Reverse Polymerization Research Articles

Development and Evaluation of Insulation Materials for Deepwater Cementing.

Marine oil and gas resources are abundant in deepwater regions, where the shallow seabed harbors natural gas hydrate layers due to the cold temperature and high-pressure environment. Hydrates are prone to thermal decomposition, which can compromise the integrity of cement sealing and even lead to accidents like blowouts. While current low-hydrated heat cement systems mitigate hydrate decomposition from cement hydration heat during the waiting period for cementing, they do not address heat transfer from deep strata to shallow hydrate layers through fluid circulation in the tubing during deep oil and gas development. Rather than utilizing costly pipe insulation technology, adjusting the thermal conductivity of well cement emerges as a cost-effective approach to prevent heat loss in the wellbore to the hydrate layer and thus inhibit hydrate decomposition. The critical aspect lies in utilizing insulation functional materials. This study delves into the functional and structural design of insulation materials suitable for cement slurry systems in well cementing, outlining the preparation methods and processes for two insulation materials (SDBW and SDBW-II) tailored for deepwater well cementing. SDBW and SDBW-II are both nuclear shell structural materials. The core is made of high-strength hollow microspheres, produced by using a reverse suspension polymerization method to form spheres followed by high-temperature sintering. The shell consists of a wear-resistant BPA epoxy resin layer, with the surface of SDBW-II also containing highly reflective glass microspheres. Incorporating 20% of material SDBW into the cement reduces the thermal conductivity of the cement stone from 0.8 to 0.31 W·(m·K)-1 while achieving a compressive strength of 6 MPa after 24 h at 20 °C. Material SDBW-II offers both thermal resistance and reflection functions, increasing reflectivity (R) from 0.3 to 0.5. By adding 20% of this material to the cement, under the same conditions, although the compressive strength decreases to 4.2 MPa, the thermal conductivity can be reduced to 0.27 W·(m·K)-1. Furthermore, there is no significant change within 180 days, demonstrating long-term thermal insulation stability. These developed insulation materials can effectively improve the thermal insulation performance of the cement sheath, thereby maintaining the stability of the upper natural gas hydrate layer in the oil and gas production process of deepwater wells, providing an innovative solution for the long-term operation of deepwater oil and gas wells.

LC-MS/MS Analysis of crude Flavonoid Compounds from <i>Justicia secunda</i> from Democratic Republic of the Congo and evaluation of their antisickling Activity

<i>Justicia secunda</i> Vahl (Acanthaceae) is a tropical herbaceous plant traditionally used by indigenous peoples of the Democratic Republic of the Congo (DRC) to treat symptoms associated with sickle cell disease (SCD), a genetic condition with life-threatening complications. Given the lack of side-effect-free drugs, alternative herbal therapies that can reduce or reverse red blood cell sickling may serve as safe and effective treatments. The primary objective of this study is to conduct a phytochemical screening of crude flavonoids extracted from <i>J. secunda</i> using LC-ESI/MS/MS. <i>J. secunda</i> extracts were evaluated for their phytoconstituents and anti-sickling properties. The anti-sickling properties were assessed through reverse sickling estimation, polymerization and oxidation inhibition, and osmotic fragility assays. Fractionation of the methanol extract and chemical profiling were performed by flash chromatography and high-performance thin-layer chromatography analysis respectively. Characterization and identification of the crude flavonoids were done using chromatography and spectroscopy methods. Chemical screening of crude flavonoids revealed the presence of 12 flavonoid O-glycosides based on one flavonol (methoxy-kaempferol) and two flavones (luteolin and apigenin). The crude flavonoid extracts demonstrated maximum reversal of sickled red blood cells (91.9 ± 0.8%), significant inhibition of hemoglobin polymerization (77.8 ± 7.6%) and hemoglobin S auto-oxidation (96.3 ± 0.2), and provided maximum protection of red blood cells against hyperhemolysis. The results validate the traditional use of <i>J. secunda</i> and identify potential compounds for the development of novel anti-sickling agents.

