Over 60 h of Stable Water-Operation for N-Type Organic Electrochemical Transistors with Fast Response and Ambipolarity.

Organic electrochemical transistors (OECTs) are of great interest in low-power bioelectronics and neuromorphic computing, as they utilize organic mixed ionic-electronic conductors (OMIECs) to transduce ionic signals into electrical signals. However, the poor environmental stability of OMIEC materials significantly restricts the practical application of OECTs. Therefore, the non-fused planar naphthalenediimide (NDI)-dialkoxybithiazole (2Tz) copolymers are fine-tuned through varying ethylene glycol (EG) side chain lengths from tri(ethylene glycol) to hexa(ethylene glycol) (namely P-XO, X = 3-6) to achieve OECTs with high-stability and low threshold voltage. As a result, the NDI-2Tz copolymers exhibit ambipolarity, rapid response (<10 ms), and ultra-high n-type stability. Notably, the P-6O copolymers display a threshold voltage as low as 0.27 V. They can operate in n-type mode in an aqueous solution for over 60 h, maintaining an on-off ratio of over 105. This work sheds light on the design of exceptional n-type/ambipolar materials for OECTs. It demonstrates the potential of incorporating these ambipolar polymers into water-operational integrated circuits for long-term biosensing systems and energy-efficient brain-inspired computing.

Release Pattern of Light Aromatic Hydrocarbons during the Biomass Roasting Process.

Roasting is an important step in the pretreatment of biomass upgrading. Roasting can improve the fuel quality of biomass, reduce the O/C and H/C ratios in the biomass, and provide the biomass with a fuel quality comparable to that of lignite. Therefore, studying the structure and component evolution laws during biomass roasting treatment is important for the rational and efficient utilization of biomass. When the roasting temperature is 200-300 °C, the cellulose and hemicellulose in the biomass undergo a depolymerization reaction, releasing many monocyclic aromatic hydrocarbons with high reactivity. The proportion of monocyclic aromatic hydrocarbons in biomass roasting products can be effectively regulated by controlling the reaction temperature, residence time, catalyst, baking atmosphere, and other factors in the biomass roasting process. This paper focuses on the dissociation law of organic components in the pretreatment process of biomass roasting.

Numerical Analysis on Heat Transfer Characteristics of Supercritical CO2 in Heated Vertical Up-flow Tube.

It is great significance to understand the mechanism of heat transfer deterioration of supercritical CO2 for heat exchanger design and safe operation in the supercritical CO2 Brayton cycle. Three-dimensional steady-state numerical simulation was performed to investigate the behavior of supercritical CO2 heat transfer in heated vertical up-flow tube with inner diameter di = 10 mm and heated length Lh = 2000 mm. Based on the characteristics of inverted-annular film boiling at subcritical pressure, the heat transfer model of supercritical CO2 flowing in the heated vertical tube was established in this paper. The mechanisms of heat transfer deterioration (HTD) and heat transfer recovery (HTR) for supercritical CO2 were discussed. Numerical results demonstrate that HTD is affected by multiple factors, such as the thickness and property of vapor-like film near the wall, the turbulence intensity near the interface between liquid-like and vapor-like, and in the liquid-like core region as well as the distribution of radial velocity vector. Among the above factors, the change of turbulent kinetic energy caused by the buoyancy effect seems to be a more important contributor to HTD and HTR. Furthermore, the influences of heat flux and mass flux on the distribution of wall temperature were analyzed, respectively. The reasons for the difference in wall temperature at different heat fluxes and mass fluxes were explained by capturing detailed thermal physical properties and turbulence fields. The present investigation can provide valuable information for the design optimization and safe operation of a supercritical CO2 heat exchanger.