Gold nanoparticles (AuNPs) decorated CNTs are promising materials for photocatalytics and biosensors. However, the synthesis of AuNPs chemically linked to the walls of MWCNTs is challenging and toxic ...products such as thionylchloride (SOCl
) or 1-ethyl-3(dimethyl-amino) propyl carbodiimide hydrochloride (EDAC) need to be used. This work reports a new approach to prepare gold nanoparticles decorated multiwalled carbon nanotubes (MWCNTs) by using cysteaminium chloride via the formation of a Zwitterionic acide-base bond. The grafting process consists of 3 mains steps: oxidation, thiolation and decoration of AuNPs on the surface of MWCNTs. The completion of each step has been verified out by both spectroscopic (Raman, UV-Vis, FT-IR) and Scanning Electron Miscroscopy (SEM). The chemical bonding states of synthesized products have been proven by X-ray photoelectron spectroscopy (XPS).
Display omitted
•DWCNTs-Gr hybrid thin film was successfully synthesized by LPCVD method.•A novel structure of DWCNTs-Gr hybrid thin film modified SPE was prepared.•An electrochemical sensor using ...ChOx enzyme for detection of As(V) was developed.•A high sensitive sensor was achieved with low LOD for As(V) detection.
In this work, we demonstrate the preparation of hybrid thin films based on double-walled carbon nanotubes and graphene for electrochemical sensing applications. The hybrid films were synthesized on polycrystalline copper foil by thermal chemical vapor deposition under low pressure. This carbonaceous hybrid film has exhibited high transparency with a transmittance of 94.3 %. The occurrence of this hybrid material on the electrode surface of screen-printed electrodes was found to increase electroactive surface area by 1.4 times, whereas electrochemical current was enhanced by 2.4 times. Such a highly transparent and conductive hybrid film was utilized as a transducing platform of enzymatic electrochemical arsenic(V) sensor. The as-prepared sensor shows the linear detection of arsenic(V) in the range from 1 to 10 ppb, with a limit of detection as low as 0.287 ppb. These findings provide a promising approach to develop new multifunctional electrochemical sensing systems for environmental monitoring and biomedical diagnostics.
In practice, pavements or slabs are subjected to wide range of length changes during their service life. In case of cement-based materials, their length changes due to shrinkage and/or temperature ...variations induce tensile stress which can result in cracking detrimental for durability. Generally, aggravating circumstances are observed due to the length change restraint. This contribution focuses on experimental results of tests performed on rubberized concrete produced by partly replacing natural sand (0–4 mm) by rubber aggregates up to 40% by volume. The rubber aggregates are obtained by grinding of used tyres. Effect of rubber aggregate on brittleness index (BI) and on damage evolution was investigated by conducting three-point bending tests on notched beam. Results of these tests confirmed that the both BI and damage decrease with the increase of rubber aggregate content in the concrete. Acoustic emission (AE) technique was applied to detect damage mechanism in concrete by analyzing AE parameters. The Elastic Quality Index (EQI) was adopted to take into account two mutually exclusive properties which govern the sensitivity to cracking, namely strain capacity and tensile strength. Results obtained from the tests performed at 20 °C, 40 °C and 70 °C showed that rubberized concrete exhibits EQI values within acceptable limits for the design of cement-based pavements.
► Rubber aggregates from recycled tyres were used in replacement of sand in concrete. ► Mechanical properties were quantified by different experimental techniques. ► Rubberized concrete is suitable for durability of large area applications such as slabs. ► The composite may address the demand for the conservation of a clean environment.
