The large-scale synthesis of atomically thin, layered MoS2/graphene heterostructures is of great interest in optoelectronic devices because of their unique properties. Herein, we present a scalable synthesis method to prepare centimeter-scale, continuous, and uniform films of bilayer MoS2 using low-pressure chemical vapor deposition. This growth process was utilized to assemble a heterostructure by growing large-scale uniform films of bilayer MoS2 on graphene (G-MoS2/graphene). Atomic force microscopy, Raman spectra, and transmission electron microscopy characterization demonstrated that the large-scale bilayer MoS2 film on graphene exhibited good thickness uniformity and a polycrystalline nature. A centimeter-scale phototransistor prepared using the G-MoS2/graphene heterostructure exhibited a high responsivity of 32 mA/W with good cycling stability; this value is 1 order of magnitude higher than that of transferred MoS2 on graphene (2.5 mA/W). This feature results from efficient charge transfer at the interface enabled by intimate contact between the grown bilayer MoS2 (G-MoS2) and graphene. The ability to integrate multilayer materials into atomically thin heterostructures paves the way for fabricating multifunctional devices by controlling their layer structure.Keywords: bilayer MoS2; graphene; heterostructure; large-scale; uniformity;

Multistimuli-responsive polymers are materials of emerging interest but synthetically challenging. In this work, supramolecular assembly was employed as a facile and effective approach for constructing 3,3′,5,5′-azobenzenetetracarboxylic acid (H4abtc)/poly(diallyldimethylammonium chloride) (PDAC) supramolecules. Structural transformations of H4abtc can be induced by light, mechanical force, and heat and influenced by free volume. Thus, the fabricated free-standing H4abtc/PDAC film underwent bending/unbending movements upon treatment with light, humidity, or temperature, as asymmetric structural transformations on either side of the film generated asymmetric contraction/stretching forces. Fast rates of shape recovery were achieved for the film on exposure to gently flowing humid nitrogen. The bending/unbending motions are controllable, reversible, and repeatable. Hence, this light-, humido-, and thermo-responsive film has great potential in device applications for advanced functions.Keywords: actuator; azobenzene; multistimuli-responsive polymers; polyelectrolytes; supramolecular chemistry;

The exploration of cathode materials with high electrochemical performances is critical to improve the energy and power densities of lithium ion batteries (LIBs). Iron fluoride (FeF3) has been proposed as an ideal candidate of LIBs cathode material because of the high discharge plateau and theoretical capacity. In this study, a precursor-mediated method was proposed to synthesize FeF3 nanocrystals (NCs) with different microstructures. These FeF3 NCs were obtained through the thermal decomposition of the precipitated ammonium hexafluoroferrate [(NH4)3FeF6] precursor, and the morphology and crystallinity could be adjusted by varying the ethanol/water volume ratio in the procursor precipitation process. Electrochemical studies demonstrated that FeF3 NC, derived from (NH4)3FeF6 precipitated from the solution with the ethanol/water volume ratio of 20, delivered the initial specific capacity of 217.6 mAh g−1 at 0.2C, associated with excellent rate capability up to 20C (93.8 mAh g−1), and showed the capacity retention of 80.6% after 500 cycles at 20C. These results indicate a tunable and convenient strategy towards nanostructured metals fluorides for high power LIBs.

Hydroxyl functionalized carbon dots (H-CDs) were prepared by monoesterification of ethylene glycol. The H-CDs exhibit a narrow size distribution of 1–4 nm and enhanced photoluminescent (PL) intensity due to an increased amount of electron donor hydroxyl groups. According to fluorescence spectra, the H-CDs exhibit a high sensitivity to Fe3+ with a detection limit of 2.56 nM, which is superior to the detection limit of CDs (7.4 μM). The quenching fluorescence is primarily controlled by the formation of a chelate compound based on the complexation between Fe3+ and the hydroxyl on the surface of the H-CDs. Furthermore, we demonstrate that paper impregnated with H-CDs exhibits a high sensitivity to Fe3+ by fluorescence quenching. In the future, the modified CDs can be developed for high sensitivity fluorescent probes by optimizing the chemical structures and microstructures.

Hybrid supercapacitors (HSCs) have attracted increasing attention as they can deliver energy densities sufficient for batteries and power densities of supercapacitors. The exploration of novel types of capacitor cathode materials with higher energy densities than conventional active carbons is in demand. Here, a series of copolymers of aniline (ANI) and 2-aminoterephthalic acid (ATA) were synthesized by the chemical oxidation polymerization at different molar ratios of monomers (ANI/ATA). The morphologies of the products varied from nanoparticles to nanorods and then returned to granular nanoparticles with the increase of the ATA amount. The copolymer nanorods synthesized at an ANI/ATA ratio of 8 : 2 exhibited a high specific capacitance (198 F g−1 at the current density of 20 mA g−1), excellent rate capability (the maximum current density of 50 A g−1), and excellent cycling stability (capacitance retention of 78.5% after 1000 cycles at 2 A g−1). The appropriate amount of carboxyl groups enabled the delocalization of charge along the polymer backbone and the one-dimensional nanostructures facilitated the anion diffusion to the electrode, which enhanced the electrochemical activity of the copolymer significantly. The excellent rate capability as well as the anion doping/dedoping energy storage mechanism impelled the copolymer to be employed as the supercapacitor cathode of HSCs. The energy density of 153.9 W h kg−1 and the power density of 3011.5 W kg−1 of HSCs are obtained with commercial meso-carbon microbeads (MCMBs) and Li4Ti5O12 (LTO) as anode materials, respectively.

Anisotropic light-switching properties are of great importance in advanced photodetectors, light-gated transistors, and energy storage devices. However, controlling the light-switching conductance of anisotropic materials remains challenging because of the difficulties in tuning the electronic interactions and microstructure in the longitudinal and transverse directions, respectively. We present a transparent and flexible photo-responsive film of azobenzene–poly(methyl methacrylate) (Azo–PMMA) close-packed on the sidewalls of horizontally aligned carbon nanotubes (HACNTs). The alignment leads to an anisotropic electrical conductivity (σ). The aligned composite film shows a steady increase in σ in the longitudinal (σ∥) and transverse directions (σ⊥) during UV irradiation and a continuous decrease after irradiation. The light-switching conductance shows good cycling performance over 25 cycles, which is consistent with the isomerisation of the azobenzene groups in Azo–PMMA. Light-switching conductance is demonstrated in two directions, originating from the light-induced switch to a greater proportion of more conductive cis-Azo isomers, photo-doping and the film contracting during the trans-to-cis photo-isomerisation. The anisotropic Azo–PMMA/HACNT composite film with a light-switchable conductivity paves the way towards the fabrication of anisotropic photo-controllable materials by molecular design and microstructure modulation.

For the next generation of lithium-ion batteries (LIBs), single Li-ion polymer electrolytes (SPEs) are widely considered an effective substitute to traditional dual-ion electrolytes, due to their ability to restrain the salt concentration gradient and the polarization loss in the cells. A new single-ion conductor with an alternating structure is synthesized by the simple radical copolymerization of lithium 4-styrenesulfonyl(phenyl-sulfonyl)imide and maleic anhydride. Its SPE membrane composite with poly(vinylidene fluoride-co-hexafluoropropylene) exhibits both high lithium ion conductivity (σLi+ = 2.67 mS cm−1) and transference number (tLi+ = 0.98). The full cell with the prepared SPE sandwiched between a LiFePO4 cathode and a Li4Ti5O12 anode shows good cycling stability and rate capability. These results suggest that this novel electrolyte is promising for application in next-generation LIBs.

