ABSTRACT
Developing a respiratory analysis disease diagnosis platform for the H2S biomarker has great significance for the real-time detection of various diseases. However, achieving highly sensitive and rapid detection of H2S gas at the parts per billion level at low temperatures is one of the most critical challenges for developing portable exhaled gas sensors. Herein, Cu2O-multiwalled carbon nanotube (MWCNT) heterostructures with excellent gas sensitivity to H2S at room temperature and a lower temperature were successfully synthesized by a facile two-dimensional (2D) electrodeposition in situ assembly method. The combination of Cu2O and MWCNTs via the principle of optimal conductance growth not only reduced the initial resistance of the material but also provided an ideal interfacial barrier structure. Compared to the response of the pure Cu2O sensor, that of the Cu2O-MWCNT sensor to 1 ppm of H2S increased nearly 800 times at room temperature, and the response time decreased by more than 500 s. In addition to the excellent sensitivity with detection limits as low as 1 ppb, the Cu2O-MWCNT sensor was extremely selective with low-temperature adaptability. The sensor had a response value of 80.6 to 0.1 ppm of H2S at -10 °C, which is difficult to achieve with sensors based on oxygen adsorption/desorption mechanisms. The sensor was used for the detection of real oral exhaled breath, confirming its feasibility as a real-time disease monitoring sensor. The Cu2O-MWCNT heterostructures maximized the advantages of the individual components and laid the experimental foundation for future applications of highly sensitive portable breath analysis platforms for monitoring H2S.
Subject(s)
Body Fluids , Nanotubes, Carbon , Adsorption , Breath Tests , Cold TemperatureABSTRACT
2D heterostructure nanoarrays have emerged as a promising sensing material for rapid disease detection applications. In this study, a bio-H2S sensor based on Cu2O/Co3O4 nanoarrays was proposed, the controllable preparation of the nanoarrays being achieved by exploring the experimental parameters of the 2D electrodeposition in situ assembly process. The nanoarrays were designed as a multi-barrier system with strict periodicity and long-range order. Based on the interfacial conductance modulation and vulcanization reaction of Cu2O and Co3O4, the sensor exhibited superior sensitivity, selectivity, and stability to H2S in human blood. In addition, the sensor exhibited a reasonable response to 0.1 µmol L-1 Na2S solution, indicating that it had a low detection limit for practical applications. Moreover, first-principles calculations were performed to study changes in the heterointerface during the sensing process and the mechanism of rapid response of the sensor. This work demonstrated the reliability of Cu2O/Co3O4 nanoarrays applied in portable sensors for the rapid detection of bio-H2S.
ABSTRACT
Microorganisms that facilitate the decomposition of agricultural wastes are of importance during composting processes. Here, we assessed if microbial agents, comprising Clonostachys rosea, Bacillus amylolyticus and Rhodospirillum photometricum can facilitate the decomposition of a compost mix of vegetable waste, chicken manure, sawdust, and biochar. The results showed that inoculating the compost mix with the microbial agents elevated the compost temperature, increased the thermophilic period, and enhanced cellulose degradation. Microbial agent inoculation also changed the diversity and richness of decomposing microbial communities. Among the microbial agents, the mixture of C. rosea and B. amylolyticus performed better than other mixtures. Taken together, the results confirmed that the microbial agents comprising C. rosea can enhance the composting process by ameliorating the physiochemical conditions of agricultural wastes and promoting the diversity and proliferation of beneficial bacteria involved in the decomposition of cellulose.
Subject(s)
Composting , Microbiota , Soil , Agriculture , Manure/microbiology , CelluloseABSTRACT
Magnetism is a promising external intervention for gas sensitivity based on a heterogeneous interfacial structure caused by the regulation of the heterogeneous interface conductivity and the surface oxygen adsorption. In this study, Cu2O/NiO heterostructure-ordered nanoarrays were prepared with a two-dimensional (2D) electrodeposition in situ assembly method for H2S gas detection at room temperature under the action of a magnetic field. The nanoarrays were multibarrier structures with a strictly periodic structure that was greater than hundreds of microns in size. The experimental data confirmed that the response of 50 ppm of H2S based on the nanoarrays was improved by nearly 61% with a relatively weak magnetic field. Particularly at a low concentration (≤20 ppm), the effect of the magnetic field enhancement on the sensitivity was more obvious. We attributed the enhancement of the gas sensitivity with the magnetic field to the regulation of the Cu2O-NiO interface conductance and the surface oxygen adsorption. This study demonstrated that a magnetic field could significantly enhance the gas sensitivity based on heterostructures. Results of this study provide an important reference for the application of magnetism in gas detection and the design of new gas-sensitive materials.
