Poly(vinyl alcohol) Chains Grafted onto the Surface of Copper Oxide Nanoparticles: Application in Synthesis and Characterization of Novel Optically Active and Thermally Stable Nanocomposites Based on Poly(amide-imide) ContainingN-trimellitylimido-L-valine Linkage

Who didn't consult the doctor? Understanding sociodemographic factors in relation to health care uptake before suicide

OBJECTIVE

This study aimed to establish differences between suicide decedents and a reference population across various health care settings.

METHODS

This population-wide registration study combined death statistics, sociodemographic data and health care data from Statistics Netherlands. From 2010 to 2016, 12,015 suicide cases and a random reference group of 132,504 were included and assigned to one of the three health care settings; mental health (MH) care, primary care or no care. Logistic regression analyses were performed to determine differences in suicide risk factors across settings.

RESULTS

In the 1-2 year period before suicide, 52% of the suicide decedents received MH care, 41% received GP care only and 7% received neither. Although sociodemographic factors showed significant differences across settings, the suicide risk profiles were not profoundly distinctive. A decreasing trend in suicide risk across health care settings became apparent for male gender, income level and being in a one-person or one-parent household, whereas for other factors (middle and older age, non-Western migration background, couples without children and people living in more sparsely populated areas), risk of suicide increased when health care setting became more specialized.

LIMITATIONS

Because of the data structure, 18 months of suicide decedents' health care use were compared with two years health care use of the reference group, which likely led to an underestimation of the reported differences.

CONCLUSION

Although there are differences between suicide decedents and a reference group across health care settings, these are not sufficiently distinctive to advocate for a setting-specific approach to suicide prevention.

Recent advances in chemical surface modification of metal oxide nanoparticles with silane coupling agents: A review

Nowadays, metal oxide nanoparticles (NPs) have been applied in various fields of nanotechnology including catalysis of chemical reactions, drug delivery, water treatment, textile industries, polymer composites, adhesives, and coatings. The greatest challenge in relation to metal oxide NPs is high tendency to aggregation. Chemical surface modification of metal oxide NPs has gained widely interest to control of dispersion and aggregation of NPs. Silane modifiers are one of the most important bifunctional modifiers that are frequently used for surface treatment of metal oxide NPs. In this review paper, we first focus on the synthesis, surface thermodynamic properties, surface modification techniques, and kinetic of silanization reaction of metal oxide NPs. Then, the recent development in using silane modifiers for treatment of metal oxide NPs in various applications were investigated. It was found that the unmodified NPs have high surface energy and are thermodynamically unstable. The thermodynamic properties of NPs including G_m^s, H_m^s, and S_m^sincrease with decreasing the particle size. Aggregation phenomena is the simple way to reduce the excess surface energy of NPs that leads to an increase in particle size. Therefore, the chemical surface modification of NPs using silane modifiers can be used as an effective method for the prevention of NPs agglomeration and improvement of NPs stability.

Structure/property relationship of polyvinyl alcohol/dimethoxydimethylsilane composite membrane: Experimental and theoretical studies

A novel mixed matrix composite has been prepared using solution-casting method at different volume concentrations of polyvinyl alcohol; PVA (50, 67, 75 and 80%) and fixed amount of dimethoxydimethylsilane in air atmosphere. The hydrolyzed dimethyldisilanol acts as in-situ cross linker through a wet-out condensation between the hydroxyl moieties of Si_OH and PVA_OH. Such process improves the mechanical properties of composite membranes as compared to pristine PVA which has been determined as function of varied membrane components to evaluate the structure/property relationships. Furthermore, DFT (B3LYP)/6-31G(d) geometry and frequency computations were carried out for the suggested dimeric PVA structures via 1,3-diol linkage followed by condensation and hydrogen bonding interaction. Vibrational interpretations of composite membranes were proposed based on the computed wavenumbers, Cartesian coordinates displacements for the suggested hydrolyzed products involving the dominant PVA/Si_OH/Si_OC/Si_OSi functional groups compared with those given in literatures. FTIR and EDX provide clear evidences for incorporating silicon to 3D network. Meanwhile, the infrared de-convoluted spectral interpretations ensure 17-30% cross-linked SiOC within the network of composite membranes.

