Self-assembled boron nitride nanosheet-based aerogels as support frameworks for efficient thermal energy storage phase change materials

Phase change materials (PCMs) are promising in many fields related to energy utilization and thermal management. However, the low thermal conductivity and poor shape stability of PCMs restrict their direct thermal energy conversion and storage. The desired properties for PCMs are not only high thermal conductivity and excellent shape stability, but also high latent heat retention. In this study, the boron nitride nanosheets (BNNSs) were bridged by small amounts of GO nanosheets and successfully self-assembled into BNNS/rGO (BG) aerogels by hydrothermal and freeze-drying processes. The BG aerogels with interlaced macro-/micro-pores have been proven to be ideally suited as support frameworks for encapsulating polyethylene glycol (PEG). The obtained composite PCMs exhibit high thermal conductivity (up to 1.12 W m-1 K-1), excellent shape stability (maintain at 90 °C for 10 min), and high latent heat (187.2 J g-1) with a retention of 97.3% of the pure PEG, presenting great potential applications in energy storage systems and thermal management of electronic devices.

Multi-biofunctional graphene oxide-enhanced poly-L-lactic acid composite nanofiber scaffolds for ovarian function recovery of transplanted-tissue

In this study, we successfully constructed the new graphene oxide/poly-L-lactic acid (GO/PLLA) nanofiber scaffolds with a hydrophilic surface and porous network structure that were highly favorable for cell infiltration. When employed these new nanofiber scaffolds for a wide range of tissue engineering applications, it was expected to promote graft tissue survival and angiogenesis. The new GO/PLLA nanofiber scaffold with an appropriate concentration of 1.0 wt% was applied for the restoration of ovarian function and reserve in mice with primary ovarian insufficiency (POI). After co-transplanting the normal ovarian cortex loaded on these new nanomaterials into the in situ ovarian tissue of POI mice, the fusion of transplanted ovarian cortex with damaged ovarian tissue was improved, as well as the ovarian function and the follicle numbers. Moreover, angiogenesis was observed clearly and proved to exist in the transplanted tissue and nanomaterials, with the most conspicuous effect after co-transplantation with 1.0 wt% GO/PLLA nanofiber scaffold. In addition, nitric oxide (NO) production by phosphorylated endothelial nitric oxide synthase (p-eNOS) in vivo was proven to be involved in the effect of GO and PLLA on the improved survival rate of the transplanted ovarian cortex. This study provides a new method for the fertility preservation of ovarian tissue cryopreservation and transplantation, as well as a new strategy for the transplantation of other organs.

Novel preparation of attapulgite-reduced graphene oxide hydrogel composite and its application in flexible solid-state supercapacitors

After graphite oxide assisted the liquid phase shear exfoliation of attapulgite, the good dissociation and dispersion of attapulgite rod crystals are realized. Due to the spatial hindrance effect of attapulgite, which prevents the stacking of RGO sheets, the attapulgite-reduced graphene oxide three-dimensional porous hydrogel with abundant pore structure enables rapid transfer of electrolyte ions and exhibits good electrochemical performance and rate performance. The assembled flexible solid-state supercapacitor has a high operating voltage window and good flexibility and cycle stability. At a current density of 0.1 mA cm^-2, it has an area specific capacitance of 127.33 mF cm^-2. A series of solid-state supercapacitors can be used as the power supply for LED lights.

Graphene oxide-supported cobalt tungstate as catalyst precursor for selective growth of single-walled carbon nanotubes

Graphene oxide-supported uniform cobalt tungstate nanoparticles (CoWO₄/GO) were prepared, which can be used as catalyst precursors for the diameter-controlled growth of single-walled carbon nanotubes (SWCNTs).

Liquid-Phase Exfoliation of Kaolinite by High-Shear Mixer with Graphite Oxide as an Amphiphilic Dispersant

In this study, a simple, effective, and versatile method was used for the exfoliation of kaolinite by high-shear mixer with graphite oxide as an an amphiphilic dispersant. During the liquid-phase exfoliation process, the co-exfoliation of kaolinite and graphite oxide was realized. Compared with the directly exfoliated kaolinite, when 5% graphite oxide was added to facilitate exfoliation, 95% of the obtained nanosheets were distributed between 0.1 and 0.7 μm, in which the number of layers was less than 5, and part of them were curled into nanoscrolls structure with a length of 0.2-0.9 μm. The Brunauer-Emmett-Teller surface area of the graphite oxide assisted exfoliated kaolinite was 2.1 times that of the directly exfoliated kaolinite. Meanwhile, the graphite oxide assisted exfoliated kaolinite exhibited excellent adsorption properties for MB, whose theoretical maximum adsorption capacity was 250 mg/g, significantly higher than that of the directly exfoliated kaolinite, which was about 111 mg/g. It has been verified that the exfoliation method is efficient and facile and can be applied extensively.

