Changes In Chemical Structure Research Articles

Puncture Resistance and UV aging of Nanoparticle-Loaded Waterborne Polyurethane-Coated Polyester Textiles.

The goal of this research was to investigate the effect of different types of nanoparticles on the UV weathering resistance of polyurethane (PU) treatment in polyester-based fabrics. In this regard, zinc oxide nanoparticles (ZnO), hydrophilic silica nanoparticles (SiO2 (200)), hydrophobic silica nanoparticles (SiO2 (R812)), and carbon nanotubes (CNT) were mixed into a waterborne polyurethane dispersion and impregnated into textile samples. The puncturing resistance of the developed specimens was examined before and after UV-accelerated aging. The changes in chemical structure and surface appearance in nanoparticle-containing systems and after UV treatments were documented using microscopic pictures and infrared spectroscopy (in attenuated total reflectance mode). Polyurethane impregnation significantly enhanced the puncturing strength of the neat fabric and reduced the textile's ability to be deformed. However, after UV aging, mechanical performance was reduced both in the neat and PU-impregnated specimens. After UV treatment, the average puncture strength of all nanoparticle-containing systems was always greater than that of aged fabrics impregnated with PU alone. In all cases, infrared spectroscopy revealed some slight differences in the absorbance intensity of characteristic peaks for polyurethane polymer in specimens before and after UV rays, which could be related to probable degradation effects.

Comparison of cell response to chromatin and DNA damage.

DNA-targeting drugs are widely used for anti-cancer treatment. Many of these drugs cause different types of DNA damage, i.e. alterations in the chemical structure of DNA molecule. However, molecules binding to DNA may also interfere with DNA packing into chromatin. Interestingly, some molecules do not cause any changes in DNA chemical structure but interfere with DNA binding to histones and nucleosome wrapping. This results in histone loss from chromatin and destabilization of nucleosomes, a phenomenon that we call chromatin damage. Although the cellular response to DNA damage is well-studied, the consequences of chromatin damage are not. Moreover, many drugs used to study DNA damage also cause chromatin damage, therefore there is no clarity on which effects are caused by DNA or chromatin damage. In this study, we aimed to clarify this issue. We treated normal and tumor cells with bleomycin, nuclease mimicking drug which cut predominantly nucleosome-free DNA and therefore causes DNA damage in the form of DNA breaks, and CBL0137, which causes chromatin damage without direct DNA damage. We describe similarities and differences between the consequences of DNA and chromatin damage. Both agents were more toxic for tumor than normal cells, but while DNA damage causes senescence in both normal and tumor cells, chromatin damage does not. Both agents activated p53, but chromatin damage leads to the accumulation of higher levels of unmodified p53, which transcriptional activity was similar to or lower than that of p53 activated by DNA damage. Most importantly, we found that while transcriptional changes caused by DNA damage are limited by p53-dependent activation of a small number of p53 targets, chromatin damage activated many folds more genes in p53 independent manner.

Identification of Cutinolytic Esterase from Microplastic-Associated Microbiota Using Functional Metagenomics and Its Plastic Degrading Potential.

Plastic pollution has threatened biodiversity and human health by shrinking habitats, reducing food quality, and limiting the activities of organisms. Therefore, global interest in discovering novel enzymes capable of degrading plastics has increased considerably. Within this context, the functional metagenomic approach, which allows for unlocking the functional potential of uncultivable microbial biodiversity, was used to discover a plastic-degrading enzyme. First, metagenomic libraries derived from microplastic-associated microbiota were screened for esterases capable of degrading both tributyrin and polycaprolactone. Clone KAD01 produced esterase highly active against p-nitrophenyl esters (C2-C16). The gene corresponding to the enzyme activity showed moderate identity (≤ 55.94%) to any known esterases/cutinases. The gene was extracellularly expressed with a 6× histidine tag in E. coli BL21(DE3), extracellularly. Titer of the enzyme (CEstKAD01) was raised from 21.32 to 35.17U/mL by the statistical optimization of expression conditions and media components. CEstKAD01 was most active at pH 7.0 and 30°C. It was noteworthy stable over a wide pH (6.0-10.0) and temperature (20-50°C). The enzyme was active and stable in elevated NaCl concentrations up to 12% (w/v). Pre-incubation of CEstKAD01 with Mg2+, Mn2+, and Ca2+ increased the enzyme activity. CEstKAD01 displayed an excellent tolerance against various chemicals and solvents. It was determined that 1mg of the enzyme caused the release of 5.39 ± 0.18mM fatty acids from 1g apple cutin in 120min. Km and Vmax values of CEstKAD01 against p-nitrophenyl butyrate were calculated to be 1.48mM and 20.37µmol/min, respectively. The enzyme caused 6.94 ± 0.55, 8.71 ± 0.56, 7.47 ± 0.47, and 9.22 ± 0.18% of weight loss in polystyrene, high-density polyethylene, low-density polyethylene, and polyvinyl chloride after 30-day incubation. The scanning electron microscopy (SEM) analysis indicated the formation of holes and pits on the plastic surfaces supporting the degradation. In addition, the change in chemical structure in plastics treated with the enzyme was determined by Fourier Transform Infrared Spectroscopy (FTIR) analysis. Finally, the degradation products were found to have no genotoxic potential. To our knowledge, no cutinolytic esterase with the potential to degrade polystyrene (PS), high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polyvinyl chloride (PVC) has been identified from metagenomes derived from microplastic-associated microbiota.

