Surface Functionalization Of Nanoparticles Research Articles

Curing epoxy with electrochemically synthesized MnxFe3-xO4 magnetic nanoparticles

Typically, surface functionalization of nanoparticles was practised as a useful strategy to enhance curing of thermoset nanocomposites after gelation takes place. By contrast, modification of bulk composition of nanoparticles for crosslinking facilitation was not reported. In this work, manganese (Mn)-doped Fe3O4 magnetic nanoparticles were synthesized via cathodic electrodeposition and characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), dispersive X-ray spectrometry (EDAX), and vibrating sample magnetometry (VSM). Low-filled epoxy nanocomposites containing Fe3O4 and Mn2+-doped Fe3O4 were then prepared to study the effect of cationic exchange between the first main transition series of periodic table of elements (Fe2+ cations were replaced by Mn2+ cations in Fe3O4) on epoxy curing reaction with a linear aliphatic amine. Nonisothermal differential scanning calorimetry (DSC) was used to evaluate epoxy crosslinking. Cure Index demonstrated that Mn2+ cations played the role of catalyst in epoxy/amine curing reaction, so that a shift from Poor to Good and Excellent cure was detected.

Surface-Functionalized Nanoparticles as Efficient Tools in Targeted Therapy of Pregnancy Complications.

Minimizing exposure of the fetus to medication and reducing adverse off-target effects in the mother are the primary challenges in developing novel drugs to treat pregnancy complications. Nanomedicine has introduced opportunities for the development of novel platforms enabling targeted delivery of drugs in pregnancy. This review sets out to discuss the advances and potential of surface-functionalized nanoparticles in the targeted therapy of pregnancy complications. We first describe the human placental anatomy, which is fundamental for developing placenta-targeted therapy, and then we review current knowledge of nanoparticle transplacental transport mechanisms. Meanwhile, recent surface-functionalized nanoparticles for targeting the uterus and placenta are examined. Indeed, surface-functionalized nanoparticles could help prevent transplacental passage and promote placental-specific drug delivery, thereby enhancing efficacy and improving safety. We have achieved promising results in targeting the placenta via placental chondroitin sulfate A (plCSA), which is exclusively expressed in the placenta, using plCSA binding peptide (plCSA-BP)-decorated nanoparticles. Others have also focused on using placenta- and uterus-enriched molecules as targets to deliver therapeutics via surface-functionalized nanoparticles. Additionally, we propose that placenta-specific exosomes and surface-modified exosomes might be potential tools in the targeted therapy of pregnancy complications. Altogether, surface-functionalized nanoparticles have great potential value as clinical tools in the targeted therapy of pregnancy complications.

Curing epoxy with polyvinylpyrrolidone (PVP) surface-functionalized ZnxFe3-xO4 magnetic nanoparticles

Curing reaction of epoxy nanocomposites depends to a large extent on the microstructure and the functionality of nanoparticles. In this work, cathodic electrochemical deposition was practised in synthesis of bare superparamagnetic iron oxide (SPIOs), polyvinylpyrrolidone (PVP) coated SPIOs (PVP-SPIOs), and zinc (Zn) doped PVP-SPIOs (Zn-doped PVP-SPIOs). The resulting SPIOs were fully characterized with X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM), and vibrating sample magnetometry (VSM) analyses. The results demonstrated formation of highly-curable epoxy nanocomposite by gradual replacement of some iron atoms in the bulk structure of PVP-SPIOs with Zn2+cations (Zn-doped PVP-SPIOs). Analyses also approved successful surface functionalization of PVP-SPIOs nanoparticles according to calculations based on the Cure Index (CI) that quantified cure quality of epoxy in the presence of PVP-SPIOs and Zn-doped PVP-SPIOs. Epoxy/PVP-SPIOs curing under nonisothermal DSC enlarged curing window thanks to dipole–dipole interactions between amid group of PVP and the oxirane rings of epoxy. The cure of epoxy changed from Poor to Good state at high (CI changed from 1.42 to 1.60) and low (CI changed from 1.67 to 1.81) heating rates by changing the bulk of PVP-SPIO via Zn doping. Catalyzing effect of Zn2+ through Lewis acid action was the reason for such phenomenon.