Subject(s)
Magnetic Fields , Oxygen , Magnetic PhenomenaABSTRACT
The electronic properties and interfacial contact of the graphene-based heterostructure graphene/CrSiTe3 (Gr/CrSiTe3) are modulated by tuning the interfacial distance, along with application of an external electric field. Our first-principles calculations show that the gap is enlarged to 27.6 meV in Gr/CrSiTe3 when the interfacial distance is reduced to a distance of 2.75 Å. Gr/CrSiTe3 changes from an n-type to a p-type Schottky contact with a decrease in interfacial space. The most significant effect of applying a positive electric field is the presence of a p-type Schottky contact along with an increase of interfacial charge transfer to graphene, while an electric field in the opposite direction enhances the n-type Schottky contact effectively with a decrease of interfacial charge transfer to graphene. The Schottky contact transforms into an Ohmic contact when a positive electric field of 0.41 eV Å-1 is applied to this interface. The work proposes an approach to manipulate the interfacial properties, which can be very useful for future experimental studies and graphene-based interfaces.
ABSTRACT
2D heterostructures are promising gas sensor materials due to their surface/interface effects and hybrid properties. In this research, Cu2O/Fe2O3 heterostructure ordered arrays were synthesized using an in situ electrodeposition method for H2S detection at low temperatures. These arrays possess a periodic long range ordered structure with horizontal multi-heterointerfaces, leading to superior gas sensitivity for synergistic effects at the heterointerfaces. The sensor based on the Cu2O/Fe2O3 heterostructure ordered arrays exhibits a dramatic improvement in H2S detection at low temperatures (even as low as -15 °C). The response is particularly significant at room and human body temperatures since the conductivity of the arrays can change by up to three orders of magnitude in a 10 ppm H2S atmosphere. These good performances are also attributed to the formation of metallic Cu2S conducting channels. Our results imply that the Cu2O/Fe2O3 heterostructure ordered arrays are promising candidates for high-performance H2S gas sensors that function at low temperatures as well as breath analysis systems for disease diagnosis.
ABSTRACT
Using first principles theory, we investigated the behavior of the one-dimensional (1D) topological edge states of high temperature superconductiviing FeSe/SrTiO3 films with Te atoms substitution to Se atoms in the bottom (top) layer in single-layer FeSe, as a function of strain. It was discovered that the 1D topological edge states are present in single-unit-cell FeSe film on SrTiO3, but are absent when more than 50% Se atoms are replaced by Te atoms. Stress induced displacive phase transformation exists in FeSe/SrTiO3 film when Te atoms substitute Se atoms in the bottom (top) layer in single-layer FeSe under 3% strain respectively. The 1D topological edge states are present under 3% (1.8%) strain in FeSe/SrTiO3 films with Te substitution Se in the bottom (top) layer in single-layer FeSe, even up to 5%, respectively. This indicates that the bonding angle of Se-Fe-Se (Te) and the distance of Te (or Se) atoms to the Fe plane are correlated with the topological edge states. Our findings provide an effective interface system that provides both superconducting and topological states, opening a new route for realizing 2D topological superconductors with proximity effect.
ABSTRACT
The nanostructures with uniform long-range ordered structure are of crucial importance for performance standardization of high-quality surface-enhanced Raman scattering (SERS) spectra. In this paper, we described the fabrication and SERS properties of Au decorated Cu (Au@Cu) nanoarrays. The Cu nanoarrays with uniform long-range ordered structure were first synthesized by in-situ electrochemistry assembly on insulated substrate. The Cu nanoarrays can reach a size of centimeters with strictly periodic nano-microstructure, which is beneficial for the production and performance standardization of SERS substrates. Then Au nanoparticals were decorated on the Cu nanoarrays by galvanic reaction without any capping agent. The obtained Au@Cu nanoarrays exhibit excellent SERS activity for 4-Mercaptopyridine, and the sensitivity limit is as low as 10-8 M. Therefore, this facile route provides a useful platform for the fabrication of SERS substrates based on nano ordered arrays.
