Robust Fe3O4/SiO2-Pt/Au/Pd magnetic nanocatalysts with multifunctional hyperbranched polyglycerol amplifiers

Enhanced oil recovery using hyperbranched polyglycerol polymer-coated silica nanoparticles

Functionalized Fe₃O₄-SiO₂ magnetic nanoparticles (Fe-Si-MNPs) coated with hyperbranched polyglycerol polymer were prepared and tested for oil recovery from oil in water (O/W) emulsions. The structure, chemistry, and surface modifications of the newly developed demulsifier (PSiMNPs) were analyzed, and the percentage demulsification efficiency (%η_dem) was tested at differing concentrations of surfactant (C_sur), oil (C_oil), and demulsifier (D_PSiMNPs). The developed PSiMNPs can be separated from the solution by a magnetic field, regenerated using ethanol, and reused several times. The reported %η_dem was ≥80% for all the studied C_oil. The %η_dem improved as the C_sur and pH decreased, with maximum values of 98.8% and 98.5% achieved at C_sur = 0.05 g/L and a pH = 4, respectively. A D_PSiMNPs = 100 mg/L was sufficient to achieve %η_dem of 99.4% for C_oil = 100 mg/L and slightly decreased to ~93% for C_oil ~4000 mg/L. The PSiMNPs can be reused up to 15 times with a steady %η_dem of 89.1% for C_oil = 100 mg/L and 88.6% for C_oil = 4000 mg/L. The adsorption of oil on the PSiMNPs follows Freundlich isotherm with maximum adsorption capacity (q_max) of 192.8 g/mg and Langmuir constant (b) of 28.06 mg/L for C_oil = 900 mg/L. The q_max of the recycled PSiMNPs slightly decreased to 189.08 g/mg. The kinetic of oil recovery follows the PSO with a K₂ of 0.0169 g/mg. min. Surface modification of Fe-Si-MNPs enhanced the oil adsorption, increased the adsorption capacity, and extended the service life resulting in a better cost and process feasibility.

Ag2CO3 containing magnetic nanocomposite as a powerful and recoverable catalyst for Knoevenagel condensation

In this paper, the synthesis, characterization and catalytic application of a novel magnetic silica-supported Ag2CO3 (MS/Ag2CO3) with core-shell structure are developed. The MS/Ag2CO3 nanocomposite was prepared through chemical modification of magnetic MS nanoparticles with AgNO3 under alkaline conditions. The structure, chemical composition and magnetic properties of MS/Ag2CO3 were investigated by using VSM, PXRD, FT-IR, EDX and SEM techniques. The MS/Ag2CO3 nanocomposite was used as an effective catalyst for the Knoevenagel condensation under solvent-free conditions at 60 °C in an ultrasonic bath. The recovery and leaching tests were performed to study the nature of the MS/Ag2CO3 catalyst under applied conditions.

Biosensing platform on ferrite magnetic nanoparticles: Synthesis, functionalization, mechanism and applications

Ferrite magnetic nanoparticles (FMNPs) are gaining popularity to design biosensors for high-performance clinical diagnosis. The fusion of information shows that FMNPs based biosensors require well-tuned FMNPs as detection probes to produce large and specific biological signals with minimal non-specific binding. Nevertheless, there is a noticeable lacuna of information to solve the issues related to suitable synthesis route, particle size reduction, functionalization, sensitivity towards targeted intercellular biological tiny particles, and lower signal-to-noise ratio. Therefore it allows exploring unique characteristics of FMNPs to design a suitable sensing device for intracellular measurements and diseases detection. This review focuses on the extensively used synthesis routes, their advantages and limitations, crystalline structure, functionalization, along with recent applications of FMNPs in biosensors, taking into consideration their analytical figures of merit and range of linearity. This work also addresses the current progress, key factors for sensitivity, selectivity and productivity improvement along with the challenges, future trends and perspectives of FMNPs based biosensors.

