Mathematical Modeling of Water-Soluble Astaxanthin Release from Binary Polysaccharide/Gelatin Blend Matrices

Water-soluble AstaSana astaxanthin (AST) was loaded into 75/25 blend films made of polysaccharides (carboxymethyl cellulose (CMC), gum Arabic (GAR), starch sodium octenyl succinate (OSA), water-soluble soy polysaccharides (WSSP)) and gelatin (GEL) at levels of 0.25, 0.5, and 1%, respectively. Due to the presence of starch granules in the AST formulation, the supplemented films exhibited increased surface roughness as compared to the AST-free films. Apart from the CMC/GEL carrier, the migration of AST to water (25 °C, 32 h) was incomplete. Excluding the CMC-based carrier, the gradual rise in the AST concentration decreased the release rate. The Hopfenberg with time lag model provided the best fit for all release series data. Based on the quarter-release times (t25%), the 0.25% AST-supplemented OSA/GEL film (t25% = 13.34 h) ensured a 1.9, 2.2, and 148.2 slower release compared to the GAR-, WSSP- and CMC-based carriers, respectively. According to the Korsmeyer–Peppas model, the CMC-based films offered a quasi-Fickian release of AST (n < 0.5) with the burst effect (t100% = 0.5–1 h). In general, the release of AST from the other films was multi-mechanistic (n > 0.5), i.e., controlled at least by Fickian diffusion and the polymer relaxation (erosion) mechanism. The 1% AST-added WSSP/GEL system provided the most linear release profile.

UV-A Treatment of ZrO2 Thin Films Fabricated by Environmental Friendlier Water-Based Solution Processing: Structural and Optical Studies

An environmentally friendlier solution processing has been introduced to fabricate zirconium oxide (ZrO2) films on quartz substrates, using spin coating of simple water-based solution. The films cured with UV-A = 330 nm for different times (40, 80, 120 min) were investigated for structural and optical properties and compared with thermally annealed film (at 350 °C). XRD and Raman spectroscopy showed amorphous structure in all the samples with no significant phase transformation with UV-A exposure. AFM microscopy showed smooth and crack free films with surface roughness ≤2 nm that reduced with UV-A exposure. Ultraviolet-visible (UV–Vis) spectroscopy demonstrated optical transmittance ≥88% and energy band gap variations as 4.52–4.70 eV. Optical constants were found from spectroscopic ellipsometry (SE). The refractive index (n) values, measured at 470 nm increased from 1.73 to 2.74 as the UV-A exposure prolonged indicating densification and decreasing porosity of the films. The extinction coefficient k decreased from 0.32 to 0.19 indicating reduced optical losses in the films under the UV-A exposure. The photoluminescence (PL) spectra exhibited more pronounced UV emissions which grew intense with UV-A exposure thereby improving the film quality. It is concluded that UV-A irradiation can significantly enhance the optical properties of ZrO2 films with minimal changes induced in the structure as compared to thermally treated film. Moreover, the present work indicates that water-based solution processing has the potential to produce high-quality ZrO2 films for low cost and environmental friendlier technologies. The work also highlights the use of UV-A radiations as an alternate to high temperature thermal annealing for improved quality.

Effect of Concentration of Nd3+ on the Photoluminescence and Ferroelectric Properties of Bi4-xNdxTi3O12 Films

Lead-free films of Bi4-xNdxTi3O12 were deposited on Pt(111)/Ti/SiO2/Si(100) substrate via spin-coating methods. It is shown that there are no secondary phases in Bi4-xNdxTi3O12 films and clear interfaces between the Bi4-xNdxTi3O12 films and substrates when the films are annealed at 700 ℃. And the Bi4-xNdxTi3O12 films also exhibit a blue light emission peak at 437 nm and a yellow light emission peak at 580 nm. There are narrower band gaps, higher dielectric constant and lower dielectric loss when Nd3+ concentration varies from 0 to 0.85. And the Bi3.15Nd0.85Ti3O12 film possesses the minimum of band gap energy (2.67 eV). Moreover, Bi3.55Nd0.45Ti3O12 film exhibits a minimal leakage current density and a maximal remanent polarization, which is highly beneficial for the potential applications in multi-functional devices.

Optical, Structural, and Dielectric Properties of Composites Based on Thermoplastic Polymers of the Polyolefin and Polyurethane Type and BaTiO3 Nanoparticles

In this work, new films containing composite materials based on blends of thermoplastic polymers of the polyurethane (TPU) and polyolefin (TPO) type, in the absence and presence of BaTiO3 nanoparticles (NPs) with the size smaller 100 nm, were prepared. The vibrational properties of the free films depending on the weight ratio of the two thermoplastic polymers were studied. Our results demonstrate that these films are optically active, with strong, broad, and adjustable photoluminescence by varying the amount of TPU. The crystalline structure of BaTiO3 and the influence of thermoplastic polymers on the crystallization process of these inorganic NPs were determined by X-ray diffraction (XRD) studies. The vibrational changes induced in the thermoplastic polymer’s matrix of the BaTiO3 NPs were showcased by Raman scattering and FTIR spectroscopy. The incorporation of BaTiO3 NPs in the matrix of thermoplastic elastomers revealed the shift dependence of the photoluminescence (PL) band depending on the BaTiO3 NP concentration, which was capable of covering a wide visible spectral range. The dependencies of the dielectric relaxation phenomena with the weight of BaTiO3 NPs in thermoplastic polymers blends were also demonstrated.

