Reverse Microemulsion Polymerization Research Articles

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.

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.

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.

Efficient and robust dual modes of fluorescence sensing and smartphone readout for the detection of pyrethroids using artificial receptors bound inside a covalent organic framework

In the study, we have developed an efficient and robust method using dual modes of fluorescence sensing and smartphone readout for the detection of pyrethroids using artificial receptors inside a covalent organic framework. Carbazole-conjugated frameworks (CCFs) were used to prepare efficient fluorescent probes that combine stability with light-emitting activity. CN linkages between aldehydes and amines formed Schiff bases, allowing the development of layered structures, creating exceptionally stable frameworks. Artificial receptors that can bind compounds inside the CCFs with high affinity, for both the detection and absorption of λ-cyhalothrin (LC), were constructed using room-temperature reverse microemulsion polymerization. Under optimum conditions, the fluorescence sensing correlation with the concentration of LC showed good linearity in the range of 0.8–175 μg L−1 with a detection limit of 0.368 μg L−1. The smartphone-based visible readout exhibited a good effect, with a detection limit of 4.067 μg L−1, and recovery of 88 %–103% in food samples. A parallel analysis in food samples was conducted by high-performance liquid chromatography, the results showed good consistency, indicating the practicability of the developed method. Dual mode analysis can avoid the disadvantages of a single response, providing excellent sensitivity, specificity, and efficiency through a strong binding force between the target and the artificial receptors.

N-doped carbon dots derived from covalent organic frameworks embedded in molecularly imprinted polymers for optosensing of flonicamid

After applied, flonicamid reaches the interior of agricultural products and shifts to ecosystem, which proliferating the hazardous risk to consumers. In this study, nitrogen-doped carbon dots derived from covalent organic frameworks embedded in molecularly imprinted polymers (COF-derived NCDs@MIPs) were prepared by reverse microemulsion polymerization. The COF-derived NCDs@MIPs were used as a potential candidate for the optosensing of flonicamid in food samples, which combined the merits of superior physicochemical properties with the high stability of N-doped carbon dots, an efficient fluorescence-resonance charge-transfer strategy, and good specific and sensitive MIP technology. The performance of the proposed optosensing system was measured in phosphate buffered saline (PBS, pH = 7.0) over the flonicamid concentration range of 0.03–0.3 μg g−1 with a limit of detection of 0.004 μg g−1. A selectivity study was employed to evaluate the influence of five neonicotinoids on the selectivity of the COF-derived NCDs@MIPs for flonicamid molecules, which showed good affinity for flonicamid in comparison with that of the non-imprinted polymer (NIP). The application of the proposed optosensing technique in spiked food samples revealed a good recovery (86.7–98.1%). The development of easily synthesized COF-derived NCDs@MIPs with excellent performance will be greatly beneficial for trace detection of flonicamid.

Carbon dots-embedded epitope imprinted polymer for targeted fluorescence imaging of cervical cancer via recognition of epidermal growth factor receptor.

A carbon dots-embedded epitope imprinted polymer (C-MIP) was fabricated for targeted fluorescence imaging of cervical cancer by specifically recognizing the epidermal growth factor receptor (EGFR). The core-shell C-MIP was prepared by a reverse microemulsion polymerization method. This method used silica nanoparticles embedded with carbon dots as carriers, acrylamide as the main functional monomer, and N-terminal nonapeptides of EGFR modified by palmitic acid as templates. Aseries of characterizations (transmission electron microscope, dynamic light scattering, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, zeta potential,and energy dispersive X-ray spectroscopy) prove the successful synthesis of C-MIP. The fluorescence of C-MIP isquenched by the epitopes of EGFR due to the specific recognition of epitopes of EGFR through their imprinted cavities (analytical excitation/emission wavelengths, 540nm/610nm). The linear range of fluorescence quenching is 2.0 to 15.0μgmL-1 and the determination limit is 0.73μgmL-1. The targeted imaging capabilities of C-MIP are demonstrated through in vitro and in vivo experiments. The laser confocal imaging results indicate that HeLa cells (over-expression EGFR) incubated with C-MIP show stronger fluorescence than that of MCF-7 cells (low-expression EGFR), revealing that C-MIP can target tumor cells overexpressing EGFR. The results of imaging experiments in tumor-bearing mice exhibit that C-MIP has a better imaging effect than C-NIP, which further proves the targeted imaging ability of C-MIP in vivo. Graphical abstract An oriented epitope imprinted polymer embedded with carbon dots was prepared for the determination of the epitopes of epidermal growth factor receptor and targeted fluorescence imaging of cervical cancer.

