Hydroxyl Research Articles

Impact of the Three-Dimensional Arrangements of Polyhydroxylated Crosslinkers on the Resulting Properties of Chitosan-Based Hydrogels

Chitosan was subjected to a crosslinking reaction with three polyhydroxylated diacids (glucaric (GlcA), mannaric (ManA), and mucic (MucA) acids) that only differ in the spatial orientation of their hydroxyl groups. This work aimed to obtain experimental evidence of the impact of the three-dimensional arrangement of the crosslinkers on the resulting properties of the products. In all the cases, the products were hydrogels, and their chemical structures were fully elucidated by FT-IR spectroscopy and conductometric titration. Thermogravimetric and morphological studies were also carried out. The specific surface area of all the products was similar and higher than that of native chitosan. Moreover, all hydrogels were characterized in terms of viscoelastic properties and long-term stability under external perturbation. Furthermore, their lead adsorption efficiency and swelling capacity were assessed. Despite the resemblant chemical structure in all the hydrogels, Ch/ManA exhibited the highest lead adsorption capacity, (Ch/ManA: 93.8 mg g−1, Ch/GlcA: 82.9 mg g−1, Ch/MucA: 79.2 mg g−1), while Ch/GlcA exhibited a remarkably higher swelling capacity (i.e., ~30% more than Ch/MucA and ~40% more than Ch/ManA). The results obtained herein evidenced that the selection of the polyhydroxylated crosslinker with the appropriate three-dimensional structure could be crucial to finely adjust the final materials’ features.

Cellulose based molecularly imprinted polymer by hydroxyl functional allocation strategy with dual selectivity of boric acid affinity and molecular structure limitation to bortezomib: Preparation strategy, selectivity exploration, and metabolism study

Bortezomib is widely recognized as an effective drug for the treatment of multiple myeloma, but its metabolism in vivo has not been reported. There are extremely high requirements for selectivity and enrichment ability of pretreatment methods due to the complex biological matrix and trace metabolites. Urgently, a novel magnetic porous cellulose molecularly imprinted polymers (B-MPCMIP) based on bortezomib was developed for the first time using the magnetic porous cellulose (MPC) as the both carrier and functional monomer by the hydroxyl functional allocation strategy of cellulose, which showed the dual selectivity towards bortezomib through the boric acid affinity and molecular structure limitation. Firstly, the cis dihydroxy groups of cellulose was occupied by phenylboronic acid; then, another hydroxyl group in cellulose was modified by silane reagent to introduce reaction site for grafting MIP; subsequently, the phenylboronic acid was removed to release the cis dihydroxy groups of cellulose as the functional monomer for MIP; finally, MIP was prepared on the surface of MPC with the MPC as the both carrier and functional monomer for obtaining B-MPCMIP, which can recognize the bortezomib through the boric acid affinity molecular structure limitation. A series of characterization studies showed that B-MPCMIP had a porous structure, good thermal stability, ultra-high magnetism, mesoporous structure, and superhydrophilicity. B-MPCMIP showed good adsorption capacity (Qmax: 4.4 mg/g) and fast adsorption effect (adsorption equilibrium time: 30 min). Adsorption capacity of B-MPCMIP were also inspected under different temperature and pH conditions. The strong pH adsorption dependence indicates that B-MPCMIP mainly adsorbs bortezomib through the boric acid affinity, as the affinity between the cis dihydroxy groups in B-MPCMIP and the boric acid group in bortezomib is strongest at pH 8.5. Furthermore, B-MPCMIP exhibited excellent selectivity towards bortezomib with the imprinting factor, selectivity coefficient, and relative selectivity coefficient up to 8.6, 17, and 14, respectively. B-MPCMIP had outstanding reusability and stability, which remained 96 % of adsorption capacity after multiple recycling. B-MPCMIP-HPLC and B-MPCMIP-UPLC-MS/MS methods were successfully applied to enrich and detect bortezomib and its metabolites in mouse plasma and liver. The methods showed good selectivity, sensitivity, and accuracy. The maximum concentration of bortezomib in plasma and liver was detected as 34.3 μg/mL and 84.2 μg/mL. And six metabolites of bortezomib through oxidative deboronation were triumphantly detected and identified by B-MPCMIP-UPLC-MS/MS method.