Tuning the Band Gap and Carrier Concentration of Titania Films Grown by Spatial Atomic Layer Deposition: A Precursor Comparison

Spatial atomic layer deposition retains the advantages of conventional atomic layer deposition: conformal, pinhole-free films and excellent control over thickness. Additionally, it allows higher deposition rates and is well-adapted to...

Gas flow-assisted vacuum drying: Identification of a novel process for attaining high-quality perovskite films

Controlling the nucleation and crystal growth in solution-processed metal halide perovskite (MHP) thin films is the pivotal point in fabricating homogenous and pinhole-free films. Using scalable coating and printing techniques,...

Sol–Gel Processing of Water-Soluble Carbon Nitride Enables High-Performance Photoanodes

In spite of the enormous promise that polymeric carbon nitride (PCN) materials hold for photoelectrochemical (PEC) applications, the fabrication of high-quality PCN photoelectrodes has been a largely elusive goal to date. Here we tackle this challenge by devising, for the first time, a sol–gel approach that enables facile preparation of photoanodes based on poly(heptazine imide) (PHI), a polymer belonging to the PCN family. The sol–gel process capitalizes on the use of a water-soluble PHI precursor composed of nanosized (~10 nm) particles that allows formation of a non-covalent hydrogel. The hydrogel can be deposited on a conductive substrate resulting in formation of mechanically stable porous polymeric thin layers (~400 nm), in contrast to the commonly obtained loosely attached thick particulate coatings. The resulting photoanodes exhibit unprecedented PEC performance in methanol reforming in neutral pH electrolytes with photocurrents of up to 177±27 mA cm^-2 (1 sun illumination) and 320±40 mA cm^-2 (2 sun illumination) at 1.23 V vs. RHE, maintaining such high photocurrents even down to ~0 V vs. RHE. These parameters permit effective operation even without any external electric bias, as demonstrated by bias-free photoreforming of methanol and glycerol, and highly selective (~100%) photooxidation of 4-methoxybenzyl alcohol (4-MBA). The robust binder-free films derived from sol–gel processing of water-soluble PCN thus represent a new paradigm for high-performance ‘soft-matter’ photoelectrocatalytic systems, and pave the way for further applications in which high-quality PCN films are required.

Controlling the flux of reactive species: a case study on thin film deposition in an aniline/argon plasma

The plasma based synthesis of thin films is frequently used to deposit ultra-thin and pinhole-free films on a wide class of different substrates. However, the synthesis of thin films by means of low temperature plasmas is rather complex due to the great number of different species (neutrals, radicals, ions) that are potentially involved in the deposition process. This contribution deals with polymerization processes in a capacitively coupled discharge operated in a mixture of argon and aniline where the latter is a monomer, which is used for the production of plasma-polymerized polyaniline, a material belonging to the class of conductive polymers. This work will present a particular experimental approach that allows to (partially) distinguish the contribution of different species to the film growth and thus to control to a certain extent the properties of the resulting material. The control of the species flux emerging from the plasma and contributing to the film growth also sheds new light on the deposition process, in particular with respect to the role of the ion component. The analysis of the produced films has been performed by means of Fourier Transform Infrared spectroscopy (FTIR) and Near Edge X-ray Absorption Fine Structure spectroscopy (NEXAFS).

Interrogating helical nanorod self-assembly with fractionated cellulose nanocrystal suspensions

The helical self-assembly of cholesteric liquid crystals is a powerful motif in nature, enabling exceptional performance in many biological composites. Attempts to mimic these remarkable materials by drying cholesteric colloidal nanorod suspensions often yield films with a non-uniform mosaic-like character, severely degrading optical and mechanical properties. Here we show—using the example of cellulose nanocrystals—that these problems are due to rod length dispersity: uncontrolled phase separation results from a divergence in viscosity for short rods, and variations in pitch can be traced back to a twisting power that scales with rod length. We present a generic, robust and scalable method for fractionating nanorod suspensions, allowing us to interrogate key aspects of cholesteric self-assembly that were previously hidden by colloid dispersity. By controlled drying of fractionated suspensions, we can obtain mosaic-free films that are uniform in colour. Our findings unify conflicting observations and open routes to biomimetic artificial materials with performance that can compete with that of nature’s originals.