Optical and Material Characteristics of MoS2/Cu2O Sensor for Detection of Lung Cancer Cell Types in Hydroplegia.

In this study, n-type MoS2 monolayer flakes are grown through chemical vapor deposition (CVD), and a p-type Cu2O thin film is grown via electrochemical deposition. The crystal structure of the grown MoS2 flakes is analyzed through transmission electron microscopy. The monolayer structure of the MoS2 flakes is verified with Raman spectroscopy, multiphoton excitation microscopy, atomic force microscopy, and photoluminescence (PL) measurements. After the preliminary processing of the grown MoS2 flakes, the sample is then transferred onto a Cu2O thin film to complete a p-n heterogeneous structure. Data are confirmed via scanning electron microscopy, SHG, and Raman mapping measurements. The luminous energy gap between the two materials is examined through PL measurements. Results reveal that the thickness of the single-layer MoS2 film is 0.7 nm. PL mapping shows a micro signal generated at the 627 nm wavelength, which belongs to the B2 excitons of MoS2 and tends to increase gradually when it approaches 670 nm. Finally, the biosensor is used to detect lung cancer cell types in hydroplegia significantly reducing the current busy procedures and longer waiting time for detection. The results suggest that the fabricated sensor is highly sensitive to the change in the photocurrent with the number of each cell, the linear regression of the three cell types is as high as 99%. By measuring the slope of the photocurrent, we can identify the type of cells and the number of cells.

All-reflective RGB LED flashlight design for effective color mixing.

Red, green, and blue (RGB) light-emitting diode (LED) is a narrow-band light source that can improve visual contrast, and thus, can be used for special illumination. In this study, three RGB LEDs, each provided with two reflective mirrors, are used to design an all-reflective color temperature-adjustable LED flashlight. The LED flashlight features an adjustable color temperature ranging from 2000 K to 6500 K, a uniformity of illuminance of 0.68, an average difference of uniformity of approximately 25%, and a color uniformity of 0.0042.

Lung cancer cells detection by a photoelectrochemical MoS2 biosensing chip.

This research aims to explore the potential application of this approach in the production of biosensor chips. The biosensor chip is utilized for the identification and examination of early-stage lung cancer cells. The findings of the optical microscope were corroborated by the field emission scanning electron microscopy, which provided further evidence that the growth of MoS2 is uniform and that there is minimal disruption in the electrode, hence minimizing the likelihood of an open circuit creation. Furthermore, the bilayer structure of the produced MoS2 has been validated through the utilization of Raman spectroscopy. A research investigation was undertaken to measure the photoelectric current generated by three various types of clinical samples containing lung cancer cells, specifically the CL1, NCI-H460, and NCI-H520 cell lines. The findings from the empirical analysis indicate that the coefficient of determination (R-Square) for the linear regression model was approximately 98%. Furthermore, the integration of a double-layer MoS2 film resulted in a significant improvement of 38% in the photocurrent, as observed in the device's performance.

Ultrafast ablation dynamics in fused silica with a white light beam probe.

This study demonstrates a non-degenerate pump-probe spectroscopy with a white light beam probe based on a regenerative, amplified, mode-locked, Ti:sapphire laser. This white light beam probe is produced by supercontinuum generation of sapphire crystal after ultra-short pulse excitation. To implement the pump-probe experimental operation, the ablation dynamics with and without fresh spot measurements in fused silica samples are demonstrated. Combining the time-resolved differential reflection profiles in the white light range and X-ray photoelectron spectroscopy spectra of fused silica, the following ablation dynamics processes can be observed: Without fresh spot measurements, once carriers are excited, first, the three absorption bands of the intrinsic defect sites are observed within 750 fs. Then, a fast recovery is observed. This recovery comes from defect-trapped carriers excited to conduction bands through hot-carrier-phonon interactions. In the final step, a rapidly rising signal is observed after 800 fs. This signal rise comes from the creation of free-electron plasma, the density of which increases with increasing excitation energy accumulation. With fresh spot measurements, time delay of carrier dynamics among the three bands can be identified clearly within 750 fs. The intrinsic defect sites of fused silica play the key role during the ultrafast laser ablation process.

Suppression of surface recombination in surface plasmon coupling with an InGaN/GaN multiple quantum well sample.

Temperature-dependent picosecond non-degenerate four-wave-mixing experiments were performed to explore the carrier dynamics in an InGaN/GaN multiple quantum well sample, in which light emission enhancement with surface plasmon (SP) coupling has been identified. In the time-resolved photoluminescence results, we can identify the faster carrier decay time of the sample with surface plasmon coupling. The faster decay time is due to this sample's ability to create additional channels for effective carrier recombination. In the four-wave-mixing results, a slower grating decay time of the sample with surface plasmon coupling was measured. The diffusion coefficients and surface recombination velocities of photo-created carriers were estimated by modeling the decay rate of transient grating signals. For the sample for which surface plasmon coupling exists, smaller diffusion coefficients and slower surface recombination velocities can be estimated when the temperatures are above 150 K. The carriers coupling with some SP modes is not the only mechanism contributing to emission enhancement. In the InGaN/GaN multiple quantum well sample, surface recombination suppressed by SP coupling is another factor for increased light emission efficiency.

