CO NH Research Articles

Lignin‐based nitrogen and phosphorus‐containing polylactic acid with flame‐retardant performances

AbstractPolylactic acid (PLA) is a new type of biodegradable material that has been applied in many fields such as extrusion, injection molding, film drawing, and spinning. In contrary, it does not have flame retardancy. In this paper, N‐PCDL was synthesized by amidation reaction between COOH of PCDL and NH2 of tetraethylenepentamine (TEPA), followed by an Atherton‐Todd reaction of unreacted NH2 at the other end of TEPA with PH of DOPO to prepare a novel lignin‐based flame retardant containing nitrogen and phosphorus (NP‐PCDL). The Fourier transform infrared spectroscopy (FT‐IR) and nuclear magnetic hydrogen spectroscopy (1H NMR) analysis results showed that proton peaks of CONH, PN, and NH appeared in the NP‐PCDL spectrum, while the characteristic absorption peak of PH bond disappeared in DOPO, the X‐ray photoelectron spectroscopy (XPS) results showed that the degraded lignin consisted of elements C and O, while NP‐PCDL consisted of elements C, O, N and P. The above results indicated that NP‐PCDL was successfully prepared. NP‐PCDL accounted for 3% (mass percentage, the same below), 5% and 10% of PLA, then lignin based flame‐retardant PLA composites were prepared by internal mixing and injection molding. Thermogravimetric analysis (TGA) showed that the residual carbon of PLA/3% NP‐PCDL, PLA/5% NP‐PCDL and PLA/10% NP‐PCDL at 800°C were higher than that of pure PLA, with the increase of 56.56%, 97.54%, and 301.64%, respectively; The analysis of SEM, XPS, and Raman showed that PLA/NP‐PCDL formed dense, regular and highly graphitized residual carbon with phosphorus nitrogen structure during the combustion process. At the same time, NH3, H2O and PO˙ free radicals were released, which could dilute combustible gases, destroy free radical chain reaction, isolate combustible gases and heat, so as to play a flame‐retardant role.

Study on the pyrolysis characteristics, kinetics, thermodynamics, volatile products, and chemical reactions of micron polyamide waste, a typical marine plastic microfragment

AbstractThe pollution of waste plastic microfragments to the marine ecosystems is an increasingly serious problem. Pyrolysis is widely recognized as a viable technique for the treatment of such plastic waste materials. The pyrolysis behaviors, characteristic parameters, kinetics, thermodynamics, volatiles, and possible chemical reactions during the pyrolysis of micron polyamide waste (the main component of fishing gear abandoned in the marine environment) are studied in inert atmosphere in the present work. The results show that the pyrolysis of micron polyamide may be regarded as a one‐step reaction. The peak and average reaction rates decrease significantly when the heating rate increases. The calculated kinetic parameters can effectively predict the pyrolysis behaviors of micron polyamide. The pyrolysis of micron polyamide is characterized as an endothermic reaction that occurs non‐spontaneously. Furthermore, the information of volatiles was obtained. The volatiles with higher content were –CH2 groups, CO2, and lactam, and the volatiles with smaller content were: –NH groups, NH3, HCN, H2O, CO, and amide derivatives. In addition, an analysis was conducted to explore the potential chemical reactions.Highlights The pyrolysis of micron polyamide can be considered as a one‐step reaction. The obtained kinetic parameters can well predict the pyrolysis process. Pyrolysis of micron polyamide is a non‐spontaneous and endothermic reaction. Specific volatile products are determined by Fourier transform infrared and mass spectrometry. The chemical reactions that may occur during the pyrolysis have been inferred.

Comparison between [68Ga]Ga-PSMA-617 and [18F]FET PET as Imaging Biomarkers in Adult Recurrent Glioblastoma.