Viscoelastic behavior of silicone/clay nanocomposite coatings

Rubber/clay nanocomposites (RCNs) have attracted an emerging interest from academia and industry alike due to their outstanding tunable properties. The present paper addresses the viscoelastic behavior of silicone/clay systems in order to get an understanding of physical interactions in the RCNs systems as well as making possible interpretation of the effect of nanoparticle shape and surface functionality on viscoelastic behavior of molten RCNs. Rheological behavior determination of silicone/clay composites provides insight into dependency of properties of resulting nanocomposite coatings on processing and preparation conditions. The effect of bare and (3-aminopropyl) triethoxysilane (APTES) functionalized platy and tubular clays on viscoelastic behavior of silicone rubber nanocomposites were investigated by rheometric mechanical spectrometer (RMS). The analysis was set to the strain and frequency sweep tests, where the linear viscoelastic zone of the uncured nanocomposites were determined by dynamic strain sweep and then frequency sweep to probe into the role of dispersion of nanoparticles in silicone matrix. Well-known Han, Cole-Cole and van Gurp-Palmen models were applied to peruse silicone/clay interaction and to find additional information on rheological properties of nanocomposites under the influence of the shape, surface chemistry and content of nanoparticles. The findings depicted the effective role of physical interactions on APTES-functionalized clay on appropriate dispersion of clays throughout silicone matrix. This effect was more obvious in the presence of platelet-like clays in view of improved intercalation and/or exfoliation.

Toward Smaller Aqueous-Phase Plasmonic Gold Nanoparticles: High-Stability Thiolate-Protected ∼4.5 nm Cores.

Most applications of aqueous plasmonic gold nanoparticles benefit from control of the core size and shape, control of the nature of the ligand shell, and a simple and widely applicable preparation method. Surface functionalization of such nanoparticles is readily achievable but is restricted to water-soluble ligands. Here we have obtained highly monodisperse and stable smaller aqueous gold nanoparticles (core diameter ∼4.5 nm), prepared from citrate-tannate precursors via ligand exchange with each of three distinct thiolates: 11-mercaptoundecanoic acid, α-R-lipoic acid, and para-mercaptobenzoic acid. These are characterized by UV-vis spectroscopy for plasmonic properties; Fourier transform infrared (FTIR) spectroscopy for ligand-exchange confirmation; X-ray diffractometry for structural analysis; and high-resolution transmission electron microscopy for structure and size determination. Chemical reduction induces a blueshift, maximally +0.02 eV, in the localized surface plasmon resonance band; this is interpreted as an electronic (-) charging of the monolayer-protected cluster (MPC) gold core, corresponding to a -0.5 V change in electrochemical potential.

Understanding the surface functionalization of myricetin-mediated gold nanoparticles: Experimental and theoretical approaches

In this study, flavonoid myricetin-mediated gold nanoparticles (Myr-AuNPs) were synthesized and their molecular interactions were evaluated through a combined experimental and theoretical study. The physicochemical properties of the synthesized Myr-AuNPs were characterized using TEM, FT-IR, and XRD analysis. The average particle size of the Myr-AuNPs was found to be 6 nm with spherical in shape. FT-IR results indicated that the hydroxyl groups of myricetin interacts with Au3+ ions during the nanoparticles formation. Consequently, density functional theory (DFT) was used to evaluate the possible molecular interactions of myricetin hydroxyl groups with Au3+ ions. Interestingly, the DFT results confirmed that the 5′-hydroxyl group of ring B in myricetin was more suitable and highly stable to interact with Au3+ ions during the nanoparticles formation in aqueous medium. Further, this study emphasized that the synthesized Myr-AuNPs exhibits excellent pH, temperature, and storage stability. In addition to this, biocompatibility study recommended that Myr-AuNPs is safe for therapeutic applications. This is the first detailed report on the molecular interaction between the hydroxyl groups of myricetin and Au3+ ions during the nanoparticle formation.

