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[Display omitted] • PAMAs with ultrahigh pH response were recyclable. • PAMAs were used to recover cellulase with a narrow pH range. • Cellulase was recovered by co-precipitating with PAMAs. • PAMAs improved cellulase recovery effect of substrate re-adsorption. • 50% of cellulase amount was saved in CCR hydrolyzate with adding PAMA-1. The high cost of the enzymatic hydrolysis of lignocellulose is a major problem for the industrialization of lignocellulose-based sugar platform technology. Cellulase recovery is a vital approach to reduce the enzymatic hydrolysis cost. In this study, ultrahigh pH-responsive copolymers (PAMAs) were obtained from methacrylamide, sodium methacrylate and [2-(methacryloyloxy)ethyl]-trimethylammonium chloride. A PAMA addition method coupled with substrate reabsorption was used to efficiently recover cellulase in a narrow pH range. The enzymatic hydrolysis system of corncob resides (pH = 5.0) was supplemented with 1.0 g/L PAMA-1. After hydrolysis, the PAMAs coprecipitate with cellulase when adjusting the pH value of the hydrolysate to 4.4. When coupled with substrate reabsorption, 50 % of the cellulase was recovered. This method therefore represents a feasible solution to reduce the high enzymatic hydrolysis cost of the industrialization of lignocellulose-based sugar platform technology. [ABSTRACT FROM AUTHOR]

We have conducted an investigation on the quasinormal spectrum of electromagnetic perturbation surrounding the Bardeen black hole which is enveloped by perfect fluid dark matter. With the metric at hand, the influence of the dark matter parameter α and the magnetic charge g on the horizon radii of black hole are studied. It turns out that for fixed g, both the Cauchy horizon and event horizon radius increase with the decrease of α . But, with the increase of g, the Cauchy horizon radius increases while the event horizon radius decreases. Applying the sixth-order WKB approximation method, we have assessed the complex frequencies of the quasinormal modes. Our findings reveal that the oscillation frequency and decay rate of the electromagnetic perturbation are intensified with the augmentation of the dark matter parameter α and the spherical harmonic index l respectively. Furthermore, as the magnetic charge g increases, the real component of the quasinormal modes frequencies undergoes escalation, while the imaginary component experiences a decrease. Notably, the variation in α and g demonstrates that the imaginary components exhibit an almost linear correlation with the real components. These phenomena serve to distinguish the Bardeen black hole surrounded solely by perfect fluid dark matter. [ABSTRACT FROM AUTHOR]

The cost of lignocellulosic enzymatic hydrolysis was reduced by enhancing enzymatic hydrolysis and recycling cellulase. Lignin-grafted quaternary ammonium phosphate (LQAP) with sensitive temperature and pH response, was obtained by grafting quaternary ammonium phosphate (QAP) onto enzymatic hydrolysis lignin (EHL). LQAP dissolved under the hydrolysis condition (pH 5.0, 50 °C) and enhanced the hydrolysis. After hydrolysis, LQAP and cellulase co-precipitated by the hydrophobic binding and electrostatic attraction, when lowering pH to 3.2, and cooling to 25 °C. LQAP had significant performances of pH-UCST response, enzymatic hydrolysis enhancement and cellulase recovery at the same time. When 3.0 g/L LQAP-100 was added to the system of corncob residue, SED@48 h increased from 62.6 % to 84.4 %, and 50 % of amount of cellulase was saved. Precipitation of LQAP at low temperature was mainly attributed to the salt formation of positive and negative ions in QAP; LQAP enhanced the hydrolysis for its ability to decrease the ineffective adsorption of cellulase by forming a hydration film on lignin and through the electrostatic repulsion. In this work, a lignin amphoteric surfactant with temperature response, was used to enhance hydrolysis and recover cellulase. This work will provide a new idea for reducing the cost of lignocellulose-based sugar platform technology, and high-value utilization of industrial lignin. A sensitive pH-UCST-type LQAP was used to significantly enhance lignocellulosic enzymatic hydrolysis and efficiently recycle cellulase, and the process is sustainable while realizing the value-added utilization of industrial lignin. [Display omitted] [ABSTRACT FROM AUTHOR]

This Letter demonstrates a 1500-V enhancement-mode (E-mode) GaN-based high electron mobility transistors (HEMTs) based on the recessed-free structure. The E-mode GaN-based HEMTs fabricated based on the ultrathin barrier epitaxial structure have a small gate interface traps density (Dit) of ∼1012 cm−2 eV−1, which can be attributed to the avoidance of AlGaN etching in the gate region. Meanwhile, a small threshold voltage (Vth) hysteresis of 19 mV and a small subthreshold swing of 101 mV/dec are achieved in the fabricated devices with a Vth around 1.91 V. A small Vth shift of 0.05 V was achieved under positive gate voltage stress, indicating that the devices have good Vth stability. Meanwhile, a high yield of more than 90% has been achieved on 6-in. wafer, which provides a good scheme for the commercialization of E-mode HEMTs. [ABSTRACT FROM AUTHOR]

