prolonged UV exposure, but the assignment of some particles to either blue or white layers of mask could still be made based on spectral characteristics.

64-channel label-free fluorescence detection and single-particle counting device.

A 64-channel detection system for laser-induced fluorescence (LIF) detection at the cell level is established and applied to single event counting. Generally, fluorescence detection at the cellular level requires a dyeing label to enhance the scattered light intensity for the photodetector. However, the dyeing labels, such as fluorophores, probes, and dyes, complicate sample preparation and increase cytotoxicity in the process. Therefore, label-free detection becomes essential for in vivo research. The presented 64-channel detection system is designed for label-free detection with the ability to record feeble emissions. Two linear photodetector devices are included in the system, extending the wavelength detection range to 366-680 nm with an improved spectral resolution at an average of 4.9 nm. The performance of the system was validated by detecting unlabeled human hepatocytes (L-02) and other cell-level biologic samples. In addition, the 64-channel detection system was also used for particle counting with a quartz microfluidic chip. The counting method is based on fluorescence spectra differs from those of other devices (i.e., flow cytometry and cell-sorting equipment), which use isolated irradiance intensities.

9‐3: Student Paper: Widening the Wavelength Absorption Range of Indium Gallium Zinc Oxide Phototransistors through the Capping layer

We propose indium gallium zinc oxide (IGZO) phototransistors with an extended wavelength detection range by a capping layer composed of hafnium oxide (HfO2). A HfO2 capping layer enables the generation of oxygen vacancies by strongly attracting oxygen ions in the back channel of IGZO. IGZO phototransistors with the capping layer exhibit improved optoelectronic characteristics, such as photoresponsivity of 149.48 A/W, photosensitivity of 1.17 × 106, detectivity of 3.64 × 1010 Jones under the green light (532 nm) illumination of 10 mW/mm2.

Single-shot multi-color fluorescence microscopy via a colorimetry camera.

Multi-color fluorescence microscopy presents highly detailed biological samples interactively. However, current multi-color methods suffer from an intricate optical setup, complicated image analysis, or a long acquisition time. To address these issues, here we develop a simple multi-color method based on a customized colorimetry camera to enable the detection of multiple structures from single-shot acquisition. The unfiltered channel (W pixels) and color channels (R, G, B, and NIR pixels) in this customized camera simultaneously provide a broad detection wavelength range and high detection sensitivity. We built a simple optical setup by replacing the monochrome camera in a basic fluorescence microscopy system with a colorimetry camera, and developed effective image analysis procedures to reconstruct a multi-color image from a single frame of a raw image. We demonstrated single-shot four-color wide-field fluorescence imaging on fixed cos-7 cells with < 5% cross talk, which is comparable to the best reported values. Our method greatly simplifies both the optical system and image analysis in the widely used method of multi-color fluorescence microscopy, thus offering an effective and easy way to study multiple objects at the same time.

A Heterostructured Graphene Quantum Dots/β-Ga2O3 Solar-Blind Photodetector with Enhanced Photoresponsivity.

The superior optical and electronic characteristics of quasi-two-dimensional β-Ga2O3 make it suitable for solar-blind (200-280 nm) photodetectors (PDs). The metal-semiconductor-metal (MSM) PDs commonly suffer from low photoresponsivity, slow response speed, and a narrow detection wavelength range despite their simple fabrication process. Herein, we report a high-performance MSM PD by integrating exfoliated β-Ga2O3 flakes with zero-dimensional graphene quantum dots (GQDs), which exhibits the advantages of enhancing the photoresponsivity, shortening the photoresponse time, and stimulating a broad range of photon detection. The hybrid GQDs/β-Ga2O3 heterostructure PD is sensitive to deep-ultraviolet (DUV) light (250 nm) with an ultrahigh responsivity (R of ∼2.4 × 105 A/W), a large detectivity (D* of ∼4.3 × 1013 Jones), an excellent external quantum efficiency (EQE of ∼1.2 × 108%), and a fast photoresponse (150 ms), which is superior to the bare β-Ga2O3 PD. These improvements result from effective charge transfer due to the introduction of GQDs, which enhance the light absorption and the generation of electron-hole pairs. In addition, the hybrid GQDs/β-Ga2O3 PD also exhibits better photoelectric performance than the bare β-Ga2O3 PD at a 1000 nm wavelength. As a conclusion, the hybrid GQDs/β-Ga2O3 DUV photodetector shows potential applications in commercial optoelectronic products and provides an alternative solution for the design and preparation of high-performance photodetectors.

