A PIID-DTBT based semi-conducting polymer dots with broad and strong optical absorption in the visible-light region: Highly effective contrast agents for multiscale and multi-spectral photoacoustic imaging

As a hybrid imaging technique, photoacoustic imaging (PAI) can provide multiscale morphological information of tissues, and the use of multi-spectral PAI (MSPAI) can recover the spatial distribution of chromophores of interest, such as hemoglobin within tissues. Herein, we developed a contrast agent that can very effectively combine multiscale PAI with MSPAI for a more comprehensive characterization of complex biological tissues. Specifically, we developed novel PIID-DTBT based semi-conducting polymer dots (Pdots) that show broad and strong optical absorption in the visible-light region (500–700 nm). The performances of gold nanoparticles (GNPs) and gold nanorods (GNRs), which have been verified as excellent photoacoustic contrast agents, were compared with that of the Pdots based on the multiscale PAI system. Both ex vivo and in vivo experiments demonstrated that the Pdots have better photoacoustic conversion efficiency at 532 nm than GNPs and showed similar photoacoustic performance with GNRs at 700 nm at the same mass concentration. Photostability and toxicity tests demonstrated that the Pdots are photostable and biocompatible. More importantly, an in vivo MSPAI experiment indicated that the Pdots have better photoacoustic performance than the blood and therefore the signals can be accurately extracted from the background of vascular-rich tissues. Our work demonstrates the great potential of Pdots as highly effective contrast agents for the precise localization of lesions relative to the blood vessels based on multiscale PAI and MSPAI.

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Targeted blue nanoparticles as photoacoustic contrast agent for brain tumor delineation

Distinguishing a tumor from non-neoplastic tissue is a challenging task during cancer surgery. Several attempts have been made to use visible or fluorescent agents to aid in the visualization of a tumor during surgery. We describe a novel method to delineate brain tumors, using a highly sensitive photoacoustic imaging technique that is enhanced by tumor-targeting blue nanoparticles serving as a contrast agent. Experiments on phantoms and on rat brains, ex vivo, demonstrate the high sensitivity of photoacoustic imaging in delineating tumors containing contrast agent at a concentration much lower than needed for visualization by the naked eye. The limit of detection of the system for the nanoparticles is about 0.77 μg/mL in water (equivalent to 0.84 μmol/L Coomassie Blue dye). The present exploratory study suggests that photoacoustic imaging, when used with strongly optical absorbing contrast agents, could facilitate cancer surgery intraoperatively by revealing the distribution and extent of the tumor.      

Co-Al spinel-based nanoparticles synthesized by flame spray pyrolysis for glycerol conversion

The catalytic properties of Co-Al spinel nanoparticles prepared by liquid-feed flame spray pyrolysis (L-F FSP) were investigated in the glycerol conversion in gas phase in an atmosphere of hydrogen. Reduction at 1123?K of the as-synthesized spinel nanoparticles induced the formation a new phase containing metallic cobalt species. Although, the reducibility of cobalt oxides is greatly decreased due to interaction with aluminium species, this strong interaction may prevent the aggregation of Co particles under the harsh reduction conditions. X-ray photoelectron spectroscopy (XPS) of the reduced spinel nanoparticles at 1123?K revealed that the Co/Al atomic ratio has decreased to Co/Al?=?0.11, which may indicate a redistribution of the aluminum and cobalt species at the surface of the sample submitted to the reduction in a flow of hydrogen at 1123?K. X-ray diffraction (XRD) and high resolution electron microscopy (HRTEM) also reinforced the formation of metallic cobalt species after reduction of cobalt from the spinel nanoparticles at 1123?K. The main products obtained from the conversion of glycerol in the gas phase were hydroxyacetone, pyruvaldehyde, lactic acid and lactide. FSP ensured uniform dispersion of the active metal on a support material.     