Superoleophobic polyethylene glycol grafted graphene oxide/polyamide 6 nanofibrous composite membrane for highly efficient separation of oil/water emulsion

Graphene oxide (GO) has been applied for membrane-based oil/water emulsion separation processes due to its ease of functionalization, substantial surface area, and abundant hydrophilic hydroxyl and carboxyl functional groups. In this study, the dispersion of GO in polyamide 6 (PA6) was improved through grafting of GO with polyethylene glycol (PEG). The prepared GO-PEG was integrated into PA6 nanofibers at different loading levels and the oil/water emulsion separation of the resulting PA6/GO-PEG membranes was compared as a function of GO-PEG content. The homogeneous dispersion of GO-PEG at a 2 wt% loading level within PA6 nanofibers (designated as PA6/GO-PEG2) resulted in a nanofibrous composite membrane that exhibited exceptional mechanical strength (approximately 16.29 MPa), and remarkable hydrophilic properties (water contact angle of 12.30°). Moreover, a remarkable underwater superoleophobicity was exhibited by PA6/GO-PEG2 and provided an underwater oil contact angle of 150.41°. Notably, the optimal characteristics were showcased by the PA6/GO-PEG2 nanofibrous membrane, offering an impressive water flux rate of 813 L/m2h and an outstanding oil rejection efficiency of 99.26 % when subjected to an oil/water emulsion under a pressure of 1 bar. Furthermore, robust antifouling properties were displayed by PA6/GO-PEG2, in which 95.69 % of the water flux rate was maintained and reached 778 L/m2h, and excellent oil rejection efficiency remained at 98.59 % even after 15 cycles of oil/water separation. These results highlight the potential of the PA6/GO-PEG2 nanofibrous membrane as a highly promising candidate for practical applications in oil/water separation, owing to its superior performance and enduring antifouling characteristics.

Kraft lignin-based polyurethanes: Bulk properties, stability and adhesion to native aluminum surfaces

Lignin as a byproduct from pulp and paper manufacturing has been extensively investigated as raw material for polymer developments. Although, fundamental topics related to the adhesion mechanisms of lignin-based reactive polyurethanes (LPU) still remain unclear. In this work, LPU thin films on native aluminum surface were prepared and characterized. Diluted in THF, employed as the solvent, reactive mixtures of 4,4′-methylene diphenyl isocyanate (4,4′-MDI) and the soluble fraction of three lignins (liquid hydroxypropylated Kraft lignin and two powder Kraft lignins with different pH) were used for LPU thin film deposition via spin coating on aluminum (PVD layer on silicon wafer). The resulting film thickness ranged from 8 nm to several micrometers. The chemical state of the three LPU compositions was assessed in bulk by infrared attenuated total reflectance (IR-ATR) and in the thin films by infrared external reflection absorption spectroscopy (IR-ERAS). Binding energies of 4,4′-methylene diphenyl diisocyanate with aliphatic and aromatic hydroxyl groups were estimated using Density Functional Theory (DFT) simulations. Thus, besides the elucidation of the bulk chemical state of LPUs, the relation to adhesion and stability of LPUs to a native aluminum surface was evaluated. In addition, film topography and homogeneity were monitored by SFM. All lignin types form uniform and homogeneous films. Results revealed a higher consumption of isocyanate groups (NCO) in the formulation with the alkaline Kraft lignin than with the acid one, despite its lower hydroxyl content. A gradient of unreacted NCO was observed in LPU thin films obtained with the powder Kraft lignin types. Residual NCO is also found in thicker films, while the thinnest films did not contain unreacted NCO anymore, indicating the activating effect of the native aluminum surface on LPU formation.