Tuning the bandgap of thin-layered two-dimensional transition metal dichalcogenide (2D TMDCs) nanocrystals by controlling their composition or structure is considered to be an important method of tailoring light absorption, electron transition and carrier mobility. However, the large-scale synthesis of TMDs with a tunable bandgap on graphene remains challenging owing to the difficulty in controlling the uniformity of the layer thickness. Herein, we report the large-area synthesis of a uniform monolayer MoS2(1−x)Se2x film on a monolayer graphene using low-pressure chemical vapour deposition to realize a 2D heterostructure. The resultant centimetre-scale monolayer MoS2(1−x)Se2x film on graphene showed a highly crystalline structure and a tunable bandgap from 1.82 eV to 1.66 eV, which could be controlled by tuning the atomic ratio of S to Se. A phototransistor with the MoS2(1−x)Se2x/graphene heterostructure exhibited a high responsivity of 40.64 mA W−1 under light irradiation of 465 nm with good stability up to 50 cycles. A high photocurrent arose from the efficient charge transfer from MoS2(1−x)Se2x to graphene with a high carrier mobility based on the good electronic interaction. Thus, the large-scale high-quality bandgap-tunable MoS2(1−x)Se2x/graphene heterostructure with controllable structures and electronic properties could be developed and integrated into advanced optoelectronic devices.

Designing an energy-dense and thermal-stable photo-isomerizable chromophore/hybrid template is a challenge for devising a highly customizable solar-heat conversion and storage technology. This study presents the templated assembly of close-packed 2-chloro-4,6-bis(4-(phenyldiazenyl)phenoxy)-1,3,5-triazine (bis-azobenzene chromophores) covalently bound to reduced graphene oxide (RGO-bis-Azo). The steric configuration and energy of bis-Azo (trans- and cis-isomers), calculated by density functional theory, are influenced by intra- and inter-molecular steric hindrance due to high grafting density and the bundling effect. This results in a dramatic increase in enthalpy and activation energy of the isomerization. The RGO-bis-Azo hybrid combines a high energy density of 80 W h kg−1, the maximum power density of 2230 W kg−1 and a tunable heat release time from 2 min to 5520 h. These findings pave the way for developing a chromophore/hybrid template for solar thermal fuel by optimizing molecular interaction.

Three-dimensional (3D) graphene materials have attracted a lot of attention for efficiently utilizing inherent properties of graphene sheets. However, 3D graphene materials reported in the previous literature are constructed through covalent or weak non-covalent interactions, causing permanent structure/property changes. In this paper, a novel 3D graphene material of dynamic interactions between lamellas with 2-ureido-4[1H]-pyrimidinone as a supra-molecular motif has been synthesized. This 3D graphene material shows enhanced sheet interactions while the cross-linking takes place. With proper solvent stimulation, the integrated 3D graphene material can disassemble as isolated sheets. The driving force for the 3D structure assembly or disassembly is considered to be the forming or breaking of the multiple hydrogen bonding pairs. Furthermore, the 3D material is used as an intelligent dye adsorber to adsorb methylene blue and release it. The controllable and reversible characteristic of this 3D graphene material may open an avenue to the synthesis and application of novel intelligent materials.

All-carbon composites are ideal heat-dissipating materials because they possess a high thermal conductivity (K), excellent mechanical properties, high temperature resistance, low coefficient of thermal expansion, outstanding chemical stability, and so on. The rapid development of science and technology has put forward the need for a higher K of all-carbon composites. Different from individual carbon materials, all-carbon composites have assembled structures, including the interface, orientation, and pores, which provide challenges and opportunities to improve the thermal and mechanical properties. Until now, a number of studies have reported on how to adjust the K of various all-carbon composites by controlling their microstructures and mesostructures. This review compiles recent research progress on highly thermally conductive all-carbon composites, including flexible carbon papers (carbon nanotube paper, graphene paper, exfoliated graphite paper), stiff carbon blocks (graphite block, carbon fiber block), and porous carbon foams (pitch-based carbon foam, graphene-based carbon foam, three dimensional graphene-carbon nanotube-based carbon foam). The key structures and their control methods related to their high K are outlined. Finally, the strategies and challenges in the development of highly thermally conductive all-carbon composites are presented.

•Fluorinated graphene hydrogels (FGHs) were synthesized via the hydrothermal process.•The FGH electrodes were fabricated without any binder and conductive additive.•The fluorine content and CF bond configurations were adjusted by the temperature.•The FGHs show the maximum power density of 50.05 kW kg−1.Fluorinated graphene hydrogels (FGHs) are synthesized through a one-step hydrothermal process and applied as the binder/additive-free electrode materials for supercapacitors. Along with the reduction of graphene oxide (GO), fluorine atoms incorporate into the graphene framework through the substitution process with the residual phenol, ether or carbonyl groups, forming different fluorine species subsequently. The fluorine content and the CF bond configuration are easily adjusted by the hydrothermal temperature. X-ray photo electron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectra indicate the mainly existent of semi-ionic CF bonds in the prepared FGHs. The semi-ionic CF bonds in FGHs facilitate the ion transport, enhance the electrical conductivity and provide active sites for the faradic reaction. Therefore, the electrochemical performances of FGHs are better than the fluorine-free graphene hydrogel prepared by the same hydrothermal process. FGH prepared at the hydrothermal temperature of 150 °C exhibit the highest specific capacitance (227 F g−1) and the best rate capability. The corresponding symmetric supercapacitor delivers the power density as high as 50.05 kW kg−1 at the current density of 50 A g−1. These results indicate the FGHs are the ideal electrode materials with the great potential in the field of high-power supercapacitors.

Flexible anisotropic films manufactured from one-dimensional aligned nanomaterials can be potentially used in electronic skin and thermal interface applications due to their anisotropic properties. However, high anisotropy also makes the fabrication of aligned polymeric composites with a highly ordered structure and good interface properties very problematic. In this work, transparent, flexible, and robust anisotropic films containing aniline-grafted horizontally aligned carbon nanotube (G−HACNT)/polyimide (PI) composites have been synthesized. The obtained uniform G−HACNT/PI composite films are characterized by a variety of excellent anisotropic properties. Thus, the film electrical (σ) and thermal (κ) conductivities in the longitudinal direction are one order of magnitude higher than the corresponding values measured in the transverse direction (σ//:σ⊥ = 15.3, κ///κ⊥ = 10.1). Furthermore, the tensile strength in the longitudinal direction exceeds that in the transverse direction by 52.9%. The high anisotropy of the flexible films (observed even at 200 °C) with extremely low contents of G−HACNTs (less than 0.1 wt%) originates from the well-aligned nanostructures and preferentially oriented crystalline PI chains. Hence, the flexible and robust G−HACNT/PI composite films with uniformly aligned structures pave the way for fabricating in-plane anisotropic polymeric nanocomposites by controlling interactions between the nanotube and PI components.

A three-dimensional (3D) carbon nanotube/exfoliated graphite block (CNT/EGB) was prepared by growing vertical aligned carbon nanotube (VACNT) at the surface of SiO2-coated exfoliated graphite plate (EGP) through chemical vapor deposition followed by hot-pressing. In such 3D CNT/EGB, EGPs were bridged by the VACNTs in the cross-plane direction, and the interface between EGPs and VACNTs was covalently bonded by SiC which formed by reaction of SiO2 and the adjacent carbon of EGPs and VACNTs. The length and growth density of VACNTs were adjusted by the growth time and concentration of catalysts. Thermal conductivity and mechanical strength of CNT/EGB were controlled by the growth states of VACNTs and hot-pressing. CNT/EGB showed a maximum cross-plane thermal conductivity (k⊥) of 38 W/mK, which is more than twice as much as that of EGB (14 W/mK). A remarkable increase in k⊥ was attributed to the efficient heat flow of VACNTs bridging EGPs in the cross-plane direction and the thermal conductive SiC interface between VACNTs and EGPs. Additionally, the increased bending (76 MPa) and compressive strength (59 MPa) of CNT/EGB was due to the combination of strong pull-out effect of high-density nanotubes and the strong covalent interconnections between VACNTs and EGPs.