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.

Highly Compressive Boron Nitride Nanotube Aerogels Reinforced with Reduced Graphene Oxide

Boron nitride nanotubes (BNNTs), structural analogues of carbon nanotubes, have attracted significant attention due to their superb thermal conductivity, wide bandgap, excellent hydrogen storage capacity, and thermal and chemical stability. Despite considerable progress in the preparation and surface functionalization of BNNTs, it remains a challenge to assemble one-dimensional BNNTs into three-dimensional (3D) architectures (such as aerogels) for practical applications. Here, we report a highly compressive BNNT aerogel reinforced with reduced graphene oxide (rGO) fabricated using a freeze-drying method. The reinforcement effect of rGO and 3D honeycomb-like framework offer the BNNTs/rGO aerogel with a high compression resilience. The BNNTs/rGO aerogels were then infiltrated with polyethylene glycol to prepare a kind of phase change materials. The prepared phase change material composites show zero leakage even at 100 °C and enhanced thermal conductivity, due to the 3D porous structure of the BNNTs/rGO aerogel. This work provides a simple method for the preparation of 3D BNNTs/rGO aerogels for many potential applications, such as high-performance polymer composites.

Application of Hole-Transporting Materials as the Interlayer in Graphene Oxide/Single-Wall Carbon Nanotube Silicon Heterojunction Solar Cells

Solid-state hole-transporting materials, including the traditional poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), and recently developed 4,4′-(naphthalene-2,6-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (NAP) and (E)-4′,4‴-(ethene-1,2-diyl)bis(N,N-bis(4-methoxyphenyl)-[1″,1‴-biphenyl]-4-amine) (BPV), have been applied as a hole-transporting interlayer (HTL) for graphene oxide/single-walled carbon nanotube–silicon (GOCNT/Si) heterojunction solar cells, forming a GOCNT/HTL/Si architecture. The influence of the thickness of the HTL has been studied. A new AuCl3 doping process based on bath immersion has been developed and proved to improve the efficiency. With the AuCl3-doped GOCNT electrodes, the efficiency of GOCNT/PEDOT:PSS/Si, GOCNT/NAP/Si, and GOCNT/BPV/Si devices was improved to 12.05 ± 0.21, 10.57 ± 0.37, and 10.68 ± 0.27 % respectively. This study reveals that the addition of an HTL is able to dramatically minimise recombination at the heterojunction interface.

The dispersion and aggregation of graphene oxide in aqueous media

Graphene oxide (GO), as a typical two-dimensional material, possesses a range of oxygen-containing groups and shows surfactant and/or polyelectrolyte-like characteristics. Herein, GO sheets with narrow size distribution were prepared by an ultracentrifugation-based process and the aggregation behaviour of GO in pure water and an electrolyte aqueous solution were studied using laser light scattering (LLS). When adding common electrolytes, such as NaCl and MgCl2, into the GO dispersions, aggregation occurs and irreversible coagulation eventually occurs too. However, the GO dispersion can still remain stable when adding excess AlCl3. The zeta potential of the GO dispersion changes from negative to positive after the addition of access AlCl3, indicating that electrostatic repulsion is still responsible for the dispersion of GO, which is in good agreement with the LLS results. This finding on the dispersion of GO may be applied in the solution processing of GO. It also expands the scope of the design and preparation of new GO-based hybrid materials with different functions.

Design of graphene oxide/gelatin electrospun nanocomposite fibers for tissue engineering applications

2D graphene oxide (GO) is used to enhance the mechanical properties of gelatin electrospun fibers. The GO does not show any significant influence on cell viability and cell attachment even though the expression of osteoblast gene is affected.

A new view of graphene oxide biosafety in a water environment using an eatable fish as a model

A comprehensive evaluation on the biosafety of graphene oxide (GO) was developed by combining 16S rRNA sequencing, gene expression detection, histology and a scanning electron microscope assay on fish.