ABSTRACT
In this paper, we performed density functional theory (DFT) calculations to investigate the geometric structures, electronic structures and visible-light absorbance of MoS2/AlN heterostructure based on van der Waals interaction. The calculated formation energy indicated that the designed MoS2/AlN heterostructure could be experimentally prepared. The Mo-N stacked MoS2/AlN heterostructure exhibited more considerable optical absorption in visible-light region than MoS2 and AlN monolayers. More interestingly, the band gaps were sensitive to strain, which led to an obvious shift of optical absorption spectra along the direction of the infrared region. The two most energetically favorable twisted MoS2/AlN heterostructures (Mo-N and Mo-HAl) had similar band structures, which were different from the non-twisted MoS2/AlN heterostructure. With different rotation angles, their band structures all exhibited an indirect band gap and almost had the same values of indirect band gaps, indicating that the indirect band gaps had no clear dependence on rotation angles.
ABSTRACT
The researches for new quantum spin Hall (QSH) insulators with large bulk energy gap are of much significance for their practical applications at room temperature in electronic devices with low-energy consumption. By means of first-principles calculations, we proposed that methyl-decorated stanene (SnCH3) film can be tuned into QSH insulator under critical tensile strain of 6%. The nonzero topological invariant and helical edge states further confirm the nontrivial nature in stretched SnCH3 film. The topological phase transition originates from the s-p xy type band inversion at the Γ point with the strain increased. The spin-orbital coupling (SOC) induces a large band gap of ~0.24 eV, indicating that SnCH3 film under strain is a quite promising material to achieve QSH effect. The proper substrate, h-BN, finally is presented to support the SnCH3 film with nontrivial topology preserved.
ABSTRACT
Gas sensors with high sensitivity at and below room temperature, especially below freezing temperature, have been expected for practical application. The lower working temperature of gas sensor is better for the manufacturability, security and environmental protection. Herein, we propose a H2S gas sensor with high sensitivity at and below room temperature, even as low as -30 °C, based on Cu2O/Co3O4 nano/microstructure heteroarrays prepared by 2D electrodeposition technique. This heteroarray was designed to be a multi-barrier system, and which was confirmed by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and scanning probe microscopy. The sensor demonstrates excellent sensitivity, sub-ppm lever detection, fast response, and high activity at low temperature. The enhanced sensing property of sensor was also discussed with the Cu2O/Co3O4 p-p heterojunction barrier modulation and Cu2S conductance channel. We realize the detection of the noxious H2S gas at ultra-low temperature in a more security and environmental protection way.
ABSTRACT
Based on first-principles calculations, the electronic and topological properties of halogenated (F-, Cl-, Br- and I-) arsenene are investigated in detail. It is found that the halogenated arsenene sheets show Dirac type characteristic in the absence of spin-orbital coupling (SOC), whereas energy gap will be induced by SOC with the values ranging from 0.194 eV for F-arsenene to 0.255 eV for I-arsenene. Noticeably, these four newly proposed two-dimensional (2D) systems are verified to be quantum spin Hall (QSH) insulators by calculating the edge states with obvious linear cross inside bulk energy gap. It should be pointed out that the large energy gap in these 2D materials consisted of commonly used element is quite promising for practical applications of QSH insulators at room temperature.
ABSTRACT
Heterostructure materials with a strictly periodic arrangement in hundreds of microns based on tunneling modulation are ideal candidates for micro-nanodevice applications. In this paper, we propose a Cu2O/SnO2 periodical heterostructure film, which is prepared by electrochemical deposition in a quasi-2D ultra-thin liquid layer. The surface morphology and the component of the film were analyzed by scanning electron microscopy (SEM), scanning probe microscopy (SPM) and transmission electron microscopy (TEM). The influences of frequency and amplitude of periodic deposition potential on the morphology and regular distribution of the interface were studied. The photoresponsivity of this material was researched, and the response behaviors for different illumination conditions were recorded carefully. Based on the tunneling modulation mechanism, it exhibits reasonable photoresponsivity to UV light.