Reverse Microemulsion Synthesis of Mesopore Phloroglucinol‐Resorcinol‐Formaldehyde Carbon Aerogel Microsphere as Nano‐Platinum Catalyst Support for ORR

AbstractCarbon aerogel (CA) microspheres are modified CA materials that can be prepared by reverse microemulsion and ambient pressure drying and without solvent exchanged. However, mesopore size of traditional resorcinol‐formaldehyde (RF) carbon aerogel microsphere is too small (3‐5 nm) to support nano‐platinum catalyst. In this study, we utilize reverse microemulsion polymerization and ambient pressure drying to develop a series of phloroglucinol‐resorcinol‐formaldehyde (PRF) carbon aerogel microspheres. These carbon aerogel microspheres possess large mesopore size (10–30 nm) and high specific surface area (1300–2000 m2 g−1). Compared with commercial Pt/C, the PRF carbon aerogel as nano‐platinum catalyst support shows the better and durable catalytic activity. The initial mass and electrochemical active surface area of the best performance of Pt/CA are 2.9 and 2.8 times higher than that of commercial Pt/C respectively. After the accelerated stability test (ADT), Pt/CA still keeps a mass and electrochemical active surface area up to 0.15 A mg−1 and 86.4 m2 g−1, while the commercial Pt/C lost to 0.02 A mg−1 and 42.8 m2 g−1. The stability of Pt/CA shows about 7.5 times enhancements compared to commercial Pt/C.

A fluorescent nanoprobe for 4-ethylguaiacol based on the use of a molecularly imprinted polymer doped with a covalent organic framework grafted onto carbon nanodots.

An efficient and rapid fluorescent nanoprobe is described for the determination of the aroma compound 4-ethylguaiacol (4-EG). A molecularly imprinted polymer was doped with a covalent organic framework (COF) grafted onto carbon nanodots that was prepared by one-pot reverse microemulsion polymerization. Amino groups at the surface of carbon nanodots coordinate to the COFs to produce a strong bond and this warrants thermal and chemical stability of the probe. Remaining free amino groups interact with the phenolic hydroxyl groups of 4-EG through acid-base pairing interactions. The probe, with excitation/emission maxima at 350/440nm, responds to 4-EG due to the charge transfer to the carbon nanodots. Under optimized conditions, fluorescence drops linearly as the concentrations of 4-EG increase from 0.025 to 1 μg mL-1, with a detection limit of 17 ng mL-1. The probe was applied to the determination of 4-ethylguaiacol in Chinese Baijiu and wine samples after pretreatment by a single dilution step. The recoveries of spiked samples ranged from 78.4to 110.1%. Graphical abstract Schematic presentation of the synthesis of a fluorescent nanoprobe based on molecularly imprinted polymers doped with covalent organic framework grafted onto carbon nanodots. It was used as an efficient and rapid nanoprobe for 4-ethylguaiacol detection with high selectivity and sensitivity.

An investigation into the relationship between the electrical conductivity and particle size of polyaniline in nano scale

Polyaniline nanoparticle (nPANI) was successfully synthesized through ultrasonic-assisted reverse microemulsion polymerization method. The effect of four parameters including concentration of aniline (ANI) as monomer, molar ratio of dodecybenzene sulfonic acid (DBSA) as surfactant to ANI, molar ratio of ammonium peroxydisulfate (APS) as oxidant to ANI and polymerization temperaturewere systematically studied in terms of the structural characterizations of nPANI by applying the Taguchi method of experimental design. Data analysis indicated that there is a dependency between conductivity and particle size in the nanoscale; the maximum conductivity of nPANI was obtained when the diameter of the particles was 30 nm.

A dual-function molecularly imprinted optopolymer based on quantum dots-grafted covalent-organic frameworks for the sensitive detection of tyramine in fermented meat products.

Molecular imprinting is a technique for polymerization using a template molecule to produce cavities in the polymer with high selectivity. The successful synthesis of a dual-function molecularly-imprinted optopolymer (MIOP) based on quantum dots-grafted covalent-organic frameworks as adsorbents has allowed the simultaneous detection of tyramine by optosensing and solid-phase extraction coupled with high performance liquid chromatography (SPE-HPLC). The MIOP, obtained by a one-pot reverse microemulsion polymerization, selectively measured tyramine from fermented meat products. Under optimized conditions, the relative fluorescence intensity of the optosensing method increased linearly at tyramine concentrations from 35 to 35,000 µg/kg, with a detection limit of 7.0 µg/kg. For SPE-HPLC, the linear range was from 20 to 2000 µg/kg, with a detection limit of 5 µg/kg. The optosensing based on MIOP is a rapid and selective method that would be suitable for detecting TYM in food, while SPE-HPLC also provided good levels of accuracy, sensitivity, and selectivity.