Using non-destructive evaluation to monitor the influence of processing parameters on the curing process of thermoset polymers

The processing parameters used to manufacture thermoset polymers highly impact their curing process and final properties. However, these parameters, including stoichiometry and temperature, are difficult to monitor and control. This work presents a novel method to non-destructively evaluate in real-time the curing kinetics, mechanical properties, and chemical structure of an epoxy resin due to variations in the processing parameters using ultrasonics and Fourier transform infrared spectroscopy (FTIR). Samples with a different curing agent to epoxy ratio and varying curing temperatures were manufactured and tested. Changes in chemical structure and longitudinal sound speeds were monitored during the resin’s curing process, showing variations in the cure kinetics and final mechanical properties as a function of the processing parameters. The influence of these parameters on the glass transition temperature and thermal decomposition of the epoxy was also determined. Using ultrasonics and FTIR has the potential to non-destructively aid in the tailoring of polymeric materials by performing in-situ monitoring during their curing process. This method can also be implemented as quality control in both an in-field and manufacturing setting.

Insights into the carbonization mechanism of bituminous coal-derived carbon materials for lithium-ion and sodium-ion batteries

Despite recent interest in the low-temperature carbonization of coal to prepare disordered carbon materials for the anodes of lithium-ion (LIBs) and sodium-ion batteries (SIBs), the carbonization mechanism is still poorly understood. We selected bituminous coal as the raw material and investigated the chemical, microcrystal, and pore structure changes during the carbonization process from coal to the resulting disordered carbon. These structural changes with temperature below 1 000 °C show an increase in both interlayer spacing (3.69–3.82 Å) and defect concentration (1.26–1.90), accompanied by the generation of a large amount of nano-microporous materials. These changes are attributed to the migration of the local carbon layer and the release of small molecules. Furthermore, a decrease in interlayer spacing and defect concentration occurs between1 000 °C and 1 600 °C. In LIBs, samples carbonized at 1 000 °C showed the best electrochemical performance, with a reversible capacity of 384 mAh g−1 at 0.1 C and excellent rate performance, maintaining 170 mAh g−1 at 5 C. In SIBs, samples carbonized at 1 200 °C had a reversible capacity of 270.1 mAh g−1 at 0.1 C and a high initial Coulombic efficiency of 86.8%. This study offers theoretical support for refining the preparation of carbon materials derived from coal.

Co-Effects of Nitrogen Fertilizer and Straw-Decomposing Microbial Inoculant on Decomposition and Transformation of Field Composted Wheat Straw.