Characteristics of P-Type and N-Type Photoelectrochemical Biosensors: A Case Study for Esophageal Cancer Detection.

P-type and N-type photoelectrochemical (PEC) biosensors were established in the laboratory to discuss the correlation between characteristic substances and photoactive material properties through the photogenerated charge carrier transport mechanism. Four types of human esophageal cancer cells (ECCs) were analyzed without requiring additional bias voltage. Photoelectrical characteristics were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis reflectance spectroscopy, and photocurrent response analyses. Results showed that smaller photocurrent was measured in cases with advanced cancer stages. Glutathione (L-glutathione reduced, GSH) and Glutathione disulfide (GSSG) in cancer cells carry out redox reactions during carrier separation, which changes the photocurrent. The sensor can identify ECC stages with a certain level of photoelectrochemical response. The detection error can be optimized by adjusting the number of cells, and the detection time of about 5 min allowed repeated measurement.

Dependence of surface atomic arrangement of titanium dioxide on metallic nanowire nucleation by thermally assisted photoreduction.

Through studying the optical, electrical and photocatalytic properties of anatase TiO(2) films with different preferred orientations, (101) and (004), this study clarified the relationship between the formation of metallic nanowires by thermally assisted photoreduction process and surface atomic bonding conditions of TiO(2). Experimental results show that the (101) anatase films which yielded much more Ag nanowires than the (004) oriented films and exhibited more complex superficial atomic bonding, which could be demonstrated by the Gaussian bands in photoluminescence spectra. This might lead to higher carrier concentration and mobility, as well as longer life time for photo-exited electrons and consequently a greater photocatalytic activity for reducing metallic ions. The fact that the anatase (101) surface acted as the preferred nucleation sites for Ag nanowires was supported by high resolution transmission electron microscopy lattice image of a TiO(2) nanofiber where an Ag nanowire was grown.

Co-dosing Ozone and Deionized Water as Oxidant Precursors of ZnO Thin Film Growth by Atomic Layer Deposition.

Characteristics of atomic layer deposition (ALD)-grown ZnO thin films on sapphire substrates with and without three-pulsed ozone (O3) as oxidant precursor and post-deposition thermal annealing (TA) are investigated. Deposition temperature and thickness of ZnO epilayers are 180 °C and 85 nm, respectively. Post-deposition thermal annealing is conducted at 300 °C in the ambience of oxygen (O2) for 1 h. With strong oxidizing agent O3 and post-deposition TA in growing ZnO, intrinsic strain and stress are reduced to 0.49% and 2.22 GPa, respectively, with extremely low background electron concentration (9.4 × 1015 cm-3). This is originated from a lower density of thermally activated defects in the analyses of thermal quenching of the integrated intensity of photoluminescence (PL) spectra. TA further facilitates recrystallization forming more defect-free grains and then reduces strain and stress state causing a remarkable decrease of electron concentration and melioration of surface roughness.

Enhancing carrier transport and carrier capture with a good current spreading characteristic via graphene transparent conductive electrodes in InGaN/GaN multiple-quantum-well light emitting diodes.

In this work, InGaN/GaN multiple-quantum-wells light-emitting diodes with and without graphene transparent conductive electrodes are studied with current-voltage, electroluminescence, and time-resolved electroluminescence (TREL) measurements. The results demonstrate that the applications of graphene electrodes on LED devices will spread injection carriers more uniformly into the active region and therefore result in a larger current density, broader luminescence area, and stronger EL intensity. In addition, the TREL data will be further analyzed by employing a 2-N theoretical model of carrier transport, capture, and escape processes. The combined experimental and theoretical results clearly indicate that those LEDs with graphene transparent conductive electrodes at p-junctions will have a shorter hole transport time along the lateral direction and thus a more efficient current spreading and a larger luminescence area. In addition, a shorter hole transport time will also expedite hole capture processes and result in a shorter capture time and better light emitting efficiency. Furthermore, as more carrier injected into the active regions of LEDs, thanks to graphene transparent conductive electrodes, excessive carriers need more time to proceed carrier recombination processes in QWs and result in a longer carrier recombination time. In short, the LED samples, with the help of graphene electrodes, are shown to have a better carrier transport efficiency, better carrier capture efficiency, and more electron-hole recombination. These research results provide important information for the carrier transport, carrier capture, and recombination processes in InGaN/GaN MQW LEDs with graphene transparent conductive electrodes.