The aim of this prospective clinical study was to evaluate the potential of the prostate specific membrane antigen (PSMA) targeting ligand, [68Ga]-PSMA-Glu-NH-CO-NH-Lys-2-naphthyl-L-Ala-cyclohexane-DOTA ([68Ga]Ga-PSMA-617) as a positron emission tomography (PET) imaging biomarker in recurrent glioblastoma patients. Patients underwent [68Ga]Ga-PSMA-617 and O-(2-[18F]-fluoroethyl)-L-tyrosine ([18F]FET) PET scans on two separate days. [68Ga]Ga-PSMA-617 tumour selectivity was assessed by comparing tumour volume delineation and by assessing the intra-patient correlation between tumour uptake on [68Ga]Ga-PSMA-617 and [18F]FET PET images. [68Ga]Ga-PSMA-617 tumour specificity was evaluated by comparing its tumour-to-brain ratio (TBR) with [18F]FET TBR and its tumour volume with the magnetic resonance imaging (MRI) contrast-enhancing (CE) tumour volume. Ten patients were recruited in this study. [68Ga]Ga-PSMA-617-avid tumour volume was larger than the [18F]FET tumour volume (p = 0.063). There was a positive intra-patient correlation (median Pearson r = 0.51; p < 0.0001) between [68Ga]Ga-PSMA-617 and [18F]FET in the tumour volume. [68Ga]Ga-PSMA-617 had significantly higher TBR (p = 0.002) than [18F]FET. The [68Ga]Ga-PSMA-617-avid tumour volume was larger than the CE tumour volume (p = 0.0039). Overall, accumulation of [68Ga]-Ga-PSMA-617 beyond [18F]FET-avid tumour regions suggests the presence of neoangiogenesis in tumour regions that are not overly metabolically active yet. Higher tumour specificity suggests that [68Ga]-Ga-PSMA-617 could be a better imaging biomarker for recurrent tumour delineation and secondary treatment planning than [18F]FET and CE MRI.

Actionable insights into hazard mitigation of typical 3D printing waste via pyrolysis

3D printing waste (3DPW) contains hazardous substances, such as photosensitizers and pigments, and may cause environmental pollution when improperly disposed of. Pyrolysis treatment can reduce hazards and turn waste into useful resources. This study coupled thermogravimetric (TG), TG-Fourier transform infrared spectroscopy-gas chromatography/mass spectrometry, and rapid pyrolysis gas chromatography/mass spectrometry analysis to evaluate the pyrolytic reaction mechanisms, products, and possible decomposition pathways of the three typical 3DPW of photosensitive resin waste (PRW), polyamide waste (PAW), and polycaprolactone waste (PCLW). The main degradation stages of the typical 3DPW occurred at 320–580 °C. The most appropriate reaction mechanisms of PRW, PAW and PCLW were D1, A1.2 and A1.5, respectively. The main pyrolysis processes were the decomposition of the complex organic polymers of PRW, the breaking of the NH–CH2 bond and dehydration of –CO–NH– of PAW, and the breaking and reorganization of the molecular chains of PCLW, mainly resulting in toluene (C7H8), undecylenitrile (C11H21N), tetrahydrofuran (C4H8O), respectively. Unlike the slow pyrolysis, the rapid pyrolysis produced volatiles consisting mainly of phenol, 4,4'-(1-methylethylidene)bis- (C15H16O2) for PRW; 1,10-dicyanodecane (C12H20N2) for PAW; and ɛ-caprolactone (C6H10O2) for PCLW. These pyrolysis products hold great potential for applications. The findings of the study offer actionable insights into the hazard reduction and resource recovery of 3D printing waste.

The enhancement of mechanical, physical, and thermal properties of modified asphalt mixture with lignin from mahogany sawdust in the presence of diphenylmethane 4,4′-diisocyanate