Hydrophilic bismuth sulfur nanoflower superstructures with an improved photothermal efficiency for ablation of cancer cells

Nanomaterials with intense near-infrared (NIR) absorption exhibit effective photon-to-thermal energy transfer capabilities and can generate heat to ablate cancer cells, thus playing a pivotal role in photothermal cancer therapeutics. Herein, hydrophilic flower-like bismuth sulfur (Bi₂S₃) superstructures with uniform size and improved NIR absorption were controllably synthesized via a facile solvothermal procedure assisted by polyvinylpyrrolidone (PVP), which could adjust the product morphology. Induced by an 808-nm laser, the as-prepared Bi₂S₃ nanoflowers exhibited much higher photothermal conversion efficiency (64.3%) than that of Bi₂S₃ nanobelts (36.5%) prepared in the absence of PVP. This can be attributed not only to the Bi₂S₃ nanoflower superstructures assembled by 3-dimensional crumpled-paper-like nanosheets serving as many laser-cavity mirrors with improved reflectivity and absorption of NIR light but also to the amorphous structures with a lower band gap. Thus, to achieve the same temperature increase, the concentration or laser power density could be greatly reduced when using Bi₂S₃ nanoflowers compared to when using Bi₂S₃ nanobelts, which makes them more favorable for use in therapy due to decreased toxicity. Furthermore, these Bi₂S₃ nanoflowers effectively achieved photothermal ablation of cancer cells in vitro and in vivo. These results not only supported the Bi₂S₃ nanoflowers as a promising photothermal agent for cancer therapy but also paved an approach to exploit new agents with improved photothermal efficiency.

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Fabrication of thin film dye sensitized solar cells with solar to electric power conversion efficiency over 10%

Techniques of TiO₂ film fabrication for dye-sensitized solar cells having a conversion efficiency of global air mass 1.5 (AM 1.5, 1000 W/m²) solar light to electric power over 10% are reported. Newly implemented fabrication technologies consist of pre-treatment of the working photoelectrode by TiCl₄, variations in layer thickness of the transparent nanocrystalline-TiO₂ and applying a topcoat light-scattering layer as well as the adhesion of an anti-reflecting film to the electrode's surface. TiCl₄ treatments induce improvements in the adhesion and mechanical strength of the nanocrystalline TiO₂ layer. Optimization of the thickness of the TiO₂ layer, acting as the working electrode, affects both the photocurrent and the photovoltage of the devices. Covering of the TiO₂ photoanode by an anti-reflecting film results in enhancement of the photocurrent. Each of these components of film fabrication exerts a significant influence on the overall photovoltaic parameters of the devices resulting in improvements in the net energy conversion performance.     

GABRIELA: A new detector array for -ray and conversion electron spectroscopy of transfermium elements

With the aid of the Geant4 Monte Carlo simulation package a new detection system has been designed for the focal plane of the recoil separator VASSILISSA situated at the Flerov Laboratory of Nuclear Reactions, JINR, Dubna. GABRIELA (Gamma Alpha Beta Recoil Investigations with the ELectromagnetic Analyser VASSILISSA) has been optimised to detect the arrival of reaction products and their subsequent radioactive decays involving the emission of - and β-particles, fission fragments, γ- and X-rays and conversion electrons. The new detector system is described and the results of the first commissioning experiments are presented.     

Material challenges for solar cells in the twenty-first century: directions in emerging technologies

Photovoltaic generation has stepped up within the last decade from outsider status to one of the important contributors of the ongoing energy transition, with about 1.7% of world electricity provided by solar cells. Progress in materials and production processes has played an important part in this development. Yet, there are many challenges before photovoltaics could provide clean, abundant, and cheap energy. Here, we review this research direction, with a focus on the results obtained within a Japan–French cooperation program, NextPV, working on promising solar cell technologies. The cooperation was focused on efficient photovoltaic devices, such as multijunction, ultrathin, intermediate band, and hot-carrier solar cells, and on printable solar cell materials such as colloidal quantum dots.