Improvements of the increase of selenium-modified rate on the structural characteristics and antioxidant properties of Lycium barbarum polysaccharides by subcritical water method

Effects of the increase of the selenium-modified rate on the structural characteristics and antioxidant abilities of the selenized polysaccharides (Se-PS) were seldom reported. In this work, LBP1-1 purified from Lycium barbarum polysaccharides (LBP) was selenized by the subcritical water (SW) versus the traditional hot water (HW) method to obtain Se-modified SW-SeLBP1-1 and HW-SeLBP1-1, respectively. The results revealed that SW-SeLBP1-1 contained 17.49 ± 0.35 mg Se/g, significantly higher than 5.68 ± 0.05 mg/g of HW-Se-LBP1-1 and the reported before. The selenization time was reduced from 7 h to 20 min. Se modifications were mainly achieved by Se substitutions of hydrogen atoms in hydroxyl groups of LBP1-1. Xylose and galactose in LBP1-1 could be easily and regularly modified by Se, the Se modifications of the other monosaccharides showed significant different between the two methods. The generated C-O-Se groups could readily make SW-SeLBP1-1 formed a more orderly network structure than that of HW-SeLBP1-1 when Se-modified rate increased 11.81 %, resulting in its antioxidant activities increasing over 17.3 % in vitro.

Effects of low-molecular-weight organic acids on the transport of polystyrene nanoplastics: An insight at the structure of organic acids

Plastic nanoparticles are extensively used in various products, leading to inevitable pollution in soil. Understanding their transport in soils where various organic substances exist is crucial. This study examined the impact of low-molecular-weight organic acids (LMWOAs) on the transport of polystyrene nanoplastics (PS-NPs) through saturated quartz sand. The experiments involved three dibasic acids—malonic acid (MA1), malic acid (MA2) and tartaric acid (TA) — and four monobasic acids— formic acid (FA), acetic acid (AA), propanoic acid (PA) and glycolic acid (GA) —under different pH levels (4.0, 5.5, 7.0) and in the presence of cations (Na+, Ca2+). The results demonstrated that in the presence of Na+, dibasic acids significantly enhanced PS-NPs transport, with TA being the most effective, followed by MA2 and MA1. This enhancement is attributed to the adsorption of LMWOAs onto the nanoparticles and sand, creating a more negative ζ-potential, which increases the electrostatic repulsion and decreases the PS-NPs deposition, thereby facilitating the transport. Applying the Derjaguin-Landau-Verwey-Overbeek theory, higher pH levels increased the energy barrier and secondary energy minimum, decreasing PS-NPs deposition. Moreover, dibasic acids significantly enhanced the hydrophilicity of PS-NPs. Conversely, monobasic acids, except for GA, slightly reduced the hydrophilicity of PS-NPs, as indicated by a small increase in the water contact angle, hereby minimally affecting PS-NPs transport. As for GA, although it is a monobasic acid, the additional -OH group in its molecular structure promoted PS-NPs transport, similar to dibasic acids. For example, GA also significantly enhanced the hydrophilicity of PS-NPs. In the presence of Ca2+, the enhancement of PS-NPs transport by LMWOAs was comparable to that with Na+, primarily due to the complex-forming and bridging effects of Ca2+ with the organic acids and PS-NPs. These findings provide important insights into predicting and analyzing the transport behaviors of PS-NPs.

Pentahomoserine functionalized graphene oxide decorated polyamide thin film for enhanced separation of green tea polyphenols

The isolation of valuable compounds from the byproducts of food processing industries presents a significant contemporary challenge. Thin film nanocomposite (TFN) membranes have been identified as potential media for separating bioactive compounds. In this work, pentahomoserine functionalized graphene oxide (FGO) based TFN membranes were prepared for the effective separation of tea polyphenols epigallocatechin (EGC) and epigallocatechin gallate (EGCG). The nanocomposite selective polyamide (PA) layer was prepared through the dispersion of FGO in an aqueous monomer solution. The prepared membranes possess high average surface roughness with improved hydrophilicity and thermal stability. Additionally, FGO membranes contain more hydroxyl or carboxyl groups with cross-linked PA layer through interfacial polymerization (IP) process. Moreover, FGO membranes featured increased hydroxyl or carboxyl groups, facilitating cross-linking with the PA layer via intermolecular forces. The effects of amine functionality on the membrane characteristics such as surface morphology, roughness and hydrophilicity were also investigated. Remarkably, the membranes demonstrated rejection efficiency of 96.3% towards polyphenols. Furthermore, comprehensive assessments of reusability performance of the membrane highlighted their potential for industrial applications. This study provides valuable insights into the fabrication of highly efficient TFN membranes for biomolecule separation across diverse technological domains.

Understanding Variations in Ferrate Detection through the ABTS Method in the Presence of Electron-Rich Organic Compounds.