Oriented surface epitope imprinted polymer-based quartz crystal microbalance sensor for cytochrome c

A quartz crystal microbalance (QCM) sensor for detecting cytochrome c based on an oriented surface epitope imprinted polymer was fabricated in this paper. By using the palmitic acid-modified epitope of cytochrome c as the template and the 3-aminopropyltriethoxysilane as the monomer, we prepared a new oriented surface epitope imprinted polymer by the reverse microemulsion polymerization. The prepared oriented imprinted polymer had better imprinting effect than the non-oriented imprinted polymer. And compared to previous studies, this polymerization method is simple and could be carried out at room temperature in the presence of oxygen, under regular atmospheric conditions. Then, by combining the advantages of molecularly imprinted polymers and QCM sensors, we used the prepared polymer to establish a QCM sensor. The described sensor showed good sensitivity and selectivity towards cytochrome c. The linear range was from 0.005 μg mL−1 to 0.050 μg mL−1 and the detection limit was 3.6 ng mL−1 which is lower than most of previous works. Besides, it could be used for real sample analysis and had satisfactory reproducibility and accuracy. This work proposed a new way of fabricating oriented surface epitope imprinted polymers-based QCM sensors for selectively detecting proteins at very low concentrations.

Interfacial characterization and supercapacitive behavior of PEDOT nanotubes modified electrodes

PEDOT nanotubes were chemically synthesized using a hexane/water reverse microemulsion polymerization and deposited onto ITO substrate. FTIR polarized specular reflectance spectra are consistent with AOT molecules organized inside the PEDOT nanotubes. The electrochemical properties of PEDOT nanotubes were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy in comparison with PEDOT:PSS modified electrodes. The results indicates an increase in the capacitance and a decrease in the charge transfer resistance for the PEDOT nanotubes in comparison with PEDOT:PSS films due to the higher exposure of the electroactive sites in the nanostructured material. Galvanostatic charge/discharge curves were performed and a maximum specific capacitance of 160 F·g−1 was revealed, indicating that this material has potential to be used in supercapacitors development.

Sensitive detection of pyrraline with a molecularly imprinted sensor based on metal-organic frameworks and quantum dots

A novel opto-sensor was constructed by anchoring the molecularly imprinted polymers (MIPs) onto the surfaces of metal-organic frameworks (MOFs) and CdSe/ZnS quantum dots (QDs) via one-step reverse micro-emulsion polymerization. It was used for highly selective and sensitive detection of pyrraline (PRL) in milk powders. High selectivity was guaranteed by molecular imprinting, and sensitivity was improved by double signal amplification using the CdSe/ZnS QDs nanocrystals as fluorescent elements and MOFs as an imprinting matrix. The QDs were introduced into the molecularly imprinted sensor as a tentacle to sense bonding interactions between the MIPs and target molecules and to transduce them into fluorescent signals. The opto-sensor had a high fluorescence quantum yield because of the use of hydrophobic CdSe/ZnS QDs and the reverse micro-emulsion. Under optimized conditions, the fluorescence intensity of the opto-sensor was linear with increasing PRL concentration over the range 5×10−6–1×10−3molL−1, with a detection limit of 3.9×10−6molL−1. Recoveries of 90–110% were achieved in direct selective detection of PRL in milk powders.

Epoxy‐based PANI/zinc oxide/glass fiber nanocomposite coating for corrosion protection of carbon steel

In this work, a nanocomposite based on conductive polyaniline (PANI) was polymerized, via reverse microemulsion polymerization, in the presence of phosphoric acid and dodecylbenzenesulfonic acid. Applied simultaneously, these acids act as dopants, increasing the solubility of PANI in organic solvents. They further improve the corrosion protection performance of PANI by forming phosphate‐metal complex on metal surface. Zinc oxide nanoparticles were added to the PANI mixture before introducing ammonium persulfate. The final product of polymerization was added to an epoxy resin which served as the matrix for the coating. In order to improve coating elasticity, which can enhance coating resistance against impacts, E‐glass fiber (GF) was added to the coating formulation. It was observed that, with an optimized w/w%, the PANI/zinc oxide/GF composite improved the coating characteristics. Coatings were further subjected to stress‐strain and DC polarization tests, and their cross‐sections were investigated at break point by means of SEM. DC polarization plots revealed that the addition of zinc oxide can also shift the corrosion potential of steel toward positive potentials.

Application of Quantum Dot-Molecularly Imprinted Polymer Core-Shell Particles Sensitized with Graphene for Optosensing of N(ε)-Carboxymethyllysine in Dairy Products.