Copper based on diaminonaphthalene-coated magnetic nanoparticles as robust catalysts for catalytic oxidation reactions and C-S cross-coupling reactions

In this work, the immobilization of copper(ii) on the surface of 1,8-diaminonaphthalene (DAN)-coated magnetic nanoparticles provides a highly active catalyst for the oxidation reaction of sulfides to sulfoxides and the oxidative coupling of thiols to disulfides using hydrogen peroxide (H2O2). This catalyst was also applied for the one-pot synthesis of symmetrical sulfides via the reaction of aryl halides with thiourea as the sulfur source in the presence of NaOH instead of former strongly basic and harsh reaction conditions. Under optimum conditions, the synthesis yields of sulfoxides, symmetrical sulfides, and disulfides were about 99%, 95%, and 96% respectively with highest selectivity. The heterogeneous copper-based catalyst has advantages such as the easy recyclability of the catalyst, the easy separation of the product and the less wastage of products during the separation of the catalyst. This heterogeneous nanocatalyst was characterized by FESEM, FT-IR, VSM, XRD, EDX, ICP and TGA. Furthermore, the recycled catalyst can be reused for several runs and is economically effective.

Low molecular weight glycerol derived coatings on magnetic nanoparticles: role of initiator, temperature, rate of monomer addition, enhanced biocompatibility and stability

Biocompatible polymer coatings for magnetic nanoparticles have shown to drastically increase their usability towards biomedical applications. The coatings imprint characteristics such as stability, resistance to non-specific adsorption and tolerance in complex media for biomedicine. Herein, a thorough investigation towards the anionic ring-opening polymerization of glycidol on the surface of carbon-coated cobalt nanoparticle was performed. Reaction parameters that influence polymer growth have been investigated. Thereafter, a maximal achievable hyperbranched polyglycidol M_w of up to 1148 g mol⁻¹ under optimal reaction conditions was obtained. With this coating, the dispersion stability of the particles could be substantially increased, the non-specific adsorption of proteins could be decreased to 10% while retaining an efficient magnetic separation.

A highly efficient coating process of magnetic nanoparticles with hyperbranched polyglycidol was investigated and the resulting particles were tested towards their biocompatible capabilities.

Hyperbranched Poly(ester-enamine) from Spontaneous Amino-yne Click Reaction for Stabilization of Gold Nanoparticle Catalysts

Hyperbranched polymers have garnered much attention due to attractive properties and wide applications, such as drug-controlled release, stimuli-responsive nano-objects, photosensitive materials and catalysts. Herein, two types of novel hyperbranched poly(ester-enamine) (hb-PEEa) were designed and synthesized via the spontaneous amino-yne click reaction of A₂ monomer (1, 3-bis(4-piperidyl)-propane (A_2a ) or piperazine (A_2b )) and B₃ monomer (trimethylolpropanetripropiolate). According to Flory's hypothesis, gelation is an intrinsic problem in an ideal A₂ +B₃ polymerization system. By controlling the polymerization conditions, such as monomer concentration, molar ratio and rate of addition, a non-ideal A₂ +B₃ polymerization system can be established to avoid gelation and to synthesize soluble hb-PEEa. Due to abundant unreacted alkynyl groups in periphery, the hb-PEEa can be further functionalized by different amino compounds or their derivates. The as-prepared amphiphilic PEG-hb-PEEa copolymer can readily self-assemble into micelles in water, which can be used as surfactant to stabilize Au nanoparticles (AuNPs) during reduction of NaBH₄ in aqueous solution. As a demonstration, the as-prepared PEG-hb-PEEa-supported AuNPs demonstrate good dispersion in water, solvent stability and remarkable catalytic activity for reduction of nitrobenzene compounds.

Recent Novel Hybrid Pd–Fe3O4 Nanoparticles as Catalysts for Various C–C Coupling Reactions

The use of nanostructure materials as heterogeneous catalysts in the synthesis of organic compounds have been receiving more attention in the rapid developing area of nanotechnology. In this review, we mainly focused on our own work on the synthesis of hybrid palladium–iron oxide nanoparticles. We discuss the synthesis of Pd–Fe3O4—both morphology-controlled synthesis of Pd–Fe3O4 and transition metal-loaded Pd–Fe3O4—as well as its application in various C–C coupling reactions. In the case of rose-like Pd–Fe3O4 hybrid nanoparticles, thermal decomposition can be used instead of oxidants or reductants, and morphology can be easily controlled. We have developed a method for the synthesis of nanoparticles that is facile and eco-friendly. The catalyst was recyclable for up to five continual cycles without significant loss of catalytic activity and may provide a great platform as a catalyst for other organic reactions in the near future.

