A FTIR and DFT Combination Study to Reveal the Mechanism of Eliminating the Azeotropy in Ethyl Propionate-n-Propanol System with Ionic Liquid Entrainer.

Ionic liquids (ILs) have presented excellent behaviors in the separation of azeotropes in extractive distillation. However, the intrinsic molecular nature of ILs in the separation of azeotropic systems is not clear. In this paper, Fourier-transform infrared spectroscopy (FTIR) and theoretical calculations were applied to screen the microstructures of ethyl propionate-n-propanol-1-ethyl-3-methylimidzolium acetate ([EMIM][OAC]) systems before and after azeotropy breaking. A detailed vibrational analysis was carried out on the v(C=O) region of ethyl propionate and v(O-D) region of n-propanol-d1. Different species, including multiple sizes of propanol and ethyl propionate self-aggregators, ethyl propionate-n-propanol interaction complexes, and different IL-n-propanol interaction complexes, were identified using excess spectroscopy and confirmed with theoretical calculations. Their changes in relative amounts were also observed. The hydrogen bond between n-propanol and ethyl propionate/[EMIM][OAC] was detected, and the interaction properties were also revealed. Overall, the intrinsic molecular nature of the azeotropy breaking was clear. First, the interactions between [EMIM][OAC] and n-propanol were stronger than those between [EMIM][OAC] and ethyl propionate, which influenced the relative volatilities of the two components in the system. Second, the interactions between n-propanol and [EMIM][OAC] were stronger than those between n-propanol and ethyl propionate. Hence, adding [EMIM][OAC] could break apart the ethyl propionate-n-propanol complex (causing the azeotropy in the studied system). When x([EMIM][OAC]) was lower than 0.04, the azeotropy still existed mainly because the low IL could not destroy the whole ethyl propionate-n-propanol interaction complex. At x(IL) > 0.04, the whole ethyl propionate-n-propanol complex was destroyed, and the azeotropy disappeared.

Facile production of chitin from shrimp shells using a deep eutectic solvent and acetic acid.

High purity chitin was extracted from shrimp shells by a green, sustainable, and efficient one-pot approach using a deep eutectic solvent consisting of choline chloride and glycerol (ChCl-Gl) combined with a small amount of acetic acid. Under the conditions of an acetic acid concentration of 7.5 wt% and reaction temperature of 120 °C, the purity of isolated chitin was up to 96.1%, which was superior to that of 87.7% obtained by conventional chemical method. In addition, the viscosity-average molecular weight and crystallinity of the extracted chitin were revealed to be larger than for the latter. Moreover, the deep eutectic solvent could be recycled at least three times without losing the quality of the extracted chitin. This facile approach combining recyclable DES with a small amount of acetic acid was expected to be used for the green and sustainable production of chitin from shrimp shells.

Development of active packaging films based on liquefied shrimp shell chitin and polyvinyl alcohol containing ß-cyclodextrin/cinnamaldehyde inclusion.

To maintain the freshness of fruits and to meet environmental and consumer needs, a biobased packaging film with long-lasting antimicrobial activity was developed in this article. Liquefied ball-milled shrimp shell chitin/polyvinyl alcohol (LBSC/PVA) blend films containing varying concentrations (0, 1, 2, 3, 4, 5 wt%) of the ß-cyclodextrin/cinnamaldehyde (ß-CD/CA) inclusion were prepared and characterized. The association between ß-CD and CA and the sustained release behavior of CA were explored. The physicochemical property, antimicrobial activity and food preservation performance of the films were investigated. Results showed that CA was successfully encapsulated into the cavity of CD by host-guest interactions, which greatly improved the sustained release of CA. The 3 wt% ß-CD/CA/LBSC/PVA blend film showed optimized mechanical properties with a tensile strength of 41.5 MPa and an elongation at break of 810 %. In addition, the incorporation of ß-CD/CA inclusion significantly enhanced the antimicrobial activity and food preservation performance of the blend films. Moreover, the 3 wt% ß-CD/CA/LBSC/PVA blend film exhibited evidently longer lasting antimicrobial activity and cherry tomato preservation performance than the 3 wt% CA/LBSC/PVA blend film, further demonstrating the critical role of ß-CD in delaying CA release. These novel ß-CD/CA/LBSC/PVA blend films may have a potential use in active food packaging.

Antioxidant and antibacterial properties of essential oils-loaded ß-cyclodextrin-epichlorohydrin oligomer and chitosan composite films.

Chitosan (CS) is becoming increasingly popular in food packaging due to its natural degradability and great film-forming properties. Nevertheless, its poor antibacterial properties and inadequate antioxidant properties prevent it from being used effectively. In this study, ß-cyclodextrin-epichlorohydrin (ß-CD-EP) oligomers were prepared and encapsulated with natural essential oils cinnamaldehyde and thymol, and then the inclusion complexes (IC) were incorporated into chitosan in various contents to afford a series of CS-IC composite films. The impacts of IC on the morphological, mechanical, thermal, and water resistance properties, antioxidant and antibacterial activities of chitosan films, as well as the loading and sustained release behavior of IC, were thoroughly examined. The results turned out that the essential oils were well-loaded with high encapsulation efficiency and showed a significant slow-release effect. It was also found that the tensile strength and the elongation at break decreased with increasing IC contents, while the thermal stability was enhanced. The incorporation of IC dramatically promoted the antioxidant and antibacterial properties of the chitosan films towards Gram-positive bacteria. Based on our findings, chitosan films containing essential oils-loaded ß-CD-EP oligomers may serve as an effective food packaging material.