Carbon nanotubes (CNTs) with well aligned, highly regular structures possess advanced properties like high crystalline orientation and low thermal interface resistance. These properties enable them to become effective thermal interface materials (TIMs) in thermal management. However, the application is constrained by their fragility in the external environment. Additionally, air gaps and defects make aligned CNTs a poor thermally conducting model. Therefore, aligned CNT/polymer composites have been widely developed to acquire the combination of high thermal conductivity and other excellent properties. There are still some challenges which require further studies on improving the CNT quality, enhancing the interfacial strength and reducing the interface thermal resistance. This paper reviews recent progress in the thermal conduction of CNTs and their polymer composites. The synthesis methods are discussed along with the thermal conducting property dependence on the aligned CNT structure and morphology as well as the interface properties in details.

A large capacity storing solar energy as latent heat in a close-cycle is essentially important for solar thermal fuels. This paper presents a solar thermal molecule model of a photo-isomerizable azobenzene (Azo) molecule covalently bound to graphene. The storage capacity of the Azo depending on isomerization enthalpy (ΔH) is calculated based on density functional theory. The result indicates that the ΔH of Azo molecules on the graphene can be tuned by electronic interaction, steric hindrance and molecular hydrogen bonds (H-bonds). Azo with the withdrawing group on the ortho-position of the free benzene shows a relatively high ΔH due to resonance effect. Moreover, the H-bonds on the trans-isomer largely increase ΔH because they stabilize the trans-isomer at a low energy. 2-hydroxy-4-carboxyl-2′,6′,-dimethylamino-Azo/graphene shows the maximum ΔH up to 1.871 eV (107.14 Wh kg-1), which is 125.4% higher than Azo without functional groups. The Azo/graphene model can be used for developing high-density solar thermal storage materials by controlling molecular interaction.

An important method for establishing a high-energy, stable and recycled molecular solar heat system is by designing and preparing novel photo-isomerizable molecules with a high enthalpy and a long thermal life by controlling molecular interactions. A meta- and ortho-bis-substituted azobenzene chromophore (AZO) is covalently grafted onto reduced graphene oxide (RGO) for solar thermal storage materials. High grafting degree and close-packed molecules enable intermolecular hydrogen bonds (H-bonds) for both trans-(E) and cis-(Z) isomers of AZO on the surface of nanosheets, resulting in a dramatic increase in enthalpy and lifetime. The metastable Z-form of AZO on RGO is thermally stabilized with a half-life of 52 days by steric hindrance and intermolecular H-bonds calculated using density functional theory (DFT). The AZO–RGO fuel shows a high storage capacity of 138 Wh kg−1 by optimizing intermolecular H-bonds with a good cycling stability for 50 cycles induced by visible light at 520 nm. Our work opens up a new method for making advanced molecular solar thermal storage materials by tuning molecular interactions on a nano-template.

Nitrogen and fluorine co-doped graphene (NFG) with the N and F content as high as 3.24 and 10.9 at% respectively was prepared through the hydrothermal reaction of trimethylamine tri(hydrofluoride) [(C2H5)3N·3HF] and aqueous-dispersed graphene oxide (GO) as the anode material for lithium ion batteries (LIBs). The N and F co-doping in graphene increased the disorder and defects of the framework, enlarged the space of the interlayer, wrinkled the nanosheets with many open-edge sites, and thus facilitated Li ion diffusion through the electrode compared with sole-N or F doped graphene. X-ray photoelectron spectroscopy (XPS) analysis of NFG demonstrated the presence of active pyridine and pyrrolic type N, and highly electrically conductive graphitic N and the semi-ionic C–F bond in the structure. The N and F doping content and the component types of N and F functional groups could be controlled by the hydrothermal temperature. The NFG prepared at 150 °C exhibited the best electrochemical performances when tested as the anode for LIBs, including the high coulombic efficiency in the first cycle (56.7%), superior reversible specific discharge capacity (1075 mA h g−1 at 100 mA g−1), excellent rate capabilities (305 mA h g−1 at 5 A g−1), and outstanding cycling stability (capacity retention of ∼95% at 5 A g−1 after 2000 cycles), which demonstrated that NFG was a promising candidate for anode materials of high-rate LIBs.

Light-driven flexible actuators based on a photo-responsive polymer draw much attention due to their great ability for rapid and reversible light-to-work transduction based on a large deformation. An azobenzene chromophore with disulfonic groups (AAZO) was noncovalently grafted on the side-chain of a cationic polymer, poly(diallyldimethylammonium chloride) (PDAC), by electrostatic interaction in a specific weight ratio. A supramolecular assembly of cross-linked AAZO/PDAC showed a reversible isomerization on irradiation by UV light followed by a reversion with a good cycling stability for 50 cycles. Light-driven actuators based on the AAZO/PDAC film exhibited a large deformation by rolling-up into a tube with double walls even when the light was off, along with a spontaneous shape recovery. This photomechanical deformation arose from different rates and degrees of structural transformation of AAZO/PDAC between the front (facing UV light) and back side with the segmental motion of polymers.

Effective conversion of light into heat is an emerging field showing great potential for large-scale applications, markedly driven by novel molecules and structures. Unfortunately, until now, it is still hindered by a low storage capacity and short-time storage. A nano-template for covalently attaching new azobenzene chromophores on graphene as solar thermal fuels is presented here, in which the intermolecular hydrogen bond and proximity-induced interaction, resulting from a high functionalization density and inter-planar bundling interaction, remarkably improve both the storage capacity and lifetime. This nanoscopic template exhibits a high energy density up to 112 W h kg−1 and long-term storage with a half-life of more than one month (33 days), which are also confirmed by the calculations using density functional theory, simultaneously maintaining an excellent cycling stability tuned by visible light for 50 cycles. Our work develops a promising class of solar thermal fuels with high energy density, which outperform previous nano-materials and are comparable to commercial soft-packing Li-ion batteries.

Hierarchical graphene oxide/polyaniline (GO/PANI) nanocomposites deposited on flexible substrates were synthesized by one-step interfacial electrochemical polymerization. PANI nanorods were coated on the surface of GO to form a three-dimensional nanostructure, which was prepared by the polymerization at the water/chloroform interface. The current density for interfacial electrochemical polymerization was up to 0.5 mA cm−2, which is one-fold higher than that used in conventional electrochemical methods for nanostructures. Fourier transform infrared spectra, Raman and ultraviolet-visible absorption spectra indicated that PANI in a highly doped state showed a strong π–π electronic interaction with GO, resulting in an increased degree of conjugation. The flexible all-solid-state supercapacitors using GO/PANI nanocomposites exhibited a high specific capacitance of 1095 F g−1 at 1 A g−1, good rate capability and cycling performance, thus showing an energy density of 24.3 W h kg−1 and the maximum power density of 28.1 kW kg−1. This performance outperforms numerous previous solid-state supercapacitors that used carbon-based/PANI nanocomposites because of the synergistic effect of GO and PANI based on hierarchical nanostructures controlled by interfacial electrochemical polymerization.

High-quality fluorographene (FG) was prepared by solvothermal exfoliation of fluorinated graphite (F-graphite) through intercalation of acetonitrile and chloroform with low boiling points. High-yield production of FG was demonstrated by wrinkled few-layered structures with disordered edges and poor regularity along the stacking direction. X-ray photo electron spectroscopy (XPS) spectra indicated that the intercalation of chloroform led to the partial transformation from covalent C–F bonds to semi-ionic C–F bonds. A lithium primary battery (Li-battery) using a FG cathode exhibited a remarkable discharge rate performance because of good Li+ diffusion and charge mobility through nanosheets. FG nanosheets exfoliated using chloroform showed a high specific capacity of 520 mA h g−1 and a voltage platform of 2.18 V at a current density of 1 C, accompanied by a maximum power density of 4038 W kg−1 at 3 C, which is almost four times higher than that of F-graphite. The results indicate that the solvothermal exfoliation using a low-boiling-point solvent is a facile, efficient and high-yield approach to prepare high-purity FG nanosheets for high-performance Li-batteries.