Fabrication of cellulose nanocrystals-incorporated dense Janus membranes for enhanced desalination and oily saline wastewater treatment via membrane distillation

Conventional hydrophobic membranes used in membrane distillation (MD) face significant challenges, such as severe membrane fouling and wetting, when treating surfactant-containing oily wastewater. Current strategies to modify surfaces for anti-fouling and anti-wetting purposes are often complex and time consuming, potentially compromising the flux in MD. This study investigates the characteristics and performance of novel fabricated Janus membranes for the treatment of oily hypersaline wastewater in membrane distillation applications. Janus membranes, which have a dense polyamide layer containing cellulose nanocrystal nanoparticles, were synthesized using the reverse interfacial polymerization (R–IP) method on a polyvinylidene fluoride (PVDF) substrate. Characterization using scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) revealed that the modified Janus membranes exhibited an enhanced hydrophilicity and structural integrity due to the incorporation of cellulose nanocrystal nanoparticles. The fabricated membranes showed a dense surface layer without visible pores or cracks, with micron-scale patterned structures and widely distributed wrinkles, particularly at higher concentrations of cellulose nanocrystal nanoparticles. The desalination performance was evaluated in an air gap membrane distillation setup, where the modified Janus membranes demonstrated higher water vapor fluxes and stable salt rejection, even in the presence of surfactants. The wettability and fouling resistance of the Janus membranes were evaluated, with the PVDF-RIP0.5C membrane showing the highest hydrophilicity and underwater oleophobicity, thereby preventing oil adhesion and membrane fouling. These results underline the potential of Janus membranes with incorporated cellulose nanocrystal nanoparticles for efficient desalination and treatment of oily saline wastewater in the MD process.

Direct and specific detection of methyl-paraoxon using a highly sensitive fluorescence strategy combined with phosphatase-like nanozyme and molecularly imprinted polymer

Methyl paraoxon (MP) is a highly toxic, efficient and broad-spectrum organophosphorus pesticide, which poses significant risks to ecological environment and human health. Many detection methods for MP are based on the enzyme catalytic or inhibition effect. But natural biological enzymes are relatively expensive and easy to be inactivated with a short service life. As a unique tool of nanotechnology with enzyme-like characteristics, nanozyme has attracted increasing concern. However, a large proportion of nanozymes lack the intrinsic specificity, becoming a main barrier of constraining their use in biochemical analysis. Here, we use a one-pot reverse microemulsion polymerization combine the gold nanoclusters (AuNCs) with molecularly imprinted polymers (MIPs), polydopamine (PDA) and hollow CeO2 nanospheres to synthesize the bright red-orange fluorescence probe (CeO2@PDA@AuNCs-MIPs) with high phosphatase-like activity for selective detection of MP. The hollow structure possesses a specific surface area and porous matrix, which not only increases the exposure of active sites but also enhances the efficiency of mass and electron transport. Consequently, this structure significantly enhances the catalytic activity by reducing transport distances. The introduced MIPs provide the specific recognition sites for MP. And Ce (III) can excite aggregation induced emission of AuNCs and enhance the fluorescent signal. The absolute fluorescence quantum yield (FLQY) of CeO2@PDA@AuNCs-MIPs (1.41 %) was 12.8-fold higher than that of the GSH-AuNCs (0.11 %). With the presence of MP, Ce (IV)/Ce (III) species serve as the active sites to polarize and hydrolyze phosphate bonds to generate p-nitrophenol (p-NP), which can quench the fluorescent signal through the inner-filter effect. The as-prepared CeO2@PDA@AuNCs-MIPs nanozyme-based fluorescence method for MP detection displayed superior analytical performances with wide linearities range of 0.45–125 nM and the detection limit of 0.15 nM. Furthermore, the designed method offers satisfactory practical application ability. The developed method is simple and effective for the in-field detection.