Facile synthesis of graphene oxide-silver nanocomposite for decontamination of water from multiple pollutants by adsorption, catalysis and antibacterial activity

Here in, we presented a facile one-step method for the synthesis of Graphene oxide-silver (GO-Ag) nanocomposite and its applications as a sorbent for the elimination of some toxic pollutants from aqueous medium, as an efficient catalyst in the individual as well as simultaneous reduction reactions of multiple compounds, and as an antibacterial agent for the destruction of some harmful microorganisms existent in wastewater. GO was prepared using a modified Hummers method and Ag nanoparticles were integrated on GO sheets by chemical reduction of Ag⁺ ions on the surfaces of GO sheets. The composition and morphology of the nanocomposite was extensively characterized with elemental dispersive X-ray analysis (EDX), Fourier transform infra-red (FT-IR) spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). The GO-Ag nanocomposite demonstrated remarkable adsorption capacities and recyclability for malachite green (MG) and ethyl violet (EV) dyes. Various experimental parameters affecting adsorptive behavior of nanocomposite like temperature, pH, time of contact between dye and adsorbent, and adsorbent dose were evaluated thoroughly. Experimental data was simulated with different adsorption isotherms and kinetic models to evaluate adsorption behavior of both dyes and results confirmed the adsorption of both the dyes to be followed by pseudo 2nd order kinetic model and Langmuir adsorption model. Moreover, adsorbent was regenerated in suitable media for both dyes without any loss in removal efficiency. The catalytic performance for the 2-nitroaniline (2-NA) reduction was investigated in detail. Most importantly, the prepared nanocomposite was found to have potential to adsorb multiple pollutants all together as well as to catalyze the simultaneous reduction of a mixture of dyes (MG, MO, and EV) and 2-NA. An additional advantage of the GO-Ag nanocomposite was its antibacterial activity acquired to the presence of Ag nanoparticles. Two bacterial strains (Gram-negative bacterium, E. coli and the Gram-positive bacterium, S. aureus) were used to test antibacterial activity of composite and the results confirmed the remarkable performance of the nanocomposite in destroying harmful pathogens.

C–P bond construction catalyzed by NiII immobilized on aminated Fe3O4@TiO2 yolk–shell NPs functionalized by (3-glycidyloxypropyl)trimethoxysilane (Fe3O4@TiO2 YS-GLYMO-UNNiII) in green media

An efficient, versatile and novel method for the C–P cross-coupling reaction with a high yield of products using Fe₃O₄@TiO₂YS-GLYMO-UNNi^II as a magnetic nanostructured catalyst in the presence of WERSA was reported.

Magnetofluorescent nanohybrid comprising polyglycerol grafted carbon dots and iron oxides: Colloidal synthesis and applications in cellular imaging and magnetically enhanced drug delivery

Multifunctional nanohybrids are attracting increasing attention for potential biomedical applications such as bioimaging and drug delivery due to their combined advantages of individual components. However, challenges in the improvement of their synthesis and colloidal stability to facilitate practical biomedical applications still remain. In this work, we report an efficient synthetic approach to fabricate magnetofluorescent nanohybrid (IO-PG-CD) comprising fluorescent carbon dots (CDs) and magnetic iron oxide nanoparticles (IOs) through polyglycerol (PG) mediated covalent linkage in aqueous media. CDs and IOs are first grafted with PG layer, and then functionalized with carboxyl and amino groups, respectively. The resulting CD-PG-COOH and IO-PG-NH₂ handled as simple chemical compounds are integrated through EDC/NHS crosslinking to obtain the desired IO-PG-CD nanohybrid. The unprecedented hydrophilicity of PG layer endows IO-PG-CD nanohybrid with excellent colloidal stability in various physiological media, facilitating biomedical applications in vitro and in vivo. IO-PG-CD nanohybrid exhibits low cytotoxicity and its uptake by cells can be obviously enhanced by external magnetic attraction. The internalized IO-PG-CD nanohybrid emits multicolor fluorescence as observed by confocal fluorescence microscopy, demonstrating much better photostability than the nanoparticle labeled with organic dye. Taking advantage of enormous chelating carboxyl groups on the surface of IO-PG-CD nanohybrid, platinum-based anticancer drug was loaded on the surface (IO-PG-CD/Pt) through complexation and delivered into cancer cells in a magnetically enhanced manner, killing the cancer cells efficiently in vitro. Moreover, in vivo cancer therapy indicates that the external magnetic attraction also obviously improves the anticancer efficacy of IO-PG-CD/Pt in HeLa subcutaneous xenografts.