Although straw is an abundant and useful agricultural byproduct, it, however, exhibits hardly any decomposition and transformation. Despite the successful application of chemical and biological substrates for accelerating straw decomposition, the co-effects and mechanisms involved are still unknown. Herein, we performed a 120 day field trial to examine the co-effects of a nitrogen fertilizer (N) and a straw-decomposing microbial inoculant (SDMI) on the straw mass, nutrient release, and the straw chemical structure of composted wheat straw in the Chaohu Lake area, East China. For this purpose, four treatments were selected with straw: S (straw only), NS (N + straw), MS (SDMI + straw), and NMS (N + SDMI + straw). Our results indicated that NMS caused a higher straw decomposition rate than S, NS, and MS (p < 0.05) after 120 days of composting. The N, P, and K discharge rates in treating with NMS were higher than other the treatments at 120 days. The A/OA ratios of the straw residues were gradually increased during the composting, but the treatment of NMS and MS was lower than the CK at the latter stage. The RDA showed that the decomposition rate, nutrient release, and the chemical structure change in the straw were cumulative, while respiration was strongly correlated with lignin peroxidase, manganese peroxidase, and neutral xylanase. In conclusion, nitrogen fertilizer or straw-decomposing microbial inoculant application can improve the decomposition rate and nutrient release with oxidase activity intensified. However, the co-application of nitrogen fertilizer and a straw-decomposing microbial inoculant promoted straw decomposition and enzyme activity better than a single application and showed a lower decomposition degree, which means more potential for further decomposing after 120 days.

Selected Chemical and Physical Properties of Pine Wood Chips Inoculated with Aspergillus and Penicillium Mold Fungi

Mold fungi representing genera of Penicillium and Aspergillus commonly develop on the surface of freshly harvested wood chips during storage. As a result, they are often considered as low-quality material and intended for incineration. Thus, the aim of the present study was to investigate the effect of wood chips infestation with mold fungi representing genera of Aspergillus and Penicillium on their basic chemical and physical properties, such as: chemical structure (evaluated with FTIR spectroscopy), mass loss and hygroscopicity, after an incubation of 3, 6 and 9 weeks. Based on the visual assessment and ergosterol content analysis, it was found that inoculation of wood chips with molds led to the intense fungal development on their surface. However, as observed in FTIR spectra, the presence of molds caused no changes in wood chemical structure. Furthermore, no mass loss and no significant increase in the hygroscopicity of wood were observed. Therefore, pine wood chips overgrown by studied genera of fungi seem to be a valuable material for various applications.

Methylation and Demethylation of Emerging Contaminants Changed Bioaccumulation and Acute Toxicity in Daphnia magna.

Contaminants of emerging concern (CECs) in the environment undergo various transformations, leading to the formation of transformation products (TPs) with a modified ecological risk potential. Although the environmental significance of TPs is increasingly recognized, there has been relatively little research to understand the influences of such transformations on subsequent ecotoxicological safety. In this study, we used four pairs of CECs and their methylated or demethylated derivatives as examples to characterize changes in bioaccumulation and acute toxicity in Daphnia magna, as a result of methylation or demethylation. The experimental results were further compared to quantitative structure-activity relationship (QSAR) predictions. The methylated counterpart in each pair generally showed greater acute toxicity in D. magna, which was attributed to their increased hydrophobicity. For example, the LC50 values of methylparaben (34.4 ± 4.3 mg L-1) and its demethylated product (225.6 ± 17.3 mg L-1) differed about eightfold in D. magna. The methylated derivative generally exhibited greater bioaccumulation than the demethylated counterpart. For instance, the bioaccumulation of methylated acetaminophen was about 33-fold greater than that of acetaminophen. In silico predictions via QSARs aligned well with the experimental results and suggested an increased persistence of the methylated forms. The study findings underline the consequences of simple changes in chemical structures induced by transformations such as methylation and demethylation and highlight the need to consider TPs to achieve a more holistic understanding of the environmental fate and risks of CECs.

Assessment of the in-situ electrogenerated chloramines damaging polyamide NF membrane during secondary wastewater treatment

Nanofiltration (NF) membrane is susceptible to chlorine damage during secondary wastewater treatment, rendering it critical to investigate the structure changes in polyamide membrane in chlorine-exposed environments. In this work, chlorinated secondary wastewater was pre-treated using an electro-oxidation (EO) process, and then the potential damage to polyamide membranes during the EO-NF process was assessed by the performance of NF90 nanofiltration membrane after exposure to the EO effluent. We observed a 90% reduction in the retention of Ca2+ and Mg2+ by the NF membrane at high concentration of chloramine (i.e., 20 mg/L), which was attributed to the formation of N-chloramides due to the binding of chloramine to the lone electron pair of the polyamide. Compared with the pristine membrane directly exposed to the chloramine-containing EO effluent, the NF membrane deposited with a biofouling layer did not exhibit any changes in chemical structure and compositions, probably because the biofouling layer blocked the chlorination of polyamide. Therefore, the biofouling layer formed by the deposition and development of microorganism on the membrane surface could prolong the lifetime of the polyamide membrane during the treatment of municipal wastewater in the EO-NF system.

