Aqueous Alcohol Solutions Research Articles

Design of TDI modified oil‐in‐water emulsion and its application in explosive ink

AbstractIn order to solve the short stabilization time of the water‐in‐oil emulsion binder system and the shortcomings of the critical blast size of the explosive ink molding sample, a water‐in‐oil emulsion binder was designed with polyvinyl alcohol (PVA) aqueous solution as the aqueous phase, fluorocarbon resin (FEVE) ethyl acetate solution as the oil phase, and toluene diisocyanate (TDI) added to modify the water‐in‐oil emulsion binder. The hexanitrohexaazaisowurtzitane(CL‐20)based explosive ink was made by incorporating submicron CL‐20 into the binder system, and the print‐formed samples were tested for microscopic morphology, crystallographic analysis, mechanical susceptibility, and detonation transmission performance. The results showed that the explosive ink‘s viscosity was moderate and suitable for direct printing, and the formed sample‘s surface particles were uniformly dispersed and had a honeycomb structure. The crystal form of CL‐20 explosive in the explosive ink did not change, the molded sample‘s impact and frictional sensitivities were 1 J and 32 N lower than those of submicron CL‐20, respectively, and the detonation velocity of the molded sample was 6655 m/s. The critical detonation size and critical detonation thickness were 1×0.0078 mm and 0.1 mm, respectively, and a critical detonation corner turning of 90°–160° could be achieved. The results show that the prepared binder system is stable for a long time, and the explosive ink molding samples have excellent blast transmission performance.

Performance of alkali and Cu-modified ZSM-5 during catalytic ozonation of polyvinyl alcohol in aqueous solution.

A novel hierarchical Cu/ZSM-5 was prepared over alkaline treatment and incipient wet impregnation method for the catalytic ozonation of polyvinyl alcohol (PVA). Under the optimum preparation conditions, hierarchical Cu/ZSM-5 exhibited an excellent mineralization performance during the PVA degradation process, and the removal rate of TOC after 60min of reaction was 47.86%, much higher than that of ozonation alone (5.40%). Its high catalytic activity could attribute to the large pore volume (0.27 cm3/g) and pore size (6.51nm) which are beneficial for the distribution of loaded copper and adsorption performance for PVA. Compared to ·OH, 1O2 (2.66 times in 10min) contributed more to the removal of PVA. The degradation of PVA was a combined process of direct ozone oxidation, catalytic ozonation and adsorption. With its high catalytic performance and stability, hierarchical Cu/ZSM-5 has a very broad application prospect in the process of catalytic ozonation of refractory pollutants.

Dependence of Slippery and Elastic Properties of Thin Polymer Films on the Grafted Flexible Sidechain Amount

In modern life, people face a wide number of sticky problems when adhesion is highly undesirable: water and dirt stick to clothes, useful materials stick to the walls of their containers and cannot be fully used, water sticking and freezing on airplane wings affects handling and can be dangerous, biological liquids can stick and form clots inside medical devices threatening patients' lives, etc. Slippery liquid-infused porous surfaces (SLIPSs) with pressure stable omniphobicity could help to solve these issues. Lubricant depletion from porous surface and subsequent degradation of omniphobic properties is the major problem for SLIPS. It could be resolved by attaching flexible, liquid-like sidechains to the polymer matrix. Understanding the relationship between the structure of such polymer films and wetting effects is therefore of great importance. The present work is devoted to the study of droplet pinning on crosslinked polydimethylsiloxane (PDMS) polymer films with varied amounts of attached flexible PDMS sidechains and clarification of the relationship between slippery and viscoelastic properties of the films. An one-stage approach to the synthesis of such slippery coatings on smooth and porous substrates in "eco-friendly" pressurized CO2 solutions is proposed. Pinning force and Young's modulus (E) of the films on silicon substrates with variation of the grafted sidechains amount (x) are measured. The non-monotonic dependence of the pinning force on the amount of sidechains is obtained: the pinning force decreases at small x values (region I) and starts to increase at higher x (region II). The effects of the grafted sidechains amount, as well as matrix softening, are discussed for each case. It is demonstrated that the proposed method of film synthesis allows one to obtain thin, uniform coatings on fabrics without gluing the fibers. Such coatings with an optimal amount of PDMS sidechains demonstrate decreased sliding angles for droplets of water and aqueous alcohol solutions, as compared to PDMS coatings without grafted sidechains. The proposed technique may be of interest for deposition of coatings on porous surfaces having a complex morphology, such as textiles, aerogels, porous electrodes, etc.

