Naien Shi

Formation of graphene oxide gel via the π-stacked supramolecular self-assembly

Graphene oxide gel (GOG) possesses intrinsic three-dimensional (3D) networking architecture with large surface area and high porosity. Here, we report a novel method of fabrication of GOG by self-assembling a ferrocene-decorated graphene oxide sheets (GOS) at room temperature. Our systematic investigations reveal that Fc plays a critical role in the formation of such unique 3D architecture, as it functions as an effective interlayer cross-linker through the π–π interaction. The morphology, crystal structure, chemical bonding, porosity and thermal stability of the as-prepared GOG have been studied. This work successfully provides a facile and efficient way to form GOG and will extend the potentials of GOG as a promising electro-active material in carbon-based electronics or catalytic reactors.

Coralloid Co2P2O7 Nanocrystals Encapsulated by Thin Carbon Shells for Enhanced Electrochemical Water Oxidation

Core-shell nanohybrids containing cheap inorganic nanocrystals and nanocarbon shells are promising electrocatalysts for water splitting or other renewable energy options. Despite that great progress has been achieved, biomimetic synthesis of metal phosphates@nanocarbon core-shell nanohybrids remains a challenge, and their use for electrocatalytic oxygen evolution reaction (OER) has not been explored. In this paper, novel nanohybrids composed of coralloid Co2P2O7 nanocrystal cores and thin porous nanocarbon shells are synthesized by combination of the structural merits of supramolecular polymer gels and a controllable thermal conversion technique, i.e., temperature programmable annealing of presynthesized supramolecular polymer gels that contain cobalt salt and phytic acid under a proper gas atmosphere. Electrocatalytic tests in alkaline solution show that such nanohybrids exhibit greatly enhanced electrocatalytic OER performance compared with that of Co2P2O7 nanostructure. At a current density of 10 mA cm(-2), their overpotential is 0.397 V, which is much lower than that of Co2P2O7 nanostructures, amorphous Co-Pi nanomaterials, Co(PO3)2 nanosheets, Pt/C, and some reported OER catalysts, and close to that of commercial IrO2. Most importantly, both of their current density at the overpotential over 0.40 V and durability are superior to those of IrO2 catalyst. As revealed by a series of spectroscopic and electrochemical analyses, their enhanced electrocatalytic performance results from the presence of thin porous nanocarbon shells, which not only improve interfacial electron penetration or transfer dynamics but also vary the coordination environment and increase the number of active 5-coordinated Co(2+) sites in Co2P2O7 cores.

A highly sensitive fluorescent sensor based on small molecules doped in electrospun nanofibers: detection of explosives as well as color modulation

Fluorescent polymer nanofibers have wide applications in the fields of nano-photonics, nano-optoelectronics, chemical sensors and light-emitting diodes. The doping of small fluorophores into low-cost polymers is a proven alternative route to produce cost-effective and high-performance optical materials. In order to gain deep insight into the photophysical processes of small molecule-doped polymer nanofiber systems and obtain highly sensitive and cost-effective explosive fluorescent sensors, a new type of highly sensitive low-cost sensor for nitro-compounds was synthesized based on PEO/MePyCz (polyethylene oxide/4-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-9-(pyren-1-yl)-9H-carbazole) composite nanofibers. It exhibited fast response and high quenching efficiency towards DNT vapor, which may be attributed to an improved exciton migration of MePyCz in PEO in addition to the large driving force of the electron transfer and the nanofibrous structures. Additionally, it promoted a fluorescence resonance energy transfer process in the polymer fibrous matrix with a green-emitting material of 2-(thiophen-2-yl)-fluoren-9-one. The sensing composite nanofibrous film had good sensitivity and selectivity and might be constructed into a portable detector for explosives.

Electrical characteristics and carrier transport mechanisms of write-once-read-many-times memory elements based on graphene oxide diodes

We demonstrated write-once-read-many-times (WORM) memory devices based on graphene oxide (GO) film sandwiched between ITO and LiF/Al electrode. The devices showed irreversible electrical transition from the low conductivity (OFF) state to the high conductivity (ON) state and the ON/OFF current ratio between the conductivities of two states was over 5.7 × 104. The results of I-V data, AFM and SEM images indicated that the WORM memory characteristics of GO diodes were mainly attributed to charge trapping at GO layers and interfacial properties between GO and LiF/Al electrode.

Facile synthesis of shape and size tunable porphyrinoid coordination polymers: from copper porphyrin nanoplates to microspindles

Size tunable copper porphyrin dispersed nanoplates, assembled nanoplates, and microspindles have been controllably fabricated by a simple surfactant-assisted solution route.