Three-dimensional hierarchical carbon nanocoil–graphite (CNC–GT) nanocomposite blocks were prepared by the growth of CNCs at the interlayer of expanded GT using chemical vapor deposition followed by hot-pressing. The distribution and density of the CNCs were tuned by vacuum impregnation for catalyst loading and growth time, respectively. Helical CNCs with spring-like structures were observed by scanning electron microscopy and transmission electron microscopy. The CNC–GT blocks showed a higher density and lower porosity than GT due to the intercalation of CNC fillers. The thermal conductivities of the CNC–GT blocks in the cross-plane (λ⊥) and in-plane (λ‖) directions were controlled by the consolidating pressure and growth time of the CNCs. The remarkable increase in λ⊥ and the resilience of the CNC–GT blocks were further optimized using microstructures of CNCs at the interface. The maximum λ⊥ of the CNC–GT blocks (∅ 3 cm × 2 mm) of up to 23.6 W m−1 K−1 was about five-fold higher than that of GT at 4.9 W m−1 K−1. This feature arose from improved phonon transfer in the cross-plane through intercalated CNCs at the interlayer. Moreover, a high resilience ratio of 84.1% and a low compressibility (17%) were also obtained for the CNC–GT blocks due to the excellent elasticity of CNCs. The CNC–GT blocks with high λ⊥, good resilience properties and dimensional stability could be developed to be highly thermally conductive and resilient interface materials for heat sealing.

The studies of the self-assembly processes of nanoparticles (NPs) will benefit the understanding of both the fundamental properties of nanomaterials and the bottom-up fabrication technologies at nanoscales. The NPs can self-assemble into complex microscale structures, which have been reported and attracted increasing attention in recent years. In this paper, a kind of bowknot-shaped structure formed from the individual (CdS)/CdTe NPs has been fabricated. Interestingly, the bowknot structure twists upon ultraviolet (UV) light irradiation. Special multiparticle assemblies of the double-flower-shaped structures are identified. The structural transformation process could be attributed to photocorrosion of CdS under the UV light. The bowknot-shaped topotactic structure is also important for the transformation of NP superstructures (NP-S). These results indicate that the photoetching technique could adjust the transformation among different NP superstructures, which offers a new method to fabricate novel NP-S. Both irradiated and unirradiated NP-S have been applied in photoelectrochemical devices to verify the photovoltaic effect.

Optically actuated shape recovery materials receive much interest because of their great ability to control the creation of mechanical motion remotely and precisely. An infrared (IR) triggered actuator based on shape recovery was fabricated using polyurethane (TPU) incorporated by sulfonated reduced graphene oxide (SRGO)/sulfonated carbon nanotube (SCNT) hybrid nanofillers. Interconnected SRGO/SCNT hybrid nanofillers at a low weight loading of 1% dispersed in TPU showed good IR absorption and improved the crystallization of soft segments for a large shape deformation. The output force, energy density and recovery time of IR-triggered actuators were dependent on weight ratios of SRGO to SCNT (SRGO:SCNT). TPU nanocomposites filled by a hybrid nanofiller with SRGO:SCNT of 3:1 showed the maximum IR-actuated stress recovery of lifting a 107.6 g weight up 4.7 cm in 18 s. The stress recovery delivered a high energy density of 0.63 J/g and shape recovery force up to 1.2 MPa due to high thermal conductivity (1.473 W/mK) and Young’s modulus of 23.4 MPa. Results indicate that a trade-off between the stiffness and efficient heat transfer controlled by synergistic effect between SRGO and SCNT is critical for high mechanical power output of IR-triggered actuators. IR-actuated shape recovery of SRGO/SCNT/TPU nanocomposites combining high energy density and output forces can be further developed for advanced optomechanical systems.Keywords: carbon nanotube; high density; infrared actuators; reduced graphene oxide; shape recovery;

Nanoparticle (NP) self-assemblies have attracted an increasing amount of attention in recent years because of their potential application in the construction of novel nanodevices. The controllable transformation of NP self-assemblies (NPS) between a polar and nonpolar environment is required for many specific applications because of their different properties in different environments. In this article, water-soluble luminescent CdS/CdTe NPS were synthesized using thioglycolic acid as a capping agent. The stiff and straight NPS bundles became loose after phase transfer from an aqueous to an organic phase. Subsequently, the NPS transferred to the aqueous phase. The loose structure transformed into many twisted nanoribbons. Additionally, hybrid photodetectors made using the organic-soluble NPS and P3HT polymers were fabricated, and we found that the NPS/P3HT blend may be perfect for light detection. The organic-soluble NPS are potentially useful for the fabrication of semiconductor nanojunctions.Keywords: nanoparticle self-assemblies; phase transfer; photodetectors; structural transformations; twisted nanoribbons;

The ability to tune the microstructures, bandgap, conductance, chemical environment and thermal storage of carbon nanomaterials such as carbon nanotubes, graphene and fullerenes by optical modulation or response is important to design and fabricate advanced optoelectronic nanodevices. This review is focused on optical control and regulation of structures, properties, interface and interaction of a new generation of photo-responsive carbon nanomaterials/azobenzene moieties (Carbon–AZO) hybrids. The optical switching properties of Carbon–AZO hybrids resulting from the photo-isomerization between trans and cis isomers are highlighted and discussed in terms of photo-energy conversion devices including switches, sensors, detectors, fuels and storage. A wide range of advanced energy conversion devices using Carbon–AZO hybrids can be developed in the future by the optimization of the chemical structure, steric conformation, electrostatic environment and functionalization of specific molecules.

Carbon fabric (CF)-carbon nanotube array (CNTA)/MnO2 composites with a 3D porous structure are prepared by the electrochemical deposition for high-performance electrochemical capacitors. MnO2 nanoflowers assembled with the petal-like nanosheets uniformly attach on the surface of CNTs. Electrochemical characterization indicates that the maximum specific capacitance of CF-CNTA/MnO2 reach to 740 F g−1 (based on MnO2 alone) with a mass loading of 0.34 mg cm−2 at the scan rate of 2 mV s−1, which is much better than that of MnO2 electrodeposited on the stainless steel and the CF. And the specific capacitance can remain 326 F g−1 even with a mass loading of 4.09 mg cm−2. While a reasonable area-normalized capacitance of 2081 mF cm−2 is achieved with this high mass loading at 0.1 mV s−1. The rate capability measurement shows the CF-CNTA/MnO2 achieved a high retention of 70% with a scan rate range of 2–200 mV s−1, which outperform others 3D porous MnO2-based electrodes reported previously. These excellent electrochemical performances are attributed to large surface area, 3D porous structure and aligned ion diffusion channels of the CF-CNTA/MnO2 composite electrodes.Graphical abstractHighlights► Carbon fabric-carbon nanotube array (CF-CNTA) acts as a unique substrate. ► CF-CNTA/MnO2 composites are prepared by electrodeposition method. ► CF-CNTA/MnO2 shows the maximum specific capacitance of 740 F g−1. ► A reasonable area-normalized capacitance of 2081 mF cm−2 is achieved. ► CF-CNTA/MnO2 obtains an excellent rate capacity and cycle stability.

A highly flexible nanocomposite film of bacterial cellulose (BC) and graphene oxide (GO) with a layered structure was presented using the vacuum-assisted self-assembly technique. Microscopic and X-ray diffraction measurements demonstrated that the GO nanosheets were uniformly dispersed in the BC matrix. The interactions between BC and GO were studied by Fourier transformation infrared spectroscopy. Compared with pristine BC, the integration of 5 wt% GO resulted in 10% and 20% increase in Young's modulus and tensile strength of the composite film. The electrical conductivity of the composite film containing 1 wt% GO after in situ reduction showed a remarkable increase by 6 orders of magnitude compared with the insulated BC.Highlights► A mechanically strong and flexible nanocomposites film of bacterial cellulose (BC) and graphene oxide (GO) was obtained. ► GO nanosheets were uniformly dispersed in the BC matrix. ► The BC/GO film shows in 10% and 20% increase in Young's modulus and tensile strength with 5 wt% GO. ► The conductivity of the BC/GO film with 1 wt% reduced GO showed a remarkable increase by 6 orders of magnitude.

