UV-Light-Tunable p-/n-Type Chemiresistive Gas Sensors Based on Quasi-1D TiS\u3csub\u3e3\u3c/sub\u3e Nanoribbons: Detection of Isopropanol at ppm Concentrations

The growing demand of society for gas sensors for energy-efficient environmental sensing stimulates studies of new electronic materials. Here, we investigated quasi-one-dimensional titanium trisulfide (TiS3) crystals for possible applications in chemiresistors and on-chip multisensor arrays. TiS3 nanoribbons were placed as a mat over a multielectrode chip to form an array of chemiresistive gas sensors. These sensors were exposed to isopropanol as a model analyte, which was mixed with air at low concentrations of 1–100 ppm that are below the Occupational Safety and Health Administration (OSHA) permissible exposure limit. The tests were performed at room temperature (RT), as well as with heating up to 110 oC, and under an ultraviolet (UV) radiation at λ = 345 nm. We found that the RT/UV conditions result in a n-type chemiresistive response to isopropanol, which seems to be governed by its redox reactions with chemisorbed oxygen species. In contrast, the RT conditions without a UV exposure produced a p-type response that is possibly caused by the enhancement of the electron transport scattering due to the analyte adsorption. By analyzing the vector signal from the entire on-chip multisensor array, we could distinguish isopropanol from benzene, both of which produced similar responses on individual sensors. We found that the heating up to 110 oC reduces both the sensitivity and selectivity of the sensor array

UV-Light-Tunable p-/n-Type Chemiresistive Gas Sensors Based on Quasi-1D TiS3 Nanoribbons: Detection of Isopropanol at ppm Concentrations

The growing demand of society for gas sensors for energy-efficient environmental sensing stimulates studies of new electronic materials. Here, we investigated quasi-one-dimensional titanium trisulfide (TiS(3)) crystals for possible applications in chemiresistors and on-chip multisensor arrays. TiS(3) nanoribbons were placed as a mat over a multielectrode chip to form an array of chemiresistive gas sensors. These sensors were exposed to isopropanol as a model analyte, which was mixed with air at low concentrations of 1–100 ppm that are below the Occupational Safety and Health Administration (OSHA) permissible exposure limit. The tests were performed at room temperature (RT), as well as with heating up to 110 °C, and under an ultraviolet (UV) radiation at λ = 345 nm. We found that the RT/UV conditions result in a n-type chemiresistive response to isopropanol, which seems to be governed by its redox reactions with chemisorbed oxygen species. In contrast, the RT conditions without a UV exposure produced a p-type response that is possibly caused by the enhancement of the electron transport scattering due to the analyte adsorption. By analyzing the vector signal from the entire on-chip multisensor array, we could distinguish isopropanol from benzene, both of which produced similar responses on individual sensors. We found that the heating up to 110 °C reduces both the sensitivity and selectivity of the sensor array

Laterally extended atomically precise graphene nanoribbons with improved electrical conductivity for efficient gas sensing

Narrow atomically precise graphene nanoribbons hold great promise for electronic and optoelectronic applications, but the previously demonstrated nanoribbon-based devices typically suffer from low currents and mobilities. In this study, we explored the idea of lateral extension of graphene nanoribbons for improving their electrical conductivity. We started with a conventional chevron graphene nanoribbon, and designed its laterally extended variant. We synthesized these new graphene nanoribbons in solution and found that the lateral extension results in decrease of their electronic bandgap and improvement in the electrical conductivity of nanoribbon-based thin films. These films were employed in gas sensors and an electronic nose system, which showed improved responsivities to low molecular weight alcohols compared to similar sensors based on benchmark graphitic materials, such as graphene and reduced graphene oxide, and a reliable analyte recognition. This study shows the methodology for designing new atomically precise graphene nanoribbons with improved properties, their bottom-up synthesis, characterization, processing and implementation in electronic devices

Expression, purification, crystallization and preliminary X-ray structure analysis of Vibrio cholerae uridine phosphorylase in complex with thymidine

A high-resolution structure of the complex of Vibrio cholerae uridine phosphorylase (VchUPh) with its physiological ligand thymidine is important in order to determine the mechanism of the substrate specificity of the enzyme and for the rational design of pharmacological modulators. Here, the expression and purification of VchUPh and the crystallization of its complex with thymidine are reported. Conditions for crystallization were determined with an automated Cartesian Dispensing System using The Classics, MbClass and MbClass II Suites crystallization kits. Crystals of the VchUPh–thymidine complex (of dimensions ∼200–350 µm) were grown by the sitting-drop vapour-diffusion method in ∼7 d at 291 K. The crystallization solution consisted of 1.5 µl VchUPh (15 mg ml(−1)), 1 µl 0.1 M thymidine and 1.5 µl reservoir solution [15%(w/v) PEG 4000, 0.2 M MgCl(2).6H(2)O in 0.1 M Tris–HCl pH 8.5]. The crystals diffracted to 2.12 Å resolution and belonged to space group P2(1) (No. 4), with unit-cell parameters a = 91.80, b = 95.91, c = 91.89 Å, β = 119.96°. The Matthews coefficient was calculated as 2.18 Å(3) Da(−1); the corresponding solvent content was 43.74%

Crystallization and preliminary X-ray study of Vibrio cholerae uridine phosphorylase in complex with 6-methyluracil