Robust and reliable gate scheme is crucial in developing the enhancement-mode (E-mode) AlGaN/GaN metal–insulator–semiconductor (MIS)-high electron mobility transistors (HEMTs). This work reports on a method of mixed oxygen and fluorine plasma pretreatment combined with selected bi-layer gate dielectrics to improve the performances of partially recessed-gate MIS-HEMTs. The fabricated E-mode HEMTs exhibit significantly boosted threshold voltage of 2.5 V and gate breakdown voltage of 26 V, as well as improved device reliability on 6-in wafer under both bias and temperature stresses. Remarkably reduced ${V}_{\text {th}}$ shift is found even at 250 °C high temperature. Furthermore, measurements on gate breakdown lifetime show a ten-year lifetime of the fabricated devices when the gate bias is kept below 13.1 V which demonstrates a promising scheme in fabricating the E-mode HEMT products. [ABSTRACT FROM AUTHOR]

Buffer related electron trapping and hot electron injection are responsible for Ron degradation in devices, but the effects of substrate termination are still uncertain. In this work, both positive and negative substrate bias are applied to investigate the different vertical trapping mechanisms in 650 V gallium nitride (GaN) power devices. Ron shows an instant and significant increase under vertical bias stress, and the magnitude of downward buffer electron trapping induced Ron increase is relatively larger than that induced by upward trapping. Additionally, the substrate floated and grounded GaN devices are also submitted to both off-state and semi-on-state stresses to investigate the effects of substrate termination on hot electron injection induced Ron increase. The intensity of the upward electron trapping increases faster with temperature resulting in a higher Ron increase than the downward situation. The hot electron effect is only obvious when the substrate is grounded, suggesting that the main injection destination is not in the buffer. The substrate floated device exhibits a lower Ron increase after both off-state and semi-on-state stresses at elevated temperatures. Substrate floated packages are suggested to ensure reliable dynamic performance of device, especially for high voltage application design. [ABSTRACT FROM AUTHOR]

In this work, we performed an investigation on the electrical characteristics of the interfaces of SiON/AlGaN and SiON/GaN by fabricating a partially gate-recessed metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT) and a fully gate-recessed metal-insulator-semiconductor field-effect transistor (MIS-FET). The fabricated MIS-HEMT exhibits a smaller static on-resistance (Ron) of 12.7 Ω · mm, while the MIS-FET achieves the normally-off operation. As a result of over-etching in the gate trench, a higher trap state density of 2 × 1013 cm−2eV−1 at the SiON/GaN interface in comparison to SiON/AlGaN interface (8 × 1012 cm−2eV−1), leading to a more obvious degradation of subthreshold swing, was extracted after performing the high temperature IDS−VGS tests. In addition, compared with the MIS-FET, the traps distributed at the SiON/AlGaN interface are found to be located at a deeper energy level, which make the device more stress sensitive and can cause a greater threshold voltage (Vth) shift in the drain-bias stress measurement. The drain-bias stress at off-state increases the ionized trap density and makes the ionized traps unrecoverable within 1000 s in the MIS-HEMT. This work reveals the different properties of traps states at the SiON/AlGaN and SiON/GaN interfaces, and their effects on the device reliability. [ABSTRACT FROM AUTHOR]

In this work, gate-first technology was developed in an AlGaN/GaN high-electron-mobility transistor (HEMT) based on a high-quality in situ SiNx gate dielectric, targeting for high-stability power applications. The effect of the high-temperature annealing process on the Ni/SiNx gate stack was systematically investigated. Almost the same basic electrical performances were observed from gate-first and gate-last processed devices. Furthermore, the annealing-like effect on the gate-stack-located trap states was revealed in gate-first devices with obvious enhancement in threshold voltage stability, validating the high compatibility of the in situ SiNx technology with the gate-first GaN HEMT technology. [ABSTRACT FROM AUTHOR]

Abstract: A high-speed humidity sensor based on a nanostructured chiral sculptured thin film (CSTF) was fabricated and tested. The sensing principle is based on the shift of the central wavelength of the circular Bragg regime of the CSTF caused by adsorption and desorption of water vapor in the void regions of the CSTF. Spectral changes due to varying relative-humidity (RH) levels in the ambient environment were measured by a spectrometer. The CSTF sensor exhibited excellent reversibility and reproducibility from 40% to 100% RH. Moreover, the adsorption time of the sensor was measured to be as low as ∼140ms, making it promising for many high-speed humidity-sensing applications. [Copyright &y& Elsevier]