Fluorescent aptasensor based on DNA-AgNCs emitting in the visible red wavelength range for detection of kanamycin in milk

Fluorescence sensors detect veterinary drug residues in milk, which are usually interfered with by the complex milk matrix. The specific DNA template can produce DNA stabilized silver nanoclusters (DNA-AgNCs) emitting in the visible red wavelength range. This will reduce the fluorescence interference of milk by avoiding the fluorescence signal generated by the inherent component of milk in the relatively short wavelength range. Furthermore, the red fluorescence has relatively high penetration, which can also reduce the impact of interfering substances. Here, on the basis of fluorescence resonance energy transfer (FRET), we designed a fluorescent aptasensor using DNA-AgNCs and gold nanoparticles (AuNPs) to detect kanamycin (KAN) residue in milk. Due to electrostatic interaction, DNA adsorbs on the AuNPs. The decrease in the distance between DNA-AgNCs and AuNPs generates FRET, which causes the fluorescence of DNA-AgNCs to be quenched. When KAN is added, the aptamer and KAN can specifically bind with high affinity, resulting in a weakening of the electrostatic interaction between DNA-AgNCs and AuNPs. This results in a decrease in FRET between DNA-AgNCs and AuNPs, and recovery of the fluorescent signal intensity of DNA-AgNCs. The designed sensor has satisfactory specificity and sensitivity for the detection of KAN residues. The applied strategy showed the limit of KAN detection to be as low as 22.6 nM. Moreover, this work provides a way for reducing the interference of the milk background fluorescence signal in the fluorescence sensor and has broad application prospects.

Study on Graphene Field Effect Tube Photoelectric Sensor

As a special device that converts the measured physical quantity into electrical signal or other signal output according to specific rules, the sensor becomes the nerve ending connecting the natural world and the electronic world. Photoelectric sensors, as an important branch of sensors, play a central role in applications such as optical communication, imaging and detection, as electronic systems perceive external eyes. At present, the main sensor products in the market have defects such as limited detection wavelength, low responsivity and complex structure. In view of these problems and practical needs, combined with the advantages of graphene with wide detection wavelength range, high influence and high electron mobility, this paper proposes a graphene field effect tube photoelectric sensor with silicon nitride protective layer, and its preparation process, environmental stability test and photoelectric response characteristics are studied and analyzed. The results have potential application value. Graphene field effect transistor photoelectric sensor has many excellent characteristics, such as wide detection band, high response, good environmental stability and easy preparation and integration. It provides a new research idea for MEMS photoelectric sensor and has a very broad application prospect.

Molecularly imprinted photoelectrochemical sensor for detecting tetrabromobisphenol A in indoor dust and water.

The gradual emissions of tetrabromobisphenol A (TBBPA) from the primitive recycling of E-waste createhuman health threats, which urgently require to develop an efficient, rapid yet simple detection method. The present study conducts a highly sensitive molecularly imprinted photoelectrochemical sensor (MIPES) containingmolecularly imprinted (MI)-TiO2, Au, and reduced graphene oxide for the trace detection of TBBPA in indoor dust and surface water from an E-waste recycling area. The photocurrent response is used to evaluate the sensing performance of the MIPES toward TBBPA detection. The working potential for amperometry is 0.48V. The wavelength range for photoelectrochemical detection is 320-780nm. The sensorshows a detection range of1.68 to 100nM with a low limit of detection of 0.51nM (LOD = 3 sb/S) and a limit of quantification of 1.68nM (LOQ = 3.3 LOD). In addition, the MIPES sensor exhibits rapid, excellent reproducibility, selectivity, and long-term stability toward TBBPA detection. The relative standarddeviation of three measurements for real samples is less than 7.0%, and the recovery range is 90.0-115%. The surface of molecular imprinting contributes to the high charge separation and sensing photocurrent response of TBBPA, which is confirmed by single-particle photoluminescence spectroscopy. The present study provides a new facile sensorwith highly sensitive yet rapid responseto detect environmental pollutants in E-waste by using the MIPES.

A Review of Phototransistors Using Metal Oxide Semiconductors: Research Progress and Future Directions.

Metal oxide thin-film transistors have been continuously researched and mass-produced in the display industry. However, their phototransistors are still in their infancy. In particular, utilizing metal oxide semiconductors as phototransistors is difficult because of the limited light absorption wavelength range and persistent photocurrent (PPC) phenomenon. Numerous studies have attempted to improve the detectable light wavelength range and the PPC phenomenon. Here, recent studies on metal oxide phototransistors are reviewed, which have improved the range of light wavelengths and the PPC phenomenon by introducing an absorption layer of oxide or non-oxide hybrid structure. The materials of the absorption layer applied to absorb long-wavelength light are classified into oxides, chalcogenides, organic materials, perovskites, and nanodots. Finally, next-generation convergence studies combined with other research fields are introduced and future research directions are detailed.

