Ni-doped ZnS nanoparticles are synthesized by simple hydrothermal process for the utilization in UV photodetectors. Surface morphology of the prepared samples is investigated through high resolution ...transmission electron microscopy (HRTEM), which reveals that the prepared nanoparticles are smaller than 20 nm. The well visualized selected area electron diffraction rings suggests the nanocrystalline nature of the prepared nanoparticles with (hkl) planes (111), (220) and (311). The structural analysis is done by x-ray diffraction (XRD) studies; which reveal the decrease in crystallite size with increase in Ni-doping concentration. The device performance of the photodetectors is tested under UV-A light (wavelength ≈365 nm) and found that the ability of the prepared devices increases with increase in Ni-doping concentration. This can be attributed to the enhanced surface to volume ratio and increase in charge carrier concentration. The adsorption-desorption of oxygen molecules on the nanoparticles' surface is considered to be the mechanism for UV photodetection.
•Synthesis of Ni-doped ZnS Nanoparticles.•Effect of Ni-doping on UV photodetection ability of ZnS nanoparticles.•Understanding UV photodetection mechanism through oxygen adsorption/desorption.
Polypyrrole (PPy) nanomaterials have been synthesized with varying concentrations (10–40 mM) of anionic surfactant camphor sulphonic acid (CSA) using the chemical polymerization method, and then ...utilized for electromagnetic interference (EMI) shielding applications in the X-band of the microwave frequency range (8.2–12.4 GHz). An observable systematic change in the morphology of the prepared PPy has been noted, with highly aggregated globules transforming into fibular-like structures with an average diameter of approximately 80–120 nm as the CSA concentration increased. Raman and Fourier-transform infrared (FTIR) measurements indicate an increase in the relative intensities of the bipolaronic to polaronic bands, suggesting an improved conjugation of PPy with increasing CSA concentration. The electrical conductivity at room temperature has also been found to increase significantly, from 2.55 S/cm to 35.80 S/cm, as the concentration of CSA surfactant increased from 10 mM to 40 mM. Additionally, the shielding effectiveness (SE) for reflection (SE
R
), SE for absorption (SE
A
), and total SE (SE
T
) have been found to increase with increasing CSA concentration in PPy. The SE
T
values have been found exceeding 35 dB throughout the X-band of the microwave region in PPy nanomaterials with CSA concentrations ≥ 20 mM. It has been observed that CSA-directed polypyrrole exhibits high electrical conductivity, where the SE for absorption (SE
A
) dominates over the SE for reflection (SE
R
). This study suggests that the properties of PPy can be easily tailored for its potential utilization in the fabrication of various EMI shielding devices with improved performance.
Polyaniline (PAni) thin film has been synthesized using chemical oxidation route to be used as highly sensitive and selective ammonia (NH
3
) sensors. In situ dip-coating chemical polymerization ...method has been used to grow PAni thin films on glass substrates. The morphological and structural properties of deposited thin film have been examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and Fourier-transform infrared (FTIR) spectroscopy techniques. Raman and FTIR analysis confirm the successful growth of PAni with long-chain conjugation, whereas SEM micrograph reveals the growth of nanofibrous structured polyaniline. An amorphous structure of the prepared polyaniline with perpendicular periodicity of the conjugated polymer chains has been observed through XRD analysis. The ammonia gas sensing properties, in terms of change in electrical resistance, of the prepared thin film sensor have been investigated at room temperature for different concentrations (25–150 ppm) of ammonia. The deposited film has sensitivity as high as 245% and selectivity (%) of ~ 67% towards ammonia gas (at 150 ppm). The gas sensing response of the deposited film is found to be increased with increasing concentration of ammonia and the observed behaviour is well corroborated with modified Freundlich’s sensitivity versus chemical concentration relation. The effect of humidity on the sensing response and other parameters associated with the figure of merits of sensor like response time, recovery time, selectivity, stability etc. have also been studied. The compensation of charge carriers, i.e. polarons and bipolarons, under the electron donating ammonia gas is considered to be the mechanism of gas sensing for the deposited PAni film. The synthesized PAni thin film sensor with low cost, high sensitivity, selectivity and durability can be utilized for the development of industrial ammonia sensor.