Multiple free radical scavenging reactions of aurones.

A series of naturally occurring 3',4'-dihydroxy aurones have been studied with regard to multiple free radical scavenging reactions in the gas and two liquid phases using density functional theory (DFT). All of the aurones prefer to perform (2 + n)-HAT mechanism to trap 2 + n free radicals, where n is the sum of the numbers of catechol and guaiacyl units in the gas and benzene phases. The second HAT reaction favours occurring in the same catechol moiety of the first HAT mechanism occurring OH group due to the formation of a stable quinone and the highly exothermic step of the final stable product formation. The catechol and guaiacyl moieties show increased potency for the second and fourth H+/e‒ reactions. In the water phase, aurones can perform multiple H+/e‒ reactions through n1PL-ET-n2HAT-(n+1-n2)ET mechanism, where n1 is the number of OH groups and n2 is the number of guaiacyl moieties.

Electrocatalytic performance of tyrosinase detection in Penaeus vannamei based on a [(PSS/PPy)(P2Mo18/PPy)5] multilayer composite film modified electrode.

Polyoxometalates (POMs) are widely used in the preparation of sensors that detect the content of substances because of their excellent electron transfer capabilities. In this paper, a [(PSS/PPy)(P2Mo18/PPy)5] multilayer composite film modified electrode was prepared by the potentiostatic deposition method. The electrochemical performance of the modified electrode was studied by cyclic voltammetry under the conditions of different modified layers, different supporting electrolytes and different sweep rates. Different concentrations of tyrosinase were catalyzed by the modified electrode under a suitable supporting electrolyte, and the electrochemical sensing of tyrosinase by the modified electrode was studied. The research results show that the modified electrode has good stability and reproducibility for electrochemical sensing of tyrosinase, and the response current has a good linear relationship with the amount of tyrosinase added. Taking peak III as an example, the detection limit (S/N = 3) was 2.7649 U mL-1. It can be known from the timing ampere curve that as the concentration of tyrosinase in the reaction system continues to increase, its response current increases stepwise, providing a linear curve in the range of 3.66 U mL-1 to 26.87 U mL-1, and the minimum detection limit (S/N = 3) reaches 0.0021 U mL-1. The [(PSS/PPy)(P2Mo18/PPy)5] multilayer composite membrane modified electrode was used to detect tyrosinase in Penaeus vannamei. The spiked recovery of the sample was 96.3-100.8%, indicating that the modified electrode has high accuracy and can be used for the detection of tyrosinase in actual samples.

Production of cellulose nanofibrils and films from elephant grass using deep eutectic solvents and a solid acid catalyst.

A new strategy was developed to produce cellulose nanofibrils (CNFs) and films from raw elephant grass using deep eutectic solvents and a recyclable spent coffee-derived solid acid (SC-SO3H) catalyst with assistance of ultrasonic disintegration and a suction filtration film forming method. The effects of a solid acid and reused solid acid were comprehensively studied by comparing with catalyst-free conditions and using sulfuric acid as the catalyst. The CNF fibers obtained from this novel SC-SO3H catalyst method showed the longest fiber length. The corresponding films achieved the strongest tensile strength of 79.8 MPa and the elongation at break of 13.6%, and best thermostability. In addition, the performance of CNFs and films prepared by the fourth recovered SC-SO3H-4 catalyst was close to that obtained with the first use. The SC-SO3H could be reused by a simple decantation method, meaning this novel method has the potential for green and sustainable preparation of CNFs and films.

In situ generated silica reinforced polyvinyl alcohol/liquefied chitin biodegradable films for food packaging.

In previous report, polyvinyl alcohol/liquefied ball-milled chitin (PVA/LBMC) blend films with good antibacterial activity were successfully prepared. To further develop a biodegradable food packaging material, various amounts of nano-silica were introduced in situ by the hydrolysis of Na2SiO3 to give a series of silica-reinforced PVA/LBMC blend films. Their structure, morphology, mechanical and thermal properties, food preservation and degradation behavior in soil were comprehensively characterized. The results showed that when the content of Na2SiO3 was 0.2 wt %, the blend film 4PVA-LBMC-0.2Si displayed the optimized performance. Its tensile strength, and the maximum weight loss rate temperature reached 51 MPa and 307 ℃, respectively, which were significantly improved than those of silica-free film. The preservation tests of cherries showed its good fresh keeping performance. Although the degradation rate of silica-reinforced blend films in the soil was slightly decreased, it remained at a good level of 43 % after 30 days of burial.

Biosynthesis of CdS nanoparticles in banana peel extract.

Cadmium sulfide (CdS) nanoparticles (NPs) were synthesized by using banana peel extract as a convenient, non-toxic, eco-friendly 'green' capping agent. Cadmium nitrate and sodium sulfide are main reagents. A variety of CdS NPs are prepared through changing reaction conditions (banana extracts, the amount of banana peel extract, solution pH, concentration and reactive temperature). The prepared CdS colloid displays strong fluorescence spectrum. X-ray diffraction analysis demonstrates the successful formation of CdS NPs. Fourier transform infra-red (FTIR) spectrogram indicates the involvement of carboxyl, amine and hydroxyl groups in the formation of CdS NPs. Transmission electron microscope (TEM) result reveals that the average size of the NPs is around 1.48 nm.