Intelligent Identification of MoS2 Nanostructures with Hyperspectral Imaging by 3D-CNN.

Increasing attention has been paid to two-dimensional (2D) materials because of their superior performance and wafer-level synthesis methods. However, the large-area characterization, precision, intelligent automation, and high-efficiency detection of nanostructures for 2D materials have not yet reached an industrial level. Therefore, we use big data analysis and deep learning methods to develop a set of visible-light hyperspectral imaging technologies successfully for the automatic identification of few-layers MoS2. For the classification algorithm, we propose deep neural network, one-dimensional (1D) convolutional neural network, and three-dimensional (3D) convolutional neural network (3D-CNN) models to explore the correlation between the accuracy of model recognition and the optical characteristics of few-layers MoS2. The experimental results show that the 3D-CNN has better generalization capability than other classification models, and this model is applicable to the feature input of the spatial and spectral domains. Such a difference consists in previous versions of the present study without specific substrate, and images of different dynamic ranges on a section of the sample may be administered via the automatic shutter aperture. Therefore, adjusting the imaging quality under the same color contrast conditions is unnecessary, and the process of the conventional image is not used to achieve the maximum field of view recognition range of ~1.92 mm2. The image resolution can reach ~100 nm and the detection time is 3 min per one image.

Electrochemical formation of crooked gold nanorods and gold networked structures by the additive organic solvent.

Crooked gold nanorods (CGNRs) and gold network structures are fabricated using a simple electrochemical approach. The growth solution is prepared by surfactant solution as micelle templates with isopropanol (IPA) solvent. The shape of crooked nanorods and networks structure depend on the amount of added IPA solvent. To investigate the influence of isopropanol solvent on the CGNRs, the amount of IPA was varied in the range from 0.05 to 0.2 mL. It was found that the aspect ratios (gamma) of CGNRs were in the range from 1.06 to 1.46, and the UV-vis absorption measurement revealed a pronounced red-shift of the surface plasmon resonance (SPR) band from 532 to 560 nm. High-resolution transmission electron microscopy (HRTEM) showed that the formation of crooked nanorod structure was induced by aggregation of many small gold nuclei between the several large gold nanoparticles during growth, causing the small gold nuclei to link the gold nanoparticles. The CGNRs have a polycrystalline structure via the analysis from selected-area electron diffraction (SAED).

Efficient Carrier Injection, Transport, Relaxation, and Recombination Associated with a Stronger Carrier Localization and a Low Polarization Effect of Nonpolar m-plane InGaN/GaN Light-Emitting Diodes.

Based on time-resolved electroluminescence (TREL) measurement, more efficient carrier injection, transport, relaxation, and recombination associated with a stronger carrier localization and a low polarization effect in a nonpolar m-plane InGaN/GaN light emitting diode (m-LED), compared with those in a polar c-LED, are reported. With a higher applied voltage in the c-LED, decreasing response time and rising time improve device performance, but a longer recombination time degrades luminescence efficiency. By using an m-LED with a stronger carrier localization and a low polarization effect, shorter response, rising, and recombination times provide more efficient carrier injection, transport, relaxation, and recombination. These advantages can be realized for high-power and high-speed flash LEDs. In addition, with a weaker carrier localization and a polarization effect in the c-LED, the slower radiative and faster nonradiative decay rates at a larger applied voltage result in the slower total decay rate and the lower luminescence efficiency. For the m-LED at a higher applied voltage, a slow decreasing nonradiative decay rate is beneficial to device performance, while the more slowly decreasing and overall faster radiative decay rate of the m-LED than that of the c-LED demonstrates that a stronger carrier localization and a reduced polarization effect are efficient for carrier recombination. The resulting recombination dynamics are correlated with the device characteristics and performance of the c- and m-LEDs.

Growth and characterization of textured well-faceted ZnO on planar Si(100), planar Si(111), and textured Si(100) substrates for solar cell applications.

In this work, textured, well-faceted ZnO materials grown on planar Si(100), planar Si(111), and textured Si(100) substrates by low-pressure chemical vapor deposition (LPCVD) were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and cathode luminescence (CL) measurements. The results show that ZnO grown on planar Si(100), planar Si(111), and textured Si(100) substrates favor the growth of ZnO(110) ridge-like, ZnO(002) pyramid-like, and ZnO(101) pyramidal-tip structures, respectively. This could be attributed to the constraints of the lattice mismatch between the ZnO and Si unit cells. The average grain size of ZnO on the planar Si(100) substrate is slightly larger than that on the planar Si(111) substrate, while both of them are much larger than that on the textured Si(100) substrate. The average grain sizes (about 10-50 nm) of the ZnO grown on the different silicon substrates decreases with the increase of their strains. These results are shown to strongly correlate with the results from the SEM, AFM, and CL as well. The reflectance spectra of these three samples show that the antireflection function provided by theses samples mostly results from the nanometer-scaled texture of the ZnO films, while the micrometer-scaled texture of the Si substrate has a limited contribution. The results of this work provide important information for optimized growth of textured and well-faceted ZnO grown on wafer-based silicon solar cells and can be utilized for efficiency enhancement and optimization of device materials and structures, such as heterojunction with intrinsic thin layer (HIT) solar cells.