Red fluorescent ZnO nanoparticle grafted with polyglycerol and conjugated RGD peptide as drug delivery vehicles for efficient target cancer therapy

In the field of modern nanomedicine, ZnO nanoparticles were considered as an emerging candidate for drug delivery because of their inherent biocompatibility and stability. However, the poor dispersibility in a physiological medium obstructed their clinic applications. In this paper, the red fluorescence ZnO nanoparticles were synthesized, using a facile chemical method of polyol in boiling trimethylene glycol (TREG) with zinc acetate. The as-synthesized ZnO nanoparticles were first time grafted with PG layer through ring-opening polymerization of glycidol (ZnO-PG). As calculated from the TGA data, the weight ratio of the grafted PG was about 68 wt%. Then, the ZnO-PG engineered to conjugate with arginine-glycine-aspartate (RGD) peptide by stepwise organic reactions. Finally, anticancer drugs Doxorubicin hydrochloride (DOX) was immobilized on ZnO-PG-RGD (approximately 21.8 ± 0.9 nm) to form ZnO-PG-RGD/DOX. The drug release percentage reaches 70.6% within 48 h under pH 5.2, which was more than 3-fold higher than that pH 7.4. The properties of ZnO nanoparticles and its derivatives were detected by power XRD, TEM, EDS, FTIR, TGA, DLS, Zeta potential and UV. The grafted PG layer not only largely enhanced the dispersibility, but also inhibited ZnO nanoparticles from the uptake by U87MG and Hela cells. In contrast, ZnO-PG-RGD was selectively taken up by U87MG, not Hela cells, demonstrating an obvious targeting property. When ZnO-PG-RGD/DOX was used, U87MG cells showed specificity damaged compared with Hela cells. Thus, functionalized ZnO nanoparticle was a promising nanomaterial in cancer theranostics.

Single-Step Metal-Free Grafting of Cationic Polymer Brushes on Fluorescent Nanodiamonds

Cationic polymers are often employed in conjugation with nanomaterials, and the resultant hybrids are useful for various bioapplications. Here, a single-step metal-free method for the synthesis of fluorescent nanodiamonds (FNDs) conjugated with cationic polymer brushes is reported. Distinct from the common methods such as atom transfer radical polymerization and reversible addition fragmentation chain transfer, our ring-opening-polymerization-based method is simple and less time consuming and hazardous. Infrared spectroscopy, thermogravimetric analysis, zeta potential, and dynamic light scattering confirmed the synthesis. The produced FND-polymer brushes showed markedly higher cell labeling and internalization efficiency without noticeable cytotoxicity. Our method is general and applicable to other nanoparticles as well for uses in diverse research areas.

Synthesis and characterization of graphene oxide sheets integrated with gold nanoparticles and their applications to adsorptive removal and catalytic reduction of water contaminants