Multivariate modelling analysis for prediction of glycidyl esters and 3-monochloropropane-1,2-diol (3-MCPD) formation in periodically heated palm oil

Palm oil is a vegetable oil that is widely used for cooking and deep-frying because of its affordability. However, repeatedly heated palm oil is also prone to oxidation due to its significant content of unsaturated fatty acids and other chemical toxicants such as glycidyl esters and 3-monochloropropane-1,2-diol (3-MCPD). Initially, the physicochemical properties such as colour, viscosity, peroxide, p-anisidine and total oxidation (TOTOX) of periodically heated palm oil were investigated. Chemical profiling and fingerprinting of six different brands of palm cooking oil during heating cycles between 90 and 360 min were conducted using Fourier transform infrared (FTIR) and 1H Nuclear Magnetic Resonance (NMR) metabolomics. In addition, the multivariate analysis was employed to evaluate the 1H NMR spectroscopic pattern of repeatedly heated palm oil with the corresponding physicochemical properties. The FTIR metabolomics showed significant different of the chemical fingerprinting subjected to heating duration, which in agreement with the result of 1H NMR metabolomics. Partial least squares (PLS) model revealed that most of the physicochemical properties of periodically heated palm oil are positively correlated (R2 values of 0.98–0.99) to their spectroscopic pattern. Based on the findings, the color of the oils darkened with increased heating time. The peroxide value (PV), p-anisidine value (p-AnV), and total oxidation (TOTOX) values increased significantly due to degradation of unsaturated compounds and oxidation products formed. We identified targeted metabolites (probable carcinogens) such as 3-monochloropropane-1,2-diol (3-MCPD) and glycidyl ester (GE), indicating the conversion of 3-MCPD to GE in repeatedly heated oils based on PCA and OPLSDA models. Our correlation analysis of NMR and physicochemical properties has shown that the conversion of 3-MCPD to GE was significantly increased from 180 to 360 min cooking time. The combination spectroscopic techniques with physicochemical properties are a reliable and robust methods to evaluate the characteristics, stability and chemical's structure changes of periodically heated palm oil, which may contribute to probable carcinogens development. This study has proven that combination of NMR and physicochemical analysis may predict the formation of the probable carcinogens of heated cooking oil over time which emphasizing the need to avoid certain heating cycles to mitigate formation of probable carcinogens during cooking process.

Comparative study on the microstructure evolution and crystallization behavior of precursor-derived and mechanical alloying derived SiBCN

In this study, the chemical reactions and structural change during the transformation of the precursor into PDCs-SiBCN ceramic were investigated. Besides, the crystallization behaviors of precursor-derived (PDCs-SiBCN) and mechanical alloying derived (MA-SiBCN) SiBCN ceramics at different temperatures (1200–1700 ℃) were compared. Due to different amorphous structures derived from pyrolysis and amorphization processes, the silicon atoms units bonded by sp3 hybridization in PDCs-SiBCN and MA-SiBCN ceramics are SiC4 and SiC(4-x)Nx tetrahedral structure, respectively. Due to the phase separation of SiC(4-x)Nx tetrahedral structure at higher temperatures (>1400 ℃), PDCs-SiBCN ceramic has a higher resistance to crystallization but will suffer obvious carbothermal reduction process of Si3N4 during crystallization. Finally, the crystallization kinetics of SiC in MA-SiBCN ceramic were investigated. The temperature dependence of SiC crystallization in MA-SiBCN ceramic obeys the Arrhenius-type law with different activation energies in the low and high temperature ranges respectively due to the transition of the rate-controlling mechanisms.

Optimization of biogas potential using kinetic models, response surface methodology, and instrumental evidence for biodegradation of tannery fleshings during anaerobic digestion.

The optimization of the batch size experiment was run for a hydraulic retention time of 45 days using proteolytic enzyme pretreatment. The highest amounts of biogas were produced in comparison to conventional BDS (25:75), which is not processed with enzymes, and there was an increase in the biogas generation of 13.9 and 18.57%. The kinetic models show the goodness of fit between 0.993 and 0.998 and the correlation coefficient's value domain was [-1, 1] from a statistical perspective. The Box-Behnken design was carried out using the response surface methodology at different levels of independent parameters to optimize the process. Different instruments were evaluated to determine the chemical structure change and the contamination of the different treatments and the raw sample of tannery fleshings was determined. Thermogravimetric analysis was conducted to determine the loss of weight on thermal degradation. The Fourier transform infrared spectrometry was carried out to determine the different functional groups, such as -OH, -CH, -NH, and C-O, present in the samples of tannery fleshings. Scanning electron microscopy and energy dispersive X-ray analysis were carried out to determine the morphological alterations in the substrate, digestate, enzyme-pretreated fleshings, and the chemical composition of samples.