SIMULTANEOUS ESTIMATION OF ASPIRIN AND OMEPRAZOLE IN LABORATORY SAMPLE BY DIFFERENT UV SPECTROPHOTOMETRIC TECHNIQUES

The aim of the present work was to develop simple, precise and economic UV- spectrophotometric methods for the simultaneous estimation of aspirin and omeprazole in a laboratory sample. The absorbance maxima (λmax) for detection of aspirin and omeprazole were selected as 274 nm and 302 nm, respectively, for simultaneous equation method while wavelength range for detection of aspirin and omeprazole were selected as 270 nm - 276 nm and 300 nm - 305 nm, respectively for area under curve method. Absorbance ratio method uses the ratio of absorbances at two selected wavelengths, one which is an isoabsorptive point and other being the λ max of one of the two components. From the overlay spectra of two drugs, it is evident that aspirin and omeprazole show an isoabsorptive point at 238.6 nm. In zero crossing first derivative spectrophotometry, aspirin showed zero crossing point at 301nm and omeprazole showed zero crossing point at 274nm. Linearity for aspirin was between 25- 125 μg/mL and omeprazole it was 3-15 μg/mL. These methods were successfully applied for estimation of aspirin and omeprazole in the laboratory sample.

Determination of phenylethyl alcohol in rose dew by micellar capillary electrochromatography

Rose dew has emerged as one of the superior products in the field of skin care after rose essential oil. However, at present, there is no quality control standard for rose dew. To this end, a micellar capillary electrochromatography (MEKC) method was developed to determine the amount of phenylethyl alcohol, one of the characteristic components of rose dew. The factors affecting the MEKC performance, including the concentrations of borax and sodium dodecyl sulfate (SDS), separation voltage, injection conditions, and detection conditions, were optimized. The capillary length was selected as 48.5 cm, and the effective capillary length was 40 cm. The new capillary was treated successively with methanol, sodium hydroxide (NaOH) solution, and deionized water for 10 min, 60 min, and 30 min when it was used for the first time. Under the running process, the capillary was flushed with 0.5 mol/L NaOH, deionized water, and running buffer solution (10 mmol/L Na2B2O7+15 mmol/L SDS) for 2 min, 2 min, and 3 min each. Between two runs, the capillary was balanced with the running buffer solution for 5 min. Sample injection was performed under a pressure of 5 kPa for 5 s. The separation voltage was set at a positive value of 20 kV. The capillary was maintained at a constant temperature of 20 ℃ using an air refrigeration system. A photo-diode array (PDA) detector with a detection wavelength range of 190-600 nm was coupled to the capillary for monitoring the target molecule, and the optimum wavelength was fixed at 208 nm. Under the optimized conditions, the rose dew samples could be separated and detected within 7 min. The linearity for phenylethyl alcohol detection was found to be 0.50 to 1000 mg/L, with a correlation coefficient (r2) of 0.9990. The limit of detection (LOD, S/N=3) and limit of quantification (LOQ, S/N=10) of the method were calculated to be 0.091 mg/L and 0.35 mg/L, respectively. The accuracy was tested by spiking phenylethyl alcohol into the rose dew samples at mass concentrations of 10, 100, and 500 g/L. The recoveries ranged from 98.1% to 102.7%, and the relative standard deviations (RSD; n=3) were less than 2.8%. This MEKC method is fast, sensitive, inexpensive, and highly effective for the determination of phenylethyl alcohol in rose dew. With the advantages of good stability, anti-matrix interference ability, and high sensitivity, this method represents a simple, sensitive, accurate, and robust strategy for the quality control of rose dew and related products.

High-sensitivity fiber-optic humidity sensor based on microfiber overlaid with niobium disulfide

Humidity sensors by exploiting transition metal dichalcogenides have attracted enormous attention in various applications. Here, we demonstrate a high-sensitivity fiber-optic humidity sensor based on microfibers overlaid with niobium disulfide (NbS2). Our experimental results show that this type of humidity sensor has high sensitivity, and good repeatability and reversibility. In the RH range of 72–97%, a sensitivity of up to 1.05 dB/RH% and an excellent linearity correlation of 99.5% were achieved. The transmission spectrum of the humidity sensor indicates that this sensor has a wide wavelength detection range from 1530 to 1565 nm. We applied the sensor to monitor human breath with a fast response. We anticipate that the humidity sensor will be useful for the environmental monitoring, food production, and semiconductor industries.