Su-Yuan Xie

Single-crystal-like hematite colloidal nanocrystal clusters: synthesis and applications in gas sensors, photocatalysis and water treatment

A facile and efficient one-pot solvothermal synthetic route based on a simplified self-assembly is proposed to fabricate spherical hematite colloidal nanocrystal clusters (CNCs) of uniform shape and size. The as-prepared hematite CNCs are composed of numerous nanocrystals of approximately 20 nm in size, and present a single-crystal-like characteristic. A possible formation process based on the nucleation–oriented aggregation–recrystallization mechanism is proposed. Our experiments demonstrated that both the surfactant and the mixed solvent play very critical roles in controlling the size of primary nanocrystals and the final morphology of single-crystal-like spherical CNCs. Compared with other hematite nanostructures, the spherical hematite CNCs show outstanding performance in gas sensing, photocatalysis and water treatment due to their large surface area and porous structure. In addition, interesting tertiary CNCs formed by further assembly of secondary spherical CNCs were observed for the first time.

Chlorofullerenes featuring triple sequentially fused pentagons

The triple sequentially fused pentagons (TSFP) motif is one of the basic subunits that could be used for constructing fullerenes, but it violates the isolated pentagon rule (IPR) and has not been found in carbon cages to date. The properties of TSFP-incorporating fullerenes are thus poorly explored both theoretically and experimentally. Reported herein are four chlorinated derivatives of three different fullerene cages, all with the TSFP motif. X-ray crystallographic analyses indicate that the molecular strain inherent to the pentagon adjacency of a TSFP is significantly relieved upon exohedral chlorination, leaving one of the four pentagon fusion sites unsaturated and rendering the present derivatives chiral. This unique reactivity, in stark contrast to that of previously reported non-IPR fullerenes containing double fused pentagons or triple directly fused pentagons, can be rationalized by density functional theory calculations, and are expected to stimulate further studies of these new members of the fullerene family, both theoretically and experimentally.

Two Ih-symmetry-breaking C60 isomers stabilized by chlorination

One abiding surprise in fullerene science is that I(h)-symmetric buckminsterfullerene C(60) (ref. 1) (I(h)-C(60) or (#1,812)C(60), the nomenclature specified by symmetry or by Fowlers spiral algorithm) remains the sole C(60) species experimentally available. Setting it apart from the other 1,811 topological isomers (isobuckminsterfullerenes) is its exclusive conformity with the isolated-pentagon rule, which states that stable fullerenes have isolated pentagons. Although gas-phase existence of isobuckminsterfullerenes has long been suspected, synthetic efforts have yet to yield successful results. Here, we report the realization of two isobuckminsterfullerenes by means of chlorination of the respective C(2v)- and C(s)-symmetric C(60) cages. These chlorinated species, (#1,809)C(60)Cl(8)(1) and (#1,804)C(60)Cl(12)(2), were isolated in experimentally useful yields. Structural characterization by crystallography unambiguously established the unique pentagon-pentagon ring fusions. These distinct structural features are directly responsible for the regioselectivity observed in subsequent substitution of chlorines, and also render these unprecedented derivatives of C(60) isomers important for resolving the long-standing puzzle of fullerene formation by the Stone-Wales transformation scheme.

Crystal Structures of Saturn‐Like C50Cl10 and Pineapple‐Shaped C64Cl4: Geometric Implications of Double‐ and Triple‐Pentagon‐Fused Chlorofullerenes

Fullerenes are spherical cage carbon molecules constructed from hexagons and exactly 12 pentagons. Theoretically, according to the so-called Isolated Pentagon Rule (IPR), fullerenes with isolated pentagons are relatively stable and synthesizable. This same rule predicts that fullerenes with fused pentagons are too reactive to be isolated. IPR-violating fullerenes, however, have been reported to be stabilized by either encapsulation with metal atoms (or their carbide/ nitride clusters) or external derivatization. Fullerenes featuring fused pentagons have been characterized by computationally corroborated C NMR spectroscopy. Detailed information regarding their geometries and intermolecular interactions, however, requires single-crystal X-ray characterization, as in the case of Sc3N@C68. [9] The crystal structures of two double-fused-pentagon endohedral metallofullerenes, namely La@C72(C6H3Cl2) [10] and Tb3N@C84, [11] have also been determined. Highly accurate structural parameters established by X-ray crystallography are rare for exohedral derivatives of IPR-violating fullerenes. Prinzbach et al., for example, have recently reported the crystal structures of polybrominated dodecahedrane, which is the smallest IPR-violating fullerene derivative known to date. Herein we report two crystal structures of IPR-violating fullerenes (C50 (no. 271) and C64 (no. 1911)) [2,13] stabilized by exohedral chlorination. The former is the smallest fullerene for which a cage can be constructed without triplets of directly or sequentially fused pentagons, while the latter is a triple-fused-pentagon fullerene. The crystallographic data reported herein provide unequivocal structural information for these IPR-violating fullerene derivatives (e.g., detailed geometric parameters, molecular curvature, pyramidalization angles, aromaticity, intermolecular interactions) and the property implications thereof. The X-ray structures of C50Cl10 (1) and C64Cl4 (2) are shown in Figure 1. The symmetries of these IPR-violating chlorofullerenes are identical to those of their carbon cage parents, in other wordsD5h-C50 (1a) for 1 and C3v-C64 (2a) for 2. The former is a Saturn-like chlorofullerene molecule constructed symmetrically from five pairs of two fused pentagons whose fused edges are covalently bound by ten chlorines in a manner that resembles the rings around Saturn (another Saturn-like halogenated molecule is C60F20, which was synthesized by Taylor). In contrast, 2 has a pineappleshaped structure with four chlorine atoms covalently attached