The road infrastructure condition, which can be easily damaged by the occurrence of potholes due to the weak adhesion between asphalt and aggregate, disrupts economic activity and requires high maintenance costs. This problem needs to be overcome by adding adhesive to modify the asphalt. Lignin is a sustainable biopolymer that can serve as a natural asphalt binder. Lignin isolated from mahogany sawdust combined with diphenylmethane 4,4′-diisocyanate has never been used to modify asphalt mixtures. This modification can improve the properties of the asphalt mixture, which is very important in road pavement engineering. This study aims to modify asphalt mixtures with lignin isolated from mahogany sawdust combined with diphenylmethane 4,4′-diisocyanate and investigate their physical, mechanical, and thermal characteristics. The isolated lignin was prepared for a modified asphalt mixture by reacting with diphenylmethane 4,4-diisocyanate and adding asphalt. Next, the asphalt mixture was mixed with sand aggregate in an extruder at 150 °C. The results showed an improvement in mechanical, physical, and thermal properties. The optimum composition of asphalt and lignin was 60:40 with a compressive strength value of 3.107 MPa, a water absorption value of 0.246%, and a melting point of 238 °C. The Fourier-transform infrared spectroscopy (FT-IR) spectrum showed a small band at 1715 cm−1, indicating the CO carbonyl group of the NH–CO–O urethane bond. The morphology showed that the surface structure of the modified asphalt mixture becomes more homogeneous due to the interaction between asphalt and polyurethane, which is the result of the reaction of lignin isolate with diphenylmethane 4,4′-diisocyanate.

Random and block architectures of N-arylitaconimide monomers with methyl methacrylate

Abstract “Itaconimide” is the members of imide (–CO–NH–CO–) family with reactive exocyclic double bond and it is easily obtained from the renewable resource i.e. D-glucose. The polymerization of various N-arylitaconimide (NAI) monomers with methyl methacrylate (MMA) have been reported to improve the glass transition temperature (T g) and thermal stability of poly(methyl methacrylate) (PMMA). In literature, these studies have been done mostly using conventional free radical polymerization methods, which restricts the architecture of copolymers to “random” only. The block copolymers of NAI and MMA are an important due to the combination of glassy PMMA and thermally stable poly(NAI), which offers its applications for higher temperature service. The architectural control of polymers in provisions of its topology, composition, and various functionalities is possibly obtained using reversible-deactivation radical polymerizations (RDRPs). In RDRPs, the concentration of free radical is controlled in such a way that the termination reactions are minimized (normally in range of 1–10 mol%), and not allowed to obstruct with the desired architecture. However, this is possible by achieving (or by establishing) a rapid dynamic equilibrium between propagating radical and dormant species (i.e. R–X). Among all RDRPs, the atom transfer radical polymerization (ATRP) is very popular and adaptable method for the synthesis of polymers with specifically controlled architecture. Two different architectures of NAI and MMA copolymers are reported using ATRP process. The effect of various pedant groups on the rate constants of propagation (k p) and thermal properties NAI and MMA copolymers is studied. The poly(NAI-ran-MMA)-b-poly(MMA) are stable up to 200 °C and degraded in three steps. Whereas, the poly(NAI-ran-MMA)-b-poly(NAI) are stable up to 330 °C and degraded in two steps. The density functional theory methods are used for calculation of equilibrium constants (K ATRP) for the ATRP process for the series of laboratory synthesized alkyl halides. A good agreement was observed between the experimentally determined and theoretically calculated K ATRP values. The mechanistic studies are carried for poly(NAI-ran-MMA) copolymer system using statistical model discrimination method along with 1H decoupled 13C NMR spectroscopy. For studying the mechanism of copolymerization of NAI and MMA via ATRP methods, “trimer model or penultimate model” will be more accurate than “dimer model or terminal model”.

Specific discrimination of zinc and manganese ions by label free dual emissive carbon dots by ratio-metric mode