Here, we report the facile synthesis of graphene oxide–gold (GO–Au) nanocomposites and their use as adsorbents for the removal of toxic industrial dyes from water and as catalysts for the individual and simultaneous reduction of a dye and a nitro compound in aqueous medium. GO sheets were prepared using a modified Hummers method while Au nanoparticles were integrated on GO sheets by reducing Au(iii) ions on the surfaces of GO sheets using sodium citrate as a reducing agent. The prepared composite was characterized with field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), elemental dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Fourier transform infra-red (FT-IR) spectroscopy and thermal gravimetric analysis (TGA). The GO–Au nanocomposite demonstrated efficient adsorption capacities and recyclability for malachite green (MG) and ethyl violet (EV) dyes. The effects of various experimental parameters including temperature, pH, contact time, and adsorbent dose were studied. From the simulation of experimental data with different adsorption isotherms and kinetic models it was found that the adsorption of both the dyes followed the Freundlich adsorption model and a pseudo-second order kinetic model, respectively. Moreover, the adsorbent showed better recyclability for both dyes without any compromise on the removal efficiency. Similarly, the catalytic performance for the reduction of 2-nitroaniline (2-NA) has been investigated in detail by using the prepared nanocomposite as a catalyst. Most importantly, we reported the simultaneous adsorption of cationic and anionic dyes from water using the prepared nanocomposite as well as the simultaneous catalytic reduction of a mixture of EV and 2-NA. So, considering the facile synthesis process and the efficient removal of a variety of dyes and the catalytic performance this work opens up a tremendous opportunity to bring GO based nanocomposites from experimental research to practically applied materials for wastewater treatment.

Preparation of graphene oxide–gold (GO–Au) nanocomposites as adsorbents and catalysts for decontamination of water.

Development of Antifouling Hyperbranched Polyglycerol Layers on Hydroxyl Poly-p-xylylene Coatings

Antifouling surfaces that are resistant to protein adsorption and cell adhesion are desirable for many biomedical devices, such as diagnostic devices, biosensors, and implants. In this study, we developed an antifouling hyperbranched polyglycerol (hPG) surface on hydroxyl poly-p-xylylene (PPX-OH). PPX-OH was deposited via chemical vapor deposition (CVD), and an hPG film was then developed via the ring-opening reaction of glycidol. The hPG film greatly reduced the adhesion of L929 cells and platelets as well as protein adsorption. The addition of alkenyl groups in the hPG layer allows the conjugation of biomolecules, such as peptides and biotin, and elicits specific biological interactions. Since the CVD deposition of PPX-OH could be applied to most types of materials, our approach makes it possible to decorate an antifouling hPG film on most types of materials. Our method could be applied to biosensors, diagnostics, and biomedical devices in the future.

Polyglycerol mediated covalent construction of magnetic mesoporous silica nanohybrid with aqueous dispersibility for drug delivery

Construction of nanohybrids with chemical and colloidal stability is of great importance for the exploration of their potential applications in biomedical field. In this work, a versatile strategy based on polyglycerol (PG) mediated covalent linkage is developed to fabricate a core-satellite nanohybrid, termed MMSN, consisting of a mesoporous silica nanoparticle (MSN) as a core and many superparamagnetic iron oxide nanoparticles (SPION) on the outer surface. In this synthetic strategy, the PG grafted SPION is derivatized to convert partial periphery hydroxyl groups to carboxyl moieties, followed by attachment to aminated MSN through amide bonds. The PG layer accounting for ~17wt% of MMSN not only serves as a tether to connect the two nanoparticles but also greatly enhances the colloidal stability of the nanohybrid, resulting in no significant change in hydrodynamic diameter and zeta potential during four months. Taking advantage of the combined porosity and magnetic property of the nanohybrid, a photosensitizer chlorin e6 (Ce6) is loaded on MMSN and efficiently delivered into target cells under magnetic guidance, leading to an enhanced efficacy of photodynamic therapy (PDT). The versatile strategy presented here opens up a new route to rational design and fabrication of multifunctional nanohybrids for various biomedical purposes.

Bottom-Up Strategy To Prepare Nanoparticles with a Single DNA Strand

We describe the preparation of cross-linked, polymeric organic nanoparticles (ONPs) with a single, covalently linked DNA strand. The structure and functionalities of the ONPs are controlled by the synthesis of their parent linear block copolymers that provide monovalency, fluorescence and narrow size distribution. The ONP can also guide the deposition of chloroaurate ions allowing gold nanoparticles (AuNPs) to be prepared using the ONPs as templates. The DNA strand on AuNPs is shown to preserve its functions.

C–C coupling reactions using a gold(iii) phosphorus complex confined within metal–organic framework fibers in aqueous solution

HPG@KCC-1/PPh₂/Au NPs were used for the first time as a catalyst for the C–C cross-coupling between allylarenes or methyl acrylate and benzoxazole, and they showed excellent catalytic activities under green conditions.

