Shengju Zhou

Toward highly efficient CdS/CdSe quantum dot-sensitized solar cells incorporating a fullerene hybrid-nanostructure counter electrode on transparent conductive substrates

At present, the performance of quantum dot-sensitized solar cells (QDSCs) is still much lower than that of conventional dye-sensitized solar cells. Besides efforts on the development of photoanodes, a new generation of materials for counter electrodes is also urgently needed to optimize the structure of QDSCs and improve their power conversion efficiency (PCE). Here, fullerene (C60) films on transparent conductive substrates have been prepared through a cost-effective doctor blade process, which were subsequently applied as counter electrodes in QDSCs. Compared to conventional counter electrodes composed of Pt or activated carbon (AC) electrodes, the C60-based counter electrodes exhibit better electrocatalytic activity, lower charge-transfer resistance and higher exchange current density. Based on these merits, the QDSC with C60-based counter electrode and a polysulfide electrolyte shows an improved PCE of 4.18% under simulated 100 mW cm−2 AM 1.5 illumination. In contrast, the PCEs of the QDSC using Pt or activated carbon as counter electrode under the same conditions are only 1.17% and 3.48%, respectively. Stability test reveals that the C60-based counter electrode has good stability at room temperature.

Fluorescent vesicles formed by simple surfactants induced by oppositely-charged carbon quantum dots

We show for the first time that stable fluorescent vesicles can be constructed by mixing oppositely-charged carbon quantum dots (CQDs) and simple surfactants in water, and can be potentially used as a new generation of biomarkers and drug delivery vehicles.

Robust onionlike structures with magnetic and photodynamic properties formed by a fullerene C60–POM hybrid

We report for the first time the synthesis of a covalently-linked fullerene C60-Dawson POM hybrid, which can form onionlike structures with rich magnetic, electrochemical and photodynamic properties.

Carbon quantum dots in ionic liquids: a new generation of environmentally benign photoluminescent inks

Carbon quantum dots (CQDs) have appeared as attractive photoluminescent (PL) materials that overcome the poor photostability of organic dyes and the environmental hazards of heavy metal-containing quantum dots. Engineering CQDs into PL inks that can find applications in anti-counterfeiting and information encryption is promising. However, current methodologies are limited by several disadvantages, including blocking of the writing/printing tools caused by the slow evaporation of the solvent and the aggregation-induced quenching of CQDs in their dry state, when practical applications are concerned. Herein, a new generation of CQD-based PL inks applying room-temperature ionic liquids (RTILs) as the solvent was prepared. The concept presented herein relies on functionalizing the CQDs with the same or similar cationic moieties as those involved in RTILs and facilely obtaining the PL inks through a one-step phase transfer of the as-prepared water-soluble CQDs to the hydrophobic RTILs. The so-obtained CQDs/RTILs inks are highly photoluminescent and compatible with most commonly used writing and templating tools including gel ink pens, brush pens and stamps. Letters or patterns obtained by these PL inks show impressive photostability under various harsh conditions.

Self-Organization and Vesicle Formation of Amphiphilic Fulleromonodendrons Bearing Oligo(poly(ethylene oxide)) Chains

A new series of N-methylfulleropyrrolidines bearing oligo(poly(ethylene oxide))-appended Percec monodendrons (fulleromonodendrons, 4a-f) have been synthesized. The substituted position of the oligo(poly(ethylene oxide)) chain(s) on the phenyl group of the Percec monodendron for 4a-f was varied, which is at the 4-, 2,4-, 3,5-, 3,4,5-, 2,3,4- and 2,4,6- position, respectively. 4a-e are obtained as solids at 25 °C and can self-organize into lamellar phases as revealed by X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) measurements, while 4f appears as a viscous liquid. The substitution patterns of the oligo(poly(ethylene oxide)) chain(s) also significantly influence the solubility of 4a-f, especially in ethanol and water. Formation of self-organized supramolecular structures of 4d and 4e in water as well as 4d in ethanol is evidenced from UV-vis and dynamic light scattering (DLS) measurements. Further studies in water using various imaging techniques including transmission electron microscopy (TEM), freeze-fracture TEM (FF-TEM), cryo-TEM and atomic force microscopy (AFM) observations revealed the formation of well-defined vesicles for 4d and plate-like aggregates for 4e, indicating that the aggregation behavior of the fulleromonodendrons is highly dependent on their molecular structures. For 4d in ethanol, only irregular aggregates were noticed, indicating the solvent also plays a role on regulating the aggregation behavior. After functionalization with the Percec monodendrons, 4a-f can preserve the intriguing electrochemical properties of pristine C60 as revealed by cyclic voltammetries. The thermotropic properties of 4a-f have also been investigated. It was found that all of them show good thermal stability, but no mesophases were detected within the investigated temperature ranges.

