Search

The selective transformation of lignin to value‐added biochemicals (e. g. phenolic acids) in high yields is incredibly challenging due to its structural complexity and many possible reaction pathways. Phenolic acids (PA) are key building blocks for various aromatic polymers, but the isolation of PAs from lignin is below 5 wt.% and requires harsh reaction conditions. Herein, we demonstrate an effective route to selectively convert lignin extracted from sweet sorghum and poplar into isolated PA in a high yield (up to 20 wt.% of lignin) using a low‐cost graphene oxide‐urea hydrogen peroxide (GO‐UHP) catalyst under mild conditions (<120 °C). The lignin conversion yield is up to 95 %, and the remaining low molecular weight organic oils are ready for aviation fuel production to complete lignin utilization. Mechanistic studies demonstrate that pre‐acetylation allows the selective depolymerization of lignin to aromatic aldehydes with a decent yield by GO through the Cα activation of β‐O‐4 cleavage. A urea‐hydrogen peroxide (UHP) oxidative process is followed to transform aldehydes in the depolymerized product to PAs by avoiding the undesired Dakin side reaction due to the electron‐withdrawing effect of the acetyl group. This study opens a new way to selectively cleave lignin side chains to isolated biochemicals under mild conditions. [ABSTRACT FROM AUTHOR]

The piezophototronic effect has been widely explored to improve the performance of optoelectronic devices. However, modulation of piezoelectric charges varies with different energy band structures. Thus, it is important to investigate the specific role of the piezophototronic effect from a theoretical perspective. Herein, the piezophototronic effect in anisotype p‐Si/n‐ZnO heterojunction photodiodes with type‐II energy band diagrams through analytical derivation and numerical simulation is thoroughly studied. It is found that both the depletion region and quasineutral region have a decisive effect on photocurrent in their respective regions. Specifically, modulations of piezoelectric charges on depletion region current and quasineutral region current are opposite and compensate each other, resulting in reduced piezophototronic effect. Heterojunctions under short diode conditions are preferred for better piezophototronic effect as modulation on quasineutral region current is weakened while that on depletion region current remains unchanged. The effects of doping concentration, absorption coefficient, and minority carrier lifetime of semiconductor materials on device characteristics are also studied. This work provides deeper insight into the underlying device physics of the piezophototronic effect. [ABSTRACT FROM AUTHOR]

The piezo‐phototronic effect can modulate the dynamics of photo‐generated carriers by utilizing external‐strain–induced piezoelectric charges (piezo‐charges). Most of the current researches focus on the modulation effect on the optoelectronic properties of p–n junctions. There are only a few studies focusing on the metal‐oxide–semiconductor (MOS) structures. In this work, a PEDOT:PSS/Al2O3/n‐ZnO tri‐layer MOS tunneling junction is fabricated and the piezo‐phototronic effect on its photo‐carriers dynamic and performances is systematically investigated. The photoresponsivity to 365 nm laser illumination is reduced because of the negative piezo‐charges generated at the Al2O3/n‐ZnO interface. Meanwhile but unexpectedly, the similar phenomenon utilizing the positive piezo‐charges at the Al2O3/n‐ZnO interface is observed. The in‐depth working mechanisms are carefully investigated by analyzing the effect of piezo‐charges on the energy band diagram. Strain induced piezo‐charges could feasibly adjust the intermediate oxide layer's barrier height and width so that the tunneling effect can be efficiently modulated by the piezo‐phototronic effect, leading to the effective control over the MOS tunneling junction's photo‐carriers dynamic and corresponding photoresponses. This work provides an in‐depth understanding for the piezo‐phototronic effect on the MOS tunneling junction and provides guidance for the subsequent researches on the coupling of piezo‐phototronic effect and tunneling effect. [ABSTRACT FROM AUTHOR]

An editorial is presented on restrictions having negative mental health and psycho-social consequences. Topics include communities across the globe subjected to periods of quarantine, lockdowns, stay-athome orders; and people at risk of untoward outcomes as the health status decline without effective treatment.