Poly(3,4-ethylenedioxythiophene) (PEDOT) microspheres were formed after the demulsifying treatment when acetone was used as the deemulsifier and dodecylbenzene sulfonic acid (DBSA) was used as the surfactant. We compared the properties of PEDOT with and without the demulsifying treatment as well as observed the morphological and structural changes along this treatment. PEDOT chains changed from rigid to coil conformation during the demulsifying treatment due to the strong interaction between polar acetone molecules and PEDOT chains, which induced PEDOT morphological transformation. Meanwhile, the close solubility parameters of acetone and PEDOT allowed the acetone molecules to penetrate into PEDOT agglomerates and fulfilled this morphological change. The investigation about the acetone volumes and the types of organic solvent to the morphology of PEDOT after the demulsifying treatment demonstrated the morphological transformation is an automatic process initiated by the appropriate organic solvent. PEDOT microspheres after the demulsifying treatment exhibited better capacitance behavior than that of PEDOT without this treatment when they were applied as the electrodes of supercapacitors.Highlights► PEDOT microspheres were synthesized through the demulsifying treatment. ► PEDOT was partially reduced and de-doped by using acetone as the deemulsifier. ► The change of PEDOT chains to coil conformation initiated this morphological change. ► The effective organic solvents should feature strong dipole and suitable solubility. ► The specific capacitance of PEDOT was enhanced after the demulsifying treatment.

Vertically aligned carbon nanotubes (VACNTs) were directly grown on carbon fabric (CF) using the controllable injection chemical vapor deposition without the pretreatment of the surface of CF. Electrochemical characterization indicated that VACNT/CF electrodes achieved a relative high specific capacitance of 75 F g−1 at a current density of 1 A g−1 due to large specific surface area and low contact resistance. The specific capacitance still remained 63 F g−1 at a high current density of 100 A g−1 with the retention of 84%, which far exceeded other carbonaceous materials. This excellent rate capability of VACNT/CF electrodes was attributed to large mesopore size, three-dimensional hierarchical architecture and aligned pathway, facilitating the diffusion of electrolyte ions. In addition, the area-normalized capacitance of VACNT/CF electrodes was improved remarkably by prolonging the growth time of CNT.Graphical abstractHighlights► Vertically aligned carbon nanotubes (VACNT) were grown on carbon fabric (CF). ► The alignment of CNTs was determined by the injection speeds. ► VACNT/CF shows a specific capacitance of 77 F g−1 at scan rate of 50 mV s−2. ► The VACNT/CF achieved a high rate capability even at 100 A g−1. ► The area-normalized capacitance was improved by prolonging the growth time.

Transparent, conductive, and flexible multiwalled carbon nanotube (MWCNT)/graphene hybrids with two three-dimensional microstructures—an interconnected network and a double-layer structure—were prepared. The conductivity and performance of MWCNT/graphene films can be controlled by different microstructures. A photoswitch using a layered heterostructure of a CdTe quantum dot on an interconnected MWCNT/graphene (IN-MWCNT/graphene) electrode shows an enhanced reversible photocurrent with a higher on/off ratio than that of double-layer structures(DL-MWCNT/graphene). Electrochemical capacitors using a IN-MWCNT/graphene network also exhibit an outstanding rate capability and good cycling stability due to a large surface area and high porosity. Results indicate that the IN-MWCNT/graphene hybrid with porous structures and strong π-interaction is an excellent conductive network for multifunctional flexible devices. The performance of MWCNT/graphene hybrid films can be further optimized by the improved interface and microstructures.

Band gap, which can be tuned by changing the size of quantum dots (QDs) based on the quantum confinement effect, plays a fundamental role in electrical and optical properties of QDs. However, the tuning of the band gap by changing the size results in a series of intrinsic problems, such as the instability of the extremely small QDs, negative combination with biomolecules because of the large size of QDs, etc. Recently, several new methods have been developed to further study and improve the tuning of the band gap. In this paper, we summarized the recent progress in the fields of tuning the band gap of QDs, including alloyed QDs, core-shell QDs and doped QDs. The review has also prospected the development trend of tuning the band gap as well as their applications.

The nanoporous network formed by 1,3,5-tris(10-carboxydecyloxy) benzene (TCDB) was used as the host nanoporous network. It has been identified that a variety of guest molecules (such as triphenylene, 1-phenyloctane and copper(II) phthalocyanine (CuPc)) can be dispersed in this template to form binary supramolecular architectures, which were studied by scanning tunneling microscopy (STM). It is interesting to observe that the host network can adjust itself in response to the molecular size and shape of the guest, and the guest molecules can be excluded by some other guest molecules. The dynamics of CuPc molecules entrapped in TCDB is reported. The STM images as well as the density-functional theory (DFT) calculations reveal that the guest selectivity depends not only on geometry of guest molecules, but also on their adsorption energy in host networks.

The discharge performance of Li/CFx (x = 1) battery is improved by using multi-walled carbon nanotubes (MWCNTs) as an alternative conductive additive. Compared with the battery using acetylene black as conductive additive at the same amount, the Li/CFx battery using MWCNTs as conductive additive has higher specific capacity and energy density as well as smoother voltage plateau, especially at higher discharge rate. The specific capacity at discharge rate of 1 C is improved by nearly 26% when MWCNTs are employed as conductive additive. Meanwhile, it is also found that the discharge performance is able to be tuned by the amount of MWCNTs and the battery containing more MWCNTs is favorable to be discharged at higher rates. The specific capacity of Li/CFx battery with 11.09 wt.% MWCNTs is approximately 712 mAh g−1 at the discharge rate of 1 C. It is proposed that the formed three-dimensional networks of MWCNTs in cathode, which enlarges the contact area of interphase and facilitates electrons delivery, accelerates the rates of lithium ion diffusion into the fluorinated layers and electrons transport in cathode at the same time, which improves the discharge performance of Li/CFx battery subsequently, especially at higher rates.

Multi-walled carbon nanotubes (MWCNTs) were grafted onto carbon fibers (CFs) using an injection chemical vapor deposition method. The orientation and length (16.6–108.6 μm) of the MWCNTs were controlled by the surface treatment of the CFs and the growth time, respectively. The interface between the MWCNTs and the CFs indicated the grafted CNTs were immobilized by embedding catalyst on CFs. Two orders of magnitude increase in the specific surface areas of CFs was obtained by grafting the MWCNT. MWCNT–CF hybrids exhibited good wettability with the epoxy resin due to the surface roughness and capillary action. Single-fiber composite fragmentation tests revealed an remarkable improvement of interfacial shear strength (IFSS) controlled by the orientation and length of MWCNTs. MWCNTs with an perpendicular alignment and long length showed a high IFSS in epoxy composites due to better wettability and a large contact interface between the hybrids and the resin. Hybrids with an optimum length (47.2 μm) of aligned MWCNTs showed a dramatic improvement of IFSS up to 175% compared to that of pristine CFs.

A highly sensitive light-driven switch assembled by Al-doped zinc oxide (AZO) nanofibers was prepared by electrospinning. Uniform electrospun porous AZO nanofibers with an average diameter of 170 nm were observed by scanning electron microscopy and transmission electron microscopy. The small radii of Al3+ and Zn vacancies occupied in the zinc oxide crystal lattice resulted in small crystal grains and a large band gap of AZO nanofibers. The reversible and enhanced photocurrent illustrated a strong Al content dependence. A photoswitch based on AZO nanofibers with an Al dopant concentration of 1 atm. % showed the highest on/off ratio of 30 after 20 cycles due to excited excitons at the defect level illuminated by the simulated solar light. The decay of the photocurrent under long time illumination was affected by the adsorption to defects. High sensitivity and enhanced photocurrent put a insightful understanding of writable photoswitches or memories using electrospun AZO nanofibers.