Photo-Controlled Self-Assembly of Nanoparticles: A Promising Strategy for Development of Novel Structures.

Photo-controlled self-assembly of nanoparticles (NPs) is an advanced and promising approach to address a series of material issues from the molecular level to the nano/micro scale, owing to the fact that light stimulus is typically precise and rapid, and can provide contactless spatial and temporal control. The traditional photo-controlled assembly of NPs is based on photochemical processes through NPs modified by photo-responsive molecules, which are realized through the change in chemical structure under irradiation. Moreover, photoexcitation-induced assembly of NPs is another promising physical strategy, and such a strategy aims to employ molecular conformational change in the excited state (rather than the chemical structure) to drive molecular motion and assembly. The exploration and control of NP assembly through such a photo-controlled strategy can open a new paradigm for scientists to deal with "bottom-up" behaviors and develop unprecedented optoelectronic functional materials.

Biodegradation of LDPE (low density polyethylene) using bacterial strain

The applications of polyethylene are enormous and they are popular because of their relatively low cost, lack of difficulty in manufacture, adaptability and durability. In the past decade, the increase in the utilization of plastics and the accumulation of polyethylene in the environment all around the globe has drawn the attention of environmentalists and scientists. The plastic materials are commonly derived from petrochemicals extracted from coal and natural gas. They are produced in a wide range in synthetic, semi synthetic organic polymers. The degradation of LDPE film was determined by residual dry weight loss of the LDPE films. The potent strain showed 42.5% degradation ability in 90 d. Degradation of LDPE results in the breakdown of the polymer backbone chain producing CO2 which was checked by gravimetric analysis. Enzyme kinetic studies showed the production of three ligninolytic extracellular enzymes- lignin, laccase and manganese peroxidase by bacterial strain AJ01 in LDPE degradation. Degradation of LDPE strips followed first order kinetics model with a rate constant (R2) of 0.9783 d-1. Estimation of protein from post treated LDPE using bacterial isolate showed a total concentration of 0.440mg/0.1mL and 0.703mg/0.2mL. LDPE degradation was confirmed by using analytical techniques such as SEM which showed changes in the surface topology of LDPE strips and FTIR analysis showed changes in complex chemical structure of LDPE post 90 d of degradation using microorganisms thereby reducing carbonyl index (CI) value.

Microfluidic-Assisted Alignment of Graphene Nanosheets for Microfiber Formation

Recently, our lab developed graphene oxide microfibers for ultrasensitive neurochemical detection with fast-scan cyclic voltammetry (FSCV). Graphene-fiber microelectrodes provide a significant advance over traditional carbon-fiber microelectrodes due to their resistance to detrimental fouling, fast electron transfer kinetics, and frequency independent behavior. Despite our recent advancement, there still exists a gap in our understanding of how specific changes in the carbon chemical structure influences adsorption and interaction of various neurochemicals at the surface. Understanding the extent to which the carbon chemical structure influences electrochemical detection is critical for designing tailor-made electrodes for ultrasensitive analyte detection. From a molecular level point-of-view, the graphene sheet consists of two regions with different structure: i) the basal plane, consisting of conjugated sp2 hybridized carbon atoms, and characterized by an atomic flatness and low defect density; and ii) the edge plane, that forms sp3 sites with a high level of defects and a variety of functional groups and dangling bonds. It is generally believed that the electrochemical properties of the basal and edge plane are significantly different, however, there has been debate concerning the electrochemical activity at the basal and edge plane. The conventional consensus is that electron transfer kinetics is faster on the edge plane in comparison with the basal plane sites, while the opposite barrier of this debate provides evidence for fast electron transfer at pristine basal plane. Moreover, how these factors influence neurochemical detection, particularly at rapid scan rates, is still lacking due to the necessity of using microelectrodes with FSCV. To date, most studies analyzing the influence of basal vs. edge plane surfaces on electrochemical detection have used macroelectrodes like highly ordered pyrolytic graphite (HOPG) which are not amenable to FSCV detection due to the large capacitive currents obtained at macroelectrodes at scan rates consisting of hundreds of volts per second. Therefore, to address this existing knowledge gap in understanding how edge vs. basal planes influence subsecond neurochemical detection, the ability to develop microelectrodes with controlled surfaces is crucial. Here, I will discuss our labs latest effort in developing graphene oxide microfibers with controllable nanosheet alignment to study the influence of basal vs. edge plane availability on neurochemical detection at rapid scan rates. To assist in nanosheet alignment, we use microfluidic channels to assist in fluid-driven control of nanosheet orientation. Using microfluidics to help develop highly controllable electrode materials provides a critical advance in our ability to develop novel carbon surfaces for detection.