The piezo‐phototronic effect is widely used to regulate the interface of multilayer structures to tune the transportation of carriers by mechanical strain‐induced piezoelectric polarization charges. Besides, such modulation of the interface can also be achieved by the flexoelectric polarization charges induced by the mechanical strain gradients. Therefore, it is expected these two kinds of polarization charges can cooperate. In this work, a flexible phototransistor array based on n‐AZO/p‐Si/n‐ZnO structure is successfully demonstrated. The piezoelectric and flexoelectric polarization charges generated at the interfaces of the collector junction and the emitter junction, combined with the natural hole barrier at the emitter‐based interface, leads to the excellent performance of phototransistor for the ultraviolet (UV) –near infrared (NIR) range. Moreover, strain/optical imaging based on the flexible phototransistor array under different wavelengths of light is systematically investigated. The physical mechanism of the coupling between piezo‐phototronic and flexoelectric effects is further studied by analyzing the energy band and found to be attributed to the improvement of the emission efficiency and base transport efficiency. This work not only proposes a high‐performance flexible phototransistor array but also provides a new methodology to effectively modulate the interface by coupling the piezo‐phototronic effect and the flexoelectric effect. [ABSTRACT FROM AUTHOR]

The piezo‐phototronic effect has been extensively investigated to improve the performance of optoelectronic devices. However, the modulations in different energy band structures are quite distinctive, and adverse effects may be produced. Therefore, it is essential to investigate the modulation law in the optoelectronic devices with different energy band structures. Here, five kinds of Si/ZnO heterojunction photodiodes (PDs) with different energy band structures are fabricated and the piezo‐phototronic effect is systematically investigated on their photoresponse performance. For the p‐Si/n‐ZnO PDs, significant performance improvement is achieved by the piezo‐phototronic effect, with the magnitude of improvement increasing with doping concentration of p‐Si. For the n‐Si/n‐ZnO PDs, performance improvement is only achieved when the n‐Si is lightly doped, with a lower magnitude compared to that of the p‐Si/n‐ZnO PDs. The in‐depth working mechanism regarding to the different energy band structures is revealed. It is concluded that when the Fermi‐level of Si moves from the bottom of conduction band to the top of the valence band, the magnitude of performance improvement in Si/ZnO heterojunction PD increases. This study not only presents an in‐depth understanding regarding the piezo‐phototronic effect in Si/ZnO heterojunction PDs, but also provides guidance to optimize the piezo‐phototronic effect in optoelectronic devices. [ABSTRACT FROM AUTHOR]

This study aimed to use a persulfate together with transition metal ions as the reagent to effectively depolymerize lignin into monophenolic compounds under mild conditions (ambient pressure, temperature <100 °C). The Box‐Behnken experimental design in combination with the response surface methodology was applied to obtain optimized reaction conditions. The results showed that this reagent could depolymerize up to 99 % of lignin dimers to mainly veratraldehyde. This reaction also successfully depolymerized industrial lignins with a high yield of phenolic oils and monophenolic compounds. Quantum chemistry calculations using the density functional theory level indicated that the persulfate free radical attacks Cβ to break the β‐O‐4 bond of lignin through a five‐membered ring mechanism. This mechanism using persulfate free radicals has a lower activation barrier than that using hydroxyl radicals. Gel permeation chromatography and 2D‐NMR spectroscopy demonstrated the effective cleavage of the β‐O‐4 bonds of lignin after depolymerization. [ABSTRACT FROM AUTHOR]