Low-cost solution-processed copper iodide as an alternative to PEDOT:PSS hole transport layer for efficient and stable inverted planar heterojunction perovskite solar cells

Inverted planar heterojunction (PHJ) perovskite solar cells have attracted great attention due to their advantage of low-temperature fabrication on flexible substrates by solution processing with high efficiency. Poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) is the most widely used hole transport layer (HTL) in inverted PHJ perovskite solar cells; however, the acidic and hygroscopic nature of PEDOT:PSS can cause degradation and reduce the device stability. In this work, we demonstrated that low-cost solution-processed hydrophobic copper iodide (CuI) can serve as a HTL to replace PEDOT:PSS in inverted PHJ perovskite solar cells with high performance and enhanced device stability. A power conversion efficiency (PCE) of 13.58% was achieved by employing CuI as the HTL, slightly exceeding the PEDOT:PSS based device with a PCE of 13.28% under the same experimental conditions. Furthermore, the CuI based devices exhibited better air stability than PEDOT:PSS based devices. The results indicate that low-cost solution-processed CuI is a promising alternative to the PEDOT:PSS HTL and could be widely used in inverted PHJ perovskite solar cells.

An Entrant of Smaller Fullerene: C56 Captured by Chlorines and Aligned in Linear Chains

A smaller fullerene C56 (#913) is stabilized, isolated, and crystallographically characterized as C56Cl10. The geometric parameters of C56Cl10 imply the otherwise unstable cage of C56 can be stabilized by chlorination through releasing its surface strains and maintaining fragmental aromaticity. An unexpected C Cl...ClC short contact, as well as the linear alignment with pearl-necklace-shaped, is revealed in C56Cl10 crystal.

Solubilization of boron nitride nanotubes

A successful attempt in the functionalization and solubilization of boron nitride nanotubes is reported, and a functionalization mechanism based on interactions of amino functional groups with nanotube surface borons is proposed.

High purity trigonal selenium nanorods growth via laser ablation under controlled temperature

By utilizing laser ablation, high purity trigonal selenium nanorods with different size have been synthesized from selenium powders. The high purity of the nanorods is attributed to freestanding growth process without catalyst or template. Its morphologies depend on both substrate temperature and reaction time. By controlling the experimental conditions, selenium nanorods with lateral dimensions in different range can be synthesized ranging from 20 nm to several hundred nanometers in width, and up to 10 μm in lengths.

Efficient Perovskite Solar Cells Depending on TiO2 Nanorod Arrays.

Perovskite solar cells (PSCs) with TiO2 materials have attracted much attention due to their high photovoltaic performance. Aligned TiO2 nanorods have long been used for potential application in highly efficient perovskite solar cells, but the previously reported efficiencies of perovskite solar cells based on TiO2 nanorod arrays were underrated. Here we show a solvothermal method based on a modified ketone-HCl system with the addition of organic acids suitable for modulation of the TiO2 nanorod array films to fabricate highly efficient perovskite solar cells. Photovoltaic measurements indicated that efficient nanorod-structured perovskite solar cells can be achieved with the length of the nanorods as long as approximately 200 nm. A record efficiency of 18.22% under the reverse scan direction has been optimized by avoiding direct contact between the TiO2 nanorods and the hole transport materials, eliminating the organic residues on the nanorod surfaces using UV-ozone treatment and tuning the nanorod array morphologies through addition of different organic acids in the solvothermal process.

C72Cl4: A Pristine Fullerene with Favorable Pentagon-Adjacent Structure

A long-sought empty non-IPR fullerene, (#11188)C72, which is more stable than the sole IPR isomer in the fullerene[72] family, has been retrieved and crystallographically characterized as (#11188)C72Cl4. Mass spectrometric data support the facile dechlorination of (#11188)C72Cl4 and, in turn, the possible stability of pristine (#11188)C72.