•Flakes-like (MoO3) successfully synthesized by evaporation-condensation method.•Au nanoparticles prevent the growth of thick layers of MoO3.•Au functionalization was performed on bare MoO3 nano ...flakes and enhance the gas sensing performance.•MoO3 NF nano flakes shows good sensitivity to Ethanol, Methanol, H2 and H2S and MoO3 nano flakes exhibit an excellent response to H2S.
Molybdenum trioxide (MoO3) nano flakes (NF) with orthorhombic structure were synthesized by evaporation-condensation method using MoO3 powder as a raw material. Gold (Au) nanoparticles were used as a catalyst, preventing the growth of thick layers of MoO3. Furthermore, Au functionalization was performed by sputtering on pure MoO3 NF for a few seconds, decorating the flakes with Au nanoparticles. Chemical sensing performances were evaluated by introducing CO, NH3, Ethanol, NO2, Methanol, H2 and H2S gases in a syntetic air baseline with a relative humidity of 40% at 25 °C. MoO3 NF shows good sensitivity to Ethanol, Methanol, H2 and H2S gases. Owing to Au functionalization the devices exhibited an excellent response to H2S at an operating temperature of 400 °C: the response was 10 times higher than the pure MoO3, and the detection limit moved toward the ppb range.
High-power and narrow-linewidth laser light is a vital tool for atomic physics, being used for example in laser cooling and trapping and precision spectroscopy. Here we produce Watt-level laser ...radiation at 457.75 nm and 460.86 nm of respective relevance for the cooling transitions of cadmium and strontium atoms. This is achieved via the frequency doubling of a kHz-linewidth vertical-external-cavity surface-emitting laser (VECSEL), which is based on a novel gain chip design enabling lasing at > 2 W in the 915-928 nm region. Following an additional doubling stage, spectroscopy of the 1 S 0 → 1 P 1 cadmium transition at 228.87 nm is performed on an atomic beam, with all the transitions from all eight natural isotopes observed in a single continuous sweep of more than 4 GHz in the deep ultraviolet. The absolute value of the transition frequency of 114 Cd and the isotope shifts relative to this transition are determined, with values for some of these shifts provided for the first time.
Volatile organic compounds are released by different sources causing air pollution. Moreover, some of these carbon-based organic chemicals are considered as biomarkers in the exhaled breath of ...individuals and can be used to identify various kinds of diseases. Hence, the increasing demand to control air quality and human health has promoted the development of monitoring systems based on high-performance gas sensing structures. This review highlights the achievements in sensing technologies for the detection of volatile organic compounds. Particularly, chemiresistive gas sensors and detection systems based on the terahertz spectroscopy method are outlined. The progress in research studies is discussed and the potential of both techniques is evaluated considering the current challenges. Afterward, a brief summary is also provided along with the advances and issues for future investigations and the manufacturing of highly sensitive and selective monitoring systems.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The inspiration behind this research is the development of tungsten oxide (WO3) nanowires based, highly sensitive and selective sensing devices directly on the active sensing platform. WO3 ...one-dimensional nanowires were synthesized via the vapour-phase growth technique. This approach allows the production of well-aligned and uniform nanowires on alumina substrates with their diameter and length in the nanometer range. The morphological and structural properties of nanowires have been investigated by means of the field effect electron microscopy, grazing incidence X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Finally, the fabricated WO3 nanowire sensing devices and their gas sensing performance were investigated in the presence of different oxidizing and reducing gases (especially environmental gases) at different temperatures. The WO3 sensors demonstrate high performance toward H2S and O3 at the optimal working temperatures of 400 and 200 °C, respectively, with the detection limit in the ppb level.
ZnO is worth evaluating for chemical sensing due to its outstanding physical and chemical properties. We report the fabrication and study of the gas sensing properties of ZnO nanomaterial for the ...detection of hydrogen sulfide (H2S). This prepared material exhibited a 7400 gas sensing response when exposed to 30 ppm of H2S in air. In addition, the structure showed a high selectivity towards H2S against other reducing gases. The high sensing performance of the structure was attributed to its nanoscale size, morphology and the disparity in the sensing mechanism between the H2S and other reducing gases. We suggest that the work reported here including the simplicity of device fabrication is a significant step toward the application of ZnO nanomaterials in chemical gas sensing systems for the real-time detection of H2S.