Enhancing moisture-electric power generation through in situ incorporation of carbon dots into polyelectrolyte membrane

The electric generation performance of traditional polyelectrolyte membrane with moisture usually fall far behind expectations due to its limited hydrophilic groups and poor directional transport capacity of protons. To this end, we introduce the suspension of carbon dots (CDs) prepared by selective oxidation etching of coal pitch with the mixture of formic acid and H2O2 under ambient temperature into the aqueous solution of polyvinyl alcohol (PVA) and poly(4-styrensulfonic acid) (PSS) to fabricate a novel hybrid membrane. This membrane (1.00 cm2) continuously delivers a voltage output of 0.83 V with a short-circuit current of 5.20 μA under proper moist conditions over a prolonged period, outperforming the power generation performance of the pristine membrane and many current moisture-enabled electric generation (MEG) devices. Moreover, CDs endow the polymer membrane with more superior mechanical properties, in favor of processing and scale integration for higher power output. With excess hydrophilic groups provided by as-prepared CDs’ suspension, the denser hydrogen-bond network can be formed in the membrane and facilitates water adsorption and the formation of a higher proton concentration gradient. CDs-induced bridging interactions between PSS chains pave a fast directional transport pathway for moveable protons, resulting in a remarkable power output. Accordingly, this work offers a facile and economic method for remoulding traditional polyelectrolyte membrane to conduct highly efficient MEG for practical applications.

Visible-light photocatalytic degradation of water-soluble polyvinyl alcohol in aqueous solution by Cu2O@TiO2: Optimization of conditions, mechanisms and toxicity analysis

Polyvinyl alcohol (PVA), a water-soluble synthetic polymer, is one of the most prevalent non-native polyvinyl alcohols found in the environment. Due to its inherent invisibility, its potential for causing severe environmental pollution is often underestimated. To achieve efficient degradation of PVA in wastewater, a Cu2O@TiO2 composite was synthesized through the modification of titanium dioxide with cuprous oxide, and its photocatalytic degradation of PVA was investigated. The Cu2O@TiO2 composite, supported by titanium dioxide, facilitated photocarrier separation and demonstrated high photocatalytic efficiency. Under alkaline conditions, the composite exhibited a 98% degradation efficiency for PVA solutions and a 58.7% PVA mineralization efficiency. Radical capture experiments and electron paramagnetic resonance (EPR) analyses revealed that superoxide radicals primarily drive the degradation process within the reaction system. Throughout the degradation process, PVA macromolecules are broken down into smaller molecules, including ethanol, and compounds containing aldehyde, ketone, and carboxylic acid functional groups. Although the intermediate products exhibit reduced toxicity compared to PVA, they still pose certain toxic hazards. Consequently, further research is necessary to minimize the environmental impact of these degradation products.

Synthesis, Structure, and Electron Density Distribution in Crystals of K2(L-Trp)2(H2O) (HTrp = Tryptophane)

The first salt of alkaline metal and L-tryptophane, K2(L-Trp)2(H2O) (I), is synthesized by the reaction of L-tryptophane (HTrp) with potassium hydroxide in an aqueous-alcohol solution. Compound I is characterized by IR and 1H NMR spectroscopy and X-ray diffraction (XRD) (CIF file CCDC no. 2184367). Compound I is found to have a layered structure due to the presence of the bridging water molecule and chelate-bridging anions. The quantum chemical calculations of the crystal structure (PBE, plane-wave basis set, 800 eV) is used to evaluate the strength of interactions of the potassium ion with the L-tryptophanate anion (depending on the coordination type) and the influence of the anion conformation on the strength of coordination, hydrophobic, and hydrophilic interactions.