An azobenzene (AZO) chromophore was covalently attached to graphene oxide (GO) through an amide linkage. The microstructure of the GO–AZO hybrid was characterized by microscopic and X-ray diffraction methods. An internal short-range ordered crystalline structure similar to graphite was observed. Spectroscopic evidence testified the strong electronic interactions between the AZO and GO in this GO–AZO hybrid system. Upon ultraviolet (UV) irradiation, the AZO moieties bonding on GO underwent a reversible trans–cis photoisomerization behavior. An optical modulated conductance of the GO–AZO film induced by the isomerization of the AZO chromophores was also monitored. The current showed a twofold increase after irradiation of UV light for 20 min.

An azobenzene molecule (AZO) with a flexible alkyl chain was attached to the sidewall of few-walled carbon nanotube (FWCNT) to form a FWCNT-chain-AZO hybrid by covalent bonding. Transmission electron microscopy image shows individually well-dispersed FWCNT packed underneath AZO molecules. The flexible spacer between the FWCNT and the AZO led to the efficient photoisomerization and thermal reversibility of the FWCNT-chain-AZO due to an increase of free volume. A light-driven electronic switch based on two FWCNT/AZO hybrids was fabricated. Current–voltage plots showed a marked continuous increase in conductance of the FWCNT-chain-AZO switch due to efficient trans-to-cis photoisomerization. Reversible conductance of the electronic switch during multiple cycles through on/off switching of the light was obtained due to reversible conformation changes.

A phthalocyanine derivative-2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine (NPc) was immobilized on graphene oxide (GO) to form a GO–NPc hybrid by the π–π stacking supermolecular method. Spectroscopic measurements showed that intermolecular interactions immediately happened after mixing the two components together and the resultant hybrid was stable even during the dilution process, which were related to the strong π–π interactions between GO and NPc. Spectroscopic evidence further indicated the stoichiometry of the GO–NPc hybrid was a mass ratio of 1:6 (GO:NPc). X-ray diffraction results demonstrated that a new layered structure existed in the hybrid. A reversible rise/decay of the photocurrent in response to the on/off illumination step was observed in a photoelectrochemical cell of the GO–NPc hybrid.

Arrays of oriented poly(3,4-ethylenedioxythiophene) (PEDOT) micro/nanorods are synthesized by electrochemical galvanostatic method at the current density of 1 mA cm−2 in the cetyltrimethylammonium bromide (CTAB) aqueous solution whose pH value is 1. The CTAB is used both as the surfactant and the supporting salt in the electrolyte solution. The electrochemical properties of PEDOT films are characterized by cyclic voltammetry and galvanostatic charge/discharge techniques, which indicate that the arrays of oriented PEDOT micro/nanorods can be applied as the electrode materials of supercapacitors. In addition, the cycling performance of PEDOT micro/nanorods is much better than that of traditional PEDOT particles. The effects of the concentration of CTAB, the current density, and pH value of electrolyte solutions on the morphologies and electrochemical properties of PEDOT films are investigated. The mechanism of different morphologies formation is discussed in this study as well.

A naphthalocyanine/few-walled carbon nanotube (NaPc/FWCNT) hybrid was synthesized by packing NaPc crystalline onto the sidewall by π–π stacking. A well-dispersed NaPc/FWCNT was observed by transmission electron microscopy. Absorption spectra of NaPc/FWCNT showed a band edge at 1150 nm due to electronic interaction. A continuous poly(3-hexylthiophene):6,6-phenyl-C61-butyric acid methyl ester:NaPc/FWCNT film was observed by atomic force microscopy. Illumination of NaPc/FWCNT film using near-infrared light at 780 nm resulted in the generation of the photocurrent attributed to efficient exciton absorption and charge transfer at the interface.

Shape-controllable polyaniline (PANI) nanostructures varying from fibers to micromats and disks were synthesized via a self-assembly process with salicylic acid (SA) as dopant. It has been achieved just by tuning the concentration of aniline, the mole ratio of SA to aniline, and the mole ratio of APS to aniline in the same reaction. The diameters of the fibers could be controlled from 30 to 400 nm by adjusting the concentration of aniline. Micromats of fibers would be formed by changing the mole ratio of SA to aniline. Disk-like PANI nanostructures were synthesized when decreasing the mole ratio of APS to aniline. Scanning electron microscopy and transmission electron microscopy were applied to investigate various kinds of morphologies. The mechanism of forming these morphologies was proposed to be adjusted by the pH value during polymerization. Ultraviolet–visible (UV–vis) absorption spectra and Raman spectra suggested that these as-prepared PANI were in conductive emeraldine state and featured obviously different molecular structures, which aroused from different reaction conditions.

A novel method combining the electrospinning method and the polymerization in microreactor was introduced to prepare core–shell poly(3,4-ethylenedioxy thiophene) (PEDOT)/polyvinyl alcohol (PVA) ultrafine fibers. The O/W emulsion of EDOT/PVA was prepared with the help of sodium dodecylsulfate as the emulsifier and the method of introducing monomers into the electrospinning solution had rarely been reported. The emulsion electrospinning was employed to obtain beaded PVA fibers with EDOT encapsulated inside the beads. Some uniform fibers exhibited core–shell structure too. EDOT in the core of the fibers was then polymerized by chlorine, resulting in PEDOT/PVA composite fibers, and the shell of the electrospun fiber was indeed a new kind of microreactor. The corresponding electrochemical measurements demonstrated the electron transport properties of the PEDOT/PVA composite fibers film, which justified its potential application in sensors.

Graphene, a rapidly rising star on the horizon of material science, has a unique two-dimensional nanostructure as well as exceptional mechanical and electronic properties. Despite its short history, graphene has exhibited great potential in various applications. In order to implement the potential applications, functionalization of graphene is necessary to obtain uniform dispersions for good processability. Two kinds are dominant for functionalization such as covalent and non-covalent methods. The former is based on the formation of covalent bonds, and the latter the interaction among molecules. In this review, we summarized briefly the recent progress of functionalized graphene sheets (FGs) in different fields, such as optoelectronic materials, sensors, energy storage materials, catalytic, reinforcing components and so on, and also prospected the development trend of FGs in the future.

An enhanced photoinduced reversible switching of graphene oxide-azobenzene (GO-AZO) hybrid was investigated as a highly sensitive photoswitch. The internal short-range ordered crystalline structure of GO-AZO hybrid was advantageous to charge transfer. The AZO moieties on GO underwent a rapid trans−cis photoisomerization upon ultraviolet irradiation due to the electron interaction between AZO and GO. The GO-AZO hybrid film showed an enhanced reversible photoswitching performance with high on/off ratio of 8 and fast response time less than 500 ms. The high sensitivity of GO-AZO switch arises from the intramolecular donor−acceptor architecture with efficient charge transfer.

In this paper, the recent development of fluorinated carbon nanotubes (F-CNTs) was introduced. The synthesizing methods of F-CNTs, including direct fluorination and plasma treatment, were discussed in detail, and the effects of factors, such as the temperature and pressure in fluorination as well as the kind of fluorine source and carbon nanotubes, on the structures and properties of F-CNTs were also summarized. In the mean time, the special physical and chemical properties of F-CNTs and the relevant applied fields were described briefly, the exisiting problems of F-CNTs were summed up, and the direction of future development was also discussed in the end.

Chiral polyaniline (PANI), of flaky, spherical and urchin-like morphologies, was synthesized in the saturated l-phenylalanine solution by adjusting the molar ratio of l-phenylalanine to aniline from 0.25 to 40. The concentration of l-phenylalanine solution was constant, which was different from the conventional synthesis. The morphologies of PANI were observed by scanning electron microscopy. The molar ratio of l-phenylalanine to aniline and the amount of aniline were proposed to be crucial to the morphologies. Circular dichroism spectra confirmed that l-phenylalanine endowed predominately one type of chirality to polyaniline by hydrogen bonding. The optical, structural and electrochemical properties of these synthesized PANI were characterized by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry, respectively. There were some insulating structures, such as oligomers, in the PANI chains, which were caused by the weak acid circumstance during the polymerization.

