To develop high-capacitance flexible solid-state supercapacitors and explore its application in self-powered electronics is one of ongoing research topics. In this study, self-stacked solvated graphene (SSG) films are reported that have been prepared by a facile vacuum filtration method as the free-standing electrode for flexible solid-state supercapacitors. The highly hydrated SSG films have low mass loading, high flexibility, and high electrical conductivity. The flexible solid-state supercapacitors based on SSG films exhibit excellent capacitive characteristics with a high gravimetric specific capacitance of 245 F g⁻¹ and good cycling stability of 10 000 cycles. Furthermore, the flexible solid-state supercapacitors are integrated with high performance perovskite hybrid solar cells (pero-HSCs) to build self-powered electronics. It is found that the solid-state supercapacitors can be charged by pero-HSCs and discharged from 0.75 V. These results demonstrate that the self-powered electronics by integration of the flexible solid-state supercapacitors with pero-HSCs have great potential applications in storage of solar energy and in flexible electronics, such as portable and wearable personal devices.

Conformational changes of peptides are critically important in the control of their biological activities. Here, a quaternary ammonium group-terminated RGD-containing peptide (RGD-NMe₃) is designed, which may undergo reversible conformational switch upon different electrochemical potentials. Potential responsive peptide interfaces are constructed on gold substrates with RGD-NMe₃ in a tetra (ethylene glycol) background. It is demonstrated that by applying positive and negative potentials, the RGD peptide can be reversibly switched between linear and cyclic conformation, which can be used in reversible controlling of cell adhesion/migration on the interface. Furthermore, by combining microfluidics, adhesion of the cells in specific areas on the surface and subsequent directional migration of the cells can be controlled. It is believed that this straightforward potential modulation mechanism for peptide conformation control may find a wide use in design responsive peptide interfaces.

By changing the packing motif of the conjugated cores and the thin-film microstructures, unipolar organic semiconductors may be converted into ambipolar materials. A combined experimental and theoretical investigation is conducted on the thin-film organic field-effect transistors (OFETs) of three organic semiconductors that have the same conjugated core structure of s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione but with different n-alkyl groups. The optical and electrochemical measurements suggest that the three organic semiconductors have very similar energy levels; however, their OFETs exhibit dramatically different transport characteristics. Transistors based on compound 1a or 1c show ambipolar transport properties, while those based on compound 1b show p-type unipolar behavior. Specifically, compound 1c is characterized as a good ambipolar semiconductor with the highest electron mobility of 0.22 cm² V⁻¹ s⁻¹ and the highest hole mobility of 0.03 cm² V⁻¹ s⁻¹. Complementary metal oxide semiconductor (CMOS) inverters incorporated with compound 1c show sharp inversions with high gains above 50. Theoretical investigations reveal that the drastic difference in the transport properties of the three materials is due to the difference in their molecular packing and film microstructures.

Photoluminescent carbon and/or silicon-based nanodots have attracted ever increasing interest. Accordingly, a myriad of synthetic methodologies have been developed to fabricate them, which unfortunately, however, frequently involve relatively tedious steps, such as initial surface passivation and subsequent functionalization. Herein, we describe a green and sustainable synthetic strategy to combine these procedures into one step and to produce highly luminescent carbon quantum dots (CQDs), which can also be easily fabricated into flexible thin films with intense luminescence for future roll-to-roll manufacturing of optoelectronic devices. The as-synthesized CQDs exhibited enhanced cellular permeability and low or even noncytotoxicity for cellular applications, as corroborated by confocal fluorescence imaging of HeLa cells as well as cell viability measurements. Most strikingly, zebrafish were directly fed with CQDs for in vivo imaging, and mortality and morphologic analysis indicated ingestion of the CQDs posed no harm to the living organisms. Hence, the multifunctional CQDs potentially provide a rich pool of tools for optoelectronic and biomedical applications.

Understanding the relationships between the molecular structure and electronic transport characteristics of single-molecule junctions is of fundamental and technological importance for future molecular electronics. Herein, we report a combined experimental and theoretical study on the single-molecule conductance of a series of oligo(phenylene ethynylene) (OPE) molecular wires, which consist of two phenyl–ethynyl–phenyl π units with different dihedral angles. The molecular conductance was studied by scanning tunneling microscopy (STM)-based break-junction techniques under different conditions, including variable temperature and bias potential, which suggested that a coherent tunneling mechanism takes place in the OPE molecular wires with a length of 2.5 nm. The conductance of OPE molecular junctions are strongly affected by the coupling strength between the two π systems, which can be tuned by controlling their intramolecular conformation. A cos² θ dependence was revealed between the molecular conductance and dihedral angles between the two conjugated units. Theoretical investigations on the basis of density functional theory and nonequilibrium Green’s functions (NEGF) gave consistent results with the experimental observations and provided insights into the conformation-dominated molecular conductance.

A series of new organic semiconductors based on s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione was successfully synthesized and characterized. The electron withdrawing carbonyl group lowers the LUMO energy levels, leading to increased electronegativities, which is beneficial for high photo-stability in air. The n-alkyl substituted compounds, 1c and 1d, crystallize with the rigid coplanar systems packed into slipped face-to-face π-stacks. Interestingly, 1c and 1d also show liquid crystalline behaviors, which give highly ordered molecular packing over large area.

Understanding the effects of intermolecular interactions on the charge-transport properties of metal/molecule/metal junctions is an important step towards using individual molecules as building blocks for electronic devices. This work reports a systematic electron-transport investigation on a series of “core-shell”-structured oligo(phenylene ethynylene) (Gn-OPE) molecular wires. By using dendrimers of different generations as insulating “shells”, the intermolecular π–π interactions between the OPE “cores” can be precisely controlled in single-component monolayers. Three techniques are used to evaluate the electron-transport properties of the Au/Gn-OPE/Au molecular junctions, including crossed-wire junction, scanning tunneling spectroscopy (STS), and scanning tunneling microscope (STM) break-junction techniques. The STM break-junction measurement reveals that the electron-transport pathways are strongly affected by the size of the side groups. When the side groups are small, electron transport could occur through three pathways, including through single-molecule junctions, double-molecule junctions, and molecular bridges between adjacent molecules formed by aromatic π–π coupling. The dendrimer shells effectively prohibit the π–π coupling effect, but at the same time, very large dendrimer side groups may hinder the formation of AuS bonds. A first-generation dendrimer acts as an optimal shell that only allows electron transport through the single-molecule junction pathway, and forbids the other undesired pathways. It is demonstrated that the dendrimer-based core-shell strategy allows the single-molecule conductance to be probed in a homogenous monolayer without the influence of intermolecular π–π interactions.

We report herein a simple method for attaching vinyl groups onto the sidewalls of carbon nanotubes (CNTs) and the application of vinyl–carbon nanotubes (CNT–CC) in fabricating polymer composites. The synthesis of CNT–CC was monitored with IR spectroscopy, Raman spectroscopy, and thermogravimetric analysis. The obtained CNT–CC showed good compatibility with the in situ polymerization of poly(methyl methacrylate) (PMMA) and exhibited no tendency for phase separation in the final composite. A transmission electron microscopy study revealed a uniform coating on the CNT–CC tubes, indicating good grafting efficiency of PMMA. The uniform dielectric PMMA coating was responsible for the lower electrical conductivity of the CNT–CC/PMMA composites versus that of the CNTs without vinyl modification. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008