(Invited) Precise Evaluation of Functional Group Distribution and Reaction Yield for Chemically Treated Carbon Nanohorns by Highly Sensitive SEM-EDS

Single-walled carbon nanohorns (CNHs) have great potential in diverse applications such as catalyst support, energy conversion, and drug carriers. Although chemical functionalization of CNHs is critical for these applications, they inherently form robust spherical “dahlia-like” aggregates, which may inhibit chemical reactivity. Herein, highly sensitive energy-dispersive X-ray spectrometry (EDS) analysis in scanning electron microscopy (SEM) is employed to elucidate the functional group distribution and the reaction yield of CNH dahlia aggregates. First, the technique clearly visualizes the elemental distribution associated with the functional groups on dahlia structures with a sufficient spatial resolution of <10 nm.1 The result exposes that the outer surface of an individual aggregate is functionalized while the inner core remains almost unreacted. Second, the SEM-EDS precisely assesses the reaction yield for functionalized CNHs.2 The sensitive elemental analysis enables the evaluation of functionalization efficiency for sequentially grown polyamidoamine dendrimers on CNH surface, which consistently explains the change of chemical structure according to the reaction process. The details about the functionalization mechanism on CNH surface will be discussed in the conference.[1] H. Nakajima, T. Morimoto, K. Kobashi, M. Zhang, I. K. Sideri, N. Tagmatarchis, and T. Okazaki, Outer-Surface Covalent Functionalization of Carbon Nanohorn Spherical Aggregates Assessed by Highly Spatial-Resolved Energy-Dispersive X-ray Spectrometry in Scanning Electron Microscopy, J. Phys. Chem. C 2020, 124, 25142-25147.[2] H. Nakajima, K. Kobashi, C. Stangel, T. Morimoto, M. Zhang, N. Tagmatarchis, and T. Okazaki, Step-by-step Characterization of a Series of Polyamidoamine Dendrimers on Carbon Nanohorn Surface, submitted.

Releases of microplastics and chemicals from nonwoven polyester fabric-based polyurethane synthetic leather by photoaging

The nonwoven PET fabrics are chemically, mechanically and thermally treated fiber aggregate without weaving, knitting or braiding, which could be used as a base to make polyurethane (PU) synthetic leather through a series of processing. Our research systematically compared the photoaging behaviors of pure non-woven PET base fabric (NPET-P) and PU synthetic leather (nonwoven PET-base fabrics with PU coating, NPET-U), and their possibilities for microplastic fibers (MPFs) generation and chemical transformation in water. NPET-U was photoaged to a higher oxidation degree with higher O/C ratios and more distinct changes in chemical structures. The amount of MPFs released from NPET-U (1.98 × 107 g/fibers) was significantly lower than that from NPET-P (4.76 × 107 g/fibers) after 360 h light irradiation (p value <0.05) with a slower degradation rate and delayed MPFs release. The lengths and diameters of released MPFs from NPET-U varied within a smaller range than that from NPET-P exposed to UV light irradiation. Natural sunlight aging of fabrics for 365 days was found to be equivalent to approximately 85.3–127.2 h UV aging in the laboratory, which indicated the lab accelerated experiments was extraordinarily intense to simulate natural sunlight aging. Furthermore, abundant calcium and sulfur-contained chemicals were detected in original fabrics and the leachate of 360 h light-aged fabrics using the inductively coupled plasma optical emission spectrometer (ICP-OES). The organic components of the leachate were separated according to their molecular weight with the changes of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and the UV response over aging time. UV stimulation aggravated the role of plastic polymers as disinfection by-product (DBP) precursors. Nevertheless, although NPET-U could produce more nitrogen-contained chemicals, it had similar formation potentials of nitrogen-containing DBPs as NPET-P. The discussion lucubrated the potential risks of the production of MPFs and chemical release in the leachate with regard to combined plastic pollution.