Investigation of copper and zinc alloy surface exposed to corrosion environment by digital image processing

Usually, corrosion processes on brass, which are manifested by discoloration of the metal or alloy surface, are a little destructive and slow in natural environment or non-acid solutions. In this context, investigation of the corrosion process under the above conditions can be a research area of great relevance because standard analysis such as weight loss and electrochemical techniques can not be applied. Here, we report on a digital image processing analysis of the evolution of copper and zinc alloy surfaces corrosion due to exposure to air, alcohol-aqueous solutions, and sugarcane liquor. For our analysis, we investigated 2D image produced by a confocal microscope from a topographic surface survey, by calculating parameters such as correlation coefficient, Hurst exponent, and bright/dark ratio to follow the early stage of the corrosion process evolution due to exposure to several conditions for different periods of time. The best fits are presented together with the image processing data to show the evolution of the surface characteristics as a function of time and treatment. We show that digital image of rough surfaces that have undergone early stage of the corrosion processes can be used to monitor surface changes. For all tested solutions, the changes in the surface can be better sensed by using the B/D ratio due to the large vertical scale but the fit was better for the correlation coefficient. Particularly for sugarcane liquor and 100% C2H5OH alcohol solution, B/D ratio varies slower than for the other solutions, thus, suggesting an inhibitory effect of this solution.

Study of the role of metalloproteinases and their inhibitors in the formation of posttoxic fibrosis and cirrhosis and the use of oxidized dextran in the experiment

Introduction Cirrhosis of the liver is one of the leading problems of modern medicine in Russia and the world, the incidence of which tends to increase at the present time, and mortality among liver diseases with cirrhosis reaches 47%.The purpose of the work is to evaluate the significance of metalloproteinases (MMPs) and their inhibitors in the formation of liver fibrosis and cirrhosis in the outcome of chronic hepatosis of mixed toxic etiology and the use of OD in the experiment.Materials and methods In Wistar rats of group 1, posttoxic chronic hepatosis was induced by injections of 50% CCl4 oil solution intraperitoneally and 6.5% aqueous solution of ethyl alcohol per os for 60 days. Animals of the 2nd (experimental) group – against the background of the injections of toxic factors from the 30th day of the experiment, for the next 60 days intraperitoneally injected 2 ml of 5% aqueous solution of oxidized dextran (Mr 40 kDa). The numerical density of Kupfer cells, expressing MMP-2, MMP-9, TIMP-1 was studied in the liver.Results From the 60th day, group 1 rats developed cirrhosis of the liver with the formation of false lobules. With the injections of oxidized dextran, the number of Kupfer cells expressing MMP-2, MMP-9 was up to 2 times less than in group 1 rats. The numerical density of Kupfer cells expressing TIMP-1 in group 2 rats was 3 times higher on day 60 than in group 1 rats. In group 2 rats, by the 90th day, a decrease in the number of Kupfer cells expressing MMP-2, MMP-9 by 2 times, and TIMP-1 by 3 times was observed.Discussion OD in chronic toxic hepatosis has an antifibrotic effect that prevents the formation of liver cirrhosis, due to both the processes of collagen degradation in the extracellular matrix under the influence of MMP-2, MMP-9, and associated with a violation of the collagen assembly process, apparently due to the “blockade of the assembly” of tropocollagens by aldehyde-aldehyde bond with oxidized dextran.Conclusion The use of OD in chronic toxic hepatosis prevents the formation of liver cirrhosis in the experiment due to increased processes of collagen degradation in the extracellular matrix under the influence of MMP-2, MMP-9.

