Electrospinning of P3HT-PEO-CdS fibers by solution method and their properties

Homogeneous composite fibers of poly(3-hexylthiophene) (P3HT)-polyethylene oxide (PEO)-Cadmium Sulfide (CdS) were manufactured by electrospinning technique using chloroform as solvent. The incorporation of CdS in the composite fibers was determined by SEM, FTIR and TGA techniques. SEM and confocal microscopy have been used to determine size, surface morphology and distribution of the fluorescence phase in the fibers. A morphology change in P3HT/PEO fibers was caused by the presence of CdS: porous morphology was obtained for low CdS concentration (3.8 wt% and less) and when the content of CdS nanoparticles is higher, they were concentrated at the center of the fibers. The photoluminescence response was modified with CdS inside the P3HT-PEO fibers. By XRD it was determined that the introduction of CdS nanoparticles in the P3HT-PEO fibers caused disorder in P3HT chains. The obtained composite fibers are promising materials for optic and electronic applications.     

Removal of strongly-bound gases from single-walled carbon nanotubes without annealing or ultraviolet light exposure

Annealing at high temperatures and exposure to strong ultra violet light are the approaches used in the past for affecting the desorption of strongly bound gases such as ammonia (NH₃) and nitrogen dioxide (NO₂) from single wall carbon nanotubes (SWCNTs) and graphene. These methods pose severe limitations in the development of devices which can operate in normal ambient conditions. The use of another gas which can influence the kinetics of desorption of gases already present on the SWCNTs has not been explored in detail. Here we show that the redistribution of substrate impurity states near Fermi Level, caused by the electrostatic forces of polar molecules like water, accelerates the desorption of gases bound on SWCNT. This phenomenon can be used to facilitate complete, rapid and non-destructive desorption of NO₂ and NH₃ molecules from SWCNT chemiresistors at room temperature. Complete desorption of these gases were achieved within minutes instead of many hours as reported previously in the literature. The method provides a practical alternative for achieving recovery in CNT-based molecule detectors in air without the risk of degradation of the SWCNTs and their sensitive polymer composites which are used to achieve high sensitivity and selectivity.     

Fully oriented cis-(CH)x: Experimental and theoretical analysis of the polarized Raman spectra

New experimental results of polarized Resonant Raman Scattering (RRS) spectra of fully oriented cis-rich (CH)_x films for the excitation wavelengths 676.4 and 600 nm are presented together with the theoretical interpretation. The three Raman active bands due to the totally symmetric vibrational modes of cis-(CH)_x are observed only in the / / / / polarized spectrum, indicating that the films are fully oriented. The contribution of the Raman active vibrational modes of the trans segments is observed in all polarized spectra and for both incident wavelengths. Also, we report the RRS spectra of the same sample thermally isomerized, without stretching, for λ_L = 676.4 nm and λ_L = 457.9 nm. We find that the depolarization ratios of the Raman bands due to the vibrational modes of trans-segments are much higher after isomerization than for an usual stretched trans (CH)_x sample.     

Autoclave‐assisted synthesis of AgNPs in Z. officinale extract and assessment of their cytotoxicity,antibacterial and antioxidant activities

In this study, the authors synthesised silver nanoparticles (AgNPs) using autoclave as a simple, unique and eco‐friendly approach. The effect of Zingiber officinale extract was evaluated as a reducing and stabiliser agent. According to transmission electron microscopy results, the AgNPs were in the spherical shape with a particle size of ∼17 nm. The biomedical properties of AgNPs as antibacterial agents and free radical scavenging activity were estimated. Synthesised AgNPs showed significant 1,1‐diphenyl‐2‐picryl‐hydrazyl free radical scavenging. Strong bactericidal activity was shown by the AgNPs on Gram‐positive and Gram‐negative bacteria. A maximum inhibition zone of ∼14 mm was obtained for epidermidis at a concentration of 60 μg/ml for sample fabricated at 24 h. The AgNPs also showed a significant cytotoxic effect against MCF‐7 breast cancer cell lines with an half maximal inhibitory concentration value of 62 μg/ml in 24 h by the MTT assay. It could be concluded that Z. officinale extract can be used effectively in the production of potential antioxidant and antimicrobial AgNPs for commercial application.Inspec keywords: nanoparticles, cancer, organic compounds, antibacterial activity, particle size, microorganisms, silver, visible spectra, ultraviolet spectra, biomedical materials, biochemistry, nanofabrication, free radicals, nanomedicine, toxicology, cellular biophysics, transmission electron microscopyOther keywords: unique approach, eco‐friendly approach, zingiber officinale, reducing agent, stabiliser agent, transmission electron microscopy results, antibacterial agents, free radical scavenging activity, synthesised AgNPs, 1‐diphenyl‐2‐picryl‐hydrazyl free radical scavenging, strong bactericidal activity, antimicrobial AgNPs, autoclave‐assisted synthesis, antioxidant activities, cytotoxic effect, silver nanoparticles, autoclave, time 24.0 hour     

Effect of BaTiO3 on the sensing properties of PVDF composite-based capacitive humidity sensors