Uridine phosphorylase catalyzes the phosphorolysis of ribonucleosides, with the nitrogenous base and ribose 1-phosphate as products. Additionally, it catalyzes the reverse reaction of the synthesis of ribonucleosides from ribose 1-phosphate and a nitrogenous base. However, the enzyme does not catalyze the synthesis of nucleosides when the substrate is a nitrogenous base substituted at the 6-­position, such as 6-methyluracil (6-MU). In order to explain this fact, it is essential to investigate the three-dimensional structure of the complex of 6-MU with uridine phosphorylase. 6-MU is a pharmaceutical agent that improves tissue nutrition and enhances cell regeneration by normalization of nucleotide exchange in humans. 6-MU is used for the treatment of diseases of the gastrointestinal tract, including infectious diseases. Here, procedures to obtain the uridine phosphorylase from the pathogenic bacterium Vibrio cholerae (VchUPh), purification of this enzyme, crystallization of the complex of VchUPh with 6-MU, and X-ray data collection and preliminary X-ray analysis of the VchUPh-6-MU complex at atomic resolution are reported

Laterally extended atomically precise graphene nanoribbons with improved electrical conductivity for efficient gas sensing

Narrow atomically precise graphene nanoribbons hold great promise for electronic and optoelectronic applications, but the previously demonstrated nanoribbon-based devices typically suffer from low currents and mobilities. In this study, we explored the idea of lateral extension of graphene nanoribbons for improving their electrical conductivity. We started with a conventional chevron graphene nanoribbon, and designed its laterally extended variant. We synthesized these new graphene nanoribbons in solution and found that the lateral extension results in decrease of their electronic bandgap and improvement in the electrical conductivity of nanoribbon-based thin films. These films were employed in gas sensors and an electronic nose system, which showed improved responsivities to low molecular weight alcohols compared to similar sensors based on benchmark graphitic materials, such as graphene and reduced graphene oxide, and a reliable analyte recognition. This study shows the methodology for designing new atomically precise graphene nanoribbons with improved properties, their bottom-up synthesis, characterization, processing and implementation in electronic devices

UV-Light-Tunable p-/n-Type Chemiresistive Gas Sensors Based on Quasi-1D TiS3 Nanoribbons: Detection of Isopropanol at ppm Concentrations

The growing demand of society for gas sensors for energy-efficient environmental sensing stimulates studies of new electronic materials. Here, we investigated quasi-one-dimensional titanium trisulfide (TiS3) crystals for possible applications in chemiresistors and on-chip multisensor arrays. TiS3 nanoribbons were placed as a mat over a multielectrode chip to form an array of chemiresistive gas sensors. These sensors were exposed to isopropanol as a model analyte, which was mixed with air at low concentrations of 1–100 ppm that are below the Occupational Safety and Health Administration (OSHA) permissible exposure limit. The tests were performed at room temperature (RT), as well as with heating up to 110 °C, and under an ultraviolet (UV) radiation at λ = 345 nm. We found that the RT/UV conditions result in a n-type chemiresistive response to isopropanol, which seems to be governed by its redox reactions with chemisorbed oxygen species. In contrast, the RT conditions without a UV exposure produced a p-type response that is possibly caused by the enhancement of the electron transport scattering due to the analyte adsorption. By analyzing the vector signal from the entire on-chip multisensor array, we could distinguish isopropanol from benzene, both of which produced similar responses on individual sensors. We found that the heating up to 110 °C reduces both the sensitivity and selectivity of the sensor array

Laterally extended atomically precise graphene nanoribbons with improved electrical conductivity for efficient gas sensing.

Narrow atomically precise graphene nanoribbons hold great promise for electronic and optoelectronic applications, but the previously demonstrated nanoribbon-based devices typically suffer from low currents and mobilities. In this study, we explored the idea of lateral extension of graphene nanoribbons for improving their electrical conductivity. We started with a conventional chevron graphene nanoribbon, and designed its laterally extended variant. We synthesized these new graphene nanoribbons in solution and found that the lateral extension results in decrease of their electronic bandgap and improvement in the electrical conductivity of nanoribbon-based thin films. These films were employed in gas sensors and an electronic nose system, which showed improved responsivities to low molecular weight alcohols compared to similar sensors based on benchmark graphitic materials, such as graphene and reduced graphene oxide, and a reliable analyte recognition. This study shows the methodology for designing new atomically precise graphene nanoribbons with improved properties, their bottom-up synthesis, characterization, processing and implementation in electronic devices.Atomically precise graphene nanoribbons are a promising platform for tailored electron transport, yet they suffer from low conductivity. Here, the authors devise a strategy to laterally extend conventional chevron nanoribbons, thus achieving increased electrical conductivity and improved chemical sensing capabilities

The X-ray structure of Salmonella typhimurium uridine nucleoside phosphorylase complexed with 2,2'-anhydrouridine, phosphate and potassium ions at 1.86 A resolution.

Uridine nucleoside phosphorylase is an important drug target for the development of anti-infective and antitumour agents. The X-ray crystal structure of Salmonella typhimurium uridine nucleoside phosphorylase (StUPh) complexed with its inhibitor 2,2'-anhydrouridine, phosphate and potassium ions has been solved and refined at 1.86 A resolution (R(cryst) = 17.6%, R(free) = 20.6%). The complex of human uridine phosphorylase I (HUPhI) with 2,2'-anhydrouridine was modelled using a computational approach. The model allowed the identification of atomic groups in 2,2'-anhydrouridine that might improve the interaction of future inhibitors with StUPh and HUPhI