Heavy metal ions incorporated within strippable PVA-TTA polymeric matrix detected by colorimetry and vibrational spectroscopies

We report the synthesis and characterization of a novel strippable polymeric matrix of polyvinyl alcohol (PVA) aqueous solutions embedded with 2-thenoyl trifluoroacetone (TTA) organic ligand for decontamination of heavy metal ions. The TTA-containing polymeric matrix was applied to several contaminated surfaces comprising various concentrations of UO22+, Cu2+, Fe3+ and Cs+ contaminants. Except for Cs+, the contaminants were found to interact with the ligand contained in the polymeric matrix, accompanied by a consequent indicative strong color change, specific to the metal contaminant. The dried coating is easily exfoliated leaving the surface decontaminated. ATR-IR and Raman spectroscopies were also applied, showing a clear spectroscopic signature of each metal contaminant, in particular when contained in a mixed ion solution. All in all, the utilization of vibrational spectroscopies is shown to provide important complementary detection signatures that are otherwise vague when surfaces comprising trace amounts of contaminants, lacking color responsive behavior, are involved.

An investigation on the microscale detonation transmission performance of HMX-based explosive ink

ABSTRACT To investigate the effect of Octogen (HMX) in the application of microscale explosive transfer sequence charges. In this paper, we designed and formulated four kinds of explosive inks with different solid contents using submicron HMX as the main explosive and polyvinyl alcohol (PVA) aqueous solution / fluorocarbon resin (FEVE) ethyl acetate solution emulsion as the binder system, studied the effect of solid content on the rheological properties of explosive inks, conducted micro loading studies using a direct ink writing molding platform, The morphology, safety performance and explosion transmission performance of the microscale printed molding samples were tested and analyzed. The results show that the ink containing 90 wt.% HMX explosive has the largest n value, has good printability, smooth surface of the molded sample, consistent, uniform particle dispersion inside the line; HMX crystalline type is still β type; critical impact energy and critical friction of the printed sample compared to the raw HMX increased by 114% and 100% respectively, critical impact energy compared to CL-20-based explosive ink printed sample increased by 67%, indicating that the printed samples have a high safety under the Mechanical Sensitivity. The detonation velocity of the printed sample is 6902 m·s−1 at a charge cross-section size of 1 mm × 1 mm. The critical detonation thickness of the printed sample is 1 × 0.095 mm, Can be stable under the corner of not more than 120 ° detonation.The results of the study show that HMX as the main charge can improve the wide applicability of direct-written explosive ink.

High-Efficiency Near-Infrared-to-Visible Photon Upconversion in Poly(vinyl alcohol) Porous Film.

Triplet-triplet annihilation photon upconversion (TTA-UC) has received significant attention in energy harvesting applications such as solar cells. The realization of high upconversion (UC) performance in the form of films is a crucial factor for the incorporation of this technology into large-area devices. Herein, we propose a porous UC film prepared by an emulsification method with a poly(vinyl alcohol) (PVA) aqueous solution and a toluene solution of chromophores (rubrene/Pd-tetraphenyltetraanthraporphyrin pair) that achieved considerable UC performance in the near-infrared (NIR) (810 nm) to visible (560 nm) range with a maximum quantum yield of 3.7% (out of 50%). Notably, the films displayed a UC emission when using an NIR light-emitting diode as a low-power-density noncoherent light source, which was confirmed by the naked eye. Excitation-power-dependent time-resolved photoluminescence measurements showed almost identical triplet lifetimes of emitter species for the films and toluene solutions; however, lower threshold intensities (Ith = 1-2 W/cm2) were observed for the films than those of the solutions (Ith = ∼10 W/cm2). An evaluation of the remaining toluene in the film and UC emission behavior in liquid nitrogen suggested that the chromophores exist as an amorphous solid in the pores, thus enabling hybrid triplet energy transfer (chromophore mobility based and exciton migration) in this unique film. The presented methodology can be generalized to other wavelengths and can enable diverse applications of the TTA-UC technology.

Designing the technology and composition of plant extracts using reduced atmospheric pressure

The study aims to establish the regimes and parameters of extraction of bioactive substances from raw plant materials by means of extraction with reduced atmospheric pressure for the purpose of manufacturing non-alcoholic functional syrups. The work is performed by leading specialists of the Kemerovo State University using conventional methods. Preparation of the extracts involves aqueous alcoholic treatment of the crushed mass of raw plant materials selected according to the functional parameters. Extraction is performed in a Soxhlet extractor with an advanced liquid ring vacuum pump. The extraction process is monitored by changes in the content of terpenoids in the extract obtained and the mass fraction of dry matter. As a result, the study establishes the parameters and regimes for carrying out and intensifying the extraction of terpenoids and dry matter from fennel, anise, caraway, and dill: pressure – 0.2 MPa, extraction temperature – 50°С, duration of the process – 45 min, solvent – 40 % aqueous alcoholic solution, raw material particle size – 2-3 mm. These process conditions guarantee the highest degree of extraction of terpenoids and dry matter from raw materials, as well as reduce the time and economic costs.