Due to the worldwide ecological and environmental issues induced by heavy metal pollution, including zinc and manganese, the ratio-metric discrimination of Zn2+ and Mn2+ based on CDs is urgently required. In this work, reduced CDs (re-CDs) with the intrinsic dual emissive peaks are obtained, and specific discrimination of Zn2+ and Mn2+ is realized by re-CDs with ratio-metric mode. With the addition of Zn2+, the fluorescent (FL) intensity at 650 nm increases obviously, while that at 680 nm progressively decreases. However, the presence of Mn2+ would induce the quenching of FL intensity at 680 nm while that at 650 nm remains constant. Then the Zn2+ and Mn2+ can be separately determined with the ratio of FL intensity at 650 nm to that at 680 mm (F650/F680). Under optimal conditions, the limit of detection (LOD) of Zn2+ is determined to be 9.09 nmol/L, and that for Mn2+ is estimated to be 0.93 nmol/L, which is much lower than previously reported work and standard level of Zn2+ and Mn2+ permitted in drinking water by WHO. Moreover, the specific recognition of Mn2+ and Zn2+ can be realized via the addition of different masking agents (ethylenediamine for Zn2+ and triethanolamine for Mn2+). Furthermore, our results reveal that the structural changes from –NH–CO to –NC–OH induced by Zn2+ contribute to the shift of FL peak from 680 to 650 nm while both static and dynamic quenching processes are involved in the detection of Mn2+. The ratio-metric probe was successfully applied to Zn2+ and Mn2+ determination in human serum samples and Sandy Lake water.

Electrospun Environment‐Friendly Poly (L‐Lactic Acid)/CO2‐Based Polyurea Nanofiber Film for Piezoelectric Sensor

AbstractDeveloping piezoelectric polymers which have environmental‐friendly raw material resources and can be used for wearable electronic devices, are of great significance for reducing dependence on fossil energy and achieving the goal of carbon neutrality. Poly (L‐lactic acid) (PLLA) is a bio‐based piezoelectric polymer and has important research value. To optimize the properties of materials, electrospinning technology is used for preparing nanofiber films by combining PLLA with CO2‐based polyurea (PU) synthesized from CO2 and diamine, and assembling the piezoelectric sensors. The results show that when the amount of PU is 16 wt%, the voltage of the PU/PLLA piezoelectric sensor is 19 V, which is 15 times that of the PLLA piezoelectric sensor and has good stability and durability. The high dipole moment of NHCONH in PU and the synergistic effect between PU and PLLA are the keys to improving the piezoelectric property of nanofiber film. This is the first report on the preparation of composite piezoelectric materials using CO2‐based polymer and PLLA. PU/PLLA piezoelectric sensor can produce a good piezoelectric response to human vital signs and motion states. As a self‐powered sensor, it has potential application in the field of intelligent wearable devices.

Acylhydrazones and Their Biological Activity: A Review.

Due to the structure of acylhydrazones both by the pharmacophore -CO-NH-N= group and by the different substituents present in the molecules of compounds of this class, various pharmacological activities were reported, including antitumor, antimicrobial, antiviral, antiparasitic, anti-inflammatory, immunomodulatory, antiedematous, antiglaucomatous, antidiabetic, antioxidant, and actions on the central nervous system and on the cardiovascular system. This fragment is found in the structure of several drugs used in the therapy of some diseases that are at the top of public health problems, like microbial infections and cardiovascular diseases. Moreover, the acylhydrazone moiety is present in the structure of some compounds with possible applications in the treatment of other different pathologies, such as schizophrenia, Parkinson's disease, Alzheimer's disease, and Huntington's disease. Considering these aspects, we consider that a study of the literature data regarding the structural and biological properties of these compounds is useful.

A novel chitosan-biochar immobilized microorganism strategy to enhance bioremediation of crude oil in soil

