Edge-carboxylated graphene nanoplatelets as oxygen-rich metal-free cathodes for organic dye-sensitized solar cells

Edge-carboxylated graphene nanoplatelets (ECGnPs) were synthesized by the simple, efficient and eco-friendly ball-milling of graphite in the presence of dry ice and used as oxygen-rich metal-free counter electrodes (CEs) in organic dye-sensitized solar cells (DSSCs), for the first time. The resultant ECGnPs are soluble in many polar solvents including 2-propanol due to the polar nature of numerous carboxylic acids at edges, allowing an electrostatic spray (e-spray) to be deposited on fluorine-doped SnO2 (FTO)/glass substrates. The ECGnP-CE exhibited profound improvements in the electrochemical stability for the Co(bpy)3 2+/3+ redox couple compared to the platinum (Pt)-CE. The charge transfer resistance (RCT), related to the interface between an electrolyte and a CE, was significantly reduced to 0.87 ?? cm2, much lower than those of (Pt)-CE (2.19 ?? cm 2), PEDOT:PSS-CE (2.63 ?? cm2) and reduced graphene oxide (rGO)-CE (1.21 ?? cm2). The DSSC based on the JK-303-sensitizer and ECGnP-CE displayed a higher photovoltaic performance (FF, Jsc, and ??, 74.4%, 14.07 mA cm-2 and 9.31%) than those with the Pt-CE (71.6%, 13.69 mA cm-2 and 8.67%), PEDOT:PSS (68.7%, 13.68 mA cm-2 and 8.25%) and rGO-CE (72.9%, 13.88 mA cm-2 and 8.94%).close3

Anti-Metastatic Effects of Plant Sap-Derived Extracellular Vesicles in a 3D Microfluidic Cancer Metastasis Model

Natural medicinal plants have attracted considerable research attention for their potential as effective drugs. The roots, leaves and stems of the plant, Dendropanax morbifera, which is endemic to southern regions of Asia, have long been used as a folk medicine to treat variety of diseases. However, the sap of this plant has not been widely studied and its bioactive properties have yet to be clearly elucidated. Here, we isolated extracellular vesicles from D. morbifera sap with the goal of improving the intracellular delivery efficiency and clinical effectiveness of bioactive compounds in D. morbifera sap. We further investigated the anti-metastatic effects of D. morbifera sap-derived extracellular vesicles (DMS-EVs) using a cancer metastasis model based on 3D microfluidic system that closely mimics the in vivo tumor environment. We found that DMS-EVs exerted a concentration-dependent suppressive effect on cancer-associated fibroblasts (CAFs), which are important mediators of cancer metastasis. DMS-EVs also altered expression level of genes, especially growth factor and extracellular matrix (ECM)-related genes, including integrin and collagen. Our findings suggest that DMS-EVs can act as anti-CAF agents to reduce CAFs in the tumor microenvironment. They further indicate the utility of our 3D microfluidic model for various drug-screening assays as a potential alternative to animal testing for use in validating therapeutic effects on cancer metastasis

Heteroatom Doped Graphene as a Metal-Free Cathode Material Compared to Pt over a Co(II)/Co(III) Electrolyte for Dye-Sensitized Solar Cell

Pristine graphene (PG), boron-doped graphene (BG) and boron and nitrogen co-doped graphene (BNG) are prepared and tested as a counter electrode (CE) in dye-sensitized solar cells (DSSCs) in conjunction with Co(bpy)3 2+/3+ redox couple. The BG CE has a lower charge-transfer resistance and much higher electrochemical stability than those of platinum (Pt) CE. As a result, the DSSC fabricated with BG CE exhibits superior power conversion efficiency to that of DSSC with Pt CE, suggesting potential to replace expensive Pt CE in DSSCs

High-performance dye-sensitized solar cells using edge-halogenated graphene nanoplatelets as counter electrodes