Here we demonstrated a simple and reliable method to prepare single or multiple core/shell structured capsules and then demonstrate how to produce single or multiple-layer hollow spheres. Those capsules or hollow spheres could be made of organic and/or inorganic functional materials depending on the experimental design. Core–shell composite capsules consisting of TiO2–polyaniline (PANI) shell and polystyrene (PS) core were prepared by using core–shell structured sulfonated-PS spheres as templates. Aniline was polymerized in the shell of sulfonated-PS spheres. Since the PANI was in situ doped by sulfonic acid, the as-synthesized composite capsules had good conductivity. After PS cores were dissolved in solvent, hollow TiO2–PANI spheres formed, which could be further calcined to produce mesoporous hollow TiO2 spheres. The cavity size of the hollow spheres was uniform, at approximately 170 nm in diameter and with a shell thickness of 30 nm. The cavity size and the shell thickness can be synchronously controlled by adjusting the sulfonation reaction time of PS spheres. Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray powder scattering were employed to characterize these as-prepared spheres.

The optical and photovoltaic properties of a photovoltaic cell with a structure of indium–tin oxide (ITO)/double ZnO/poly(3-hexylthiophene) (PAT6):PCBM/Ag have been investigated. The double layer ZnO was a composite of a sputtered ZnO layer and oriented zinc oxide nanopillars layer which was fabricated by a new method at low temperature (343 K). It is concluded that the double layer ZnO plays an important role in collecting photogenerated electrons and acts as a conducting path to the electrode. Insertion of the double layer ZnO in the photovoltaic cells produced enhanced performance with the power conversion efficiency of 1.42% under AM1.5 illumination.

A new type of photo-responsive perylene diimide–azobenzene dyad (PDI–AZO) was synthesized by covalently adjoining azobenzene chromophore to N-imide position of perylene diimide. The optical properties, photoisomerization and self-assembly morphology of the resultant composites were characterized by UV–vis absorption, photoluminescence (PL) spectra and scanning electron microscope. Larger one-dimension nanobelts were observed in self-assembly PDI–AZO due to the strong molecule stacking. The red-shifted bands arise from the larger conjugation extension by π-electron overlap of perylene ring and azobenzene chromophore. The spectral changes upon the irradiation of ultraviolet light show that larger conjugation extension does not significantly affect the photochromism rate, but it retards the further photoisomerization of azobenzene units in PDI–AZO. The PL quenching of PDI–AZO is dominated by the transfer of the excitons before reverting to the ground state accompanied by the radiation due to the larger conjugation extension.

Single-wall carbon nanotubes (SWNTs) have been covalently modified with poly[(2-methoxy,5-octoxy)1,4-phenylenevinylene] (MO-PPV) by in situ polymerization reaction to form a series of nanocomposites with well-controlled interfaces. The method provided a mean to disperse nanotubes uniformly and maximize the interfacial area at the same time. Absorption spectrum and electron microscopy imaging of the composite structure have been influenced by doped a small amount of functionalized SWNTs. Moreover, steady-state and time-resolved photoluminescence spectra quenched markedly by the introduction of internal polymer/nanotube junctions within the polymer matrix. Photovoltaic devices based on MO-PPV/SWNTs bulk heterojunctions showed much better in performance. The data suggested that such improvement was attributed to the bulk molecular heterojunctions intrinsic nanophase separation that resulted more efficient excitons separation, transportation and collection.

A chitosan (CS)-grafted multiwalled carbon nanotubes (MWCNT) composite (CS-MWCNT) was prepared via covalently grafting a biocompatible polymer CS onto the surfaces of MWCNT and was characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), and transmission electron microscopy (TEM). The interaction between MWCNT and CS was investigated and explained according to the FTIR and UV–vis results. More evidence for the presence of the CS-MWCNT was confirmed by TEM images. In the TEM images, a core-shell structure with nanotubes in the center and a CS layer lying around them was observed. The electrochemical properties of the CS-MWCNT were characterized by an electrodeposition method that involves depositing it on a Au electrode. The porous microstructure of the CS-MWCNT modified electrode was observed by scanning electron microscopy. The excellent electrocatalytic ability of the CS-MWCNT modified electrode towards hydrogen peroxide is applicable to the development of oxidase-based amperometric biosensors.

Free-standing fluorine and nitrogen co-doped graphene paper (FNGP) electrodes were synthesized by a solvothermal process as potential anodes for flexible sodium-ion batteries (SIBs). F and N co-doping in the graphene frameworks simultaneously increases structural defects, provides active sites, and enlarges the graphene interlayer distance; these properties are favourable for improving Na+ storage capabilities. In particular, the semi-ionic CF bonds in FNGP, prepared at a solvothermal temperature of 120 °C, enhance electrical conductivity and hence facilitate electron transport in the electrode. Therefore, this FNGP anode delivers a reversible capacity of 203 mAh g−1 (114.9 mAh cm−3) at 50 mA g−1 after 100 cycles and exhibits superb long-cycling stability with a reversible capacity of 56.3 mAh g−1 at 1 A g−1 after 5000 cycles. In addition, the excellent tensile strength (43.5 ± 1.8 MPa) and maintained electrochemical performance of the FNGP anode in the bent state demonstrate the promise of this electrode for applications in flexible, wearable and rolled-up devices.

Combining heat transfer and high-temperature heat resistance is very important for realising thermal management in harsh environments. Achieving high heat conduction in the through-thickness direction (k⊥) is challenging for carbon fibre (CF) reinforced SiC matrix composite (CF/SiC) based heat resistant materials due to their anisotropic structures and weak bonding between the CF and the matrix. We present a three-dimensional (3-D) hierarchical vertically aligned carbon nanotubes (VACNTs)-CF hybrid by growing VACNTs on the surface of CF fabric. The SiO2 coating enables the strong deposition of the catalyst, facilitating high-density growth of VACNT. The VACNT-CF reinforced SiC composite is prepared by stacking VACNT-CF following by precursor infiltration and pyrolysis process. The VACNT forest not only enables strong interfacial bonding between the CF and the matrix but also greatly improve the k⊥ due to the good interfacial compatibility. The VACNT-CF/SiC composite exhibits k⊥ of 16.80 W/(m K), which is higher than that of the CF/SiC (7.94 W/(m K)), due to highly thermally conductive pathways in the dense structure. The VACNT-CF/SiC composite also conducts heat rapidly in the through-thickness direction. The VACNT-CF/SiC composite with high thermal conductivity, high strength and high oxidation resistance can be used for heat dissipation and resistance by optimising the microstructure.

Tuning the bandgap of thin-layered two-dimensional transition metal dichalcogenide (2D TMDCs) nanocrystals by controlling their composition or structure is considered to be an important method of tailoring light absorption, electron transition and carrier mobility. However, the large-scale synthesis of TMDs with a tunable bandgap on graphene remains challenging owing to the difficulty in controlling the uniformity of the layer thickness. Herein, we report the large-area synthesis of a uniform monolayer MoS2(1−x)Se2x film on a monolayer graphene using low-pressure chemical vapour deposition to realize a 2D heterostructure. The resultant centimetre-scale monolayer MoS2(1−x)Se2x film on graphene showed a highly crystalline structure and a tunable bandgap from 1.82 eV to 1.66 eV, which could be controlled by tuning the atomic ratio of S to Se. A phototransistor with the MoS2(1−x)Se2x/graphene heterostructure exhibited a high responsivity of 40.64 mA W−1 under light irradiation of 465 nm with good stability up to 50 cycles. A high photocurrent arose from the efficient charge transfer from MoS2(1−x)Se2x to graphene with a high carrier mobility based on the good electronic interaction. Thus, the large-scale high-quality bandgap-tunable MoS2(1−x)Se2x/graphene heterostructure with controllable structures and electronic properties could be developed and integrated into advanced optoelectronic devices.

