A study on a broadband photodetector based on hybrid 2D copper oxide/reduced graphene oxide.

These days, photodetectors are a crucial part of optoelectronic devices, ranging from environmental monitoring to international communication systems. Therefore, fabricating these devices at a low cost but obtaining high sensitivity in a wide range of wavelengths is of great interest. This report introduces a simple solution-processed hybrid 2D structure of CuO and rGO for broadband photodetector applications. Particularly, 2D CuO acts as the active material, absorbing light to generate electron-hole pairs, while 2D rGO plays the role of a transport layer, driving charge carriers between two electrodes. Our device exhibits remarkable sensitivity to a wide wavelength range from 395 nm to 945 nm (vis-NIR region). Interestingly, our devices' responsivity and photoconductive gain were calculated (under 395 nm wavelength excitation) to be up to 8 mA W-1 and 28 fold, respectively, which are comparable values with previous publications. Our hybrid 2D structure between rGO and CuO enables a potential approach for developing low-cost but high-performance optoelectronic devices, especially photodetectors, in the future.

A visible-light photodetector based on heterojunctions between CuO nanoparticles and ZnO nanorods.

Optoelectronic devices have various applications in medical equipment, sensors, and communication systems. Photodetectors, which convert light into electrical signals, have gained much attention from many research teams. This study describes a low-cost photodetector based on CuO nanoparticles and ZnO nanorods operating in a wide range of light wavelengths (395, 464, 532, and 640 nm). Particularly, under 395 nm excitation, the heterostructure device exhibits high responsivity, photoconductive gain, detectivity, and sensitivity with maximum values of 1.38 A·W-1, 4.33, 2.58 × 1011 Jones, and 1934.5% at a bias of 2 V, respectively. The sensing mechanism of the p-n heterojunction of CuO/ZnO is also explored. Overall, this study indicates that the heterostructure of CuO nanoparticles and ZnO nanorods obtained via a simple and cost-effective synthesis process has great potential for optoelectronic applications.

Developing low-cost nanohybrids of ZnO nanorods and multi-shaped silver nanoparticles for broadband photodetectors.

Photodetectors are essential elements for various applications like fiber optic communication systems, biomedical imaging, and so on. Thus, improving the performance and reducing the material costs of photodetectors would act as a motivation toward the future advancement of those applications. This study introduces the development of a nanohybrid of zinc oxide nanorods (ZnONRs) and multi-shaped silver nanoparticles MAgNPs through a simple solution process; in which ZnONRs are hybridized with MAgNPs to enable visible absorption through the surface plasmon resonance (SPR) effect. The photodetector based on ZnONRs/MAgNPs is responsive to visible light with representative wavelengths of 395, 464, 532 and 640 nm, and it exhibits high responsivity (R), photoconductive gain (G) and detectivity (D). The maximum R is calculated from the fitting curve of the responsivity-power relation with the value of 5.35 × 103 (mA W-1) at 395 nm excitation. The highest G and D reach 8.984 and 3.71 × 1010 Jones at that wavelength. This reveals the promise of our innovative broadband photodetector for practical usage.

Functionalized silver nanoparticles for SERS amplification with enhanced reproducibility and for ultrasensitive optical fiber sensing in environmental and biochemical assays.

Plasmonic sensors have broad application potential in many fields and are promising to replace most bulky sensors in the future. There are various method-based chemical reduction processes for silver nanoparticle production with flexible structural shapes due to their simplicity and rapidity in nanoparticle fabrication. In this study, self-assembled silver nanoparticles (Ag NPs) with a plasmon peak at 424 nm were successfully coated onto -NH2-functionalized glass and optical fiber sensors. These coatings were rapidly produced via two denaturation reactions in plasma oxygen, respectively, and an APTES ((3-aminopropyl)triethoxysilane) solution was shown to have high strength and uniformity. With the use of Ag NPs for surface-enhanced Raman scattering (SERS), excellent results and good stability with the detection limit up to 10-10 M for rhodamine B and 10-8 M for methylene blue, and a signal degradation of only ∼20% after storing for 30 days were achieved. In addition, the optical fiber sensor with Ag NP coatings exhibited a higher sensitivity value of 250 times than without coatings to the glycerol solution. Therefore, significant enhancement of these ultrasensitive sensors demonstrates promising alternatives to cumbersome tests of dye chemicals and biomolecules without any complicated process.

A stretchable ultraviolet-to-NIR broad spectral photodetector using organic-inorganic vertical multiheterojunctions.

Stretchable broadband photodetectors (PDs) are attractive for applications in wearable optoelectronics and personal healthcare. However, the development of stretchable broadband PDs is limited by difficulties in obtaining materials, designing device structures, and finding reliable fabrication processes. Here, we report stretchable broadband PDs by forming organic-inorganic vertical multiheterojunctions on a three-dimensionally micro-patterned stretchable substrate (3D-MPSS). The stress-adaptable 3D-MPSS structure allows all layers of the PD coated on it to sustain tensile strains. Generation of photovoltage in the vertical hybrid structure of PbS quantum dots/ZnO nanorods as a photo-responsive material on poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) as a transport channel is considred to be the mechanism of the device response to UV-Vis-NIR. The fabricated PDs present responsivity to UV (365 nm), Vis (565 nm and 660 nm), and NIR (880 nm and 970 nm) light, as well as reliable electrical performance under applied stretching up to 30%.

