Precision excimer laser annealed Ga-doped ZnO electron transport layers for perovskite solar cells

Organic-inorganic hybrid perovskite solar cells (PSCs) continue to attract considerable attention due to their excellent photovoltaic performance and low cost. In order to realize the fabrication of PSCs on temperature-sensitive substrates, low-temperature processing of all the components in the device is required, however, the majority of the high-performance PSCs rely on the electron transport layers (ETLs) processed at high temperatures. Herein, we apply excimer laser annealing (ELA) to treat ETLs (Ga-doped ZnO, GZO) at room temperature. A synergetic improvement in optical transparency and electrical conductivity is achieved after ELA treatment, which in turn improves light absorption, enhances electron injection, and depresses charge recombination. Devices fabricated with ELA treated GZO ETL acheived a power conversion efficiency (PCE) of 13.68%, higher than that of the PSCs utilizing GZO with conventional high-temperature annealing (12.96%). Thus, ELA is a promising technique for annealing ETLs at room temperature to produce efficient PSCs on both rigid and flexible substrates

A facile strategy for preparation of fluorescent SWNT complexes with high quantum yields based on ion exchange

The fluorescent imidazolium salt (1,3-bis(9-anthracenylmethyl)imidazolium chloride, [bamim]Cl) has been grafted onto the surfaces of single-walled carbon nanotubes (SWNTs) using an ion exchange strategy based on metathesis of the K+ ion in CO2K derivatized SWNTs with [bamim]+. The resulting SWNT-[bamim] complex has been characterized with high-resoln. transmission electron microscopy (HR-TEM), XPS, elemental mapping, and elemental linear profiles anal. A blue light emission can be obsd. at 392, 414 and 438 nm for SWNT-[bamim] upon being excited at 254 nm. The quantum yield (QY) of the SWNT-[bamim] complex (0.40) is much higher than that of SWNT/[bamim]Cl (0.02), used as a control, and prepd. using a p-p stacking method, indicating that ion exchange is a far more effective strategy for retaining a high QY. Addnl., UV-Vis-NIR and Raman spectroscopy show that the SWNT-[bamim] complex can maintain the one-dimensional electronic states of SWNTs. Other imidazolium salts have also been successfully grafted onto SWNTs via the same strategy, indicating that the ion exchange process can serve as a universal strategy for the functionalization of SWNTs

Targeted delivery and controlled release of doxorubicin to cancer cells using modified single wall carbon nanotubes

A targeted drug delivery system that is triggered by changes in pH based on single wall carbon nanotubes (SWCNTs), derivatized with carboxylate groups and coated with a polysaccharide material, can be loaded with the anticancer drug doxorubicin (DOX). The drug binds at physiol. pH (pH 7.4) and is only released at a lower pH, for example, lysosomal pH and the pH characteristic of certain tumor environments. By manipulating the surface potentials of the modified nanotubes through modification of the polysaccharide coating, both the loading efficiency and release rate of the assocd. DOX can be controlled. Folic acid (FA), a targeting agent for many tumors, can be addnl. tethered to the SWCNTs to selectively deliver DOX into the lysosomes of HeLa cells with much higher efficiency than free DOX. The DOX released from the modified nanotubes has been shown to damage nuclear DNA and inhibit the cell proliferation

Fabrication of gold nano- and microstructures in ionic liquids - A remarkable anion effect

Au nano- and microstructures such as polyhedral crystals, large single-cryst. nanoplates, hollow trapeziform crystals, holey polyhedra, and dendrites were produced via microwave heating of HAuCl4·4H2O in a variety of ionic liqs. (ILs) in the absence of capping agents (polymers or surfactants) or addnl. reducing agents. The influence of the IL anions and cations on the topol. (size, shape, etc.) of Au materials was studied. The anions of the ILs control the topol. of materials, whereas the cations used in the expts. exert less influence. Also the HAuCl4 concn., reaction temp., and heating method are key parameters that help to control the topol. structures of the Au materials. For example, the thickness of the large single-cryst. nanoplates could be adjusted from 16 to 320 nm by varying the HAuCl4 concn. and reaction temp. This easy synthetic approach to Au nano- and microstructures is a seedless, 1-step, fast, template-free route that shows good reproducibility and may be further developed to produce other types of metal nanostructures that satisfy specific applications