Edge-selectively halogenated graphene nanoplatelets (XGnPs, X=C1, Br, and I) were prepared by the mechanochemically driven reaction between graphite and diatomic halogen molecules (Cl-2, Br-2 or 12). The contents of halogens (Cl, Br, and I) in XGnPs were 3.18, 1.77, and 0.66 at%, respectively, by X-ray photoelectron spectroscopy. The XGnPs as counter electrodes (CEs) showed remarkably enhanced electrocatalytic activities toward Co(bpy)(3)(3+) reduction reaction in dye-sensitized solar cells (DSSCs) with an excellent electrochemical stability. Amongst XGnPs, IGnP-CE demonstrated the lowest charge-transfer resistance (R-ct of 0.46 Omega cm(2) at the CE/electrolyte interface. This value is much lower than that of Pt-CE (0.81 Omega cm(2)). In addition, the DSSC with IGnP-CE had the highest fill factor (71.3%) and cell efficiency (10.31%), whereas those of DSSCs with Pt-CE were only 70.6% and 9.92%, respectively. (C) 2015 Elsevier Ltd. All rights reservedclose2

B‑Doped Graphene as an Electrochemically Superior Metal-Free Cathode Material As Compared to Pt over a Co(II)/Co(III) Electrolyte for Dye-Sensitized Solar Cell

We report that B-doped graphene (BG) is prepared and tested as a counter electrode (CE) in dye-sensitized solar cells (DSSCs) in conjunction with Co­(bpy)₃^2+/3+ redox couple. The BG CE has a lower charge-transfer resistance and much higher electrochemical stability than those of Pt CE. As a result, the DSSC fabricated with BG CE exhibits superior power conversion efficiency to that of DSSC with Pt CE, suggesting potential to replace expensive Pt CE in DSSCs

B-Doped Graphene as an Electrochemically Superior Metal-Free Cathode Material As Compared to Pt over a Co(II)/Co(III) Electrolyte for Dye-Sensitized Solar Cell

We report that B-doped graphene (BG) is prepared and tested as a counter electrode (CE) in dye-sensitized solar cells (DSSCs) in conjunction with Co(bpy)3 2+/3+ redox couple. The BG CE has a lower charge-transfer resistance and much higher electrochemical stability than those of Pt CE. As a result, the DSSC fabricated with BG CE exhibits superior power conversion efficiency to that of DSSC with Pt CE, suggesting potential to replace expensive Pt CE in DSSCs.close4

N-Doped Graphene Nanoplatelets as Superior Metal-Free Counter Electrodes for Organic Dye-Sensitized Solar Cells

Highly efficient counter electrodes (CEs) for dye-sensitized solar cells (DSScs) were developed using thin films of scalable and high-quality, nitrogen-doped graphene nanoplatelets (NGnP), which was synthesized by a simple two-step reaction sequence. The resultant NGnP was deposited on fluorine-doped SnO2 (FTO)/glass substrates by using electrospray (e-spray) coating, and their electrocatalytic activities were systematically evaluated for Co(bpy)(3)(3+/2+) redox couple in DSSCs with an organic sensitizer. The e-sprayed NGnP thin films exhibited outstanding performances as CEs for DSSCs. The optimized NGnP electrode showed better electrochemical stability under prolonged cycling potential, and its R-ct at the interface of the CE/electrolyte decreased down to 1.73 Omega cm(2), a value much lower than that of the Pt electrode (3.15 Omega cm(2)). The DSSC with the optimized NGnP-CE had a higher fill factor (FF, 74.2%) and a cell efficiency (9.05%), whereas those of the DSSC using Pt-CE were only 70.6% and 8.43%, respectively. To the best of our knowledge, the extraordinarily better current voltage characteristics of the DSSC-NGnP outperforming the DSSC-Pt for the Co(bpy)(3)(3+/2+) redox couple (in paticular, FF and short circuit current, J(sc)) is highlighted for the first time.close422