BTZ-copolymer loaded graphene aerogel as new type Green and metal-freevisible light photocatalyst

This paper reports a new class of efficient, green and metal-free visible-light photocatalyst made from graphene aerogel (GA) doped with a conjugated porous polymer (CMPs). Hence, we report the synthesis of a benzothiadiazole (BTZ)-based CMP loaded into GA via a one-step hydrothermal reaction between 2D graphene oxide (GO) and the CMP, performed through a green process and under mild conditions. The as-prepared GA showed a bathochromic shift in the UV–vis diffraction reflectance spectroscopy (DRS) absorption edge to 628.5 nm, demonstrating its ability to absorb light in the visible region. SEM, TEM, XPS, EDX mapping results further showed the successful loading of the BTZ-based CMP in the GA array. The synthesized GA was used as a 3D structured photocatalyst for the visible-light-driven photodecomposition of methyl orange (MO) with an efficiency of 89.2% (5 wt% CMP). When compared to that of the pure CMP (86.9%), a comparable yet small increase in the efficiency was observed. This is due to a synergistic effect between GO and loaded polymer in GA array upon the formation of CMPGA hybrid structure via chemical interaction between BTZ-Py and GO throughout the mild hydrothermal reaction, and the enhanced photocatalytic activity exhibited from 1 mg equivalent polymer in the CMPGA2 hybrid when compared to the 20 mg pure polymer. Upon repeated use, the depreciation in photocatalytic activity was low with a <5% drop over 3 cycles. These results showed the CMP-loaded GA as an efficient metal-free photocatalyst and a promising material for further investigation into other photocatalytic applications

Electrooxidation of glucose by binder-free bimetallic Pd1Ptx/graphene aerogel/nickel foam composite electrodes with low metal loading in basic medium

Many 2D graphene-based catalysts for electrooxidation of glucose involved the use of binders and toxic reducing agents in the preparation of the electrodes, which potentially causes the masking of original activity of the electrocatalysts. In this study, a green method was developed to prepare binder-free 3D graphene aerogel/nickel foam electrodes in which bimetallic Pd-Pt NP alloy with different at% ratios were loaded on 3D graphene aerogel. The influence of Pd/Pt ratio (at%: 1:2.9, 1:1.31, 1:1.03), glucose concentration (30 mM, 75 mM, 300 mM, 500 mM) and NaOH concentration (0.1 M, 1 M) on electrooxidation of glucose were investigated. The catalytic activity of the electrodes was enhanced with increasing the Pd/Pt ratio from 1:2.9 to 1:1.03, and changing the NaOH/glucose concentration from 75 mM glucose/0.1 M NaOH to 300 mM glucose/1 M NaOH. The Pd1Pt1.03/GA/NF electrode achieved a high current density of 388.59 A g−1 under the 300 mM glucose/1 M NaOH condition. The stability of the electrodes was also evaluated over 1000 cycles. This study demonstrated that the Pd1Pt1.03/GA/NF electrode could be used as an anodic electrode in glucose-based fuel cells

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals &lt;1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Influence of Pd1Ptx alloy NPs on graphene aerogel/nickel foam as binder-free anodic electrode for electrocatalytic ethanol oxidation reaction

Highly active and stable electrocatalysts for ethanol oxidation reaction (EOR) are very important for applications in fuel cells. Even though huge efforts have been devoted to enhancing their catalytic activity, preparation of open-structure electrodes by a green and binder-free method remains a challenge. It is obvious in graphene aerogel (GA) based materials due to the destruction of the original GA structure by traditional fabrication methods. In this report, Pd1Ptx alloy NPs/GA/nickel foam electrodes (Pd1Ptx/GA/NF) were prepared by a green, simple and binder-free one-step method. The results show that the mean particle size and distribution of Pd1Ptx alloy NPs and the Pd1Ptx loading ratios (at%; x = 2.92, 1.31, 1.03) on the electrodes are strongly dependent on the initial concentration of PtCl62− ions in the synthesis solution. The Pd1Ptx/GA/NF electrodes were evaluated for EOR. The Pd1Pt1.03/GA/NF electrode exhibits high activity and stability in EOR under a long operation (1000 cycles), which are attributed to the synergistic effect of the bimetallic Pd1Ptx alloy NPs on the electrode. This study introduced a binder-free, current-collector-free electrode preparation method which may provide new opportunities to develop high-performance electrodes for energy generation and storage technologies

Deposition of Pd/graphene aerogel on nickel foam as a binder-free electrode for direct electro-oxidation of methanol and ethanol

We reported a simple and green method to fabricate various palladium (0.8, 2.17, 7.65 wt%) loaded graphene aerogel deposited on nickel foam (Pd/GA/NF) as binder-free direct electrodes for electro-oxidation of methanol and ethanol. l-Ascorbic acid (vitamin C, VC) was used as a reducing agent in the process under a mild temperature of 40 °C. The morphology, chemical composition, and electrochemical performance of the prepared electrodes were characterized by optical microscopy, SEM/EDX, TEM, XRD, XPS, XRF, and cyclic voltammetry (CV), respectively. The XPS results revealed that both graphene oxide and Pd ions were simultaneously reduced by VC. The CV analysis revealed that the 7.65 wt% Pd/GA/NF electrode showed a maximum peak current density of 798.8 A g-1 (forward to backward peak current density ratio (If/Ib) of 3.11), and 874 A g-1 (If/Ib of 2.72) in methanol and ethanol electro-oxidation, respectively. The catalytic performance of the electrodes was enhanced with increasing the Pd loading. The results indicated that the 7.65 wt% Pd/GA/NF electrode exhibited a good electrocatalytic activity and an outstanding stability for alcohol electro-oxidation. The prolong CV scanning study (over 1000 cycles) showed that the 7.65 wt% Pd/GA/NF electrode achieved a better overall performance and stability in ethanol oxidation compared to methanol oxidation. The proposed electrode preparation method has a great potential for preparing various binder-free catalytic electrodes, which would be beneficial to the development of fuel cell application