Viscosity Factor (VF) Complementary to the Statistical Indicators Associated with the Rheological Behavior of Aqueous Solutions of Polyvinyl Alcohol

The rheological behavior of aqueous solutions of polyvinyl alcohol at 4, 6, 8 and 10% by weight has been studied and evaluated at temperatures of 20, 25, 30 and 35 °C, using five non-Newtonian fluid models independent of time: Ferrys, Robertson-Stiff, Williamson, Sisko, and Ellis de Haven. The classical method consists in carrying out regression analysis. Using a comparative procedure of determination coefficients and variances, the model that most appropriately adjusts the experimental data to said model is selected. From the statistical point of view, the Sisko and Robertson-Stiff models present better regression parameters; to better specify the choice of the respective rheological model, a new factor has been proposed in the literature, the viscosity factor (VF), which expresses the relationship between apparent and dynamic viscosity. The analysis of this factor for the five models confirms the greater stability of the Ellis de Haven model in terms of the coefficient of variation of the VF. The value of VF fluctuates between 1 and 2 for all ranges of temperature and concentration experienced for vinyl alcohol solutions. As a consequence of the above, for the choice of the non-Newtonian fluid model associated with the rheology of the aqueous solution of polyvinyl alcohol, it is necessary to analyze the statistical parameters and the VF factor simultaneously.

Effects of alcohols and temperature on association, micellar parameters, and energetics of mixture of cetylpyridinium bromide and polyvinyl alcohol

The mixture of polymer and surfactant is extensively employed in numerous daily used products such as detergents, perfumes, cleaning agents, foodstuffs, oil recovery procedures, paints, as well as pharmaceutical formulations. Interaction of cetylpyridinium bromide (CPB) with polyvinyl alcohol (PVA) has been investigated in water and aqueous solution of different alcohols using the conductivity technique. The type and strength of interaction between CPB and PVA during assembly process have been assessed from different micellar parameters i.e., critical micelle concentration (CMC), extent of counterion dissociation (α), Gibbs free energy (ΔGm0), enthalpy (ΔHm0), entropy (ΔSm0) of micellization etc. The CMC and α were determined from the specific conductivity vs [CPB] plots. The micellization of CPB was attained to be augmented in occurrence of PVA. The CMC values of CPB + PVA system were experienced to be increased through the elongation of chain length of carbon as well as increase of concentration of certain alcohol. The sharp increase of CMC values was also observed with the increase of temperature in a certain alcoholic medium. The values of degree of dissociation were undergone to be augmented by the increase of concentration of certain alcohol as well as the elongation of carbon chain length. The negative free energy of micellization (-ΔGm0) values reveal that the CPB + PVA system undergoes aggregation spontaneously and spontaneity of micellization experienced a reduction with the elongation of carbon chain length. Values of enthalpy (ΔHm0) of micellization were negative i.e., aggregation of CPB + PVA system is an exothermic phenomenon. The ΔHmoandΔSmo values disclose that the main interaction forces between CPB and PVA are electrostatic, hydrophobic, and ion–dipole interactions. The stability of the micelle formed was assessed from enthalpy-entropy compensation parameters.