Hydrophobic CdSe/ZnS quantum dots (QDs) coated with a molecularly imprinted polymer (MIP) sensitized with graphene (Gra-QDs@MIP) were prepared through a one-pot reverse microemulsion polymerization at room temperature. Gra-QDs@MIP was used as a molecular recognition element to construct a N(ε)-carboxymethyllysine (CML) optosensor. Graphene was used as a polymerization platform to increase the stability and kinetic binding properties of the system. Reverse microemulsion polymerization can anchor silica spheres on the surface of the QDs. This provides functional groups on the surface of Gra-QDs@MIP, which can bind CML and improve the fluorescence stability. Selective and sensitive optosensing of CML is possible at concentrations down to 3.0 μg L(-1) using Gra-QDs@MIP. Gra-QDs@MIP can be applied to dairy samples, as a recognition and response element for determining CML concentrations. The optosensing method was validated by high-performance liquid chromatography-mass spectrometry. The optosensor is economically and easily prepared, and the method is simple, fast, accurate, and reproducible.

Development and applications of molecularly imprinted polymers based on hydrophobic CdSe/ZnS quantum dots for optosensing of Nε-carboxymethyllysine in foods

A novel molecularly imprinted polymer (MIP) based on hydrophobic CdSe/ZnS quantum dots (HBQDs) was synthesized via an approach that combines MIPs for the selectivity and sensitivity with semiconductor HBQDs as optosensing material (HBQDs@MIP). Here, using a one-pot water-in-oil reverse microemulsion polymerization, the HBQDs@MIP was used as a molecular recognition element to construct an Nε-carboxymethyllysine (CML) optosensor. The HBQDs were coated with silica to endow the nanoparticles with high dispersibility and broad compatibility with hydrophilic analytes. Under optima conditions, the relative fluorescence intensity of the HBQDs@MIP decreased linearly with increasing CML concentration in the range 5–400μgL−1. The proposed method enables, detection procedures to be completed within 90min, with good recoveries, ranging from 85% to 106%. It can be applied to the rapid and cost–effective monitoring of CML in food samples.

Hybrid pseudocapacitor materials from polyaniline@multi-walled carbon nanotube with ultrafine nanofiber-assembled network shell

Porous carbon-based hybrids consisting of nanoscale building units are highlighted as supercapacitive materials for outstanding rate capability and cyclability. Herein reported are new hierarchically porous core–shell hybrids of polyaniline@multi-walled carbon nanotube (PANI@MWCNT) with ultrafine nanofiber-assembled network shell for supercapacitors via a facile reverse microemulsion polymerization route. Among various as-prepared samples, PANI@MWCNT2 hybrids (72 wt.% PANI loading) show the maximum specific capacitance of 663 F g−1 at 0.5 A g−1 with good capacitance retention of about 87% at 2 A g−1 in contrast to pure PANI (526 F g−1 with 76% retention) and other hybrids (613 and 538 F g−1 for the hybrids with 84 wt.% and 48% wt.% PANI, respectively). Moreover, 82% of initial capacitance still remains over 1000 cycles at 5 A g−1 for PANI@MWCNT2. The data clearly reveal a dramatic improvement of the hybrids in performance containing capacitance and rate capability meanwhile lifetime, thanks to unique structure features with highly surface-porous PANI nanofiber networks intimately wrapped around conductive MWCNTs helping to greatly promote faradic redox process and cycling behavior.

A triple-dimensional sensing chip for discrimination of eight antioxidants based on quantum dots and graphene.

A triple-dimensional sensing chip is developed based on simultaneous utilization of fluorescence (FL), electrochemical (ECL) and mass-sensitivity (MS) properties of a novel nanocomposites. The sensing nanomaterial is composed of CdSe/ZnS quantum dots (QDs) and graphene through a one-pot room-temperature reverse microemulsion polymerization. Here, full integration of QDs and graphene on one chip provides triple-dimensional sensing signals. It enables quick and accurate discrimination of eight analytes in a "lab-on-a-nanomaterial" approach and notably improves the overall sensor performance. Unknown samples randomly taken from the training set at concentrations of 0.7 μM are successfully classified by principal component analysis (PCA) with accuracies of 92.5%, compared with the high performance liquid chromatography (HPLC) method. We further apply it to discriminate eight antioxidants from real oil samples, and explore the mechanism.

A novel nanotube-shaped polypyrrole–Pd composite prepared using reverse microemulsion polymerization and its evaluation as an antibacterial agent

A nanotube-shaped PPy–Pd composite, as an antibacterial agent, was prepared using a unique combination of green synthesis and a microemulsion method.