BF3·Et2O-mediated Friedel–Crafts C–H bond polymerization to synthesize π-conjugation-interrupted polymer semiconductors

C–H bond functionalization offers a chance to develop a new concept of polymerization. In this article, a family of diarylfluorene-based π-conjugation-interrupted polymers (CIPs) with nonlinear or hyperbranched frameworks have been explored by BF3·Et2O-mediated Friedel–Crafts polymerization of AB, AB2 and AB4-type tertiary alcohol monomers at room temperature. Their chemical structures and optoelectronic properties have been characterized and the existence of strong intermolecular π-stacked aggregates have been observed. CIP semiconductors afford a new platform to explore novel functionality of organic devices in organic electronics or spinelectronics.

Uncommon hexagonal microtubule based gel from a simple trimesic amide

A small molecule of N,N′,N″-tris(3-methylpyridyl)-trimesic amide was assembled into a novel hexagonal microtube through intermolecular hydrogen bonds, and simultaneously formed a gel system in H2O–THF mixed solvent. Tuning gelator concentration or the preparation method can effectively control the size of the hexagonal tubes.

π-System based coordination polymer hollow nanospheres for the selective sensing of aromatic nitro explosive compounds

Herein, a type of π-system based fluorescent coordination polymer hollow nanospheres of terbium 1,3,5-benzenetrisbenzolate (TbBTB) was synthesized through a solvothermal process, and the nanospheres exhibited a good sensing performance for the detection of explosive aromatic nitro-compounds, as compared to aliphatic nitro-compounds as well as the small organic solvent molecules of dimethyl sulfoxide, chloroform and tetrahydrofuran. FESEM and TEM results showed that the spheres are 300–600 nanometers in diameter and they are composed of small nanoparticles of coordination polymer. The formation of the spheres is driven by the Ostwald ripening process under solvothermal conditions according to a series of corresponding control experiments. The sensing of aromatic nitro explosives may benefit from the special features of the nanospheres, which possess an intrinsic π-system of both π-conjugated ligands and intermolecular π–π stacking interactions, as well as their multiscale-porosity. This study may benefit the screening or design of fluorescent sensors for aromatic and aliphatic explosive nitro-compounds.

Efficiency enhancement in P3HT-based polymer solar cells with a NaYF4:2% Er3+, 18% Yb3+ up-converter

The commonly used donor material poly(3-hexylthiophene) (P3HT) confines the power conversion efficiency (PCE) in P3HT-based polymer solar cells due to its relatively large bandgap of ∼1.9 eV and the resultant limited absorption wavelength region of less than 650 nm. In this communication, the highly efficient up-conversion (UC) material NaYF4:2% Er3+, 18% Yb3+, converting near-infrared radiation into green and red emissions, is introduced into a P3HT/P3HT:[6,6] phenyl C61 butyric acid methyl ester (PC61BM) bulk heterojunction solar cell, referred to as a “bilayer cell”, to compensate for the non-absorbable wavelength region of P3HT. With an optimal UC doping concentration of 11.7% (weight ratio of UC to P3HT) in the P3HT matrix, the short-circuit current density and PCE for UC-doped bilayer cell are as high as 10.89 mA cm−2 and 3.62%, about 16.6% and 10.7% higher than the P3HT/P3HT:PC61BM bilayer cell and 22.4% and 16.4% higher than the standard P3HT:PC61BM bulk heterojunction one, respectively, although the fill factor in the UC-doped bilayer cell shows a slight decrease. The research result demonstrates that both the emission and the scattering of UC nanoparticles are beneficial to the enhancement of the solar cells electrical performances.

A polyhedral supramolecular system of endocyclic crystalline organic nanostructures: the case of triptycenes

Controlled synthesis of polyhedral crystals has acquired intense attention over the past few years due to their potential electrical and optical properties and special functionalities for integrated devices. In this work, endocyclic molecules of triptycene are self-assembled into pretty uniform polyhedra of quasi-decahedra and well-defined nanosheets via the assistance of P123 and CTAB, respectively. These nanostructures have been clearly investigated by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) and X-ray diffraction (XRD) patterns. The aromatic multi-plane triptycene molecules exhibit a definite three-dimensional assembly tendency and the assembly process can also be effectively tuned by surfactants. The above results are invaluable to the design of polyhedron supramolecular synthons and go forward through simulation as well as morphology control to certain promising nanoscale structures.