Improved Synthesis of Ag/SiO2 Colloidal Nanocomposites and Their Antibacterial Activity Against Ralstonia solanacearum 15.

Ag/SiO2 colloidal nanocomposites (NCs) were prepared through the semi-continuous chemical reduction of silver ions on a silica surface; NaBH4 was used as a primary reducing agent, while carboxymethyl cellulose (CMC) served as a secondary reductant and a stabilizer at low temperature. Silver nanoparticles (AgNPs) of an average diameter of 3.89±0.18 nm were uniformly and densely dispersed on the SiO2 surface, forming 218.6-nm-sized Ag/SiO2 NCs. The zeta potential of the Ag/SiO2 NCs (-92.6 mV) was more negative than that of silica (-24 mV), indicating their high long-term stability. Furthermore, their proposed formation mechanism was confirmed via Fourier transform infrared spectroscopy. Then, the bactericidal effect of the Ag/SiO2 was evaluated based on their minimal inhibitory concentration (MIC) against Ralstonia solanacearum 15 (R. solanacearum 15); it was 62.5 ppm, much lower than that of conventional AgNPs (500 ppm). Therefore, these highly stable Ag/SiO2 colloidal NCs with more effective antibacterial activity than conventional AgNPs are a promising nanopesticide in agriculture.

Visible photodetector based on transition metal-doped ZnO NRs/PEDOT:PSS hybrid materials.

A hybrid Cu-doped ZnO nanorods (ZnO:Cu NRs)/poly(3,4 ethylene dioxythiophene)-polystyrene sulfonate (PEDOT:PSS)-based photodetector was fabricated using a simple hydrothermal method with pre-patterned silver electrodes. In the hybrid structure, PEDOT:PSS with high mobility acts as a carrier transport layer, while ZnO:Cu NRs with high visible absorption works as an "antenna" material to generate electron-hole pairs under light illumination. As a result, the devices exhibits a high response in visible light at a wavelength of 395 nm. The responsivity and photoconductive gain of the hybrid photodetector reached 0.33 A W-1 and 1.306, respectively, which is 1.36 times higher than those of Cu-doped ZnO NRs-based ones. The response and recovery times are improved, with values of 25.21 s and 42.01 s, respectively. The development of hybrid materials for visible photodetectors enables an innovative approach for future optoelectronic devices, especially optical sensors.

Development of children born from freeze-only versus fresh embryo transfer: follow-up of a randomized controlled trial.

OBJECTIVE: To compare the longer-term development outcomes in children born after freeze-only versus fresh embryo transfer (ET) in women with an ovulatory cycle. DESIGN: Long-term follow-up study (NCT04099784) of babies born alive after the first ET in a randomized controlled trial (RCT) comparing ongoing pregnancy and live birth rates after use of a freeze-only versus fresh ET strategy (NCT02471573). SETTING: Private clinic. PATIENT(S): Of 391 couples randomized to each treatment group in the RCT, 132 (97 singleton/35 twins) and 123 (95 singleton/28 twins) in the freeze-only and fresh ET groups had live birth; 113 parents (86%) from the freeze-only group (147 babies) and 99 (80%) from the fresh ET group (120 babies) returned questionnaires for this follow-up study. INTERVENTION(S): Use of a freeze-only or fresh ET strategy after controlled ovarian hyperstimulation with a follicle-stimulating hormone/gonadotropin-releasing antagonist protocol. MAIN OUTCOME MEASURE(S): Developmental status at ≥2 years after birth, determined using the Developmental Red Flags and Ages & Stages Third Edition (ASQ-3) Questionnaires. RESULT(S): Mean age of children at the end of follow-up was 37 months. Height (95.0 ± 6.1 vs. 95.7 ± 5.6 cm) and weight (14.9 ± 2.6 vs. 14.8 ± 2.6 kg) were similar in the freeze-only and fresh ET groups (results were similar when singletons and twins were analyzed separately). Overall, ASQ-3 scores for problem solving were significantly better in the freeze-only versus fresh ET group (overall: 53.6 ± 8.4 vs. 51.1 ± 10.2), with no significant between-group difference when singletons (52.3 ± 10.1 vs. 51.0 ± 9.9) and twins (55.0 ± 5.5 vs. 51.4 ± 11.1) were analyzed separately. Fine motor skills scores were numerically higher (with P values approaching statistical significance) in the freeze-only versus fresh ET group in the overall analysis (47.8 ± 11.6 vs. 44.9 ± 12.6) and twins (49.85 ± 8.72 vs. 43.93 ± 12.71), but not singletons (46.0 ± 13.4 vs. 45.4 ± 12.6). The overall proportion of children with abnormal ASQ-3 (6.8% vs. 8.3%) or abnormal Red Flags (5.4% vs. 6.7%) findings in the freeze-only and fresh ET groups was low and did not differ significantly between groups. CONCLUSION(S): These data provide physicians with additional information on which to base decisions about the relative merits of different approaches to infertility treatment. There do not appear to be any grounds for concern about worse outcomes after use of a freeze-only strategy. However, additional studies comparing childhood development after a freeze-only strategy, fresh ET, and natural cycles are needed before firm conclusions can be drawn.