Photodegradation of polylactic acid: Characterisation of glassy and melt behaviour as a function of molecular weight

During the COVID-19 pandemic, UV-C germicidal lamps became widely available, even for household applications. However, their long-term degradation effects on the mechanical and rheological properties of polylactic acid (PLA) are still not well established. The relationship between degradation and its effects on the molecular structure and macroscale properties are hardly known. In this study, we investigated the effects of long-term exposure to UV-C irradiation on the properties of PLA and interpreted the results at the molecular scale. We performed gel permeation chromatography, Fourier-transform infrared spectroscopy and UV–Vis spectroscopy to analyse changes in chemical structure induced by the UV-irradiation. Then, we carried out thermal, rheological and tensile tests to investigate mechanical and melting properties, and we investigated the applicability of these test results to estimate molecular weight loss. We have created a 3D irradiation map that can facilitate the design of disinfection devices. Based on our results, we propose a maximum number of sterilisation cycles (13 cycles) for the tested PLA films that do not result in significant changes in tensile strength and modulus.

Upcycling waste phosphogypsum as an alternative filler for asphalt pavement

Mineral fillers are an essential component of asphalt concrete. Significant amounts of mineral fillers are used in constructing asphalt pavement. However, mineral fillers are an important non-renewable natural resource which needs to be preserved. In addition, the production of mineral fillers also consumes much energy and affects environment negatively. This study set out to explore the feasibility of upcycling waste phosphogypsum as an alternative filler for asphalt concrete. The phosphogypsum was first pretreated at 60, 160, and 800 °C, and the crystalline phase of phosphogypsum was evaluated by X-ray diffraction (XRD). Phosphogypsum with three crystalline phases and limestone powder were then mixed with base asphalt binders to prepare asphalt mastic at the filler-asphalt ratio of 1:1 at 150 °C. The chemical structural changes and thermal stability features of phosphogypsum asphalt mastic were analyzed using Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG). The viscoelasticity, high-temperature performance, and fatigue characteristics of different asphalt mastics were measured by frequency sweep, multiple stress creep and recovery (MSCR), and linear amplitude sweep (LAS), respectively. The results indicate that phosphogypsum had different crystalline phases after pretreatment at different temperatures. The addition of phosphogypsum as fillers in asphalt is mainly a physical hardening effect. The 600 °C residual mass ratio of asphalt mastic prepared from phosphogypsum pretreated at 60, 160, and 800 °C was 53.9%, 56.2%, and 58.6%. As the temperature increased, the different crystallized water states in phosphogypsum were decomposed. The replacement of mineral powder with phosphogypsum can improve the high-temperature properties of asphalt mastic and the percent recovery (R), while the nonrecoverable creep compliance (Jnr) was reduced. At the extremely high-temperature of 70 °C, the improvement of the high-temperature performance of phosphogypsum asphalt mastic is more evident than that of 46 °C. Furthermore, the addition of phosphogypsum also reduced the fatigue life of asphalt mastic. This study is expected to paving the road for the upcycling of waste phosphogypsum as an alternative filler in asphalt pavement.

Chemical Storage of Ammonia through Dynamic Structural Transformation of a Hybrid Perovskite Compound.

Toward renewable energy for global leveling, compounds that can store ammonia (NH3), a carbon-free energy carrier of hydrogen, will be of great value. Here, we report an organic-inorganic halide perovskite compound that can chemically store NH3 through dynamic structural transformation. Upon NH3 uptake, a chemical structure change occurs from a one-dimensional columnar structure to a two-dimensional layered structure by addition reaction. NH3 uptake is estimated to be 10.2 mmol g-1 at 1 bar and 25 °C. In addition, NH3 extraction can be performed by a condensation reaction at 50 °C under vacuum. X-ray diffraction analysis reveals that reversible NH3 uptake/extraction originates from a cation/anion exchange reaction. This structural transformation shows the potential to integrate efficient uptake and extraction in a hybrid perovskite compound through chemical reaction. These findings will pave the way for further exploration of dynamic, reversible, and functionally useful compounds for chemical storage of NH3.