The chitosan-biochar composite is a clean and environmentally friendly immobilized microorganisms carrier. In this study, the chitosan-biochar composite as a carrier to immobilize a compound microbial agent contained Pseudomonas aeruginosa and Bacillus licheniformis, and investigated its role in the remediation of oil-contaminated soil. When using 1% (v/v) acetic acid, 3% (m/v) chitosan solution, 0.1% biochar, 4% (v/v) NaOH solution, freeze-drying 6 h, the optimal chitosan-biochar composite material could be obtained. The specific surfacearea of the material increased to 1.725 m2/g and the average pore size also increased from 130.2260 nm to 165.2980 nm after the addition of biochar through the analysis of specific surface area and pore size, which enlarged the contact area of microorganisms and crude oil with the material. SEM showed that the bacterial successfully adhered to the surface and internal of the material. Using FTIR, the results showed that the synthesis of composite carrier material was the covalent combination of –NH2 on chitosan and –COOH on biochar, forming a new chemical bond –NH–CO-. After 60 days of remediation of oil-contaminated soil, the removal rate of crude oil by chitosan-biochar composite immobilized microorganism method was 45.82%, which was 21.26% higher than that of natural remediation. Simultaneously, several oil-degrading bacteria increased at genus level, including Nocardioides (26.79%–33.09%), Bacillus (3.01%–4.10%), Dietzia (1.84%–5.56%), Pseudomonas (0–0.78%), among which Pseudomonas belongs to exogenous bacteria. The results indicated that the chitosan-biochar composite material has high application value in removing crude oil, and further provides a new strategy for bioremediation of oil-contaminated soil.

Effect of hapten structures on development of novel antibody against capsaicin and dihydrocapsaicin

• Three novel capsaicinoids haptens were synthesized, and the antibody-eliciting properties of four hapten-protein conjugations were investigated. • Novel polyclonal antibodies against capsaicinoids were prepared, and the important role of molecular structure and electrostatic potential in producing specific antibodies was verified. • A competitive indirect ELISA (icELISA) was established for capsaicinoids detection in spicy foods. Capsaicinoids content as a basis for the evaluation of spicy taste has attracted much attention. Antibody, as an important component of immunoassay, plays an important role in the detection of capsaicinoids levels. The molecular structure of the hapten is the key factor affecting the quality of small molecule antibodies. In our study, six capsaicinoids haptens were selected with different junction arm of length and structure to analyzed immune effect by geometric structure and electrostatic potential (ESP). Among them, three haptens were capsaicinoids structural analogues, and others were designed and synthesized. The results showed that the retention of amide bond (–NH–CO–) and hydroxyl group in the benzene ring of capsaicinoids hapten as well as rigid spacer arm that linked proteins to hapten had a positive effect on the affinity of the antibody. It provided a theoretical basis for rapid screening of small molecular substance haptens. To test our hypothesis, four kinds of haptens were used to synthesize antigens and immunize animals. Comparing 28 antiserum/coating conjugates combinations tested by indirect competitive enzyme-linked immunosorbent assay (icELISA) method for capsaicinoids (i.e., capsaicin and dihydrocapsaicin), the homologous combination of Pa-B2/OVA-hapten B had been shown to be most suitable for the determination of capsaicin and dihydrocapsaicin, which was consistent with the ESP analysis. In short, ESP analysis can speed up haptens screening and reduce the workload while producing high-quality antibodies. Thus, an icELISA based on hapten B polyclonal antibody was developed with IC 50 value of 0.36 μg mL −1 and the limit of detections (LODs) of 20 µg kg −1 in spicy food samples. Moreover, these results were also validated by high performance liquid chromatography (HPLC), and showed good agreements.

Highly transparent and super-wettable nanocoatings hybridized with isocyanate-silane modified surfactant for multifunctional applications

Highly transparent and super-wettable nanocoatings for multifunctional applications with outstanding physical properties are in high demanded. However, such nanocoatings resistant to water invasion and Ultraviolet (UV) weathering remain a significant challenge. In this work, physically durable coatings based on inorganic nanoparticles (NPs) and an organic segment (isocyanate-silane modified surfactant) have been synthesized via a sol-gel approach. It is noteworthy the isocyanate-silane with –NH–CO- functional group creates a strong bonding between the highly hydrophilic surfactant and the inorganic NPs. This in-house synthesized organic segment can render the coating long-lasting wetting properties and resist to be washed away by water, while the inorganic NPs can form sturdy covalent bonds with the nano-scale hierarchical structure on the glazing substrate to improve the durability. This nanocoating demonstrates high transparency with superwetting property (water contact angle, WCA ​= ​4.4 ​± ​0.3°), effective de-frosting performance. Water invasion or UV accelerated weathering tests do not significantly affect the self-cleaning performance of nanocoating. Physical properties, including coating adhesion, hardness, Young's modulus, and abrasion resistance are systematically investigated. Interestingly, this clear coating shows prominent infrared shielding property attributed to Antimony-doped tin oxide (Sb-doped SnO2) NPs. The developed nanocoating process is easy to scale up for larger areas that require multipurpose self-cleaning functions.