Anisotropic light-switching properties are of great importance in advanced photodetectors, light-gated transistors, and energy storage devices. However, controlling the light-switching conductance of anisotropic materials remains challenging because of the difficulties in tuning the electronic interactions and microstructure in the longitudinal and transverse directions, respectively. We present a transparent and flexible photo-responsive film of azobenzene–poly(methyl methacrylate) (Azo–PMMA) close-packed on the sidewalls of horizontally aligned carbon nanotubes (HACNTs). The alignment leads to an anisotropic electrical conductivity (σ). The aligned composite film shows a steady increase in σ in the longitudinal (σ∥) and transverse directions (σ⊥) during UV irradiation and a continuous decrease after irradiation. The light-switching conductance shows good cycling performance over 25 cycles, which is consistent with the isomerisation of the azobenzene groups in Azo–PMMA. Light-switching conductance is demonstrated in two directions, originating from the light-induced switch to a greater proportion of more conductive cis-Azo isomers, photo-doping and the film contracting during the trans-to-cis photo-isomerisation. The anisotropic Azo–PMMA/HACNT composite film with a light-switchable conductivity paves the way towards the fabrication of anisotropic photo-controllable materials by molecular design and microstructure modulation.

Light-driven flexible actuators based on a photo-responsive polymer draw much attention due to their great ability for rapid and reversible light-to-work transduction based on a large deformation. An azobenzene chromophore with disulfonic groups (AAZO) was noncovalently grafted on the side-chain of a cationic polymer, poly(diallyldimethylammonium chloride) (PDAC), by electrostatic interaction in a specific weight ratio. A supramolecular assembly of cross-linked AAZO/PDAC showed a reversible isomerization on irradiation by UV light followed by a reversion with a good cycling stability for 50 cycles. Light-driven actuators based on the AAZO/PDAC film exhibited a large deformation by rolling-up into a tube with double walls even when the light was off, along with a spontaneous shape recovery. This photomechanical deformation arose from different rates and degrees of structural transformation of AAZO/PDAC between the front (facing UV light) and back side with the segmental motion of polymers.

Nitrogen and fluorine co-doped graphene (NFG) with the N and F content as high as 3.24 and 10.9 at% respectively was prepared through the hydrothermal reaction of trimethylamine tri(hydrofluoride) [(C2H5)3N·3HF] and aqueous-dispersed graphene oxide (GO) as the anode material for lithium ion batteries (LIBs). The N and F co-doping in graphene increased the disorder and defects of the framework, enlarged the space of the interlayer, wrinkled the nanosheets with many open-edge sites, and thus facilitated Li ion diffusion through the electrode compared with sole-N or F doped graphene. X-ray photoelectron spectroscopy (XPS) analysis of NFG demonstrated the presence of active pyridine and pyrrolic type N, and highly electrically conductive graphitic N and the semi-ionic C–F bond in the structure. The N and F doping content and the component types of N and F functional groups could be controlled by the hydrothermal temperature. The NFG prepared at 150 °C exhibited the best electrochemical performances when tested as the anode for LIBs, including the high coulombic efficiency in the first cycle (56.7%), superior reversible specific discharge capacity (1075 mA h g−1 at 100 mA g−1), excellent rate capabilities (305 mA h g−1 at 5 A g−1), and outstanding cycling stability (capacity retention of ∼95% at 5 A g−1 after 2000 cycles), which demonstrated that NFG was a promising candidate for anode materials of high-rate LIBs.

The nanoporous network formed by 1,3,5-tris(10-carboxydecyloxy) benzene (TCDB) was used as the host nanoporous network. It has been identified that a variety of guest molecules (such as triphenylene, 1-phenyloctane and copper(II) phthalocyanine (CuPc)) can be dispersed in this template to form binary supramolecular architectures, which were studied by scanning tunneling microscopy (STM). It is interesting to observe that the host network can adjust itself in response to the molecular size and shape of the guest, and the guest molecules can be excluded by some other guest molecules. The dynamics of CuPc molecules entrapped in TCDB is reported. The STM images as well as the density-functional theory (DFT) calculations reveal that the guest selectivity depends not only on geometry of guest molecules, but also on their adsorption energy in host networks.

The studies of the self-assembly processes of nanoparticles (NPs) will benefit the understanding of both the fundamental properties of nanomaterials and the bottom-up fabrication technologies at nanoscales. The NPs can self-assemble into complex microscale structures, which have been reported and attracted increasing attention in recent years. In this paper, a kind of bowknot-shaped structure formed from the individual (CdS)/CdTe NPs has been fabricated. Interestingly, the bowknot structure twists upon ultraviolet (UV) light irradiation. Special multiparticle assemblies of the double-flower-shaped structures are identified. The structural transformation process could be attributed to photocorrosion of CdS under the UV light. The bowknot-shaped topotactic structure is also important for the transformation of NP superstructures (NP-S). These results indicate that the photoetching technique could adjust the transformation among different NP superstructures, which offers a new method to fabricate novel NP-S. Both irradiated and unirradiated NP-S have been applied in photoelectrochemical devices to verify the photovoltaic effect.

Effective conversion of light into heat is an emerging field showing great potential for large-scale applications, markedly driven by novel molecules and structures. Unfortunately, until now, it is still hindered by a low storage capacity and short-time storage. A nano-template for covalently attaching new azobenzene chromophores on graphene as solar thermal fuels is presented here, in which the intermolecular hydrogen bond and proximity-induced interaction, resulting from a high functionalization density and inter-planar bundling interaction, remarkably improve both the storage capacity and lifetime. This nanoscopic template exhibits a high energy density up to 112 W h kg−1 and long-term storage with a half-life of more than one month (33 days), which are also confirmed by the calculations using density functional theory, simultaneously maintaining an excellent cycling stability tuned by visible light for 50 cycles. Our work develops a promising class of solar thermal fuels with high energy density, which outperform previous nano-materials and are comparable to commercial soft-packing Li-ion batteries.

Designing an energy-dense and thermal-stable photo-isomerizable chromophore/hybrid template is a challenge for devising a highly customizable solar-heat conversion and storage technology. This study presents the templated assembly of close-packed 2-chloro-4,6-bis(4-(phenyldiazenyl)phenoxy)-1,3,5-triazine (bis-azobenzene chromophores) covalently bound to reduced graphene oxide (RGO-bis-Azo). The steric configuration and energy of bis-Azo (trans- and cis-isomers), calculated by density functional theory, are influenced by intra- and inter-molecular steric hindrance due to high grafting density and the bundling effect. This results in a dramatic increase in enthalpy and activation energy of the isomerization. The RGO-bis-Azo hybrid combines a high energy density of 80 W h kg−1, the maximum power density of 2230 W kg−1 and a tunable heat release time from 2 min to 5520 h. These findings pave the way for developing a chromophore/hybrid template for solar thermal fuel by optimizing molecular interaction.

Hierarchical graphene oxide/polyaniline (GO/PANI) nanocomposites deposited on flexible substrates were synthesized by one-step interfacial electrochemical polymerization. PANI nanorods were coated on the surface of GO to form a three-dimensional nanostructure, which was prepared by the polymerization at the water/chloroform interface. The current density for interfacial electrochemical polymerization was up to 0.5 mA cm−2, which is one-fold higher than that used in conventional electrochemical methods for nanostructures. Fourier transform infrared spectra, Raman and ultraviolet-visible absorption spectra indicated that PANI in a highly doped state showed a strong π–π electronic interaction with GO, resulting in an increased degree of conjugation. The flexible all-solid-state supercapacitors using GO/PANI nanocomposites exhibited a high specific capacitance of 1095 F g−1 at 1 A g−1, good rate capability and cycling performance, thus showing an energy density of 24.3 W h kg−1 and the maximum power density of 28.1 kW kg−1. This performance outperforms numerous previous solid-state supercapacitors that used carbon-based/PANI nanocomposites because of the synergistic effect of GO and PANI based on hierarchical nanostructures controlled by interfacial electrochemical polymerization.