A multitechnique approach with theoretical insights has been employed to understand the complexation of trivalent lanthanides with two β-diketones, viz. 1-phenyl-1,3-butanedione (L 1 ) and ...4,4,4-trifluoro-1-phenyl-1,3-butanedione (L 2 ), in an ionic liquid (C6mim·NTf2). UV–vis spectral analysis of complexation using Nd3+ revealed the predominance of ML2 + and ML4 – species. The stability constants for the PB complexes were higher (β2 ∼ 10.45 ± 0.05, β4 ∼ 15.51 ± 0.05) than those for the TPB (β2 ∼ 7.56 ± 0.05, β4 ∼ 13.19 ± 0.06). The photoluminescence titration using Eu3+ corroborated the same observations with slightly higher stability constants, probably due to the higher ionic potential of Eu3+. The more asymmetric (AL2 ML4 ∼ 5.2) Eu-L2 complex was found to contain one water molecule in the primary coordination sphere of Eu3+ with more covalency of the Eu3+-O bond (Ω2 L1 = 8.5 × 10–20, Ω4 L1 = 1.3 × 10–20) compared to the less asymmetric Eu-L1 complex (AL1 ML4 ∼ 3.5) with two water molecules having less Eu–O covalency (Judd-Offelt parameters: Ω2 L1 = 7.3 × 10–20, Ω4 L1 = 1.0 × 10–20). Liquid–liquid extraction studies involving Nd3+ and Eu3+ revealed the formation of the ML4 – complex following an ‘anion exchange’ mechanism. The shift of the enol peak from 1176 to 1138 cm–1 on the complexation of the β-diketones with Eu3+ was confirmed from the FTIR spectra. 1H NMR titration of the β-diketones with La(NTf2)3 evidenced the participation of α-H of the β-diketones and protons at C2, C4, and C5 positions of the methylimidazolium ring. For the ML2 complex, 4 donor O atoms are suggested to coordinate to the trivalent lanthanides with bond distances of 2.3297–2.411 Å for La–O, 2.206–2.236 Å for Eu–O, and 2.217–2.268 Å for Nd–O, respectively, while for the ML4 complex, 8 donor O atoms were coordinated with bond lengths of 2.506–2.559 Å for La–O, 2.367–2.447 Å for Eu–O, and 2.408–2.476 Å for Nd–O. The Nd3+ ion was higher by 9.7 kcal·mol–1 than that of the La3+ ion for the 1:4 complex. The complexation energy with L1 was quite higher than that with L2 for both 1:2 and 1:4 complexes. Using cyclic voltammetry, the redox behavior of trivalent lanthanides Eu and Gd with β-diketonate in ionic liquid medium was probed and their redox energetic and kinetic parameters were determined.
•Sintering temperature greatly influence the electrical properties of BaBi4Ti4O15.•Optimum sintering condition identified for high resistivity, density and piezoelectric properties.•Influence of dc ...conductivity on dielectric dispersion has been analyzed.•Analysis with Lorentz type relation describes well the diffuseness and polarization process.•Frequency dependent peaks in ac conductivity near Tm imply relaxor-like behavior.
Barium bismuth titanate (BaBi4Ti4O15) ceramics prepared by conventional solid-state reaction method have been characterized, and influence of sintering temperature is shown to greatly affect the electrical properties. Formation of a single phase composition with orthorhombic structure and a randomly oriented plate-like microstructure is confirmed. Raman spectroscopy reveals broad over-damped low frequency modes indicating structural disorder. Room temperature dielectric response in the low frequency range (10−2–10Hz) reveals the influence of dc conductivity on dielectric dispersion. Analysis in terms of Lorentz type relation describes well the diffuseness in the dielectric data, and indicates only one polarization process in the system. The well fitting of frequency dependent maximum temperature (Tm) in ε′(T) to the non-linear Vogel–Fulcher equation and a similar trend in temperature dependent ac conductivity imply a relaxor-like nature of the material. Sintering at 1050°C for 5h is found to be favorable and yields ceramics with high density, high resistivity (4.6×1012Ωcm), low dielectric loss (tanδ∼0.05), remnant polarization (Pr=3.63μC/cm2) and a high piezoelectric charge coefficient, d33=24pC/N.