Oxalamide-Bridged Ferrocenes: Conformational and Gelation Properties and In Vitro Antitumor Activity

The N-termini of the constitutional isomeric ferrocene peptides Boc–NH–Fn–CO–Ala–OMe (1) and Boc–Ala–NH–Fn–COOMe (2) were deprotected in the acidic milieu and subjected to oxalyl chloride-mediated dimerization to afford the oxalamides −(CO–NH–Fn–CO–Ala–OMe)2 (3) and −(CO–Ala–NH–Fn–COOMe)2 (4), respectively. The goal compounds were evaluated for their conformational properties, toluene gelation ability, and effect on cell viability of tumor (HeLa, MCF7, HepG2) and normal (HEK293T) cell lines. Detailed spectroscopic analysis in solution revealed the different conformational behavior of constitutional isomers 3 and 4, and oxalamide 3 was found to have a higher degree of chiral organization due to its involvement in stronger intramolecular hydrogen bonds. Crystallographic analysis showed the presence of two symmetry-independent conformers of compound 3 stabilized by stronger intramolecular hydrogen bonds. The tested compounds self-assemble in toluene to provide supramolecular nanostructures but were unable to form a stable gel. Interestingly, the formation of a stable gel was observed when the toluene solution of 4 was sonicated. Cytotoxic evaluation of 3 and 4 revealed a weaker growth-inhibitory effect on tumor cell lines compared to cisplatin. Oxalamide 3 appeared to be more cytotoxic to HeLa and MCF7 cancer cell lines than to normal HEK293T cells, indicating its potential for drug development as an anticancer agent.

Improved interfacial shear strength in carbon fiber enhanced semi-aromatic polyamide 6T composite via in-situ polymerization on fiber surface

The interfacial property of carbon fiber (CF) reinforced semi-aromatic poly (hexamethylene terephthalamide) (PA6T) thermoplastic composite has been improved by in-situ polymerization on fiber surface. On that basis, PA6T oligomer was coated upon fiber to form a reactive polymeric layer and modified fiber surface structure. SEM, FTIR and XPS analysis were conducted to investigate its surface status, finding that CF was perfectly wetted and formed a much rougher surface on which large quantity of polar –CO–NH- groups attached. After polymerization under 320 oC for 10 min, this layer could bond tightly around fiber. And TGA results demonstrated that polymerized layer had excellent heat-resistance and possessed an initial decomposition temperature over 400 °C. A microbond test was implemented to accurately evaluated the interfacial shear strength (IFSS), meanwhile, a facile approach of “spraying” was applied to form microdroplets in quantity onto single carbon fiber within a few minutes. It was found that the fiber and the matrix was efficiently bonded and the interaction was efficaciously enhanced by the polymeric layer, thus 20.9% of IFSS and 20.9% of bulk composites’ tensile strength improvement were achieved compared to those without modification. Notably, the in-situ polymerization formed a gradient transition of interfacial modulus and raised the interphase thickness to 800 nm, thus a “buffer” in interphase region was established. Our work provided a facile method to manufacture high-performance thermoplastic composite with outstanding interfacial property and broaden its application in advanced materials field.

Backbone distortions in lactam-bridged helical peptides.