Low temperature regulated reverse interfacial polymerization for fabricating thin film composite membranes based on nanofibrous substrates

In this study, a novel thin film nanofibrous composite (TFNC) nanofiltration (NF) membranes comprised of polyacrylonitrile (PAN) nanofibrous supporting layer and polyamide (PA) compact separating layer was constructed by low-temperature-controlled reverse interfacial polymerization (LTIP-R) at − 5 °C. The strategy for lowering the temperature of organic phase solution played a crucial role in forming a dense and thin PA layer on the PAN nanofibrous substrate with submicron pores. The results revealed that the reduced evaporation rate of organic phase at low temperature was contributed to maintaining a complete and uniform interface for the following reverse IP process, effectively overcoming shortcomings of surface incompleteness and easy infiltration of PA barrier layer. Owing to the reduced thickness and the enhanced wholeness of the PA separating layer via LTIP-R, the optimized TFNC membranes exhibited NF performance with great rejection of divalent salt ions (98.2%) and an improved permeation (13.3 L‧m−2‧h−1‧bar−1). This work would provide an efficient and facile method to fabricate high performance NF membranes for practical applications.

Constructing nanofiltration membrane on hydrophobic PVDF and PTFE substrates via reverse interfacial polymerization

Polyvinylidene fluoride (PVDF) and polytetrafluoroethylene(PTFE) porous membranes are ideal substrates for preparing thin-film composite (TFC) polyamide (PA) membranes with improved solvent resistance. However, it remains difficult to construct PA skin layers on PVDF and PTFE substrates via conventional interfacial polymerization (IP) due to the hydrophobic nature of these materials. To address this challenge, a reverse IP process was proposed to construct a defect-free PA skin layer on PVDF and PTFE substrates, in which the hydrophobic PVDF and PTFE substrates were soaked with the organic phase to ensure uniform coverage of reacted solution on the substrates. This novel strategy can effectively tackle the issue of uneven wetting of the aqueous phase on hydrophobic substrates in the conventional IP process. The resultant TFC membranes (i.e. Mrev-PVDF and Mrev-PTFE) exhibit excellent nanofiltration (NF) performance in both aqueous and organic solutions. Mrev-PVDF and Mrev-PTFE have MgCl2 rejections of 96.12% and 95.17%, alongside the water permeances of 12.8 LMH/bar and 11.2 LMH/bar, respectively (Mrev-PTFE was activated with DMF). It is further shown that Mrev-PVDF and Mrev-PTFE could also reject 99.4% and 98.5% of Congo red in methanol solution at solvent permeances of over 3.3 LMH/bar, while they also perform excellently in other polar protic solvents. Consequently, this work opens a new window for constructing high-performance TFC PA membranes on hydrophobic substrates and expands the application of the TFC PA NF membrane.

Degradation behavior and mechanism of P(AM/AA/AMPS)@PLA core-shell self-degrading temporary plugging agent

Shielding temporary plugging is a simple and effective technology to protect oil–gas formation drilling fluid, with temporary plugging material as its core. However, the existing temporary plugging agents have problems such as a too-fast degradation rate under high-temperature conditions, poor degradation performance, and reservoir damage resulting from degradation products. Aiming at these problems, and with acrylamide (AM), 2-Acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA), and polylactic acid (PLA) as raw materials to prepare the self-degradation shielding temporary plugging agent DSTPA by reverse suspension polymerization, this paper has characterized its chemical composition, chemical structure and thermal stability, and studied its compatibility with drilling fluid and plugging performance. The influence of temperature, pH, and salinity on the degradation behavior of DSTPA is also investigated, and the degradation process of DSTPA is analyzed by electron microscopy (SEM) and infrared spectroscopy (FT-IR) scanning. The results show that DSTPA boasts good pressure-bearing and plugging performance, with its plugging rate above 90 % and the core damage rate lower than 5 %; DSTPA demonstrates good compatibility with drilling fluid and insignificant effect on the rheology of drilling fluid system; a small amount of DSTPA can remarkably reduce the filtration loss of drilling fluid: 1 % DSTPA addition reduces the filtration loss by 24 mL. The degradation experiments of DSTPA show that increased temperature and pH can promote the self-degradation of DSTPA, but increased salinity inhibits its self-degradation. DSTPA boasts good temperature resistance, with its complete degradation lasting 144 h under 180 ℃. FT-IR analysis and SEM analysis showed that the degradation of DSTPA was mainly due to the breaking of amide bonds and ester bonds, resulting in the collapse of the three-dimensional network structure of its molecular structure, thereby degrading into an aqueous solution with a viscosity comparable to water.