Fabrication of n-TiO
2
/p-Si heterojunction devices for the fast solar-blind self-powered ultraviolet photodetectors has been reported. To produce these devices, n-type TiO
2
thin films of thickness ...50 nm and 200 nm have been deposited by radiofrequency magnetron sputtering technique on p-type silicon substrates. X-ray diffraction (XRD) studies reveal the growth of anatase phase of TiO
2
and the scanning electron microscopy (SEM) studies confirm the deposition of rod-like nanostructures of TiO
2
of length about 10 μm and diameter 1 μm. The current-voltage (I-V) characteristics of the prepared heterojunction devices demonstrate the non-ohmic diode like behavior. The obtained values of ideality factor from I-V characteristics for both the devices are greater than 2, which suggest a trap states assisted space charge limited current (SCLC) conduction of charge transport. The I-V characteristics recorded under the illumination of UV-A radiations (λ ≈ 365 nm), demonstrate the photo-diode like behavior of the fabricated devices. The transient photoresponse of the fabricated devices of thickness 50 nm and 200 nm of TiO
2
films, recorded under zero bias conditions are as high as ~795% and 180% respectively. The response and recovery times less than unity suggest the fast photodetection ability of the fabricated devices for the next generation photodetectors.
Abstract
Background
We evaluated community health volunteer (CHV) strategies to prevent non-communicable disease (NCD) care disruption and promote coronavirus disease 2019 (COVID-19) detection among ...Syrian refugees and vulnerable Jordanians, as the pandemic started.
Methods
Alongside medication delivery, CHVs called patients monthly to assess stockouts and adherence, provide self-management and psychosocial support, and screen and refer for complications and COVID-19 testing. Cohort analysis was undertaken of stockouts, adherence, complications and suspected COVID-19. Multivariable models of disease control assessed predictors and non-inferiority of the strategy pre-/post-initiation. Cost-efficiency and patient/staff interviews assessed implementation.
Results
Overall, 1119 patients were monitored over 8 mo. The mean monthly proportion of stockouts was 4.9%. The monthly proportion non-adherent (past 5/30 d) remained below 5%; 204 (18.1%) patients had complications, with 63 requiring secondary care. Mean systolic blood pressure and random blood glucose remained stable. For hypertensive disease control, age 41–65 y (OR 0.46, 95% CI 0.2 to 0.78) and with diabetes (OR 0.73, 95% CI 0.54 to 0.98) had decreased odds, and with baseline control had increased odds (OR 3.08, 95% CI 2.31 to 4.13). Cumulative suspected COVID-19 incidence (2.3/1000 population) was suggestive of ongoing transmission. While cost-efficient (108 US${\$}$/patient/year), funding secondary care was challenging.
Conclusions
During multiple crises, CHVs prevented care disruption and reinforced COVID-19 detection.
The current research aims to investigate the effect of nickel doping on the structural and opto-electrical characteristics of zinc oxide thin films. Sol-gel spin coating technique has been utilized ...to deposit Zn
1-x
Ni
x
O (x = 0, 0.005, 0.010, and 0.015) films on glass substrates. X-ray diffraction (XRD) analysis confirms the formation of crystalline zinc oxide thin films with hexagonal wurtzite structure. Williamson-Hall analysis has been performed to study the individual contribution of lattice strain and crystallite size to the peak broadening in the XRD pattern. Scanning electron microscopy (SEM), Photoluminescence spectroscopy, and UV–visible spectroscopic techniques have been used to examine the surface morphology and optical properties of the deposited films. Transient photocurrent measurements have been performed on all the films under the exposure of ultraviolet (UV) light of wavelengths 365 and 254 nm with on/off cycle of 100 s, and various device key parameters such as sensitivity, responsivity, and quantum efficiency, etc have been determined. Sensitivities of the fabricated photodetectors (PDs) are found to be 5463%, 3809%, 3100%, and 831% for pristine ZnO, Zn
0.995
Ni
0.005
O, Zn
0.99
Ni
0.01
O, and Zn
0.985
Ni
0.015
O, respectively. The UV photodetection mechanism, which is based on the interaction between chemisorbed oxygen on the surface of ZnO and photo-generated holes, has been thoroughly discussed.