Background This study aimed to measure the preferences for mental health support among health professionals, their willingness to support the mental health of colleagues and associated factors. ...Method A descriptive cross-sectional study was performed from August to October 2022 within five hospitals located in Hanoi, Vietnam. A total of 244 health professionals participated in the study. Data on socio-economic status, health and COVID-19-related characteristics, Depression Anxiety Stress Scale (DASS-21); and preferences for mental health support services were collected by using a structured self-reported questionnaire. Multivariate logistic regression models were utilized to identify associated factors with the demand for mental support services. Results 13.9%, 17.1% and 8.6% reported having at least mild depression, anxiety and stress, respectively. There 13.9% did not seek any mental health support during the COVID-19 pandemic. The most common support included talking with friends (52.9%), family (50.8%), colleagues (47.6%) and using social networks/Internet (43.5%). There 31.1% had been aware of mental health services, but only 18.0% used this service at least once. Regarding preferences, 47.3% had a demand for mental support services, and the most preferred service was providing coping skills (25.9%), followed by skills to support others against mental problems (22.2%). Major sources of support included psychiatrists (34.4%), colleagues (29.1%) and family (27.9%). The main preferred channels for support included telephone/mobile phone (35.7%) and Internet (20.9%). Only 12.3% were willing to provide mental support for colleagues during the pandemic. Age, education, perceived mental health status, ever seeking any mental service, and DASS-21 depression score were associated with demand for mental support services. Conclusion This study found a lack of awareness of mental health services for health professionals, as well as moderate levels of demand for this service in this population. Raising awareness and developing tailored mental health support services are important to enhancing the mental well-being of health professionals in Vietnam to prepare for the next pandemic.
Permethrin, 3-Phenoxybenzyl (1 RS)-cis,trans-3-(2,2-dichlorovinyl)- 2,2-dimethylcyclopropanecarboxylate, has a wide range of applications like insecticide, insect repellent and prevents ...mosquito-borne diseases, such as dengue fever and malaria in tropical areas. In this work, we develop a prominent monitoring method for the detection of permethrin pesticide using surface-enhanced Raman scattering (SERS) optical fibre substrates. The novel SERS-active optical fibre substrates were grown and deposited silver (Ag) nano-dendrites on the end of multi-mode fibre core by laser-assisted photochemical method. The characteristic of the Ag-nanostructures could be controlled by the experimental conditions, namely, laser illumination time. Ag nanoparticles optical fibre substrates and Ag nano-dendrites optical fibre substrates were prepared with laser illumination time of 3 min and 8 min, respectively. The achieved SERS-activity optical fibre substrates were tested with Rhodamine 6G aqueous solutions. We demonstrate that the SERS activity coupled with Ag nano-dendrites optical fibre substrate has higher Raman enhancement factor due to the creation of many of hot-spots for amplifying Raman signals. Besides, the stability and reproducibility of the Ag nano-dendrites optical fibre substrate were also evaluated with stored time of 1000 hours and relative standard deviation of less than 3%. The Ag nano-dendrite optical fibre substrate was selected for detection of permethrin pesticide in the concentration range of 0.1 ppm-20 ppm with limit of quantification (LOQ) of 0.1 ppm and calculated limit of detection (LOD) of 0.0035 ppm, proving its great potential for direct, rapid detection and monitoring of permethrin.
Gas nanosensors with good “3S” (sensitivity, selectivity and stability), ultralow power consumption and low cost are increasingly needed for portable electronic devices. Herein, we demonstrate the ...facile fabrication process of individual, multiple, and networked SnO2 nanowire (NW) sensors, which can be used to detect highly toxic NO2 gas based on the Joule self-heating effect, consuming only few tens of μW of power. Systematic investigation on the gas-sensing properties reveals that the individual NW sensor shows advantages, such as better gas response shorter response–recovery time and lower power consumption over multiple and networked NW sensors. The self-heated individual NW sensor with applying a bias voltage of 25V exhibits a good response to NO2 gas concentrations as low as 1ppm with short response (∼8s) and recovery times (∼25s) and consumes only 35μW of power. In addition, the gas-response of individual NW sensors operated by either self- or external heating was compared to demonstrate the advantages of the development of the sensor concept for practical applications.