Synergistic dopa-reinforced fluid hydrosol as highly efficient coal dust suppressant

A highly efficient coal dust suppressant with low initial viscosity and high adhesion-solidification properties was fabricated by reinforcing a polyacrylic acid hydrosol with dopa and glutathione (DG) redox system. The synthesis mechanism and dust suppression properties of the dust suppressant were investigated by ultraviolet–visible spectroscopy, high-performance liquid chromatography, and nuclear magnetic resonance spectroscopy experiments combined with density functional theory calculations. The polyacrylic acid hydrosol was synthesized by free radical polymerization with an optimal concentration ratio of 0.36 % ammonium persulfate to 9 % acrylic acid; the DG redox system presented a catechol-quinone dynamic equilibrium, and the dopa polymer reinforcing adhesion was synthesized by the reverse dismutation and polymerization of dopa and dopaquinone. Results revealed that the dust suppressant system formed a multiple hydrogen bonding cross-linking network, dominated by strong double hydrogen bonding interaction formed between the carboxyl groups of dopa polymer and polyacrylic acid, and synergized by hydrogen bonds between the carboxyl groups of glutathione and PAA, and between the hydroxyl and carboxyl groups of dopa and dopaquinone. Moreover, the − OH and − COOH groups in the dust suppressant system were more tightly bonded after dehydration and can form a mesh film to effectively adhere and solidify coal dust, and the coal crust film did not raise dust at 20.526 ± 0.083 m/s wind speed.

Synthesis and performance evaluation of a micron-size silica-reinforced polymer microsphere as a fluid loss agents

A silica-reinforced polymer microsphere was prepared by reverse suspension polymerization using acrylamide (AM), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and silica nanoparticles modified with methacryloyloxypropyltrimethoxysilane as a filtrate reductant resistant to high temperature and salt contamination. The filtration volume of American Petroleum Institute (API) sodium-based bentonite fluids was reduced by 63.5% after aging with the addition of 3.0 wt% M-SiO2/ZMD at 150 °C. M-SiO2/ZMD also exhibited significant salt resistance when compared to ZMD. The test results demonstrate that M-SiO2/ZMD exhibits excellent rheological and filtration properties even at elevated temperatures. A significant filtration reduction effect was also shown in the water-based drilling fluid system. The filtrate volumes before and after aging at 150 °C were 5.2 mL and 5 mL, respectively, when the addition amount was 1.0 wt%. Finally, the possible filtration loss reduction mechanisms involved in M-SiO2/ZMD are also discussed. This study provides a new heat- and salt-resistant fluid loss reduction material for water-based drilling fluids in oilfields, and provides theoretical support for its practical application.

First Detection and Characterization of Hepatitis E Virus in Sewage Samples in Cameroon.

Hepatitis E virus (HEV) represents an important public health concern in many developing countries, including Africa. Transmission of HEV to humans by contaminated drinking water is the most important mode of transmission in low- and middle-income countries. This study aimed to assess the presence of HEV in the environment in Cameroon through molecular analysis of sewage samples. Retrospectively, a total of 157 sewage samples collected between January 2018 and December 2019 were randomly selected and analyzed by molecular techniques to detect and characterize the HEV followed by sequencing and phylogenetic analysis. Three samples (1.9%) collected from North, Far North, and Adamawa regions were positive by real-time reverse transcription polymerization chain reaction. Among these, 2 samples were positive for HEV ribonucleic acid by nested reverse transcription polymerization chain reaction and only one yielded a good sequencing product. Phylogenetic analysis of this unique HEV strain showed that this HEV strain belonged to genotype 3, subtype 3a, and clustered with swine HEV strains from Cameroon, Argentina, and the USA. This study provides preliminary data on the circulation of HEV in wastewater in Cameroon. Further studies will be needed to assess the overall situation in Cameroon.

