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Polyvinyl alcohol (PVA) is a popular material used in the packaging industry. However, it is vulnerable to moisture, which can affect its performance and durability. Introducing hydrophobic substances, such as tetraethyl orthosilicate (TEOS) and hexadecyltrimethoxysilane (HDTMS), on the top layer of PVA can help maintain the excellent properties of PVA under high-humidity conditions. The low compatibility of hydrophobic materials with the hydrophilic layers allows them to aggregate more easily. To overcome these issues, we focused on the effects of particle size when increasing the coating suspension's dispersibility. A carbon quantum dot (CQD) suspension is an appropriate novel solvent for hydrophobic TEOS/HDTMS coating suspensions because its particles are small and light and exhibit good dispersibility. The CQD suspension formed a smooth hydrophobic coating on the TEOS/HDTMS materials. Furthermore, the uniformly coated PVA with the CQD suspension exhibited a water contact angle of 110°. The water droplets remained intact without being absorbed, confirming the effectiveness of the surface coating facilitated by CQDs. These results suggested that CQDs improved the dispersibility and enhanced the coating quality of TEOS/HDTMS on PVA. Enhancing the hydrophobicity of PVA is ideal for applications in packaging and other fields. [ABSTRACT FROM AUTHOR]

We report the solvothermal synthesis of MoS2 based quantum dots (QDs) and the performance evaluation of bare QDs for the detection of aqueous As (III) oxidative state at room temperature and neutral pH over a vast range (0.1−1000 ppb). Concentration-dependent photoluminescence (PL) of the QDs enhances up to 50 ppb and then suppresses till 1000 ppb. It shows two distinctive slopes for enhancement and suppression. The enhancement is possibly due to the passivation of trap states or defects. The formation of tiny glassy As2S3 particles on the QD surface may be the possible reason for suppression. The pattern of optical absorption of QDs follows the similar patterns of PL. Still, it shows an enhanced absorbance in the near UV range below ≤300 nm, which increases with As (III) concentration up to 50 ppb and then decreases following the PL pattern. The MoS2 QDs were characterized by using transmission electron microscopy, x-ray diffraction, UV−Vis, and PL spectroscopy. The enhancement and suppression results were excellently fitted with the modified Stern−Volmer equation. The detection of arsenic is possible using these linear fit equations as calibration curves. [ABSTRACT FROM AUTHOR]

Resorcinol based reduction and capping of ultra-small colloidal silver nanoparticles (Ag NPs) optimally formed hydrogen bond driven clusters within the water-based solution. Large-area self-assembled fractal structures of Ag NPs aggregates were fabricated by solvent evaporation technique on silicon substrate. The final dried surface structures were found to be pH dependent which was adjusted to particular values after the optimal reduction of silver salt, capping of Ag NPs, followed by cluster formation at an optimum pH in the solution phase. These self-assembled surface structures show controlled enhancement of various surface optical phenomena such as Raman spectra of a model dye and luminescence of Ag NPs as a function of pH dependent fractal dimension of the resulting structures. The structure, morphology and various relevant optical properties of self-assembled fractals of Ag NPs were further established by combined use of X-Ray diffractometry (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV-Visible, photoluminescence and Raman spectroscopy analysis. Image 1 • Ag NPs were synthesized using resorcinol as reducing and capping agent and was found to be luminescent. • SPR show peaks at 353 and ~500 nm and their PL emission was observed at 411 nm and 544 nm respectively. • Fractal dimension (F D) was calculated to be 1.89 which decreases to ~1.6 with pH variation in acidic and basic. • R6G was used as probe molecules for SERS measurements which verified that the substrate has high sensitivity to SERS response. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ag@Ag 2 S core shell nanoparticles were synthesized by soft chemical route. • SPR of Ag NPs blue shifts from 408 to 378 nm with increasing sulfur ion concentration. • Ag@Ag 2 S CSNPs exhibit tunable (1.43–1.50 eV) NIR luminescence with increasing sulfur ion concentration. Abstract Ag-Ag 2 S core-shell nano-structured particles, prepared by soft chemical route, were found to be luminescent in the near-infrared (NIR) range. The silver nanoparticles were pre-synthesized with size control by poly-vinyl-pyrrolidone (PVP) polymer capping from silver nitrate solution, by reduction using sodium borohydride in solution, which were further subjected to reaction with sulfur ions in the later stage by mixing controlled amount of Na 2 S in the solution. With increasing concentration of sulfur ions, the plasmonic peak of Ag showed progressive blue shift and damping, leading to final diminishment. Enhanced NIR luminescence obtained from Ag@Ag 2 S core-shell nanoparticles were found to be asymmetric and blue shifting with reduced intensity and increasing sulfur ion concentration. The mechanism behind such a behavior is predicted due to formation of composite layer of Ag 2 S-Ag both at the surface and the volume, with Ag core at the center, diminishing in size with increasing sulfur concentration. The structure, chemical composition, morphology and final core-shell structure formation were further established by combination of X-ray diffractometry (XRD), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM) analysis. [ABSTRACT FROM AUTHOR]