The chromogenic reaction between 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and ferrate [Fe(VI)] has long been utilized for Fe(VI) content measurement. However, the presence of electron-rich organic compounds has been found to significantly impact Fe(VI) detection using the ABTS method, leading to relative errors ranging from ∼88 to 100%. Reducing substances consumed ABTS•+ and resulted in underestimated Fe(VI) levels. Moreover, the oxidation of electron-rich organics containing hydroxyl groups by Fe(VI) could generate a phenoxyl radical (Ph•), promoting the transformation of Fe(VI) → Fe(V) → Fe(IV). The in situ formation of Fe(IV) can then contribute to ABTS oxidation, altering the ABTS•+:Fe(VI) stoichiometry from 1:1 to 2:1. To overcome these challenges, we introduced Mn(II) as an activator and 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic agent for Fe(VI) detection. This Mn(II)/TMB method enables rapid completion of the chromogenic reaction within 2 s, with a low detection limit of approximately 4 nM and a wide detection range (0.01-10 μM). Importantly, the Mn(II)/TMB method exhibits superior resistance to reductive interference and effectively eliminates the impact of phenoxyl-radical-mediated intermediate valence iron transfer processes associated with electron-rich organic compounds. Furthermore, this method is resilient to particle interference and demonstrates practical applicability in authentic waters.

Effect of Mild Alkali Treatment on the Structure and Physicochemical Properties of Normal and Waxy Rice Starches

Mild alkali treatment can potentially be developed as a greener alternative to the traditional alkali treatment of starch, but the effect of mild alkali on starch is still understudied. Normal and waxy rice starches were subjected to mild alkali combined with hydrothermal treatment to investigate their changes in physicochemical properties. After mild alkali treatment, the protein content of normal and waxy rice starches decreased from 0.76% to 0.23% and from 0.89% to 0.23%, respectively. Mild alkali treatment decreased gelatinization temperature but increased the swelling power and solubility of both starches. Mild alkali treatment also increased the gelatinization enthalpy of waxy rice starch from 20.01 J/g to 25.04 J/g. Mild alkali treatment at room temperature increased the pasting viscosities of both normal and waxy rice starches, whereas at high temperature, it decreased pasting viscosities during hydrothermal treatment. Alkali treatment significantly changed the properties of normal and waxy rice starch by the ionization of hydroxyl groups and the removal of starch granule-associated proteins. Hydrothermal conditions promoted the effect of alkali. The combination of hydrothermal and alkali treatment led to greater changes in starch properties.

Influence of methane-oxygen coupled gas field on the transformation mechanism of microporosity and active structure of cryogenic pre-oxidized residual coal

Due to the impact of coal seam mining processes and the release of adsorbed gases in residual coal, a mixed gas field of methane and oxygen is formed in the goaf, which affects the oxidation process of the residual coal over a long period. In this study, to explore the low-temperature oxidation mechanism of residual coal in a hypoxic methane-containing environment, Low temperature nitrogen adsorption (LTNA) experiments and Fourier transform infrared spectroscopy (FTIR) were utilized to examine the pore development properties of residual coal and the transformation mechanisms of reactive micro-groups. The results indicate that increases in temperature and methane proportion promote the transition of various pores to larger scales, with 3 % methane inducing the formation of fine micropores, thereby increasing the specific surface area of the coal. High temperatures (80℃，100℃) and increased proportions of oxygen and methane synergistically elevate the fractal dimensions. Methane inhibits the consumption of hydroxyl groups, and a low oxygen concentration (5 %) impedes the gas production from coal oxidation. The presence of both oxygen and methane exhibits a compound effect; the strongest tendency towards spontaneous combustion occur at 1 % methane and 9 % oxygen. The findings provide valuable insights for controlling spontaneous combustion disasters in goafs.