Shielding and stealth effects of zwitterion moieties in double-functionalized silica nanoparticles

Surface functionalization of silica nanoparticles (SiO2NPs) has been considered as a promising strategy to develop target-specific nanostructures. However, finding a chemical functionalization that can be used as an active targeting moiety while preserving the nanoparticles colloidal stability in biological fluids is still challenging. We present here a dual surface modification strategy for SiO2NPs where a zwitterion (ZW) and a biologically active group (BAG) (amino, mercapto or carboxylic functionalities) are simultaneously grafted on the nanoparticles’ surface. The rationale behind this strategy is to generate colloidally stable nanoparticles and avoid the nonspecific protein adsorption due to ZW groups insertion, while the effective interaction with biosystems is guaranteed by the BAGs presence. The biological efficacy was tested against VERO cells, E. coli bacteria and Zika viruses and a similar trend was observed for all tested particles. The desirable “stealth property” to prevent nonspecific protein adhesion also generated a ZW shielding effect of the BAG functionality hindering their proper interaction and activity in cells, bacteria and viruses.

Surface functionalization of Pt nanoparticles with metal chlorides for bifunctional CO oxidation

Incorporation of a metal oxide or hydroxide species into Pt-based electrocatalysts has been shown to lower the overpotential required to oxidatively remove carbon monoxide from the catalyst surface, a reaction that is critical to preventing catalyst poisoning and deactivation in fuel cell devices. In this work, we report a general synthetic method toward Pt-metal oxide composite nanoparticles via the adsorption of metal halide ligands onto 1–2 nm colloidal Pt nanoparticles. Pt-metal oxide composite nanoparticles spanning across the first-row transition metals and post-transition metals are synthesized and characterized with transmission electron microscopy and energy dispersive X-ray scattering. CO stripping and steady-state CO oxidation experiments reveal that Mn, Fe, Co, Ni, and In oxides are capable of participating in the catalysis as a bifunctional partner and reduce the overpotential required for CO electrooxidation by ∼200 mV relative to pure Pt.

Surface functionalization of CoFe2O4 nanoparticles for driving the crystallization of the electroactive β-PVDF through judicious tailoring of the hybrid interface

Recently, extrinsic polymer-based magnetoelectric multiferroic materials have been investigated for many applications in nanoelectronics and energy harvesting. For that, poly(vinylidene fluoride) (PVDF), crystallized in β-phase, is known to present good ferroelectric and piezoelectric properties.We report here the functionalization of cobalt ferrite nanoparticles, known to be magnetostrictive, by a 1H,2H,2H-Perfluorooctanephosphonic acid (PFOP) for their better miscibility in PVDF. Hybrid self-standing films have been prepared; the degree of crystallinity (Xmc), as well as the fraction of β-polymorph, have been determined as a function of the amount of either functionalized or not nanoparticles, combining infrared (IR) spectroscopy and differential scanning calorimetry (DSC).We evidenced that the use of functionalized nanoparticles induced a better crystallinity degree as well as an improvement of the whole crystallization of β-PVDF polymorph. These results highlight the crucial role of the hybrid interface, when tailored through suitable surface chemistry, on the morphology developed by the hybrid.