Coupled Oxides/LLDPE Composites for Textile Effluent Treatment: Effect of Neem and PVA Stabilization

The polyvinyl alcohol (PVA) and neem extract were grafted onto coupled oxides (3ZT-CO) via reflux process to stabilize the particles to form 3ZT-CO/PVA and 3ZT-CO/Neem. These were then incorporated into LLDPE by melt blending process to give LLDPE/3ZT-CO/PVA and LLDPE/3ZT-CO/Neem composites. The Neem and PVA stabilized particles showed high zeta potential and dispersed homogeneously in water. The stabilization process altered the shape of the particles due to plane growth along the (002) polar direction. The stabilizers acted as capping agents and initiated the one-dimensional growth. The alkyl chain groups from PVA increased the polarity of the LLDPE/3ZT-CO/PVA and played a dominant role in the water adsorption process to activate the photocatalytic activity. This was further enhanced by the homogeneous distribution of the particles and low degree of crystallinity (20.87%) of the LLDPE composites. LLDPE/3ZT-CO/PVA exhibited the highest photodegradation (93.95%), which was better than the non-stabilized particles. Therefore, the photocatalytic activity of a polymer composite can be enhanced by grafting PVA and neem onto couple oxides. The LLDPE/3ZT-CO/PVA composite was further used to treat textile effluent. The results showed the composite was able to remove dye color by 93.95% and to reduce biochemical oxygen demand (BOD) and chemical oxygen demand (COD) by 99.99%.

Multifunctional Chitosan/Gold Nanoparticles Coatings for Biomedical Textiles

Gold nanoparticles (AuNPs), chemically synthesized by citrate reduction, were for the first time immobilized onto chitosan-treated soybean knitted fabric via exhaustion method. AuNPs were successfully produced in the form of highly spherical, moderated polydisperse, stable structures. Their average size was estimated at ≈35 nm. Successful immobilization of chitosan and AuNPs were confirmed by alterations in the fabric's spectrophotometric reflectance spectrum and by detection of nitrogen and gold, non-conjugated C=O stretching vibrations of carbonyl functional groups and residual N-acetyl groups characteristic bands by X-ray photoelectron spectroscopy (XPS) and Fourier-Transform Infrared Spectroscopy (FTIR) analysis. XPS analysis confirms the strong binding of AuNPs on the chitosan matrix. The fabrics' thermal stability increased with the introduction of both chitosan and AuNPs. Coated fabrics revealed an ultraviolet protection factor (UPF) of +50, which established their effectiveness in ultraviolet (UV) radiation shielding. They were also found to resist up to 5 washing cycles with low loss of immobilized AuNPs. Compared with AuNPs or chitosan alone, the combined functionalized coating on soy fabrics demonstrated an improved antimicrobial effect by reducing Staphylococcus aureus adhesion (99.94%) and Escherichia coli (96.26%). Overall, the engineered fabrics were confirmed as multifunctional, displaying attractive optical properties, UV-light protection and important antimicrobial features, that increase their interest for potential biomedical applications.

A simple method for the sonochemical synthesis of PVA/ZrO2-vitamin B1 nanocomposites: Morphology, mechanical, thermal and wettability investigations

Poly(vinyl alcohol) (PVA) based nanocomposites (NCs) filled by various weight percent of modified ZrO₂ nanoparticles (NPs) with vitamin B₁ (VB₁) up to 7wt% were fabricated via ultrasonication method then was cast to thin films. The ultrasonication was applied for the preparation and modification process asan easy, safe and fast method. Ultrasonic was responsible for great homogeneities of NPs into PVA matrix, which could not be achieved by mechanical or magnetically stirring. The creation of polymer NCs and changes in the structural properties were examined by X-ray diffraction. FT-IR spectroscopy indicated the possible interactions of the ZrO₂-VB₁ NPs with the PVA backbones and also, existence of absorption bands related to PVA and ZrO₂ NPs in the NC structures. The distribution of nano-fillers and uniform morphology of the NCs showed that the ZrO₂-VB₁ NPs were homogeneously dispersed in the polymer matrix in the nanosized scale. UV-Vis analysis shown that the the optical absorption were improved by evolution of ZrO₂-VB₁ NPs content. The tensile strength of PVA film was increased significantly with increasing the ZrO₂-VB₁ NPs content. Thermal gravimetric analysis confirmed that NCs displayed higher thermal stability than the pristine PVA. Also, water contact angle analysis indicated that the hydrophilicity of NC films was enhanced with increasing the concentration of ZrO₂ NPs.

Single step fabrication of CuO–MnO–2TiO2 composite thin films with improved photoelectrochemical response

CuO–MnO–2TiO₂ composite thin film having a photocurrent density of 2.21 mA cm⁻² at +0.7 V has been deposited from a homogeneous mixture of acetates of Cu and Mn and (Ti(O(CH₂)₃CH₃)₄) in the presence of trifluoroacetic acid in THF via AACVD at 550 °C.

Covalent surface modification of α-MnO2 nanorods with l-valine amino acid by solvothermal strategy, preparation of PVA/α-MnO2-l-valine nanocomposite films and study of their morphology, thermal, mechanical, Pb(ii) and Cd(ii) adsorption properties

The surface of α-manganese dioxide (α-MnO₂) nanorods was modified chemically with l-valine amino acid by a solvothermal strategy.