Thermocapillary convection in superimposed layers of self-rewetting fluids: Analytical and lattice Boltzmann computational study

Self-rewetting fluids (SRFs), such as aqueous solutions of long-chain alcohols, exhibit anomalous quadratic dependence of surface tension on temperature having a minimum and with a positive gradient. When compared to the normal fluids (NFs) that have negative gradient of surface tension on temperature, the SRFs can be associated with significantly modified interfacial dynamics, which have recently been exploited to enhance flow and thermal transport in various applications. In this work, first, we develop a new analytical solution of thermocapillary convection in superimposed two SRF layers confined within a microchannel that is sinusoidally heated on one side and maintained at a uniform temperature on the other side. Then, a robust central moment lattice Boltzmann method using a phase-field model involving the Allen-Cahn equation for interface tracking, two-fluid motion, and the energy transport for numerical simulations of SRFs is constructed. The analytical and computational techniques are generally shown to be in good quantitative agreement with one another. Moreover, the effect of the various characteristic parameters on the magnitude and the distribution thermocapillary-driven motion is studied. The thermocapillary flow patterns in SRFs are shown to be strikingly different when compared to the NFs: For otherwise the same conditions, the SRFs result in eight periodic counterrotating thermocapillary convection rolls, while the NFs exhibit only four such vortices. Moreover, the direction of the circulating fluid motion in such vortical structures for the SRFs is found to be towards the hotter zones on the interfaces, which is opposite to that in NFs. These features are found to be sustained even as the interfaces deforms in simulations. By tuning the sensitivity coefficients of the surface tension on temperature, it is shown that not only the magnitude of the thermocapillary velocity can be significantly manipulated, but also the overall flow patterns as well. It is also demonstrated that the thermocapillary convection can be enhanced if the SRF layer adjacent to the nonuniformly heated wall is made relatively thinner or has higher thermal conductivity ratio or has smaller viscosity when compared to that of the other fluid layer. The peak Marangoni velocity is found to be increased by a factor of 2 by doubling the dimensionless quadratic surface tension sensitivity coefficient and by about an order of magnitude as the fluid thickness ratio is changed from 1/3 to 3.

Microfluidic Coupling of Step Emulsification and Deterministic Lateral Displacement for Producing Satellite-Free Droplets and Particles

Step emulsification, which uses a geometry-dependent mechanism for generating uniformly sized droplets, has recently gained considerable attention because of its robustness against flow fluctuations. However, like shear-based droplet generation, step emulsification is susceptible to impurities caused by satellite droplets. Herein, we demonstrate the integration of deterministic lateral displacement (DLD) to separate the main and satellite droplets produced during step emulsification. Step-emulsification nozzles (16 μm deep) in the upstream region of the proposed device were arrayed on the sidewalls of the main channel (91 μm deep). In the downstream region, the DLD micropillars were arrayed periodically with a critical diameter (cut-off value for size-based separation) of 37 μm. When an acrylate monomer and aqueous polyvinyl alcohol solution were infused as the dispersed and continuous phases, respectively, the nozzles produced monodisperse main droplets in the dripping regime, with an average diameter of ~60 μm, coefficient of variation (CV) value below 3%, and satellite droplets of ~3 μm. Upon entering the DLD region near the sidewall, these main and satellite droplets were gradually separated through the pillars based on their sizes. Finally, off-chip photopolymerization yielded monodisperse polymeric microspheres with an average diameter of 55 μm and a CV value of 2.9% (n = 202).

Vanadium doping and phosphorus vacancy co-regulation of biotemplate derived three-dimensional cobalt phosphide to enhance pseudocapacitance performance

Poor rate performance and low cycling stability are both considered as two major disadvantages when choosing cobalt phosphide as the electrode material of supercapacitor. Herein, we developed an effective strategy to ameliorate above disadvantages by introducing of phosphorus vacancies and doping of vanadium simultaneously (the products labelled as V-CoPx-1). Besides, diatomite was selected as a template to synthesize cobalt phosphide with a diatomite morphology by a mild etching method using KOH aqueous alcohol solution as etching agent. The average oxidation state of Co ions in V-CoPx-1 decreases after the P vacancies are introduced, which can improve the electrical conductivity and provide more active sites for electrochemical reactions. Meanwhile, after the introduction of P vacancies and V heteroatoms, more point defects and unpaired electrons are generated, thus improving the ionic conductivity of the material. The diatomite morphology of V-CoPx-1 and the morphological transformation after the reduction by NaBH4 make the materials have larger specific surface area and higher porosity. The as-synthesized V-CoPx-1 possesses a superior 829 F g−1 at 1 A g−1 and improved cycling life maintaining 80.84% of its original value after 10,000 cycles. Moreover, a fabricated device with V-CoPx-1 (anode) and commercial active carbon (cathode) exhibits 43.3 Wh kg−1 at 800 W kg−1. This supercapacitor also delivers a superior rate performance maintaining 60% retention of specific capacitance from 1 A g−1 to 20 A g−1. This work provides an efficient strategy of defects regulation to boost the electrochemical performance, which hoped to offer insights for the improvement of cobalt phosphide.

