Designing Poly(3,4-ethylenedioxythiophene) Polystyrene Sulfonate/Graphene Oxide/Graphene Nanosheet/Polyethylene Glycol Phase-Change Composites with Superior Thermal Management for Photo-thermoelectric Generators.

Recently, growing interest in self-powered devices has led to the invention of new energy conversion devices. Photo-thermoelectric generators (PTEGs) have rapidly developed for their ability to harvest both light and thermal energy, but these devices are overly dependent on the continuity of energy input and cannot sustain output in an emergency situation. In the current study, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/graphene oxide (GO)/graphene nanosheets (GNPs)/polyethylene glycol (PEG) phase-change composites (PCCs) were prepared with freeze-drying and vacuum-filling processes to acquire materials suitable for imparting energy storage characteristics to PTEGs. The melting and crystallization enthalpies of the PCCs fabricated based on the PEDOT:PSS/GO/GNP aerogels can reach 211.5 and 207.6 J g-1, respectively, which increase by nearly 5% compared with pure PEG, and the growth rate of thermal conductivity of the composites is as high as 262.7% (1.12 W m-1 K-1). Meanwhile, the excellent photothermal properties and high-temperature shape stability that pure PEG does not possess can also be imparted to PCCs by the aerogels. The PTEG assembled with PCCs and thermoelectric components can achieve a continuous output of over 1500 s after 300 s of light irradiation. After integrating the output of the device during the lamp on/off period, it is found that the total output of the device during the light-off period (8.4 V and 9.6 mW) can far exceed its total output during the light-on period (2.7 V and 4.4 mW). This work provides guidance for modulating the performance of PCCs and giving PTEGs the ability to operate under emergency or extremely harsh conditions and the prepared PTEGs are highly promising for practical use.

Achieving Free-Standing PEDOT:PSS Solar Generators with Efficient All-in-One Photothermoelectric Conversion.

Poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has attracted widespread attention in solar generation due to its unique all-in-one photothermoelectric effect. However, the poor photothermal conversion, low conductivity, and unsatisfied mechanical properties limit its practical application. Herein, ionic liquids (IL) were first used to improve the conductivity of PEDOT:PSS through ion exchange, then surface-charged nanoparticles SiO2-NH2 (SiO2+) were added to promote the dispersion of IL and as a thermal insulator to decrease thermal conductivity. It resulted in a largely enhanced electrical conductivity and decreased thermal conductivity of PEDOT:PSS simultaneously. The obtained PEDOT:PSS/Ionic Liquid/SiO2+ (P_IL_SiO2+) film generated an excellent photothermal conversion of 46.15 °C, which improved ∼134 and ∼82.3% compared with PEDOT:PSS and PEDOT:PSS/Ionic Liquid (P_IL) composites, respectively. In addition, the thermoelectric performance increased by ∼270% more than P_IL films. As a result, the photothermoelectric effect for the self-supported three-arm devices produced an enormous output current and power of ∼50 µA and 13.57 nW, respectively, which showed significant improvement compared with other PEDOT:PSS films reported in the literature. Furthermore, the devices demonstrated outstanding stability with an internal resistance variation of less than 5% after 2000 cycles of bending. Our research offered significant insights into the flexible, high-performance, all-in-one photothermoelectric integration.

Constructing A/B-Side Heterogeneous Asynchronous Structure with Ag2Se Layers and Bushy-like PPy toward High-Performance Flexible Photo-Thermoelectric Generators.

The enthusiasm for environmental energy harvesting has triggered a boom in research on photo-thermoelectric generators (PTEGs), and the relevant applications are mainly focused on self-energy supply sensors owing to the limitations of their output performances. For this purpose, high-output hierarchical heterogeneous PTEGs were constructed by assembling separately optimized thermoelectric (TE) and photothermal (PT) layers. The pressure and temperature conditions of Ag2Se films during the pressing process were first explored, and the sample with the optimal performance and least defects was selected as the TE layer. At the same time, different morphologies of polypyrrole (PPy) PT layers were electrochemically synthesized. It is found that the three-dimensional structure of Bushy-PPy could effectively improve the light absorption and thus enhance the PT conversion performance. The final assembled PTEG can produce an output voltage of -9.03 mV and an output power of 3.53 µW under the irradiation of a near-infrared light source of 300 mW cm-2 without a cooling source, and it can also achieve considerable output power under visible light irradiation of different intensities. Combining its high retentions of electrical conductivity (99%) and output performance (97%) after 1000 bending-tension cycles, it is proven to be a promising next-generation wearable flexible energy harvesting device.