Directed Assembly of Nanoparticle Threshold‐Selector Arrays

AbstractThe directed assembly of ordered arrays of cubic silver nanoparticles featuring distinct electrical threshold‐switching characteristics is reported. Threshold selectors are key elements for nonvolatile resistive random‐access‐memory architectures, as they suppress sneak path currents in crosspoint arrays. Nanocubes are site‐selectively immobilized on a TiO2‐coated silicon surface via a complementary molecular surface functionalization of nanoparticles and substrate based on a Cu(I)‐catalyzed alkyne‐azide cycloaddition without any physical template. Electrical characterization of individual silver nanocubes by conductive‐probe atomic force microscopy reveals pronounced and reproducible threshold‐switching behavior, featuring ultralow OFF currents below 1 pA, steep turn‐on slopes of <50 mV dec−1 and ON‐OFF ratios in excess of 103. Numerical simulation of Ag‐ion migration dynamics in the TiO2 electrolyte using a kinetic Monte Carlo model supports a switching mechanism based on conductive filament formation from Ag nanoclusters, and their reversible rupture in the low‐voltage regime. Assembled Ag nanocube threshold selectors are proposed for applications in memristive memory architectures, in particular for future highly integrated 3D circuitry.

Role of surface functionalization of ZnO nanoparticles as sorbents for heavy metal ions

ABSTRACT The surface functionalization of ZnO nanoparticles (ZnO NPs) was carried out by a simple one pot co-precipitation method followed by a facile ligand introduction onto the surface. This technique allows for tailoring of the surface chemistry to impart the specificity and affinity toward the target analytes (heavy metal ions like Pb and Hg) depending on the ligand incorporated on the surface resulting in highly selective sorbents. The functionalized ZnO NPs were characterized using different techniques. Elemental, IR, and thermal analysis studies confirm the presence of functional groups. X-ray diffraction (XRD) shows functionalization does not result in change of ZnO NPs but reduces their crystallinity. The average crystallite size of the nanoparticles is not affected by functionalization indicating that the process is restricted to the surface only. Surface area measurements reveal that functionalization results in mesoporous structures as can be deduced from the average pore diameter. Functionalization resulted in enhanced uptake of Pb and Hg, and the kinetics were very fast. Different models were used to understand the sorption behavior. The Langmuir uptake capacity values for lead and mercury using the thiol-functionalized ZnO NPs were found to be 78 and 145 mg/g, respectively. The role of interfering ions on the sorption was evaluated to get an idea of the selective nature of the sorbent.

Structural Engineering of Semiconductor Nanoparticles by Conjugated Interfacial Bonds.

Surface functionalization of semiconductor nanoparticles plays a significant role in the manipulation of the nanoparticle physicochemical properties and diverse applications. Conventional points of anchor involve mercapto, carboxyl and phenol moieties, forming largely nonconjugated interfacial linkages. In this personal account, we summarize recent progress in surface functionalization of semiconductor nanoparticles with olefin and acetylene derivatives, where the formation of conjugated interfacial bonds leads to ready manipulation of the nanoparticle optical and electronic properties, by using Si and TiO2 nanoparticles as the illustrating examples. Finally, a perspective is included where the promises and challenges of structural engineering of semiconductor nanoparicles are highlighted.

Surface Functionality and Water Adsorption Studies of α-Aluminium (III) Oxide Nanoparticles by near Infrared Spectroscopy

The adsorption of water on aluminium (III) oxide nanoparticle surface was studied by near infrared (NIR) spectroscopy. The comparison of NIR spectra at 40% and 60% humidity were reported in this work and were analyzed using second derivative techniques. The second derivative spectra were used to understand the chemistry of adsorption of water molecules. Small amounts of samples were dried under vacuum at 230 °C before the analysis. The analysis of the spectra confirms the presence of three different hydroxyl groups on aluminium (III) oxide surface. The spectra acquired during the adsorption of water molecules show the characteristic peaks in the range of 5400-5100 cm-1 corresponding to the combination band of water molecules hydrogen bonded with hydroxyl groups. There is also evidence for the presence of free water in the bulk of aluminium oxide. Furthermore, the mass of water adsorption on Al2O3 nanoparticle surface have been determined by gravimetric analysis. The gravimetric analysis confirms the adsorption of water molecules by aluminium (III) oxide surface.