Hybrid nano-structure consisting of silver nanoparticles (Ag NPs) on two dimensional (2D) MoS 2 nanosheets (NS), prepared by liquid exfoliation method and ultrasonic mixing, showed solar energy driven enhanced photocatalytic capability on a model organic dye methylene blue (MB), having possible consequence in water purification. The Schottky junction between the Ag NP and MoS 2 NS interface induces shift of Fermi level to more negative potential, thereby increasing the life time of the charge carriers even more which leads to formation of sink for photo-excited electrons, and the Ag NPs and ultra-small (US) Ag NPs based Ag-MoS 2 samples show quick photocatalytic degradation of MB dye within 30 min (87%) and 8 min (93%), monitored by UV-Vis spectroscopy, with rate constants 64.1 × 10−3 min−1 and 88.6 × 10−3 min−1 respectively. With decreasing size of Ag NPs a wide surface area was covered and quantum confinement occurred which enhanced the electron transfer at the interface. These electrons are relocated to the constitutively existing molecular oxygen to produce numbers of influential oxidative radicals which results in effective degradation of MB. The corresponding photoluminescence spectra show blue shift and quenching with decreasing Ag NP size and lower MoS 2 number of layers, determined by Raman spectroscopy with respect to that of original MoS 2 nanosheet structures. The corresponding microstructures were determined by transmission electron microscopy (TEM), while the chemical composition was found using X-ray photoelectron spectroscopy (XPS). [Display omitted] • Ag/USAg-MoS 2 hybrid structures were prepared by liquid exfoliation method. • Ag/USAg-MoS 2 blue shift indicates increase in band gap due to quantum confinement. • Raman shows Δω was 19.76 cm−1, which confirms that, USAg-MoS 2 consist of bilayers. • Ag/USAg-MoS 2 exhibits enhanced photocatalytic activity towards MB degradation within 8 min. [ABSTRACT FROM AUTHOR]

Incorporating starch, which is a potential biodegradable substitute for petroleum-based polymers, into conventional polymers is challenging owing to limitations in processability and weak-performing resulting materials. Herein, corn starch/polyvinyl alcohol (PVA) blend films (starch: PVA ratio of 50:50) were prepared via the solvent casting method using glycerol as a plasticizer and with varying concentrations of maleic acid as the crosslinking agent. Fourier transform infrared spectroscopy revealed the molecular interactions of the maleic acid crosslinker with the polymeric network of starch and PVA through an ester linkage. The properties of the films were strongly dependent on the maleic acid concentration. An increasing maleic acid concentration imparted hydrophobicity to the film; therefore, water swelling was significantly reduced, and water resistance was enhanced. The film containing 20 wt% maleic acid exhibited excellent barrier properties, with the lowest oxygen and water vapor transmission rates of 0.5 ± 0.2 cc/m2⋅day and 232.3 ± 5.4 g/m2⋅day, respectively. Moreover, the mechanical properties of the film improved with increasing crosslinking. This study demonstrates that the addition of maleic acid leads to an improvement in the overall performance of starch/PVA blend films. Therefore, maleic acid-crosslinked films can be used as barrier materials in food packaging applications. [Display omitted] • Maleic acid crosslinked starch/PVA blend films were prepared by solvent casting. • The swelling percentage of the film significantly reduced with the increase in maleic acid concentration. • The barrier properties of the films were significantly improved. • These films have great potential to be used for packaging application. [ABSTRACT FROM AUTHOR]