ethanol-sensing mechanism Dotaz Zobrazit nápovědu
In this work, we investigate ethanol (EtOH)-sensing mechanisms of a ZnO nanorod (NRs)-based chemiresistor using a near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS). First, the ZnO NRs-based sensor was constructed, showing good performance on interaction with 100 ppm of EtOH in the ambient air at 327 °C. Then, the same ZnO NRs film was investigated by NAP-XPS in the presence of 1 mbar oxygen, simulating the ambient air atmosphere and O2/EtOH mixture at the same temperature. The partial pressure of EtOH was 0.1 mbar, which corresponded to the partial pressure of 100 ppm of analytes in the ambient air. To better understand the EtOH-sensing mechanism, the NAP-XPS spectra were also studied on exposure to O2/EtOH/H2O and O2/MeCHO (MeCHO = acetaldehyde) mixtures. Our results revealed that the reaction of EtOH with chemisorbed oxygen on the surface of ZnO NRs follows the acetaldehyde pathway. It was also demonstrated that, during the sensing process, the surface becomes contaminated by different products of MeCHO decomposition, which decreases dc-sensor performance. However, the ac performance does not seem to be affected by this phenomenon.
- Klíčová slova
- ZnO nanorods, acetaldehyde pathway, carbon contamination, ethanol-sensing mechanism, near-ambient pressure XPS,
- Publikační typ
- časopisecké články MeSH
Graphene has demonstrated great promise for technological use, yet control over material growth and understanding of how material imperfections affect the performance of devices are challenges that hamper the development of applications. In this work, we reveal new insight into the connections between the performance of the graphene devices as environmental sensors and the microscopic details of the interactions at the sensing surface. We monitor changes in the resistance of the chemical-vapor deposition grown graphene devices as exposed to different concentrations of ethanol. We perform thermal surface treatments after the devices are fabricated, use scanning probe microscopy to visualize their effects down to nanometer scale and correlate them with the measured performance of the device as an ethanol sensor. Our observations are compared to theoretical calculations of charge transfers between molecules and the graphene surface. We find that, although often overlooked, the surface cleanliness after device fabrication is responsible for the device performance and reliability. These results further our understanding of the mechanisms of sensing in graphene-based environmental sensors and pave the way to optimizing such devices, especially for their miniaturization, as with decreasing size of the active zone the potential role of contaminants will rise.
- Klíčová slova
- 2D materials, DFT, VOC, graphene, sensing,
- Publikační typ
- časopisecké články MeSH
Graphene oxides (GOs) and hydrogen-terminated nanocrystalline diamonds (H-NCD) have attracted considerable attention due to their unique electronic structure and extraordinary physical and chemical properties in various applications, including gas sensing. Currently, there is a significant focus on air quality and the presence of pollutants (NH3, NO2, etc.), as well as volatile organic compounds (VOC) such as ethanol vapor from industry. This study examines the synthesis of GO, reduced graphene oxide (rGO), thiol-functionalized graphene oxide (SH-GO), and H-NCD thin films and their combination in heterostructures. The materials were analyzed for their ability to detect NO2, NH3, and ethanol vapor at room temperature (22 °C). Among the tested materials, the SH-GO/H-NCD heterostructure exhibited the highest sensitivity, with approximately 630% for ethanol vapor, 41% for NH3 and -19% for NO2. The SH-GO/H-NCD heterostructure also demonstrated reasonable response (272 s) and recovery (34 s) times. Cross-selectivity measurements revealed that the heterostructure's response to ethanol vapor at 100 ppm remained dominant and was minimally affected by the presence of NH3 (100 ppm) or CO2 (100 ppm). The response variations were -1.3% for NO2 and 2.4% for NH3, respectively. These findings suggest that this heterostructure has the potential to be used as an active layer in low-temperature gas sensors. Furthermore, this research proposes a primary mechanism that explains the enhanced sensor response of the heterostructure compared with bare GOs and H-NCD layers.
Zinc oxide rod structures are synthetized and subsequently modified with Au, Fe2O3, or Cu2O to form nanoscale interfaces at the rod surface. X-ray photoelectron spectroscopy corroborates the presence of Fe in the form of oxide-Fe2O3; Cu in the form of two oxides-CuO and Cu2O, with the major presence of Cu2O; and Au in three oxidation states-Au3+, Au+, and Au0, with the content of metallic Au being the highest among the other states. These structures are tested towards nitrogen dioxide, ethanol, acetone, carbon monoxide, and toluene, finding a remarkable increase in the response and sensitivity of the Au-modified ZnO films, especially towards nitrogen dioxide and ethanol. The results for the Au-modified ZnO films report about 47 times higher response to 10 ppm of nitrogen dioxide as compared to the non-modified structures with a sensitivity of 39.96% ppm-1 and a limit of detection of 26 ppb to this gas. These results are attributed to the cumulative effects of several factors, such as the presence of oxygen vacancies, the gas-sensing mechanism influenced by the nano-interfaces formed between ZnO and Au, and the catalytic nature of the Au nanoparticles.