Objective: To examine the prevalence and profile of chiropractors who frequently manage people aged 65 years and older. Methods: A national cross‐sectional survey collected practitioner characteristics, practice settings and clinical management characteristics. Multiple logistic regression was conducted on 1903 chiropractors to determine the factors associated with the frequent treatment of people 65 years and older. Results: In total, 73.5% of participants report "often" treating those aged 65 years and older. These chiropractors were associated with treating degenerative spine conditions (OR [odds ratio] 2.25; 95% [confidence interval] CI 1.72‐2.94), working in a non‐urban area (OR 1.85; 95% CI 1.35‐2.54), treating low back pain (referred/radicular) (OR 1.74; 95% CI 1.26‐2.40) and lower limb musculoskeletal disorders (OR 1.50; 95% CI 1.15‐1.96). Conclusions: The majority of chiropractors report often providing treatment to older people. Our findings call for more research to better understand older patient complaints that are common to chiropractic practice and the care provided by chiropractors for this patient group. [ABSTRACT FROM AUTHOR]

Objective: To determine the prevalence and clinical management characteristics of chiropractors practising in urban and rural or remote Australia. Design: A cross‐sectional analysis of the Australian Chiropractic Research Network project data. Setting: Nationally representative sample of registered chiropractors practising in Australia. Participants: Chiropractors who participated in the Australian Chiropractic Research Network project and answered a question about practising in urban or rural or remote areas in the practitioner questionnaire. Main outcome measure: The demographics, practice characteristics and clinical management of chiropractors. Results: The majority of chiropractors indicated that they practise in urban areas only, while 22.8% (n = 435) practice in rural or remote areas only and 4.0% (n = 77) practice in both urban and rural or remote areas. Statistically significant predictors of chiropractors who practice in rural or remote areas, as compared to urban areas, included more patient visits per week, practising in more than one location, no imaging facilities on site, often treating degenerative spinal conditions or migraine, often treating people aged over 65 years, frequently treating Aboriginal and Torres Strait Islander people and frequently using biomechanical pelvic blocking or the sacro‐occipital technique. Conclusion: A substantial number of chiropractors practice in rural or remote Australia and these rural or remote‐based chiropractors are more likely to treat a wide range of musculoskeletal cases and include an Indigenously diverse group of patients than their urban‐located colleagues. Unique practice challenges for rural or remote chiropractors include a higher workload and a lack of diagnostic tools. Chiropractors should be acknowledged and considered within rural or remote health care policy and service provision. [ABSTRACT FROM AUTHOR]

Abstract: The piezo‐phototronic effect is confirmed as a promising methodology to optimize the performance of optoelectronic devices. However, not only positive effects, but also negative effects may be produced in some types of photodiodes (PDs) by the piezo‐phototronic effect, resulting in the restriction of the PDs' photoresponse performance enhancement. In order to obtain the largest possible photoresponse performance enhancement, it is essential to investigate how the piezo‐phototronic effect influences the photoresponse performance of PDs with different device configurations and structures. Here, the piezo‐phototronic effect on the photoresponse performance enhancement of anisotype (p‐Si/n‐ZnO) and isotype (n‐Si/n‐ZnO) heterojunction PDs is thoroughly investigated. The experimental results show that the piezo‐phototronic effect induced improvement of the p‐Si/n‐ZnO heterojunction PD is much larger than that of the n‐Si/n‐ZnO heterojunction PD. The energy band diagrams under compressive strains are carefully analyzed, revealing that two positive effects are introduced to the p‐Si/n‐ZnO heterojunction PD, whereas one positive and two negative effects are introduced to the n‐Si/n‐ZnO heterojunction PD by the piezo‐phototronic effect. This work presents an in‐depth understanding about the piezo‐phototronic effect on the photoresponse performances of PDs with different device configurations and structures. [ABSTRACT FROM AUTHOR]