Black Tea Extracts/Polyvinyl Alcohol Active Nanofibers Electrospun Mats with Sustained Release of Polyphenols for Food Packaging Applications

The efficiency in the capabilities to store and release antioxidants depends on the film morphology and its manufacturing process, as well as on the type and methodology used to obtain the polyphenol extracts. Here, hydroalcoholic extracts of black tea polyphenols (BT) were obtained and dropped onto different polyvinyl alcohol (PVA) aqueous solutions (water or BT aqueous extract with and without citric acid, CA) to obtain three unusual PVA electrospun mats containing polyphenol nanoparticles within their nanofibers. It was shown that the mat obtained through the nanoparticles precipitated in BT aqueous extract PVA solution presented the highest total polyphenol content and antioxidant activity, and that the addition of CA as an esterifier or PVA crosslinker interfered with the polyphenols. The release kinetics in different food simulants (hydrophilic, lipophilic and acidic) were fitted using Fick's diffusion law and Peppas' and Weibull's models, showing that polymer chain relaxation is the main mechanism in all food simulants except for the acidic, which presented an abrupt release by Fick's diffusion mechanism of about 60% before being controlled. This research provides a strategy for the development of promising controlled-release materials for active food packaging, mainly for hydrophilic and acidic food products.

Roles of hydrogen bonding interactions and hydrophobic effects on enhanced water structure strength in aqueous alcohol solutions

The structure and dynamics of water in aqueous alcohol solutions were explored using two-dimensional Raman correlation spectroscopy (2D Raman-COS) combined with the density functional theory (DFT). The spectral changes in the H–O–H bending and O:H stretching modes demonstrated that ethanol and n-propanol induced an enhancement of the water structure compared to methanol. The extent of this effect was related to the length of the alkyl chain. Comparative studies with aqueous ethylene glycol solution revealed that an enhanced water structure stemmed mainly from hydrophobic effects rather than hydrogen bonding (H-bonding) interactions. Alcohol-induced water-specific structural transitions were further analyzed using 2D Raman-COS, which showed that the free OH and strong H-bond structure of water respond preferentially to changes in alcohol content, inducing a transition in the weak H-bond structure of water. In addition, the 2D Raman-COS results indicated that the CH3 stretching mode of alcohol responds preferentially to variations in water content compared to other C–H vibrational modes. Finally, the details of the alcohol-induced water structural transitions were calculated using DFT. The 2D Raman-COS combined with DFT calculations provided insight into alcohol-induced water structural transitions and can be easily extended to other studies of water-organic chemistry.

Reaction pathways for palladium(I) reduction in laser-induced particle formation of Pd: An ab initio molecular orbital study

Previously, we have theoretically shown that the UV irradiation can decompose the PdCl42- anion into PdCl2- + Cl + Cl-, in which palladium is reduced from Pd(II) to Pd(I). In this work we perform ab initio calculations to investigate reactions that can immediately follow this reaction in aqueous alcohol solution. Geometry optimizations and harmonic vibrational analyses are done for the species pertinent to the Pd(I) reduction with the MP2(full) method. The employed basis sets are aug-cc-pVTZ-PP for Pd and aug-cc-pVTZ for other elements. Single-point energies at higher-levels of theory are obtained with the MP4(SDTQ) and QCISD(T) methods with the same basis sets. Solvent effects are also included in all calculations using the polarizable continuum model and water is used as the solvent. Based on the energetics of the relevant reactions, we find likely pathways leading to the formation of Pd(0) species.