Side‐chain‐to‐side‐chain cyclization is frequently used to stabilize the α‐helical conformation of short peptides. In a previous study, we incorporated a lactam bridge between the side chains of Lys‐i and Asp‐i+4 in the nonapeptide 1Y, cyclo‐(2,6)‐(Ac‐VKRLQDLQY‐NH 2 ), an artificial ligand of the inhibitor of DNA binding and cell differentiation (ID) protein with antiproliferative activity on cancer cells. Herein, we show that only the cyclized five‐residue segment adopts a helical turn whereas the C‐terminal residues remain flexible. Moreover, we present nine 1Y analogs arising from different combinations of hydrophobic residues (leucine, isoleucine, norleucine, valine, and tyrosine) at positions 1, 4, 7, and 9. All cyclopeptides except one build a lactam‐bridged helical turn; however, residue‐4 reveals less helix character than the neighboring Arg‐3 and Gln‐5, especially with residue‐4 being isoleucine, valine, and tyrosine. Surprisingly, only two cyclopeptides exhibit helix propagation until the C‐terminus, whereas the others share a remarkable outward tilting of the backbone carbonyl of the lactam‐bridged Asp‐6 (>40° deviation from the orientation parallel to the helix axis), which prevents the formation of the H‐bond between Arg‐3 CO and residue‐7 NH: As a result, the propagation of the helix beyond the lactam‐bridged sequence becomes unfavorable. We conclude that, depending on the amino‐acid sequence, the lactam bridge between Lys‐i and Asp‐i+4 can stabilize a helical turn but deviations from the ideal helix geometry are possible: Indeed, besides the outward tilting of the backbone carbonyls, the residues per turn increased from 3.6 (typical of a regular α‐helix) to 4.2, suggesting a partial helix unwinding.

Preparation of defect-free hollow fiber membranes derived from PMDA-ODA polyimide for gas separation

Since PMDA-ODA polyimide is insoluble, its soluble precursor PMDA-ODA poly (amic acid) (PAA) is used to prepare hollow fiber membranes (HFMs). Due to the existence of –CO–NH– and –COOH groups, PAA is subject to form hydrogen bonds with water and consequently leads to a very slow phase inversion rate during the non-solvent induced phase inversion process. Therefore, the hollow fiber spinning has to be carried out with a low take-up speed that limits the productivity. In this paper, we increased the take-up speed of PAA hollow fiber to 60 m/min by simply adding LiCl into polymer dope. Moreover, an integrally skinned defect-free PMDA-ODA hollow fiber membrane was obtained at the high take-up speed where the gas permeances were 6.8 ± 0.7, 2.2 ± 0.2, 0.4 ± 0.04 and 0.07 ± 0.01 GPU for H2, CO2, O2 and N2, respectively, with an ideal selectivity of 3.1 ± 0.3, 31 ± 3.0 and 5.7 ± 0.6 for H2/CO2, CO2/N2 and O2/N2, respectively. These results indicated a dense PMDA-ODA layer of 1 μm. To our best knowledge, this is the first time that a defect-free hollow fiber membrane for gas separation is prepared based on PMDA-ODA.

Metal-Ion-Cross-Linked Nitrogen-Doped Carbon Dot Hydrogels for Dual-Spectral Detection and Extractable Removal of Divalent Heavy Metal Ions

Nitrogen-doped carbon dots (NCDs) synthesized by the low-temperature sintering method show electronegativity rich in −COO–, −CO–NH–, −NH–, and −OH. The structure, morphology, and fluorescence performance of NCDs were successively characterized by Fourier-transform, infrared, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, photoluminescence, ultraviolet (UV), and X-ray fluorescence analyses. On the one hand, NCDs can sensitively detect Pb2+ in water with a detection limit of 3 ppb through the dual response of fluorescence emission spectra and UV absorbance spectra. On the other hand, the negatively charged NCDs combine with various positively charged heavy metal ions (Pb2+, Cu2+, Ni2+, Co2+, and Cd2+) through charge attraction and coordination to form a hydrogel, thereby removing heavy metal ions from the water. Among them, the removal rate of Pb2+ by NCDs is as high as 94.8%. It is the first time that pure NCDs have been used to remove heavy metal ions quickly and easily in the form of a reversible hydrogel. A simple way is to achieve ultrasensitive detection and high-efficiency removal of heavy metal ions in water with unitary NCDs.