- Klíčová slova
- Schottky junctions, copper oxide, gas sensing, gold, heterojunctions, interfaces, iron oxide, nitrogen dioxide, zinc oxide,
- Publikační typ
- časopisecké články MeSH
A styrene-butadiene-styrene co-polymer matrix nanocomposite filled with graphene nanoplatelets was studied to prepare chemiresistive volatile organic compounds (VOCs) room temperature sensors with considerable response and selectivity. Nanofiller concentration was estimated from the electrical conductivity percolation behaviour of the nanocomposite. Fabricated sensors provided selective relative responses to representative VOCs differing by orders of magnitude. Maximum observed average relative responses upon exposure to saturated vapours of the tested VOCs were ca. 23% for ethanol, 1600% for acetone, and the giant values were 9 × 106% for n-heptane and 10 × 106% for toluene. The insensitivity of the sensor to the direct saturated water vapour exposure was verified. Although high humidity decreases the sensor's response, it paradoxically enhances the resolution between hydrocarbons and polar organics. The non-trivial sensing mechanism is explained using the Hansen solubility parameters (HSP), enabling a rational design of new sensors; thus, the HSP-based class of sensors is outlined.
- Klíčová slova
- Hansen solubility parameter, chemiresistivity, co-polymer, graphene, organic vapour sensing, sensor,
- Publikační typ
- časopisecké články MeSH
Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, their high cost production and/or incompatibility with microfabrication technologies, due to the use of pre-deposited catalyst-seeds and/or high processing temperatures exceeding 900 °C, represent a drawback for a widespread use of these methods. Here, however, we report the synthesis of ZnO rods via a non-catalyzed vapor-solid mechanism enabled by using an aerosol-assisted chemical vapor deposition (CVD) method at 400 °C with zinc chloride (ZnCl2) as the precursor and ethanol as the carrier solvent. This method provides both single-step formation of ZnO rods and the possibility of their direct integration with various substrate types, including silicon, silicon-based micromachined platforms, quartz, or high heat resistant polymers. This potentially facilitates the use of this method at a large-scale, due to its compatibility with state-of-the-art microfabrication processes for device manufacture. This report also describes the properties of these structures (e.g., morphology, crystalline phase, optical band gap, chemical composition, electrical resistance) and validates its gas sensing functionality towards carbon monoxide.
- MeSH
- aerosoly MeSH
- katalýza MeSH
- oxid zinečnatý chemie MeSH
- Publikační typ
- audiovizuální média MeSH
- časopisecké články MeSH
- Názvy látek
- aerosoly MeSH
- oxid zinečnatý MeSH
The main bottleneck in the return of industrial butanol production from renewable feedstock through acetone-butanol-ethanol (ABE) fermentation by clostridia, such as Clostridium beijerinckii, is the low final butanol concentration. The problem is caused by the high toxicity of butanol to the production cells, and therefore, understanding the mechanisms by which clostridia react to butanol shock is of key importance. Detailed analyses of transcriptome data that were obtained after butanol shock and their comparison with data from standard ABE fermentation have resulted in new findings, while confirmed expected population responses. Although butanol shock resulted in upregulation of heat shock protein genes, their regulation is different than was assumed based on standard ABE fermentation transcriptome data. While glucose uptake, glycolysis, and acidogenesis genes were downregulated after butanol shock, solventogenesis genes were upregulated. Cyclopropanation of fatty acids and formation of plasmalogens seem to be significant processes involved in cell membrane stabilization in the presence of butanol. Surprisingly, one of the three identified Agr quorum-sensing system genes was upregulated. Upregulation of several putative butanol efflux pumps was described after butanol addition and a large putative polyketide gene cluster was found, the transcription of which seemed to depend on the concentration of butanol.