An Omnidirectionally Stretchable Photodetector Based on Organic-Inorganic Heterojunctions.

Omnidirectionally stretchable photodetectors are limited by difficulties in designing material and fabrication processes that enable stretchability in multiaxial directions. Here, we propose a new approach involving an organic-inorganic p-n heterojunction photodetector comprised of free-standing ZnO nanorods grown on a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate transport layer coated on a three-dimensional micropatterned stretchable substrate containing bumps and valleys. This structure allows for efficient absorption of stretching strain. This approach allows the device to accommodate large tensile strain in all of the directions. The device behaves as a photogated p-n heterojunction photodetector in which current modulation was obtained by sensing the mechanisms that rely on photovoltage and photogating effects. The device exhibits a high photoresponse to UV light and reliable electrical performance under applied stretching in uniaxial and omniaxial directions. Furthermore, the device can be easily and conformally attached to a human wrist. This allowed us to investigate the response of the device to UV light during human activity.

Broadband light-absorption InGaN photoanode assisted by imprint patterning and ZnO nanowire growth for energy conversion.

In this research, an InGaN-based photoanode with a broadband light-absorption range from ultraviolet to green, patterned by imprint lithography and branched by ZnO nanowires, has been applied to water splitting. Over the solar spectrum range, the absorbance increases due to the scattering effect of the micro-structure compared to that of flat surface InGaN, which reaches a maximum of over 90% at 380 nm as ZnO nanowires are further employed in this novel photoanode. Consequently, the induced photocurrent density of the InGaN photoanode with a domelike structure and ZnO nanowires on the surface shows a remarkable enhancement of seven times that of the one with a flat surface. Further investigation indicates the wet-etching process for defect removal has an essential impact on photocurrent efficiency. This design demonstrates an innovative approach for water splitting.

High-Performance Flexible Ultraviolet (UV) Phototransistor Using Hybrid Channel of Vertical ZnO Nanorods and Graphene.

A flexible ultraviolet (UV) photodetector based on ZnO nanorods (NRs) as nanostructure sensing materials integrated into a graphene (Gr) field-effect transistor (FET) platform is investigated with high performance. Based on the negative shift of the Dirac point (VDirac) in the transfer characteristics of a phototransistor, high-photovoltage responsivity (RV) is calculated with a maximum value of 3 × 10(8) V W(-1). The peak response at a wavelength of ∼365 nm indicated excellent selectivity to UV light. The phototransistor also allowed investigation of the photocurrent responsivity (RI) and photoconductive gain (G) at various gate voltages, with maximum values of 2.5 × 10(6) A W(-1) and 8.3 × 10(6), respectively, at a gate bias of 5 V. The UV response under bending conditions was virtually unaffected and was unchanged after 10,000 bending cycles at a bending radius of 12 mm, subject to a strain of 0.5%. The attributes of high stability, selectivity, and sensitivity of this flexible UV photodetector based on a ZnO NRs/Gr hybrid FET indicate promising potential for future flexible optoelectronic devices.

Ultrahigh Responsivity in Graphene-ZnO Nanorod Hybrid UV Photodetector.

Ultraviolet (UV) photodetectors based on ZnO nanostructure/graphene (Gr) hybrid-channel field-effect transistors (FETs) are investigated under illumination at various incident photon intensities and wavelengths. The time-dependent behaviors of hybrid-channel FETs reveal a high sensitivity and selectivity toward the near-UV region at the wavelength of 365 nm. The devices can operate at low voltage and show excellent selectivity, high responsivity (RI ), and high photoconductive gain (G). The change in the transfer characteristics of hybrid-channel FETs under UV light illumination allows to detect both photovoltage and photocurrent. The shift of the Dirac point (V Dirac ) observed during UV exposure leads to a clearer explanation of the response mechanism and carrier transport properties of Gr, and this phenomenon permits the calculation of electron concentration per UV power density transferred from ZnO nanorods and ZnO nanoparticles to Gr, which is 9 × 10(10) and 4 × 10(10) per mW, respectively. The maximum values of RI and G infer from the fitted curves of RI and G versus UV intensity are 3 × 10(5) A W(-1) and 10(6) , respectively. Therefore, the hybrid-channel FETs studied herein can be used as UV sensing devices with high performance and low power consumption, opening up new opportunities for future optoelectronic devices.