Capacitive humidity sensors consisting of materials such as polymers, ceramics, and piezoelectrics are widely used to monitor relative humidity levels. The effect of barium titanate (BaTiO₃) nanoparticles on the humidity sensing properties, dielectric response, thermal stability, and hydrophilicity of the polyvinylidene fluoride (PVDF)-BaTiO₃ composite films is investigated. Hydrophilicity and surface morphology of the PVDF-BaTiO₃ composite films are modified for the development of a good humidity sensor. The nanocomposite solutions are prepared by mixing an optimized concentration (2.5 wt%) of PVDF with different concentrations (0.5, 1, and 2 wt%) of BaTiO₃ nanoparticles. X-ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy, and contact angle measurements are used to characterize the structure, morphology, thermal stability, and hydrophilicity of the spin-coated sensing films. The dielectric study of PVDF-BaTiO₃ composite film shows that as the concentration of BaTiO₃ particles increase, the dielectric constant of the composite films increases as well. PVDF-BaTiO₃ (2.5 wt%-1 wt%) based capacitive sensors show stable capacitive response and low hysteresis as compared to the other concentrations of the PVDF-BaTiO₃ composites. The maximum hysteresis of the capacitive PVDF-BaTiO₃ (2.5 wt%- 1 wt%) humidity sensor is found to be ~2.5%. The response and recovery times of the PVDF-BaTiO₃ (2.5 wt%-1 wt%) based capacitive sensors are determined as 40 s and 25 s, respectively, which are significantly lower than those reported for the other PVDF composite based sensors.     

Open-cell copper foam joining: joint strength and interfacial behaviour

A copper (Cu) foam was brazed with Cu-4.0Sn-9.9Ni-7.8P filler foil for joint strength and interface analysis. Brazed 50 pores per inch (PPI) Cu foam yielded a maximum compressive strength of 14.4?MPa with a 127% increment compared to nonbrazed Cu foam. 15 PPI Cu foam produced a maximum shear strength of 2.7?MPa. Scanning electron microscopy showed that the thickness of the brazed seam decreased with increasing the Cu foam’s PPI. The formation of the Cu, Cu₃P (P: phosphorus) and Ni₃P (Ni: nickel) at the Cu/Cu foam interface was validated using energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction. EDX line scanning analysis revealed the diffusion of P and Ni into Cu foam, which took place via capillary force action.     

Photocatalytic TiO2 coating of plastic cutting board to prevent microbial cross-contamination

Kitchen cutting boards are one common source of microbial cross-contamination in foods. In this study, a method was developed to create an antimicrobial coating on HDPE cutting board using UV-activated TiO₂ nanoparticles (NPs). The antimicrobial efficacy of the developed coatings was tested against E. coli O157: H7 for 3 h at 0.5 ± 0.05 mW/cm² UVA light intensity. In addition, the effect of NP loading (0.0125, 0.0625, and 0.125 mg/cm²), and surface treatment of coatings by oxygen plasma for 1–15 min on the bactericidal efficacy was investigated. Further, the bactericidal efficacy of the TiO₂ coated cutting board on repeated use (i.e. 1, 2, 3 and 5 times) was also evaluated. The results showed that by increasing the NP loading from 0 to 0.125 mg/cm² has increased the log reduction from 0.37 to 1.18 CFU/cm². However, no significant difference (P > 0.05) in the reduction was observed between NP loadings at 0.0625 and 0.125 mg/cm². Oxygen plasma treatment of the coated surfaces for 5–15 min significantly increased (P ≤ 0.05) the log reduction compared to control sample without plasma treatment. Under the tested conditions, TiO₂ coating with 0.0625 mg/cm² NP loading followed by oxygen plasma treatment for 5 min was found to achieve the greatest reduction up to 2.67 log CFU/cm². Also, the coated-surfaces were found to retain the original bactericidal property even after up to 5 times washing treatment. The developed TiO₂ coating on cutting board showed promise to mitigate the risk of microbial cross-contamination by providing a stable antimicrobial activity for extended use. Plasma treatment further enhanced the bactericidal property of the developed coatings without affecting physical stability.     

Effect of Porous Copper Pore Density on Joint Interface: Microstructure and Mechanical Analysis

The effect of the pore density of porous copper (Cu) on brazed Cu/porous Cu was investigated. A filler with a composition of Cu-9.0Sn-7.0Ni-6.0P (Sn: Tin; Ni: Nickel; P: Phosphorus) and porous Cu with pore densities of 15 pores per inch (PPI), 25 PPI, and 50 PPI were employed. The joint strength of Cu/porous Cu was evaluated with shear tests at different brazing temperatures. Characterizations of the joint interface and fractured surface were achieved with scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The micro-hardness test of Cu/porous Cu joint interface showed a high hardness value (HV) for 50 PPI porous Cu. This result was in line with its low shear strength. It was proved that the joint strength of Cu/porous Cu is dependent on the pore density of the porous Cu structure and brittle phases of Cu₃P and Ni₃P in the brazed interface.