Effect of morphology and hydrophobization of MoS2 microparticles on the stability of poly-α-olefins lubricants

The use of MoS2 nanoparticles as additive to lubricating oils is restricted by their low stability in oily media, which limits their use despite the enormous benefits associated with their intrinsic properties in terms of reduction of friction and wear coefficients. In this context, we investigated the effect of morphologies (platelets vs spheres) and surface functionalization of nanoparticles on the stability of their suspensions in poly-α-olefins (PAO) with various viscosities, which are base oils used in wind turbines. The particles were characterized by XRD, FTIR, scanning electron microscopy, atomic force microscopy and dynamic light scattering, and the stability of the resultant formulations was followed by optical (non-contact) measurements. It was found that the dispersions had similar stability despite the larger size of platelet-like particles compared to spherical ones (1–5 μm vs 600–800 nm). The dispersibility could be increased through grafting of alkylsilane on the surface defects (the longer the alkyl chain, the more stable the formulation) and with the increase of the oil kinematic viscosity (from 34 to 1705 cps at 25 °C).

A novel aptamer-based online magnetic solid phase extraction method for simultaneous determination of urinary 8-hydroxy-2′-deoxyguanosine and monohydroxylated polycyclic aromatic hydrocarbons

In this work, an innovative aptamer-based magnetic adsorbent (Fe3O4@PDA-aptamer MNPs) was prepared by hydrothermal synthesis method followed by the surface functionalization of nanoparticles. After fixing in a steel stainless tube as sorbent of magnetic solid phase extraction (MSPE), an online magnetic solid phase extraction-high performance liquid chromatography-mass spectrometry (online-MSPE-HPLC-MS) method was developed and applied for the determination of 8-hydroxy-2′-deoxyguanosine (8-OHdG) and monohydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) simultaneously in urine. The synthesized sorbent presented outstanding features, including large specific surface area, high enrichment capacity and excellent stability. High throughput analysis can be achieved by affinity-specific adsorption of 8-OHdG and non-specific adsorption of OH-PAHs at the same time. In addition, online MSPE can greatly simplify the analysis process, reduce human errors and enhance the sensitivity. When compared with offline MSPE, a sensitivity enhancement of 30–400 times was obtained for the online method. Some experimental parameters such as the amount of the sorbent, sampling flow rate and sample volume, were optimized systematically. Under the optimal conditions, the limits of detection (LOD) were in the range of 0.028–0.114 ng mL−1, and the correlation coefficients (R2) were higher than 0.9962. The relative standard deviations (RSDs) were less than 16.1% (n = 5) and the recoveries ranged from 71% to 116%. The above results show that the rapid, sensitive and automated online-MSPE-HPLC-MS method has potential application in the simultaneous determination of 8-OHdG and PAHs in complex sample matrix to assess the environmental exposure level.

Surface functionalization of silica nanoparticles to enhance aging resistance of asphalt binder

Abstract Oxidation aging of asphalt pavement is among most prevalent factors causing pavement distresses. Introduction of silica nanoparticles (SNPs) has been found promising to reduce oxidation aging of asphalt binder. However, the effectiveness of SNPs is limited by their poor dispersion caused mainly by SNP agglomeration requiring significant mechanical energy in processing to ensure dispersion. This paper examined merits of surface functionalization of SNPs with (3-aminopropyl) triethoxysilane (APTES) to improve its dispersion in asphalt binder using conventional processing techniques at relatively high loading of SNPs with low mechanical energy input. The morphology, size, amount of amine functional groups of APTES surface-modified SNPs (APTES-SNPs) were characterized and optimized by scanning electron microscope (SEM), dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR) and fluorescence measurement. The comparison between the surface-modified and pristine SNPs on the anti-aging and rheological properties of asphalt binder was conducted. The asphalt binders which contained APTES-SNPs demonstrated much better resistance to oxidative aging as evidenced by enhanced rheological properties compared to those containing pristine SNPs. The findings from this research provides insights as to the effect of APTES-SNPs on aging resistance of asphalt binder.