The cross‐linked hyperbranched polyamide‐amines: The preparation and its adsorption for Pb(II)

AbstractIn order to prepare a new adsorbent material for the treatment of waste water containing Pb(II), hyperbranched polyamide‐amines (H‐PAMAMs) were prepared via one‐pot method, then the H‐PAMAMs were crosslinked by epichlorohydrin. The crosslinked hyperbranched polyamide‐amines (C‐H‐PAMAMs) were prepared and characterized. The selective adsorption of coexisting ions shows that the C‐H‐PAMAMs have high adsorption capacity and selectivity for Pb(II). The adsorption characteristics and mechanism of the C‐H‐PAMAMs for Pb(II) were systematically investigated. The results of batch adsorption experiments showed that the maximum Pb(II) adsorption capacity was 180.83 mg/g at pH 4.0 and 318 K. The adsorption process on the C‐H‐PAMAMs was well described by the Langmuir model, which indicated the adsorption process was spontaneous and endothermic. The X‐ray photoelectron spectroscopy analysis showed that the adsorption mechanism of the C‐H‐PAMAMs for Pb(II) was the synergistic chelation of COO and CONH. Four adsorption/desorption recycling tests showed that the the C‐H‐PAMAMs still had a high adsorption capacity for Pb(II).

GSH-responsive nanofibrous prodrug formed by a short naphthylacetic acid-terminated peptide for 6-mercaptopurine delivery

As a purine analogue, 6-mercaptopurine (6-MP) is practical in treatment of leukemia and autoimmune diseases. Here, we connected 6-MP with a naphthylacetic acid-terminated short peptide (Nap-FFYE, NF) via disulfide bonds to form a novel prodrug Nap-FFYE–CO–NH–(CH2)2–SS-6-MP (NF-SS-MP). NF-SS-MP can self-assemble to fibrous nanostructures with the diameter of ~50 nm in neutral aqueous solution. In vitro drug release experiments suggested that NF-6-MP showed sensitive GSH responsive and controlled releasing characteristics. 4-hour and 24-h cytotoxicity assay revealed that encapsulating 6-MP in NF-SS-MP nanofibers improved the killing ability of 6-MP to tumor cells in initial incubation time, and significantly reduced the toxicity of 6-MP on normal cells after 24 h incubation. From the results of cell uptake experiments, we found that NF-6-MP was easier to be absorbed by EC109 cells compared with free 6-MP, showing higher intracellular drug concentrations after incubation for 4 h, which confirmed the cytotoxicity result that nanofibrous NF-SS-MP has better ability to kill EC109 cells in a short incubation time. Thus, the developed NF-SS-MP can be used as an ideal delivery system for 6-MP in tumor treatment.

Excellent electromagnetic wave absorption properties of the ternary composite ZnFe2O4@PANI-rGO optimized by introducing covalent bonds

The ternary composite material ZnFe2O4@PANI-rGO with a core-shell structure and excellent electromagnetic absorption properties has been prepared by covalently modifying reducing graphene oxide with the binary magnetic material ZnFe2O4@PANI. The ternary composite material ZnFe2O4@PANI/rGO forms a " CO–NH ″ covalent bond between ZnFe2O4@PANI and rGO through hydrothermal routes and mechanical stirring. By comparing the two types of the connection method covalent and non-covalent bonds, it was surprised to find that formed by covalently connecting the binary ZnFe2O4@PANI material and rGO (C-ZPr) to obtain extremely excellent electromagnetic absorption performance. By adjusting the thickness from 1 mm to 4 mm, when the filler ratio is 20%, the minimum reflection loss (RLmin) at 2.1 mm was as low as −49.99 dB at 17.28 GHz and the effective absorption bandwidth (RL < 10 dB) was almost 4.32 GHz. The introduction of covalent bonds becomes a bridge connecting magnetic materials and dielectric materials, adjusting electromagnetic parameters, enhancing reflection loss, and achieving impedance matching and improved electromagnetic absorbing performance. This preparation method is expected to provide new ideas for the preparation of high-performance absorbing materials in the future.