The performances of the human-baited double net trap (HDNT) and the human-baited host decoy trap (HDT) methods were compared against the outdoor human landing catch (OHLC) method in Thailand and ...Vietnam. Two study sites were selected in each country: a rural village and a nearby forest setting. The three outdoor trap methods were rotated nightly between three set trapping positions, in a pre-assigned Latin square design. Volunteers were rotated following the trap rotation to avoid bias. The greatest number of adult mosquitoes was collected from the forest sites in both countries, showing Anopheles minimus (s.s.)Theobald (96.54%) and Anopheles dirus (s.s.) Peyton & Harrison (25.71%) as the primary malaria vectors in Thailand and Vietnam, respectively. At theThai forest site, OHLC collected significantly more anopheline mosquitoes per trap night than HDNT and HDT, with mean ± standard error values of 14.17 ± 4.42, 4.83 ± 1.56, and 4.44 ± 1.45, respectively, whilst HDNT and HDT were significantly less productive at 0.34 times and 0.31 times, respectively, than OHLC in capturing anopheline mosquitoes. However, there were no significant differences among the three methods of trapping malaria vectors for the village site. At the Vietnamese forest site, HDNT achieved the highest performance in collecting Anopheline mosquitoes at 1.54 times compared to OHLC, but there was no significant difference between the two traps. The results suggested HDNT could be a possible alternative trap to OHLC in this area. Although HDT was less efficient at attracting Anopheline mosquitoes, it was highly efficient at trapping culicine mosquitoes.
Raman spectroscopy offers a rapid and nondestructive method for qualitatively and quantitatively analyzing the molecular structure of substances. Herein, a facile and cost‐effective approach for the ...preparation of three‐dimensional (3D) surface‐enhanced Raman scattering (SERS) substrates is proposed, in which pyramid structures are fabricated using silicon anisotropic wet etching and silver dendrites are decorated on these silicon pyramid (PSi) substrates by immersing them in a mixture of hydrofluoric acid and silver nitrate for several minutes. The 3D SERS substrates, based on PSi coated with Ag dendrites, reveal high‐performance SERS enhancement (with an analytical enhancement factor reaching 3.54 × 1010) and can detect rhodamine 6G (R6G) in the presence of chemical enhancer (lithium chloride) at low concentrations down to 10−11 m. For glucose detection, 2‐thienylboronic acid is employed to faciliate glucose attachment to the substrate surface, achieving a detection limit as low as 10−6 m. The substrate exhibits good repeatability with a relative standard deviation of 11.223%, as well as reusability and long‐term stability for detection. The results also highlight the excellent sensitivity of the PSi‐based SERS substrate, which is expected to be instrumental in biochemical analysis and holds significant potential for developing noninvasive glucose sensor for diabetic patients using saliva samples.
The three‐dimensional silver dendrites/silicon pyramid surface‐enhanced Raman scattering (SERS) substrates are successfully fabricated by anisotropic wet etching of a silicon wafer and chemical deposition in a mixed solution (HF/AgNO3). The proposed SERS substrates can detect glucose at ultralow concentrations below 10−6 m and exhibits high repeatability as well as reusability and long‐term stability for detection.
This paper provides a new homogenization scheme, which is a combination of the theoretical and experimental approaches, for modeling effective transport properties of heterogeneous materials. Differ ...from the classical methods, this method considers a free conductivity of the reference matrix that is not a pre-defined parameter and can be calibrated based on an inverse analysis using available microscopic and macroscopic data. This technique is illustrated using experimental data of electrical conductivity of rocks published in literature. We show that the conductivity of the reference matrix can be approximated by linear or quadratic functions of the porosity. The proposed approach can be used to model materials containing highly contrast phases.
Display omitted
•The binding and orientation of TBZ molecular skeleton on the surface of Au NP.•The binding and orientation of TBZ molecular skeleton on the surface of AuAg BNP.•532 nm SERS of TBZ ...for Au NPs, AuAg BNPs and Ag NPs were performed for comparison.
Au-Ag bimetallic nanoparticles (BNPs) with varying molar fractions as Au0.2Ag0.8 and Au0.3Ag0.7 are prepared on porous silicon. They were demonstrated as surface-enhanced Raman scattering (SERS) substrate for the detection of thiabendazole (TBZ) molecules. The concentration of TBZ investigated is 10-7 M. The effect of the Au content on SERS properties of the Au-Ag BNPs was studied. Furthermore, the composition dependent SERS spectra and adsorption mechanism of TBZ on Au-Ag BNPs surfaces were discussed.
PDF