Surface Functionalization of MnFe2O4 Nanoparticles with Ethylenediamine for Hyperthermia Application

Biocompatible magnetic nanoparticles with enhanced heating proficiency are required for magnetic hyperthermia in order to use it efficiently in cancer treatment. In this paper, ethylenediamine functionalized monodispersed manganese iron oxide (MnFe2O4) nanoparticles were synthesized by using polyol method and functionalized nanoparticles were characterized by using X-ray diffraction, scanning electron microscope, transmission electron microscopy, vibrating sample magnetometry, fourier transform infrared spectroscopy and thermogravimetric analysis techniques for structural, morphological and magnetic analysis. Hyperthermia characteristics of functionalized MnFe2O4 nanoparticles were studied at 167.6, 251.4 and 335.2 Oe to assess the feasibility magnetic hyperthermia anticancer therapy. Outcome revealed that nanoparticles the self-heating temperature rise up to 48.76 to 56.34 °C at 5 and 10 mg mL-1 concentrations in water respectively. Specific absorption rate 94.65 W g-1 was observed at 5 mg mL-1 concentration. Biocompatibility study of functionalized nanoparticles has divulged almost no toxicity for nanoparticles.

Enhanced vibrational electron energy-loss spectroscopy of adsorbate molecules

Plasmonic excitations in metallic nanoparticles are known to depend strongly on nanoparticle size and shape. Here we explore how such excitations can be harnessed to enhance the vibrational signals from molecules adsorbed on nanoparticle surfaces, as detected using electron energy-loss spectroscopy in the scanning transmission electron microscope. We use the Born-Huang formalism in the electrostatic approximation to develop a theoretical model for electron energy-loss from an adsorbed molecule (represented by a point dipole) on the surface of a dielectric nanoparticle. We find that the adsorbate contribution to the energy-loss spectrum is approximately proportional to the square of the electric field at the adsorption site, and hence we find that the enhancement of the molecule's vibrational signal is greatest for molecules adsorbed on small, sharp nanoparticles. When the molecular frequency is near one of the nanoparticle frequencies, we generally find an asymmetric Fano-type spectrum line shape whose asymmetry is attributable to multimodal contributions. Our calculations for a molecule adsorbed on the tip of a prolate spheroidal silver nanoparticle predict that signal enhancements of several hundred times should be readily achievable, and up to several thousand times if the nanoparticle's plasmonic mode is ``tuned'' to the molecular frequency. Such enhancement effects potentially make vibrational STEM-EELS a powerful tool for the characterization of surface-functionalized nanoparticles and nanomaterials used for chemical sensing.

Cover Feature: Covalent Surface Functionalization of Calcium Phosphate Nanoparticles with Fluorescent Dyes by Copper‐Catalysed and by Strain‐Promoted Azide‐Alkyne Click Chemistry (ChemNanoMat 4/2019)

Cover Feature: Covalent Surface Functionalization of Calcium Phosphate Nanoparticles with Fluorescent Dyes by Copper‐Catalysed and by Strain‐Promoted Azide‐Alkyne Click Chemistry (ChemNanoMat 4/2019)

Graphene–semiconductor heterojunction sheds light on emerging photovoltaics

Electronic coupling of graphene atop a bulk semiconductor and the resultant interfacial energy-band reorganization create a light-sensitive junction only one atom below the front surface. Uniquely, this architecture leads to the surface being in extremely close proximity to the depletion region (typically buried several micrometres under the surface for a conventional wafer-based p–n junction solar cell), thus providing direct access to the photosensitive junction, which can be modified by surface functionalization and/or incorporation of plasmonic nanoparticles. The surface-based heterojunction, tunable carrier transport and relatively enhanced optical absorption in such 2D-layer-interfaced 3D semiconductor systems will have a transformative impact in the field of 2D optoelectronics, photovoltaics, photonics and nanoelectronics. Graphene-on-bulk semiconductors may enable new directions for ultrathin optoelectronics and photovoltaics.