Ultraflexible PEDOT:PSS/Helical Carbon Nanotubes Film for All-in-One Photothermoelectric Conversion.

Photothermoelectric (PTE) conversion can achieve the recovery of low-quality light or heat efficiently. Much effort has been devoted to the exploitation of the inorganic heterogeneous asynchronous (separate) PTE conversion system. Here, a full organic PTE film with a pseudobilayer architecture (PBA) according to the homogeneous synchronous (all-in-one) PTE conversion hypothesis was prepared via successive drop-casting a PEDOT:PSS/helical carbon nanotube (HCNT) mixture and PEDOT:PSS onto a vacuum ultraviolet treated substrate. Our results prove that the heptagon-pentagon pairs embedded in HCNTs promote a denser arrangement of the molecular chains of PEDOT, which enhances the crystallinity and affects the thermoelectric properties. The weak connection and hollow structure of HCNTs inhibit the dissipation of heat, and the zT value of the film reaches over 0.01. The PBA film shows better photothermal conversion performance than a neat PEDOT:PSS film and stably generates a temperature difference of over 25.68 °C without external cooling. A flexible PTE chip demo was manufactured, and the ideal open-circuit voltage (simulated via COMSOL) of that reaches over 1.5 mV under weak NIR stimulation (83.12 mW/cm2), which is the best value reported for an organic all-in-one PTE device, and the real maximum output power reaches 2.55 nW (166.01 mW/cm2). The chip has incredible ultraflexibility, and its inner resistance changes less than 1.42% after 10000 bending cycles and displays ultrahigh stability (similarity >90%) in a continuous periodic output. Our work fills the deficit of homogeneous synchronous PTE research for a PEDOT:PSS composite and is a preliminary attempt in an ultraflexible integrated all-in-one PTE chip design.

Polypyrrole/Helical Carbon Nanotube Composite with Marvelous Photothermoelectric Performance for Longevous and Intelligent Internet of Things Application.

Helical carbon nanotube (HCNT) is a vital member of carbon nanomaterials, but little effort was devoted to explore its unique characteristics and applications during the past few decades. Here, we report an organic thermoelectric composite with an excellent photothermoelectric (PTE) effect by conformally wrapping polypyrrole (PPy) on the intricate surface of HCNTs, which have been confirmed to have remarkable near-infrared (NIR) photothermal conversion capability and ultralow heat transportation characteristics. The results indicate that with the increasing HCNT content, PPy shell thickness reduces and exhibits denser as well as partial orientation, while the inter-ring angle slowly decreases and the bipolaron becomes dominant in carrier composition gradually. Consequently, the Seebeck coefficient increases monotonically, whereas the electrical conductivity remains nearly invariant. The final composite combines the benign thermoelectric properties, excellent photothermal response performance, and the lowest thermal conductivity of the carbon-based thermoelectric composite yet reported (0.064 W m-1 K-1). A single strip NIR light-stimulated adjustable delay switch was designed and fabricated, with the open-circuit voltage and short-circuit current under a 400 mW cm-2 NIR-stimulated approach to 720 µV and 62 nA with the discrepancy of consecutive periodic output signals less than 4.2%, exhibiting incredible stability and reliability and demonstrating the highest output voltage of a single strip among the reported organic PTE composite at room temperature. Our work fills in a gap of HCNT research, which hitherto existed in the PTE and thermoelectric field.

Constructing cellulose nanocrystal/graphene nanoplatelet networks in phase change materials toward intelligent thermal management.

The hybrid networks of cellulose nanocrystals (CNCs) and graphene nanoplatelets (GNPs) were constructed in polyethylene glycol (PEG) through the common solution compounding processing, in which GNPs provided the thermally conductive path while CNCs restricted the leakage of PEG during the phase transition. The results showed that CNCs greatly enhanced the shape stability of the composite phase change materials (PCMs) while thermal conductivity was still maintained at high level. At the contents of 8 wt% (CNCs) and 4 wt% (GNPs), the enthalpy of the composite PCM was 145.5 J/g, which was 88 % of pure PEG, and the thermal conductivity was 2.018±0.067 W/m K about 563.7 % higher than that of pure PEG. Furthermore, the composite PCMs exhibited outstanding light-thermal and electro-thermal conversion capabilities. Furthermore, the composite PCMs could be designed as the temperature stabilizing component exhibiting intelligent adaptive thermal management role, providing stable temperature condition for electronic devices in extreme environment.