Dependence of lattice strain relaxation, absorbance, and sheet resistance on thickness in textured ZnO@B transparent conductive oxide for thin-film solar cell applications.

The interplay of surface texture, strain relaxation, absorbance, grain size, and sheet resistance in textured, boron-doped ZnO (ZnO@B), transparent conductive oxide (TCO) materials of different thicknesses used for thin film, solar cell applications is investigated. The residual strain induced by the lattice mismatch and the difference in the thermal expansion coefficient for thicker ZnO@B is relaxed, leading to an increased surface texture, stronger absorbance, larger grain size, and lower sheet resistance. These experimental results reveal the optical and material characteristics of the TCO layer, which could be useful for enhancing the performance of solar cells through an optimized TCO layer.

Effects of Thickness of a Low-Temperature Buffer and Impurity Incorporation on the Characteristics of Nitrogen-polar GaN.

In this study, effects of the thickness of a low temperature (LT) buffer and impurity incorporation on the characteristics of Nitrogen (N)-polar GaN are investigated. By using either a nitridation or thermal annealing step before the deposition of a LT buffer, three N-polar GaN samples with different thicknesses of LT buffer and different impurity incorporations are prepared. It is found that the sample with the thinnest LT buffer and a nitridation step proves to be the best in terms of a fewer impurity incorporations, strong PL intensity, fast mobility, small biaxial strain, and smooth surface. As the temperature increases at ~10 K, the apparent donor-acceptor-pair band is responsible for the decreasing integral intensity of the band-to-band emission peak. In addition, the thermal annealing of the sapphire substrates may cause more impurity incorporation around the HT-GaN/LT-GaN/sapphire interfacial regions, which in turn may result in a lower carrier mobility, larger biaxial strain, larger bandgap shift, and stronger yellow luminescence. By using a nitridation step, both a thinner LT buffer and less impurity incorporation are beneficial to obtaining a high quality N-polar GaN.

Large-area few-layered graphene film determination by multispectral imaging microscopy.

A multispectral imaging method for the rapid and accurate identification of few-layered graphene using optical images is proposed. Commonly rapid identification relies on optical interference effects which limits the choice of substrates and light sources. Our method is based on the comparison of spectral characteristics with principle components from a database which is populated by correlation of micro-Raman registration, spectral characteristics, and optical microscopy. Using this approach the thickness and extent of different graphene layers can be distinguished without the contribution of the optical interference effects and allows characterization of graphene on glass substrates. The high achievable resolution, easy implementation and large scale make this approach suitable for the in-line metrology of industrial graphene production.

Numerical simulations of the current-matching effect and operation mechanisms on the performance of InGaN/Si tandem cells.

Numerical simulations are conducted to study the current-matching effect and operation mechanisms in and to design the optimized device structure of InGaN/Si tandem cells. The characteristics of short circuit current density (J sc), open circuit voltage (V oc), fill factor (FF), and conversion efficiency (η) of InGaN/Si tandem cells are determined by the current-matching effect. The similar trend of η to that of J sc shows that J sc is a dominant factor in determining the performance of InGaN/Si tandem cells. In addition, the combined effects of the J sc, V oc, and FF lead to an optimized η in the medium-indium, [Formula: see text], InGaN/Si tandem cell. At [Formula: see text], the J sc of the InGaN subcell is equal to that of the Si subcell such that an InGaN/Si tandem cell reaches the current matching condition to operate at the maximum power point. Similar to the J sc and FF, the η for low- [Formula: see text] and high-In [Formula: see text] InGaN/Si tandem cells are InGaN- and Si subcell-limited, respectively. Furthermore, the p- and n-layer thicknesses, indium content, and position of depletion region of InGaN subcell should be adjusted to reapportion the light between the two subcells and to achieve the maximum conversion efficiency. With appropriate thicknesses of p- and n-InGaN, In0.5-0.6Ga0.5-0.4 N/Si tandem cells can exhibit as high as approximately 34% to 36.5% conversion efficiency, demonstrating that a medium-indium InGaN/Si tandem cell results in a high-efficiency solar cell. Simulation results determine that the current-matching effect and operation mechanisms of InGaN/Si tandem cells can be utilized for efficiency enhancement through the optimized device structures.