- Klíčová slova
- Clostridium beijerinckii, ABE fermentation, butanol shock, transcriptome analysis,
- MeSH
- biologický transport genetika MeSH
- bioreaktory mikrobiologie MeSH
- buněčná membrána metabolismus MeSH
- butanoly toxicita MeSH
- Clostridium beijerinckii účinky léků genetika metabolismus MeSH
- fyziologický stres genetika MeSH
- glukosa metabolismus MeSH
- glykolýza genetika fyziologie MeSH
- mastné kyseliny metabolismus MeSH
- plasmalogeny biosyntéza MeSH
- proteiny tepelného šoku metabolismus MeSH
- quorum sensing genetika MeSH
- stanovení celkové genové exprese MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- butanoly MeSH
- glukosa MeSH
- mastné kyseliny MeSH
- plasmalogeny MeSH
- proteiny tepelného šoku MeSH
ETHNOPHARMACOLOGICAL RELEVANCE: Salvia officinalis L., Sambucus nigra L., Matricaria chamomilla L., Agrimonia eupatoria L., Fragaria vesca L. and Malva sylvestris L. are plants that have a long tradition in European folk medicine. To this day, they are part of medicinal teas or creams that help with the healing of skin wounds and the treatment of respiratory or intestinal infections. However, so far these plants have not been investigated more deeply than in their direct antibacterial effect. AIM OF THE STUDY: Our research is focused on adjuvants that inhibit the mechanism of antibiotic resistance or modulate bacterial virulence. Based on a preliminary screening of 52 European herbs, which commonly appear as part of tea blends or poultice. Six of them were selected for their ability to revert the resistant phenotype of nosocomial bacterial strains. METHODS: Herbs selected for this study were obtained from commercially available sources. For the extraction of active compounds ethanol was used. Modulation of virulence was observed as an ability to inhibit bacterial cell-to-cell communication using two mutant sensor strains of Vibrio campbellii. Biofilm formation, and planktonic cell adhesion was measured using a static antibiofilm test. Ethidium bromide assay was used to checked the potential of inhibition bacterial efflux pumps. The antibacterial activities of the herbs were evaluated against resistant bacterial strains using macro dilution methods. RESULTS: Alcohol extracts had antibacterial properties mainly against Gram-positive bacteria. Of all of them, the highest antimicrobial activity demonstrated Malva sylvestris, killing both antibiotic resistant bacteria; Staphylococcus aureus with MIC of 0.8 g/L and Pseudomonas aeruginosa 0.7 g/L, respectively. Fragaria vesca extract (0.08 g/L) demonstrated strong synergism with colistin (4 mg/L) in modulating the resistant phenotype to colistin of Pseudomonas aeruginosa. Similarly, the extract of S. officinalis (0.21 g/L) reverted resistance to gentamicin (1 mg/L) in S. aureus. However, Sambucus nigra and Matricaria chamomilla seem to be a very promising source of bacterial efflux pump inhibitors. CONCLUSION: The extract of F. vesca was the most active. It was able to reduce biofilm formation probably due to the ability to decrease bacterial quorum sensing. On the other hand, the activity of S. nigra or M. chamomilla in reducing bacterial virulence may be explained by the ability to inhibit bacterial efflux systems. All these plants have potential as an adjuvant for the antibiotic treatment.
- Klíčová slova
- Biofilm, Efflux pump inhibitors, Herbs, Medicinal plants, Multidrug resistance, Quorum sensing,
- MeSH
- antibakteriální látky farmakologie MeSH
- Bacteria MeSH
- biofilmy MeSH
- kolistin farmakologie MeSH
- léčivé rostliny * MeSH
- mikrobiální testy citlivosti MeSH
- Pseudomonas aeruginosa MeSH
- rostlinné extrakty farmakologie MeSH
- Staphylococcus aureus MeSH
- virulence MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- antibakteriální látky MeSH
- kolistin MeSH
- rostlinné extrakty MeSH
After cold shock, the Bacillus subtilis desaturase Des introduces double bonds into the fatty acids of existing membrane phospholipids. The synthesis of Des is regulated exclusively by the two-component system DesK/DesR; DesK serves as a sensor of the state of the membrane and triggers Des synthesis after a decrease in membrane fluidity. The aim of our work is to investigate the biophysical changes in the membrane that are able to affect the DesK signalling state. Using linear alcohols (ethanol, propanol, butanol, hexanol, octanol) and benzyl alcohol, we were able to suppress Des synthesis after a temperature downshift. The changes in the biophysical properties of the membrane caused by alcohol addition were followed using membrane fluorescent probes and differential scanning calorimetry. We found that the membrane fluidization induced by alcohols was reflected in an increased hydration at the lipid-water interface. This is associated with a decrease in DesK activity. The addition of alcohol mimics a temperature increase, which can be measured isothermically by fluorescence anisotropy. The effect of alcohols on the membrane periphery is in line with the concept of the mechanism by which two hydrophilic motifs located at opposite ends of the transmembrane region of DesK, which work as a molecular caliper, sense temperature-dependent variations in membrane properties.
- Klíčová slova
- Alcohols, Bacillus subtilis, Cold shock, Membrane fluidity, Membrane-active compounds, Two-component system,
- MeSH
- alkoholy farmakologie MeSH
- aminokyselinové motivy MeSH
- Bacillus subtilis metabolismus MeSH
- bakteriální proteiny metabolismus MeSH
- buněčná membrána účinky léků fyziologie MeSH
- desaturasy mastných kyselin biosyntéza genetika MeSH
- diferenciální skenovací kalorimetrie MeSH
- enzymová indukce účinky léků MeSH
- fluidita membrány účinky léků MeSH
- fluorescenční polarizace MeSH
- fosforylace MeSH
- hydrofobní a hydrofilní interakce MeSH
- mastné kyseliny metabolismus MeSH
- nízká teplota MeSH
- posttranslační úpravy proteinů * MeSH
- proteinkinasy metabolismus MeSH
- regulace genové exprese u bakterií účinky léků MeSH
- rekombinantní fúzní proteiny metabolismus MeSH
- reportérové geny MeSH
- signální transdukce účinky léků MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
- Názvy látek
- alkoholy MeSH
- bakteriální proteiny MeSH
- desaturasy mastných kyselin MeSH
- mastné kyseliny MeSH
- proteinkinasy MeSH
- rekombinantní fúzní proteiny MeSH
