Summary We report the first single‐chamber microbial electrochemical cell for conversion of CO2 to CH4, with an average CH4 production rate of 0.47 ± 0.05 mL day−1 cm−2 at an applied potential of 600 mV, utilizing a methanogenic microbial community collected from the formation water in the San Juan coal basin (Colorado, USA). CH4 production was only observed at the graphite rod cathode after an electrochemical pre‐treatment that facilitates biofilm formation. The carbon contained within the CH4 arose predominantly from the CO2 source, as verified by experiments during which the CO2 source was repeatedly turned off and on. Modest quantities of acetic acid and ethanol were also produced. DNA extraction and sequencing from the microbial community showed that from the Archaea kingdom, only 2 species survived prolonged exposure to CO2 and CH4 production, methanobacterium sp. (81.4%), and methanoculleus sp. (18.6%), while in the bacterial kingdom, anaerobaculum thermoterrnum (67.1%) was the predominant surviving species.
Immobilization of antibody fragments to 3‐phenoxybenzoic acid (3‐PBA), which are created by disulphide bond (S−S) reduction with tris (2‐carboxyethyl) phosphine (TCEP), is reported atop MoS2 and Cu‐doped MoS2 thin films. MoS2 and Cu‐doped MoS2 thin films are electrodeposited using previously reported methods and tested for their ability to immobilize antibody fragments, before and after annealing in Ar at 500 °C for 3 h. This annealing procedure removes excess sulphur in the as‐deposited films, and creates coordinatively unsaturated Mo sites that are highly reactive towards sulphur, as previously reported for MoS2 hydrodesulphurization catalysts. As demonstrated by electrochemical impedance spectroscopy (EIS) measurements, both annealed MoS2 and Cu‐doped MoS2 thin films adsorb antibody fragments through Mo−S bond formation, unlike the as‐deposited films. Impedance detection of 3‐PBA is reported utilizing antibody fragments bound to both materials, with a sensitivity of 2.7×108 Ω cm2 M−1 and a detection limit of 2.5×10−6 M atop MoS2, and a sensitivity of 5.9×108 Ω cm2 M−1 and a detection limit of 3.8×10−6 M atop Cu‐doped MoS2. The rms surface roughness obtained by atomic force microscopy (AFM) measurements atop annealed MoS2 and Cu‐doped MoS2 ranges from 60–140 nm, so the methods described herein are not limited to ultra‐smooth substrates.
Ni-doped MoS 2 thin films were fabricated by electrodeposition from electrolytes containing both MoS 4 2− and varying concentrations of Ni 2+ , followed by annealing at 400 °C for 2 h in an Ar atmosphere. The film resistivity decreased from 32.8 μΩ-cm for un-doped MoS 2 to 11.3 μΩ-cm for Ni-doped MoS 2 containing 9 atom% Ni. For all Ni dopant levels studied, only the X-ray diffraction (XRD) pattern expected for MoS 2 is observed, with the average grain size increasing with increasing Ni content. Ni-doped MoS 2 thin films were tested for their activity towards the hydrogen evolution reaction (HER) in 0.5 M H 2 SO 4 . Tafel equation fits reveal that the catalytic activity for the HER, as measured by the exchange current density, increases up to 6 atom% Ni, and then decreases slightly for 9 atom% Ni. Ni-doped MoS 2 thin films were also tested in 1.0 M Na 2 SO 4 for use within electrochemical supercapacitors, and the capacitance per unit area increases by 2-3x for 9 atom% Ni-doped MoS 2 relative to undoped MoS 2 . The highest capacitance obtained for Ni-doped MoS 2 during galvanostatic charge-discharge measurements is ∼300 F g −1 .
Gold nanoparticles (AuNPs) have become increasingly useful in recent years for their roles in nanomedicine, cellular biology, energy storage and conversion, photocatalysis, and more. At the single-particle level, AuNPs have heterogeneous physical and chemical properties which are not resolvable in ensemble measurements. In the present study, we developed an ultrahigh-throughput spectroscopy and microscopy imaging system for characterization of AuNPs at the single-particle level using phasor analysis. The developed method enables quantification of spectra and spatial information on large numbers of AuNPs with a single snapshot of an image (1024 × 1024 pixels) at high temporal resolution (26 fps) and localization precision (sub-5 nm). We characterized the localized surface plasmonic resonance (SPR) scattering spectra of gold nanospheres (AuNSs) of four different sizes (40–100 nm). Comparing to the conventional optical grating method which suffers low efficiency in characterization due to spectral interference caused by nearby nanoparticles, the phasor approach enables high-throughput analysis of single-particle SPR properties in high particle density. Up to 10-fold greater efficiency of single-particle spectro-microscopy analysis using the spectra phasor approach when compared to a conventional optical grating method was demonstrated.
The development of nanomaterials such as twodimensional (2D) layered materials advanced applications in many fields, including biosensors format based on field-effect transistors. The unique physical and chemical properties of 2D layered materials enable the detection limit of biomolecules as low as ∼1 pg/mL. The majority of 2D layered materials contain different structural features and defects introduced in chemical synthesis and fabrication processing. These structural features have different physicochemical properties, causing heterogeneous adsorption of bioreceptors like antibodies, enzymes, etc. Understanding the correlation between the adsorption of bioreceptors and properties of structural features is essential for building highly efficient, sensitive biosensors based on 2D layered materials. Here, we utilize a single-molecule localization-based super-resolved fluorescence imaging method to unveil the inhomogeneous adsorption of antibody fragments on 2D layered molybdenum disulfide (MoS 2 ). The surface coverage of antibody fragments on MoS 2 thin flakes is quantitatively measured and compared at different structural features and different layer thicknesses. The methodology in the current work can be extended to study bioreceptor adsorption on other types of 2D layered materials and pave a way to improve biosensors' sensitivity based on defect engineering 2D layered materials.
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