Recently, one-dimensional (1D) nanostructures have attracted the scientific community attention as sensitive materials for conductometric chemical sensors. However, finding facile and low-cost ...techniques for their production, controlling the morphology and the aspect ratio of these nanostructures is still challenging. In this study, we report the vapor-liquid-solid (VLS) synthesis of one dimensional (1D) zinc oxide (ZnO) nanorods (NRs) and nanowires (NWs) by using different metal catalysts and their impact on the performances of conductometric chemical sensors. In VLS mechanism, catalysts are of great interest due to their role in the nucleation and the crystallization of 1D nanostructures. Here, Au, Pt, Ag and Cu nanoparticles (NPs) were used to grow 1D ZnO. Depending on catalyst nature, different morphology, geometry, size and nanowires/nanorods abundance were established. The mechanism leading to the VLS growth of 1D ZnO nanostructures and the transition from nanorods to nanowires have been interpreted. The formation of ZnO crystals exhibiting a hexagonal crystal structure was confirmed by X-ray diffraction (XRD) and ZnO composition was identified using transmission electron microscopy (TEM) mapping. The chemical sensing characteristics showed that 1D ZnO has good and fast response, good stability and selectivity. ZnO (Au) showed the best performances towards hydrogen (H
). At the optimal working temperature of 350 °C, the measured response towards 500 ppm of H
was 300 for ZnO NWs and 50 for ZnO NRs. Moreover, a good selectivity to hydrogen was demonstrated over CO, acetone and ethanol.
The magic in molecules Poli, Nicola
Nature physics,
11/2019, Letnik:
15, Številka:
11
Journal Article
Recenzirano
Odprti dostop
The demonstration of high-resolution spectroscopy of Sr2 molecules trapped in an optical lattice at the ‘magic’ wavelength opens the way to precision control of molecular excitations.
Atom interferometry on optical clock transitions is being pursued for numerous long-baseline experiments both terrestrially and for future space missions. Crucial to meeting the required ...sensitivities of these experiments is the implementation of large momentum transfer (>10^{3}ℏk). Here, we show that to sequentially apply such a large momentum via π pulses places stringent requirements on the frequency noise of the interferometry laser and we find that the linewidth is required to be considerably lower than the previous estimate of approximately 10 Hz. This is due to imperfect pulse fidelity in the presence of noise and is apparent even for an atom at rest interacting with resonant light, making this a fundamental constraint on operational fidelity for a given laser and pulse sequence. Within this framework, we further present and analyze two high-power frequency-stabilized laser sources designed to perform interferometry on the ^{1}S_{0}–^{3}P_{0} clock transitions of cadmium and strontium, operating at 332 nm and 698 nm, respectively.
Preparation and characterization of different metal oxide (NiO, WO
, ZnO, SnO
and Nb
O
) nanostructures for chemical sensing are presented. p-Type (NiO) and n-type (WO
, SnO
, ZnO and Nb
O
) metal ...oxide nanostructures were grown on alumina substrates using evaporation-condensation, thermal oxidation and hydrothermal techniques. Surface morphologies and crystal structures were investigated through scanning electron microscopy and Raman spectroscopy. Furthermore, different batches of sensors have been prepared, and their sensing performances towards carbon monoxide and nitrogen dioxide have been explored. Moreover, metal oxide nanowires have been integrated into an electronic nose and successfully applied to discriminate between drinking and contaminated water.
A hybrid nanostructure based on reduced graphene oxide and ZnO has been obtained for the detection of volatile organic compounds. The sensing properties of the hybrid structure have been studied for ...different concentrations of ethanol and acetone. The response of the hybrid material is significantly higher compared to pristine ZnO nanostructures. The obtained results have shown that the nanohybrid is a promising structure for the monitoring of environmental pollutants and for the application of breath tests in assessment of exposure to volatile organic compounds.
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