Polyamide⊥TpPa-PVDF membranes for aliphatic-aromatic solvent separations

To achieve net-zero emissions, the petrochemical industry requires energy-efficient processes for solvent recovery, and traditional distillation technologies may not be adequate. Membrane separations with 2D COFs (covalent organic frameworks) have shown potential due to their tunable pore sizes and modifiable properties. However, the large pores of the COFs have provided challenges in fabricating 2D COF membranes for solvent separation. Recent research has been focused on improving the selectivities and permeation fluxes for solvent mixtures, and to achieve long-term operation, the membranes must have high chemical and mechanical stabilities. To address the issue of large pores, our research group cross-linked the Tp (2,4,6-triformylphloroglucinol) and Pa (p-phenylenediamine) monomers of the COF with TMC (trimesoyl chloride), a monomer used traditionally for reverse osmosis interfacial polymerization, which resulted in COF(TpPa) with TMC cross-linking and small pore sizes for solvent separation. Polyamide⊥TpPa-PVDF membranes were fabricated for the first time with this method, and the TMC cross-linked COF membrane successfully rejected salts and separated aromatic/alkane solvents; a toluene/benzene mixture showed a higher separation factor than methanol/isopropanol. Use of the 2D materials for reverse osmosis at 20 bar enhanced the potential of the energy-efficient membranes for use in future petrochemical industrial applications.

Patterned dense Janus membranes with simultaneously robust fouling, wetting and scaling resistance for membrane distillation

Membrane fouling, wetting and scaling are three prominent challenges that severely hinder the practical applications of membrane distillation (MD). Herein, polyamide/polyvinylidene fluoride (PA/PVDF) Janus membrane comprising a hydrophobic PVDF substrate and a patterned dense PA layer by reverse interfacial polymerization (R-IP) was developed. Direct contact MD experiments demonstrated that PA/PVDF Janus membrane could exhibit simultaneously superior resistance towards surfactant-induced wetting, oil-induced fouling and gypsum-induced scaling without compromising flux. Importantly, the size-sieving effect, rather than the breakthrough pressure of the membrane, was revealed as the critical factor that probably endowed its resistance to wetting. Furthermore, a unique possible anti-scaling mechanism was unveiled. The superhydrophilic patterned dense PA layer with strong salt rejection capability not only prevented scale-precursor ions from intruding the substrate but also resulted in the high surface interfacial energy that inhibited the adhesion and growth of gypsum on the membrane surface, while its relatively low surface -COOH density benefited from R-IP process further ensured the membrane with a low scaling propensity. This study shall provide new insights and novel strategies in designing high-performance MD membranes and enable robust applications of MD facing the challenges of membrane fouling, wetting and scaling.

Prioritizing healthcare waste disposal methods considering environmental health using an enhanced multi-criteria decision-making method

ABSTRACT The Healthcare Waste Disposal Method Selection (HCWDMS) is a complicated problem due to multiple and often contradictory criteria with different importance degrees. Thus, decision-makers are restored to multi-criteria decision-making (MCDM) methods to prioritize and select the best HCW disposal methods. This study introduces an enhanced MCDM method to deal with the HCWDMS problem. To address the problem, a comprehensive list of criteria and HCW disposal methods are identified. All the criteria are categorized into four main criteria, and Fuzzy Analysis Hierarchy Process is used to determine the weights of considered criteria and sub-criteria. The study results show that environmental, economic, technical, and social criteria are the most important in selecting disposal methods, respectively. Moreover, the sub-criteria of ‘Health Risk’, ‘Release with health effects’, and ‘Capital cost’ have the highest importance, respectively. Additionally, the methods of ‘Microwave’, ‘Sterilization by autoclave’, and ‘Reverse polymerization’ have the highest priority, respectively.