Comparative efficiency of different polyol-based deep eutectic solvents for chitin extraction from lobster shells

In this study, deep eutectic solvent (DES) prepared from choline chloride, lactic acid, and one of the four polyols (ethylene glycol, glycerol, xylitol, and sorbitol) were compared and assessed for their effectiveness in extracting chitin from lobster shells. Our results revealed that as the number of hydroxyl groups in polyols increased, the hydrogen bond network within the DESs became denser. However, this led to a corresponding increase in viscosity, which impacted the efficiency of chitin extraction. Among all prepared DESs, choline chloride-lactic acid/glycerol (CCLaGly) exhibited superior extractive ability, resulting in the extraction of pure chitin from lobster shells. The purity, crystallinity, and molecular weight of the extracted chitin using CCLaGly DES were comparable to those of chemically-isolated chitin, with purity reaching 94.76 ± 0.33 %, crystallinity at 78.78 %, and a molecular weight of 655 kDa. Additionally, the physicochemical properties of the DES-extracted chitins were characterized using Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. This study conducted a comparative analysis of polyol effects on chitin extraction from lobster shells, thereby opening a promising avenue for the utilization of various crustacean shells in sustainable biomaterial production.

Enhanced Electrocatalysis on Copper Nanostructures: Role of the Oxidation State in Sulfite Oxidation.

The influence of surface morphology and the oxidation state on the electrocatalytic activity of nanostructured electrodes is well recognized, yet disentangling their individual roles in specific reactions remains challenging. Here, we investigated the electrooxidation of sulfite ions in an alkaline environment using cyclic voltammetry on copper oxide nanostructured electrodes with different oxidation states and morphologies but with similar active areas. To this aim, we synthesized nanostructured Cu films made of nanoparticles or nanorods on top of glassy carbon electrodes. Our findings showed an enhanced sensitivity and a lower detection threshold when utilizing Cu(I) over Cu(II). Density functional theory-based thermochemical analysis revealed the underlying oxidation mechanism, indicating that while the energy gain associated with the process is comparable for both oxide surfaces, the desorption energy barrier for the resulting sulfate molecules is three times higher on Cu(II). This becomes the limiting step of the reaction kinetics and diminishes the overall electrooxidation efficiency. Our proposed mechanism relies on the tautomerization of hydroxyl groups confined on the surface of Cu-based electrodes. This mechanism might be applicable to electrochemical reactions involving other sulfur compounds that hold technological significance.

Comparative Analysis of Solution Properties and Microscopic Interactions in [emim][OTf]-[eOHpy][OTf] Mixture and [emim][OTf]-PEA Solution

N-hydroxyethylpyridinium trifluoromethanesulfonate ([eOHpy][OTf]) and 2-phenylethyl alcohol (PEA) share similar structural characteristics. This study explored the variations in properties when 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][OTf]) was dissolved in them. Measurements of excess molar volume and viscosity showed that [emim][OTf]-[eOHpy][OTf] mixture exhibited ideal mixing behavior, whereas [emim][OTf]-PEA solution deviate significantly. 1H NMR spectra revealed a reversed chemical shift of hydroxyl groups in two mixtures, attributed to the presence of different hydrogen bond acceptors. In [emim][OTf]-PEA solution, competition between anions and hydroxyl groups as acceptors led to varying proportions of hydrogen bonds with solution concentrations. Conversely, in [emim][OTf]-[eOHpy][OTf] mixtures, hydrogen bonds mainly occurred between hydroxyl groups and anions, with minimal hydrogen bonds between hydroxyl groups. Molecular dynamics simulations demonstrated negligible changes in the solvation shell structure of ions in [emim][OTf]-[eOHpy][OTf] mixture but significant alterations in [emim][OTf]-PEA solution.

Positive Potential Pretreatment of TiO2 Photoanode Towards Efficient Charge Separation

Low charge separation efficiency (ηsep) of TiO2 impedes its applications of photoelectrochemical (PEC) water splitting. A positive potential pretreatment approach has been developed to construct a surface polarization with −OH groups at a potential of 1.48 VRHE. When the pretreatment time of 6h is used, the ηsep and photocurrent density (Jph) reach up to 54% (vs. 24%, TiO2) and 0.92mAcm−2 (vs. 0.32mAcm−2, TiO2) under AM 1.5G illumination, respectively. The photovoltage can be increased from 0.17V to 0.52V. When the pretreatment time is extended to 22h, a higher Jph of 1.57mAcm−2 and ηsep of 87% can be obtained. Furthermore, the positive potential pretreated TiO2 possesses excellent PEC stability. The PEC improvements can be attributed to the surface polarization with the −OH groups and favorable surface states of Ti-OH, but not to the formation of Ti3+ or oxygen vacancies.