Synthesis and characterization of biocompatible antimicrobial N-halamine-functionalized titanium dioxide core-shell nanoparticles

As one of the most powerful biocides, N-halamine based antimicrobial materials have attracted much interest due to their non-toxicity, rechargeability, and rapid inactivation against a broad range of microorganisms. In this study, novel titanium dioxide-ADMH core-shell nanoparticles [TiO₂@poly (ADMH-co-MMA) NPs] were prepared via miniemulsion polymerization using 3-allyl-5,5-dimethylhydantoin (ADMH) and methyl methacrylate (MMA) with nano-TiO₂. The produced nanoparticles were characterized by FT-IR, TEM, TGA, and XPS. The UV stability of N-halamine nanoparticles has been improved with the addition of titanium dioxide. After chlorination treatment by sodium hypochlorite, biocidal efficacies of the chlorinated nanoparticles against S. aureus (ATCC 6538) and E. coli O157:H7 (ATCC 43895) were determined. The nanoparticles showed excellent antimicrobial properties against bacteria within brief contact time. In addition, in vitro cell cytocompatibility tests showed that the antibacterial nanoparticles had good biocompatibility.

Solution-Stable Colloidal Gold Nanoparticles via Surfactant-Free, Hyperbranched Polyglycerol-b-polystyrene Unimolecular Templates

Hyperbranched polyglycerol-block-polystyrene copolymers, denoted HPG-b-PS, are synthesized and employed as a new and effective unimolecular template for synthesizing colloidal gold (Au) nanoparticles. The coordination of noble metal precursors with polyether within the inner HPG core and subsequent in situ reduction enables the formation of well-dispersed and stable PS-capped Au nanoparticles. The inner HPG core is produced via ring opening multibranching polymerization (ROMBP) and subsequently converted into atom transfer radical polymerization (ATRP) macroinitiators for the controlled growth of polystyrene (PS) arms possessing low polydispersity (PDI < 1.31). An initial investigation into the templating parameters of HPG-b-PS was undertaken by producing templates with different arm numbers (98 and 117) and different PS chain lengths (i.e., molecular weight = 3500-13400 g/mol). It was found that the PS chain length and solvent conditions affect the quality of the resulting PS-capped colloidal Au nanoparticles. This work demonstrates, for the first time, a simple, lower-cost approach for templating nonpolar solvent-soluble PS-capped Au nanoparticles on the order of 10-30 nm in diameter.

Organic Phase Syntheses of Magnetic Nanoparticles and Their Applications

In the past two decades, the synthetic development of magnetic nanoparticles (NPs) has been intensively explored for both fundamental scientific research and technological applications. Different from the bulk magnet, magnetic NPs exhibit unique magnetism, which enables the tuning of their magnetism by systematic nanoscale engineering. In this review, we first briefly discuss the fundamental features of magnetic NPs. We then summarize the synthesis of various magnetic NPs, including magnetic metal, metallic alloy, metal oxide, and multifunctional NPs. We focus on the organic phase syntheses of magnetic NPs with precise control over their sizes, shapes, compositions, and structures. Finally we discuss the applications of various magnetic NPs in sensitive diagnostics and therapeutics, high-density magnetic data recording and energy storage, as well as in highly efficient catalysis.

A click strategy for the immobilization of palladium nanoparticles onto silica: efficient and recyclable catalysts for carbon–carbon bond formation under mild reaction conditions

The synthesis of silica-grafted palladium catalyst through “click” reaction of azide-functionalized silica with methylpropargylimidazolium bromide, for Heck and Suzuki–Miyaura coupling reactions.

Catalysis by multifunctional polyelectrolyte capsules

Gold and iron oxide modified polyelectrolyte capsules have been used as multifunctional platforms for catalysis and magnetic separation. Gold nanoparticle size and shell composition had an influence on their catalytic activity.

Versatile surface charge-mediated anti-fouling UF/MF membrane comprising charged hyperbranched polyglycerols (HPGs) and PVDF membranes

We develop a charge-modified PVDF UF/MF membrane that restricts membrane fouling derived from charged water contaminants.