Melamine foam and cellulose nanofiber co-mediated assembly of graphene nanoplatelets to construct three-dimensional networks towards advanced phase change materials.

Organic phase change materials (OPCMs) play a great role in energy management owing to their large phase change enthalpy, but their intrinsic low thermal conductivity (TC) and bad encapsulation severely restrict their applications. To overcome these problems, we developed a novel but feasible method to fabricate a graphene nanoplatelet (GNP) aerogel with compact and oriented stacking in-plane walls and many through-plane bridges via melamine foam (MF) and cellulose nanofiber (CNF) co-mediated assembly of GNPs. After impregnating paraffin wax (PW), the composite PCMs exhibit a high TC of 1.42 W m-1 K-1 at only a GNP content of 4.1 wt%, increasing by 407% compared with pure PW, and simultaneously nearly no reduction of the phase change enthalpy of PW. Meanwhile, this kind of composite PCM can not only show excellent light-to-thermal and electric-to-thermal transition ability, but also be applied in delay switch devices with satisfactory results.

Electrospun Fibrous Membranes with Dual-Scaled Porous Structure: Super Hydrophobicity, Super Lipophilicity, Excellent Water Adhesion, and Anti-Icing for Highly Efficient Oil Adsorption/Separation.

Developing highly efficient and multifunctional membranes toward oil adsorption and oil/water separation is of significance in oily wastewater treatment. Herein, a novel electrospun composite membrane with dual-scaled porous structure and nanoraised structure on each fiber was fabricated through electrospinning using biodegradable polylactide (PLA) and magnetic γ-Fe2O3 nanoparticles. The PLA/γ-Fe2O3 composite membranes show high porosity (>90%), superhydrophobic and superlipophilic performances with CH2I2 contact angle of 0°, good water adhesion ability like water droplets on a petal surface, excellent anti-icing performance, and good mechanical properties with a tensile strength of 1.31 MPa and a tensile modulus of 11.65 MPa. The superlipophilicity and dual-scaled porous structure endow the composite membranes with ultrahigh oil adsorption capacity up to 268.6 g/g toward motor oil. Furthermore, the composite membranes also show high oil permeation flux up to 2925 L/m2 h under the force of gravity. Even for oil/water emulsion, the composite membranes have high separation efficiency. We expect that the PLA/γ-Fe2O3 composite membranes can be used in oily wastewater treatment under various conditions through one-off adsorption or continuous oil/water separation, especially under low environmental temperature condition.

Constructing reduced graphene oxide/boron nitride frameworks in melamine foam towards synthesizing phase change materials applied in thermal management of microelectronic devices.

Phase change materials (PCMs) exhibit wide application prospects in many fields related to energy utilization and management and attract increasing interest. In this work, through the graphene oxide (GO)-assisted dispersion technology, GO/boron nitride (BN) nanosheets were incorporated into melamine foam and successfully deposited on the surface of the foam framework after hydrothermal reaction. Through the following freeze-drying and carbonization treatment, the composite MF/rGO/BN aerogels were obtained with integrated hybrid rGO/BN frameworks. The composite PCMs were prepared through encapsulating polyethylene glycol (PEG) within the hybrid aerogels. The encapsulation stability and thermal properties of the composite PCMs were systematically investigated. The composite PCM sample containing the highest content of rGO/BN exhibited excellent encapsulation stability, high thermal conductivity (up to 0.79 W m-1 K-1), high phase change enthalpy (160.7 J g-1) with the retention of 90.8% of the pure PEG, and excellent chemical and thermal stability. Further results clearly showed that the composite PCMs had excellent light-to-heat energy transition ability and could be used as a thermal management component to suppress the overheating of devices during the operation process, or to supply energy for thermoelectric devices under emergency conditions to ensure a continuous power supply sustained for a certain time until the safeguard procedures are adopted.

[A review of spatial epidemiology with malaria surveillance and control in China].

The monitoring and control of malaria depends largely on the spatial analysis technology and mathematical models. Visualization of malaria situation is the most popular way to present how malaria transmits. In this paper, the malaria epidemic situation and the application of spatial epidemiology of malaria in China are summarized, so as to provide the systematic epidemiological information for malaria elimination in China.