P(MMA-co-MAA)/cellulose nanofibers composites: Effect of hydrogen bonds on molecular mobility

Cellulose nanofibers (CNFs) nanocomposites were prepared using poly(methylmethacrylate-co-methacrylic acid) (PMMA-co-MAA) to investigate the macromolecular mobility within the composite, with particular focus on the effect of H-bonding. Dynamic mechanical analysis (DMA) and broadband dielectric spectroscopy (BDS) were used to fully characterize the molecular mobility for which the effect of the introduction of H-bond forming moieties and the addition of CNFs (5 and 15 wt%) were assessed. Despite similar Tg values (determined by Differential Scanning Calorimetry), a deeper analysis of the relaxation times associated with the α-relaxation evidenced a significant effect induced by CNFs, which is in fact slowing down the macromolecular relaxation processes. The activation energy of the β-relaxation remained unchanged despite the introduction of MAA units in the main chain and the successive addition of CNFs. However, the latter led to the appearance at low frequencies of a new β’-relaxation correlated with the interactions between the CNF surface -OH groups and the -COOH groups of the matrix. The γ-relaxation showed a 45 % increase in activation energy from PMMA to PMMA-co-MAA + CNF nanocomposites regardless of the CNF content, due to the possibility of CNFs to interact and hinder the motion of the main chain methyl groups in α position.

Influence of hydroxyl group density in propane alcohols-based deep eutectic solvents: Physicochemical properties and potential application as an extraction medium for bioactive compounds

Deep eutectic solvents (DES) composed of citric acid monohydrate (CAM) as hydrogen bond acceptor (HBA) and alcohol as hydrogen bond donor (HBD) were used for separating bioactive compounds from star anise. This study prepared three propane alcohols-based DES with different hydroxyl (OH) group densities in HBD. FTIR analysis verified the presence of hydrogen bond interactions between HBA and HBD, which strengthened with increasing the OH group densities. Increasing the OH group density in DES exhibited lower water content, but higher thermal stability, higher density, higher viscosity as well as enhanced the water absorption rate. All of the propane alcohols-based DES were miscible in high and semi-polar solvents as well as it also displayed frequency independence characteristics. Moreover, propane alcohols-based DES efficiently extracted bioactive compounds from star anise with high total phenolic and flavonoid contents more than traditional solvents. High bioactive phenolic and flavonoid contents in star anise extracts were the major contributors to potent antioxidant activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH, 84.50 %), azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS, 85.73 %), and ferric ion reducing antioxidant power (FRAP, 3.74 mM FeSO4). Therefore, DES was suggested to be a promising extraction medium for valuable bioactive compounds from natural sources that could be utilized as therapeutic agent for oxidative stress.

Effect of surface hydroxyl group density of support membrane on water permeance of polyamide thin-film composite membrane

Polyamide-based thin-film composite (TFC) membranes are widely used in water treatment processes. Recently, the influence of support membranes on the performance of polyamide layers has garnered considerable attention. Regarding the chemical properties of the support membranes, the surface wettability and the interaction between the amine monomer used for interfacial polymerization and the membrane surface are considered to play crucial roles. In this study, we investigated the effect of the wettability of the support membrane surface and its interaction with the amine monomer on the water permeance of TFC membranes. We prepared TFC membranes on polyketone support membranes with varying surface hydroxyl group densities and aqueous solution wettabilities. While no clear correlation was observed between the support membrane’s wettability and the water permeance of the TFC membrane, an increase in hydroxyl group density did result in higher water permeance. The hydroxyl groups interact with PIP, inhibiting PIP diffusion and potentially leading to the formation of a thinner polyamide layer, which enhances water permeance. Therefore, the interaction between the amine monomer and support membrane surface strongly affects the formation of the polyamide layer.