ABSTRACT
From first-principles calculations, the effects of h-BN and AlN substrates on the topological nontrivial properties of stanene are studied with different strains. We find that the quantum spin Hall phase can be induced in stanene film on a h-BN substrate under a tensile strain of between 6.0% and 9.3% with a stable state confirmed by the phonon spectrum, while for stanene on 5 × 5 h-BN, the quantum spin Hall phase can be preserved without strain. However, for stanene on a AlN substrate, the quantum spin Hall phase cannot be found under compressive or tensile strains less than 10%, while for 2 × 2 stanene on 3 × 3 AlN, the compressive strain needed to induce the quantum spin Hall phase is just 2%. These theoretical results will be helpful in understanding the effect of substrate and strain on stanene and in further realizing the quantum spin Hall effect in stanene on semiconductor substrates.
ABSTRACT
Based on first-principles calculations, we systematically investigated the topological surface states of Bi and Sb thin films of 1-5 bilayers in (111) orientation without and with H(F) adsorption, respectively. We find that compared with clean Bi and Sb films, a huge band gap advantageous to observe the quantum spin Hall effect can be opened in chemically decorated bilayer Bi and Sb films, and the quantum phase transition from trivial (non-trivial) to non-trivial (trivial) phase is induced for a three bilayer Bi film and single (four) bilayer Sb film. Surface adsorption is an effective tool to manipulate the geometry, electronic structures and topological properties of film materials.
ABSTRACT
We investigated the behavior of edge states in two-dimensional bilayered Bi nanoribbons by atom adsorption based on the density functional method. We found that for a clean Bi zigzag ribbon the penetration depth of well-localized edge states is a function of the momentum-space width of the edge-state dispersion. Depending on the density of adsorbed H, Br and I atoms, respectively, the edge state can be changed from localized within a very narrow region to delocalized over the whole region in real space. Changes in atomic and electronic structures and topological insulator properties associated with the atomic adsorption on the edges of zigzag bilayer nanoribbon (ZBNR) are discussed. Our work suggests that ZBNR could be a possible candidate for nanoelectronic devices under some special conditions.
ABSTRACT
A nontoxic, simple, inexpensive, and reproducible strategy, which meets the standard of green chemistry, is introduced for the synthesis of copper nanocrystals (Cu NCs) with olive oil as both reducing agent and capping agent. By changing the reaction parameters, the shape, size and surface structure of the Cu NCs can be well controlled. The obtained Cu nanocubes show excellent catalytic properties for the catalytic reduction of dyes and CO oxidation. Moreover, the prepared Cu nanocubes as substrates exhibit surface enhanced Raman scattering (SERS) activity for 4-mercaptopyridine (4-Mpy). Therefore, this facile route provides a useful platform for the fabrication of Cu NCs which have the potential to replace noble metals for certain applications.
ABSTRACT
Heterostructure material that acts as resonant tunneling system is a major scientific challenge in applied physics. Herein, we report a resonant tunneling system, quasi-2D Cu(2)O/SnO(2) p-n heterostructure multi-layer film, prepared by electrochemical deposition in a quasi-2D ultra-thin liquid layer. By applying a special half-sine deposition potential across the electrodes, Cu(2)O and SnO(2) selectively and periodically deposited according to their reduction potentials. The as-prepared heterostructure film displays excellent sensitivity to H(2)S at room temperature due to the resonant tunneling modulation. Furthermore, it is found that the laser illumination could enhance the gas response, and the mechanism with laser illumination is discussed. It is the first report on gas sensing application of resonant tunneling modulation. Hence, heterostructure material act as resonant tunneling system is believed to be an ideal candidate for further improvement of room temperature gas sensing.
Subject(s)
Copper/chemistry , Electrochemical Techniques , Hydrogen Sulfide/analysis , Tin Compounds/chemistry , Electrodes , Gases/analysis , Gold/chemistry , Lasers , Oxidation-Reduction , TemperatureABSTRACT
CdO nanosheet film can be synthesized by electrochemical deposition in an ultra-thin liquid layer by using Cd(NO(3))(2) and HNO(3) as source materials for Cd and oxygen respectively. HNO(3) is also used to adjust the pH of the electrolyte. Studies on the detailed structure indicate that the synthesized CdO nanosheet film has a face-centered cubic structure with (200)-preferred orientation. The response of the CdO nanosheet film to liquefied petroleum gas (LPG) at low temperature has been significantly improved by the novel structure of film. It has exhibited excellent sensitivity and selectivity to LPG at low temperature. A new growth mechanism of electrochemical deposition has been proposed to elaborate the formation of nanosheet in an ultra-thin liquid layer. The self-oscillation of potential in the growth interface and intermediate hydroxide are responsible for the formation of nanosheets.