Antibacterial activity and sustained release properties of curcumin-loaded chitosan microspheres/nanofiber composites membranes for wound healing applications

The application of bioactive curcumin is limited due to its poor stability, lower absorption, and fast metabolism in the human body. In the present study, chitosan/curcumin microspheres were prepared by reverse emulsion polymerization and electrospun with polyvinyl alcohol to fabricate chitosan/curcumin microspheres with polyvinyl alcohol composite nanofibrous membranes. The fiber morphology of chitosan/curcumin microspheres/polyvinyl alcohol composite nanofibrous membranes was observed by scanning electron microscopy, indicating that there are more continuous and uniform fibers of chitosan/curcumin microspheres/polyvinyl alcohol than those without chitosan/curcumin microspheres. Fourier transform infrared spectroscopy was applied to test the chemical structural changes of nanofibrous membranes, which showed that chitosan/curcumin microspheres were physically mixed with polyvinyl alcohol. The mechanical properties of the samples were tested by an electronic fabric strength machine and the tensile strength of the composite nanofibrous membranes can reach 7.e Mpa. The introduced drug release profiles indicated that after 60 h of culturing, the release rate of composite nanofibrous membranes was 69.8%. The bacterial inhibition rate of the composite nanofibrous membranes was assessed through the oscillation method. The results obtained revealed that the bacterial inhibition rate of chitosan/curcumin microspheres/polyvinyl alcohol composite nanofibers was detected up to 99.9% in the 48 h antimicrobial test.

A REVIEW OF NANOGELS AS NOVEL DRUG DELIVERY SYSTEMS

The term “nanogel” refers to highly cross-linked hydrogels with a size between 20 and 200 nm. Due to their tiny size, they have higher penetration and greater drug-loading capacity. They release the medication using mechanisms such as photochemical internalization, volume transition, pH responsiveness, thermo sensitive, and photo isomerization. They can be categorized according to whether they respond to stimuli or not as well as the kind of links that are present in the gel structure’s network chains. Using photolithography, modified pollutants, and emulsions, one can create nanogel. Reverse microemulsion polymerization, inverse mini-emulsion polymerization, and the free radical cross-linking polymerization method are all examples of polymerization. Cancer, diabetes, inflammation, and bone regeneration are just a few conditions that can be treated with nanogels. The cutting-edge medication delivery technology for both hydrophilic and hydrophobic drugs is nanogels. This article focuses on the historical data regarding herbal nanogels, which have high patient compliance, delivery rate, and efficacy when used to treat various illnesses. The topic of stimulus-responsive nanogels, including pH-and temperature-responsive systems, is also covered.

Synthesis of PDMS/PEG graft-like and block copolymers via industrially relevant reverse iodine transfer polymerization

Advanced polymer structures are gaining traction in the coatings industry where they may, for instance, give rise to antifouling and anti-icing surfaces. With a focus on industrial feasibility, a series of copolymers from poly(dimethylsiloxane) monomethacrylate (PDMSMA), methoxy poly(ethylene glycol) monomethacrylate (MPEGMA) and methyl methacrylate (MMA) were prepared via reverse iodine transfer polymerization (RITP) and reversible complexation mediated polymerization (RCMP). Using inexpensive materials and synthesis approaches scalable for larger industrial quantities, a variety of (amphiphilic) copolymers and block copolymers were prepared. Compared to semi-batch free-radical polymerization (FRP), the RITP/RCMP approaches resulted in higher conversions of the macromonomers, lower polymer dispersities, allowed synthesis of block copolymers, as well as being simpler than most other common RDRP techniques.

Nano-CaCO3/AA-AM-AMPS cross-linked polymer core-shell structural nanocomposite as high temperature and high salt resistant filtration reducer in water-based drilling fluid

Effective filtration loss control under high temperature and high salinity environments is a great challenge in oil and gas drilling engineering. In this study, a core-shell structural nano-composite (CSNC) using precipitated nano-CaCO3 as the core material and cross-linked polymer between acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA) and methylene-bis-acrylamide (MBA) as the shell was prepared by reverse emulsion polymerization. The structure of CSNC was characterized with Fourier infrared spectrum (FT-IR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscope (TEM) and particle size distribution analysis. The filtration control properties of CSNC particles were investigated in both aqueous solution and bentonite suspension with various contents of NaCl and CaCl2 respectively. The high temperature and high pressure (HTHP) filtration properties between CSNC and typical high temperature resistant filtration reducers were compared. The filtration controlling mechanism of CSNC particles were probed through zeta potential analysis, X-ray diffraction (XRD) analysis and filter cake morphologies observation. The results indicated that for the 4% w/v bentonite suspension treated with 3% w/v CSNC, the low temperature and low pressure (LTLP) filtration loss and filter cake thickness decreased by 84.2% and 76.1% respectively after thermal aging at 220 °C. When the bentonite suspension was contaminated with 30% w/v NaCl and 0.5% w/v CaCl2 respectively, incorporation of 1% w/v CSNC reduced the filtration loss by 72.5% and 86.9% after thermal aging at 200 °C. The core-shell structure, cross-linked structure, and salt tolerant sulfonic acid groups on the outer surface of CSNC in combination contributed to extraordinary filtration loss control under stringent high temperature and high salinity conditions.