Green plastics: Direct production from grocery wastes to bioplastics and structural characterization by using synchrotron FTIR

Lignocellulosic bioplastics were produced using four different green wastes: hemp, parsley stem, pineapple leaves and walnut shell. Two different solutions were used to dissolve the green wastes: trifluoroacetic acid (TFA) and pure water. The changes in their natural structures and the solvent effect during the regeneration in biofilm formation were investigated by using Synchrotron FTIR Microspectroscopy (SR-µFTIR). The presence of cellulose, hemicellulose and lignin components in the water-based biofilms was confirmed. After dissolving in TFA, the spectra demonstrated some additional bands especially in the hemicellulose region. This is due to the hydrolysis of ester bonds and conversion to carboxylic acids. Principal component analysis showed grouping due to different solvents and polymer addition. Hemp-PVA (Polyvinyl Alcohol) composite biofilms were obtained by adding polyvinyl alcohol to the hemp solution to give extra strength to the hemp biofilms. It has been shown that water-based hemp-PVA biofilms do not cause any significant spectral changes, comparing with pure hemp and PVA spectra. However, after dissolving in TFA, unlike water-based biofilms, it appears that TFA molecules are retained by PVA through hydrogen bonds of TFA’s carboxylic acid and hydroxyl groups and distinct spectral regions belong to TFA bands are clearly identified.

Molecular dynamic simulation on comprehensive performance of ferrocene-based burning rate catalysts in a solid propellent

To determine the compatibility and interaction between ferrocene (Fc) and other components in AP/HTPB/Fc-based BRCs propellant, molecular dynamics simulation (MD simulation) method was used to study the binding energy, cohesive energy density (CED), mean square displacement (MSD) and mechanical properties of mononuclear ferrocene (ethyl ferrocene, butyl ferrocene and octyl ferrocene), binuclear ferrocene (2,2-(ethyl ferrocene) propane, 2,2, -bis-(butylferrocene) propane and hydroxymethyl bis-ferrocenyl propane), ionic ferrocene (three ionic ferrocenes with ferrocene methyl dimethyl ammonium as cation, perchlorate, nitrate and picrate as anions respectively) and cyclic ferrocene (1- ferrocenyl methyl -2- ferrocenyl -3- methylbenzimidazolium, binuclear ferrocene bridged by bridged biphenylferrocene and dihydropyrazole).The binding energy results show that alkyl groups, polar groups (such as hydroxyl groups) and cyclic substituents can improve the interaction between Fc and AP/HTPB. Moreover, the electrostatic interaction between ionic ferrocene and AP is strong, but the van der Waals interaction between ionic ferrocene and HTPB is weak. The CED data show that the mixed models based on alkyl mononuclear ferrocene, catocene, cyclic ferrocene and ionic ferrocene all have high cohesive energy with good safety performance. The MSD results show that the order of anti-migration ability is cyclic ferrocene > binuclear alkyl ferrocene > mononuclear alkyl ferrocene > binuclear hydroxyl ferrocene > ionic ferrocene. Regarding to the value of mechanical parameters (K, G, E and K/G), the mixed model of AP/HTPB/ dihydropyrazole bridged binuclear ferrocene possess the best mechanical properties among the 12 models. Based on the comprehensive data, we conclude that dihydropyrazole bridged binuclear ferrocene is the most ideal ferrocene-based burning rate catalyst among 12 ferrocenes.

Facile generation of unsaturated-coordinated and atomically-dispersed hafnium active sites for the highly efficient catalytic transfer hydrogenation of levulinic acid

The sluggish kinetic of the hydrogen transfer reaction pose a significant challenge in developing efficient catalytic transfer hydrogenation (CTH) system for upgrading biomass-derived platform molecules. In this contribution, for the first time, hafnium (Hf) species have been found to coordinate with the hydroxyl groups on halloysite nanotubes surface to construct a single-atom Hf catalyst (Hf@HNTs) with unsaturated-coordinated structure at room temperature. Especially, the Hf(1.7)@HNTs delivered an impressive catalytic performance for the CTH of levulinic acid (LvA) to gamma-valerolactone (GVL) with high turn-over frequency (TOF) of 43.1 h−1 at 160 °C, considerably exceeding that of coordination-saturated HfO2 and state-of-art Hf-based catalysts. Experimental and density functional theory (DFT) studies revealed that Hf(1.7)@HNTs possessed unsaturated-coordinated and atomically-dispersed Hf-O Lewis acid-base pairs, which favored the adsorption and activation of LvA. Moreover, DFT calculations explicitly demonstrated that the energy barriers for the hydrogen transfer between the LvA and hydrogen donor were significantly reduced on the Hf(1.7)@HNTs than that of HfO2.