Highlights
Highly transparent and uniform films have been deposited by sol-gel spin coating technique.
Lattice parameters and unit cell volume increase with Nickel doping.
Crystalite size increases with Nickel concentration.
Deposited films show high sensitivity towards UV light, however, sensitivity decreases with Nickel concentration.
This paper reports the facial synthesis of polypyrrole (PPy) nanotubes by an anionic azo dye {sodium 4-4-(dimethyl-amino)-phenyldiazo phenylsulfonate} assisted chemical oxidation method and their ...deprotonation by liquid ammonia treatment. Scanning and transmission electron microscopy studies reveal the synthesis of PPy nanotubes of diameters ∼155 nm and their lengths are found to be about 2–3 μm. The deprotonation of PPy nanotubes by liquid as well as gaseous ammonia has been experimentally confirmed by Raman and FTIR studies. These spectroscopic techniques suggest the proton transfer based mechanism for deprotonation of the PPy nanotubes. The deprotonation of PPy nanotubes has also been confirmed through the electrical measurements carried out in the presence of ammonia gas at different ppm levels. Furthermore, the effect of deprotonation on the charge transport properties of PPy nanotubes has also been investigated. The temperature dependent conductivity measurements are performed on both the pristine as well as deprotonated (by liquid ammonia) PPy nanotubes in a wide range of temperature (77–400 K) and analyzed for different conduction mechanisms. However, both the samples are found to follow Mott's variable range hopping conduction process in three dimensions (3D-VRH) for the charge transport. The conduction properties of both the samples are further investigated in terms of Mott's 3D-VRH variables such as Mott's characteristic temperature, hopping distance, hopping energy, and density of states, etc.
Effect of Ammonia Based Deprotonation on the Variable Range Hopping Conduction in Polypyrrole Nanotubes. Display omitted
•Anion Azo dye assisted synthesis of PPy nanotubes.•Deprotonation of PPy nanotubes by liquid and gaseous states of ammonia.•Understanding ammonia gas sensing mechanism through PPy-ammonia interaction.•Effect of deprotonation on Mott's variable range hopping conduction.
In the present study, polyaniline (PAni) thin films have been deposited on glass substrates by in-situ chemical polymerization method using simple dip-coating technique and their opto-electrical ...properties have been studied. The structure of deposited films have been analysed with Fourier transform infrared (FTIR) and Raman spectroscopic techniques to investigate the effect of deposition times on the conjugation length, polaron/bipolaron concentrations and other molecular structure conformations. FTIR and Raman spectroscopy studies reveal increase in both the conjugation length and the polaron/bipolaron carrier concentration with increasing deposition time of the prepared PAni films. The optical properties and optical band-gap of the deposited films have been estimated through UV–visible spectroscopy. The optical band-gap of the deposited films has been found to decrease from 3.31 eV to 3.13 eV with increase in deposition time from 1.5 h to 2.5 h, and further it has been increased slightly to 3.19 eV for the PAni film deposited for 3 h. The electrical conductivity of the deposited films has been found to increase with decrease in optical band gap. The parameters estimated from FTIR, Raman, UV–visible spectroscopy and electrical measurements are in good agreement with each other. It has been observed that the optical and electrical properties of the deposited films depend on the conjugation length of PAni. The polymerization time of 2.5 h has been found to be optimum for obtaining PAni thin films with good electrical conductivity and low optical band gap.
•Polyaniline (PAni) thin films have been grown on glass substrates using in-situ polymerization method for different dipping times.•The effect of polymerization time on optical, electrical and structural properties of the PAni films has been investigated.•Observed optical and electrical properties have been well correlated to the induced structural changes of the PAni films.•Such opto-electrical behaviour suggest the possible utilization of prepared PAni films for various opto-electronic devices.