Red emissive N-doped carbon dots encapsulated within molecularly imprinted polymers for optosensing of pyrraline in fatty foods.

A novel and facile method was proposed for preparation of red emissive N-doped carbon dots encapsulated within molecularly imprinted polymers (RNCDs@MIPs) using a one-pot room-temperature reverse microemulsion polymerization. RNCDs used citric acid and urea as carbon and nitrogen sources by one-step solvothermal synthesis with the optimum emission of 620nm. Unique optical properties of RNCDs coupled with high selective MIPs make the RNCDs@MIPs conjugate capable to adsorb specific targets of pyrraline (PRL), such a binding event was then transduced to quench fluorescence response signal of the RNCDs. RNCDs@MIPs for PRL showed linearity from 0.1 to 40μg/L, with a detection limit of 65ng/L. The RNCDs@MIPs exhibited a good reproducibility of 4.67% obtained from four times of rebinding for PRL. The optosensing probe was successfully applied to thedetection of PRL in fatty foods with the spiked recovery of 85.93-106.96%.

A sensitive fluorescent assay based on gold-nanoclusters coated on molecularly imprinted covalent organic frameworks and its application in malachite green detection

Malachite green (MG), as a parasiticide, is widely used in aquaculture to increase the production of the fishery industry. It poses a great danger to both the food system and the human body. In this study, a one-pot reverse microemulsion polymerization was employed to combine the gold nanoclusters (AuNCs) with molecularly imprinted polymers (MIPs) and covalent organic frameworks (COFs) to synthesize an efficient fluorescent hybrid probe (AuNCs@COFs@MIPs) for selective detection of MG. The specific recognition of AuNCs@COFs@MIPs towards MG triggers the fluorescence quenching of AuNCs. The fluorescent response was linearly related to the concentration over the range of 10–150 nmol/L with a limit of detection of 2.78 nmol/L. In addition, the proposed probe was further applied to fish and water samples. A favorable recovery ranged from 97.34 to 101.51 % toward trace amounts of MG indicating its promising application for detecting residue of veterinary drugs.

Magnetic ion‐imprinted microspheres for the removal of heavy metal ions from aqueous solution

AbstractMagnetic ion‐imprinted microspheres (IIM) with core‐shell structure were successfully prepared by reverse emulsion polymerization and applied to adsorb heavy metal ions from sewage. The semi‐interpenetrating polymer network composed of cross‐linked polyacrylamide (PAM) and linear chitosan (CTS) was used as the microgel shell of microspheres, which can not only fully retain the active sites of CTS but also tightly encapsulate magnetic particle nuclei. In addition, ion imprinting technology was used to further improve the adsorption capacity. In this study, the effects of PAM to CTS ratio on the thermal stability, magnetic properties, and microstructure of microspheres were investigated. Adsorption studies showed that IIM exhibited excellent selective adsorption of Cu(II), and the effects of initial concentration of metal ions, adsorption time, adsorbent dosage, pH, ionic strength, and cycle times on adsorption of Cu(II) by IIM‐2 were also studied. In addition, it was revealed that pseudo‐second‐order kinetic model and Langmuir isotherm model could better simulate the adsorption kinetic and isotherm of IIM‐2 for Cu(II), respectively. At 30°C and pH 5.0, the theoretical maximum adsorption capacities for Cu(II) by IIM‐2 were 151.13 mg/g. X‐ray photoelectron spectroscopy and Zeta potential study showed that the adsorption mechanism of IIM‐2 was a combination of electrostatic interaction and ion exchange.