Coordination chemistry on the surface of single-walled carbon nanotubes

A facile method to coordinate transition metal complexes (TMCs) on single-walled carbon nanotubes (SWNTs) has been developed. Reaction of Zn(OAc)2 with carboxylic acid functionalized SWNTs (SWNT-COOH) affords SWNT complexes zipped-together' by zinc carboxylate units (termed SWNT-TMC-1 herein). Reactions of SWNT-TMC-1 with 2,2'-bipyridine or 4,4'-bipyridine gave two new SWNT-TMCs, the former being unzipped' (SWNT-TMC-2), and the latter involving an addnl. ligand bridge between the zinc ions (SWNT-TMC-3). Inclusion of 2,2'-bipyridine and 4,4'-bipyridine into the SWNT-TMCs was confirmed by IR spectroscopy. The microstructures of SWNT-TMC-2 and SWNT-TMC-3 were investigated by transmission electron microscopy (TEM), XPS, elemental mapping and linear profiles anal

Single walled carbon nanotubes as drug delivery vehicles: Targeting doxorubicin to tumors

Single walled carbon nanotubes (SWNTs) are emerging as promising delivery vehicles for cancer diagnostics and chemotherapies due to their unique properties, including, remarkable cell membrane penetrability, high drug-carrying capacities, pH-dependent therapeutic unloading, prolonged circulating times and intrinsic fluorescent, photothermal, photoacoustic and Raman properties. In this leading opinion paper, we systemically discuss and evaluate the relationship of the biological safety of SWNTs with their physicochemical properties such as their length, purity, agglomeration state, concentration and surface functionalization. Other relevant issues, including the cellular uptake mechanism, biodistribution and metabolism of SWNTs are also reviewed. The design and preparation of SWNT-based drug delivery systems (DDSs) and their pharmacokinetic, cancer targeting and therapeutic properties both in vitro and in vivo are highlighted. Future opportunities and challenges of SWNT-based DDSs are also discussed. (C) 2011 Elsevier Ltd. All rights reserved

Photochemical Behavior of High Quantum Yield SWNTs Functionalized with Anthracene Salts

Two different fluorescent single walled carbon nanotubes (SWNT) were prepd. First by a reaction of oxidized SWNT-K salt with 1,3-bis(9-anthracenylmethyl)imidazolium chloride (bamim)Cl to provide a fluorescent system SWNT-(bamim), via ion exchange and formation of KCl. Second, by phys. mixing of non-functionalized SWNTs with (bamim)Cl salt to provide SWNT/[bamim]Cl in which anthracene units adhere to the walls of the nanotube via π-π stacking interactions. The SWNT-[bamim] material exhibits a partially reversible photodimerization process that was investigated using UV/Vis spectroscopy, fluorescence emission spectroscopy, and HR-TEM. This study establishes the concept of photoinduced/photoswitchable org.-SWNT conjugated systems based on anthracene dimerization as a prototypical reaction. Hierarchical nanoscale hybrid structures based on the above materials and an understanding of their optical properties may facilitate the construction of SWNT based materials

MnO2 nanosheets as an artificial enzyme to mimic oxidase for rapid and sensitive detection of glutathione

Nanozymes are increasingly used as components in assays and diagnostics. Here, we describe a rapid and highly sensitive colorimetric assay for the detection and quantification of glutathione (GSH) employing MnO2 nanosheets as an artificial oxidase. In the assay pale yellow 3,3',5,5'-tetramethylbenzidine (TMB) is oxidized to a blue product (oxTMB) under catalyzing of MnO2 nanosheets with a significant change in absorption at 650 nm. GSH selectively inhibits this reaction with a detection limit of 300 nM. The high specificity of inhibition by GSH allows this system to be used to determine the GSH concentrations in human serum samples. The MnO2 nanosheet-based assay is simple, rapid, sensitive and selective for the quantification of GSH and surpasses detection methods based on other MnO2 nanomaterials