Naphthalene-Functionalized, Photoluminescent Room Temperature Ionic Liquids Bearing Small Counterions.

Obtaining π-conjugated room temperature ionic liquids (RTILs) is difficult because of the relatively strong π-π interaction among the π-moieties. Existing strategies by using bulky counterions greatly hindered further property optimization and potential applications of these intriguing functional fluids through simple ion exchange. Herein, four naphthalene-functionalized, π-conjugated RTILs with small counterions (Br(-) ) have been facilely synthesized with high yields. Our strategy is to attach branched alkyl chains to the cationic backbone of the target compounds (2 a-d), which effectively tune inter- and intramolecular interactions. Compounds 2 a-d have satisfactory thermal stability (up to 300 °C) and low melting points (<-19 °C). Rheological measurements revealed the fluid character of 2 a-d, whose viscosity decrease with the increase of the alkyl chain length and temperature. The presence of the π-conjugated naphthalene moiety imparts 2 a-d photoluminescent properties in bulk solutions. Moreover, the absence of strong π-π stacking among the naphthalene units in solvent-free states enables them to be used as a new generation of photoluminescent inks.

Fullerenols Revisited: Highly Monodispersed Photoluminescent Nanomaterials as Ideal Building Blocks for Supramolecular Chemistry

Fullerenols have been known for decades; however, the photoluminescent (PL) properties and applications in supramolecular chemistry of these molecules have not been well addressed. Herein, a strategy has been developed to purify the as-prepared fullerenols, and the photoluminescence and capabilities of these molecules to form supramolecular self-assemblies were systematically studied. It was found that fullerenols show wavelength-dependent emission with an absolute fluorescent quantum yield of approximately 3.5 %. The PL characteristics are reminiscent of carbon dots, especially those obtained by using the top-down method. The studied fullerenols can be used to detect Cu2+ ions with a limit of detection down to 3.50 μm. In addition, the amphiphilicity of the fullerenols can be readily tuned by ionic complexation with cationic surfactants, such as 1-tetradecyl-3-methylimidazoliumbromide (C14 mimB) and tetradecyltrimethylammonium bromide (TTAB). On increasing the concentration of the surfactant, the transition of aggregates was induced from highly ordered vesicles to honeycomb-structured crystals and finally to giant micelles. After the formation of supramolecular self-assemblies, enhancement of photoluminescence was observed, which can be ascribed to the suppression of intramolecular vibrations and motion combined with the loosely packed self-assembly array. This study provides a facile way to generate PL nanoarchitectures, which may find applications in fluorescent sensing, drug delivery, and optoelectronics.

Thermo-responsive graphene dispersions by liquid phase exfoliation of graphite aided by an alkylated Percec monodendron

Large-scale production of graphene and subsequent sample engineering is the key for fully-realizing the potential applications proposed to this intriguing two-dimensional nanomaterial. Herein, smart graphene dispersions with low defects and thermo-responsive properties can be obtained by liquid phase exfoliation of graphite using an alkylated Percec monodendron (3,4,5-trioctadecyloxybenzaldehyde, 1) as the stabilizing reagent. By simply changing the temperature, the dispersed graphene and 1 can be detached, leading to the recovery of both components. Besides noncovalent wrapping, the stabilizing reagent 1 can be also covalently attached to graphene through [3+2] cycloaddition. The covalently functionalized graphene sheets show improved dispersibility in organic solvents compared to the pristine graphene, which opens the door for their applications in various polymer matrixes. The strategy demonstrated here provides a new methodology to get smart graphene dispersions with multiple functions.摘要石墨烯的宏量制备及其后续处理工艺对全面实现这一有趣二维纳米材料的潜在应用起着至关重要的作用. 在此, 我们采用一种烷基 枝化的Percec型枝化分子(3,4,5-三十八烷基苯基醚-1-甲醛, 1)作为稳定剂, 利用液相剥离石墨粉的方法, 制备了具有低缺陷、热响应性能的 智能石墨烯分散液. 通过简单地改变温度, 便能实现处于分散状态的石墨烯与稳定剂1的分离和回收利用. 除了上述非共价缠绕, 稳定剂1 也能够通过[3+2]环加成反应共价修饰于石墨烯表面. 修饰后的石墨烯在多种有机溶剂中表现出比未修饰石墨烯更好的分散性, 从而为进 一步将其引入聚合物体系创造了条件. 本文所示的方法提供了一种制备智能石墨烯分散液以满足多种应用的新思路.