Abstract: Triboelectric nanogenerators (TENG) were invented as a highly effective technology for harvesting ambient mechanical energy. By coupling the TENG and metal‐oxide‐semiconductor field‐effect transistor, a new field of tribotronics has been recently proposed using the electrostatic potential created by triboelectrification as a gate voltage to tune/control charge‐carrier transport in semiconductors. In this work, the performance of a sliding‐electrification‐gated tribotronic transistor (SGT) and a sliding‐electrification‐gated tribotronic logic device (SGL) are theoretically investigated. The drain–source current characteristics for both the N‐channel SGT and P‐channel SGT are calculated in enhancement and depletion modes, respectively, which are found to be controlled by triboelectric charge amount, sliding distance, and drain voltage. By scaling down the conduction channel length to 10 nm, the SGT can still work and exhibit similar current characteristic and charge‐transfer process, showing the great potential of tribotronics in large‐scale array integration. Furthermore, the operation principle of a designed SGL based on two N‐channel SGTs in enhancement mode is revealed. This work could provide in‐depth understanding of physical mechanisms for tribotronic devices and design guidance for potential applications of tribotronics. [ABSTRACT FROM AUTHOR]

Wearable electronics have attracted a wide range of attention with various functions due to the development of semiconductor industry and information technology. This work focuses on a triboelectric nanogenerator-based self-charging power system as a continuous energy source for wearable electronics. The triboelectric nanogenerator has a multilayer elastomeric structure with closely stacked arches as basic functional units. Owing to material and structural innovations, this triboelectric nanogenerator performs outstanding electric output with the maximum volume charge density ≈0.055 C m−3 and practical properties for energy harvesting from body motions. Utilizing the triboelectric nanogenerator as outsole to harvest energy from walking or jogging, a pair of shoes is fabricated with the maximum equivalent charge current of each shoe being around 16.2 µA and specific fitness functions realized on each shoe separately without complex connections. [ABSTRACT FROM AUTHOR]

The piezophototronic effect is known as a three-way coupling between piezoelectric polarization, semiconductor property, and optical excitation in piezoelectric semiconductor materials to modify their energy band structures by strain-induced piezoelectric polarization charges, and thus to tune/control their optoelectronic processes of charge carrier generation, separation, recombination, and transport. In this work, the temperature dependence of the piezophototronic effect in wurtzite-structured CdS nanowires is investigated from 77 to 300 K. The piezophototronic effect is enhanced by over 550% under lower temperature due to the increased effective piezoelectric polarization surface/interface charges resulting from the reduced screening effect by decreased mobile charge carriers in CdS nanowires. Optoelectronic performances of CdS nanowires are systematically investigated under various light illuminations, strains, and temperatures. By analyzing the corresponding band diagrams, the piezophototronic effect is found to dominate the transport and separation processes of charge carriers. This study presents in-depth fundamental understanding about the piezophototronic effect and provides guidance for its future applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Oxide‐bonded SiC porous ceramics (SCPCs), synthesized via reaction bonding, exhibit significant potential for high‐temperature applications. However, incorporating sintering aids inevitably results in a considerable quantity of amorphous glass phase within SCPCs, thereby introducing risks to their high‐temperature mechanical performance. In this study, we employ in‐situ characterization techniques to investigate the high‐temperature behavior of SCPCs. Our findings reveal that SCPCs demonstrate remarkable high‐temperature self‐enhancing properties, with a critical bending strength at 800°C. Beyond this temperature, the strength declines sharply. Intriguingly, the critical bending strength is 36.6% greater than at ambient temperature. Moreover, elevated temperatures enhance the elastic modulus and promote the transition of SCPCs from multilinear to nonelastic fracture. The neck phase, which imparts strength to the SCPCs, is composed of four distinct layers along the depth direction: silicate glass, oxygen‐containing, silicon‐rich, and SiC region, as revealed by FIB‐TEM. The transformation from α to β‐cristobalite in the oxygen‐containing region improves the thermal expansion match with SiC, thereby mitigating local stress concentration. Furthermore, the compressive stress within the neck region intensifies with increasing temperatures, thereby inhibiting crack propagation. This work provides a basis for the high‐temperature applications of SCPCs. [ABSTRACT FROM AUTHOR]