Surface Functionalization Agent Research Articles

Chromogenic Detection of Fe2+ Using Schiff base–naphthalene-2-ol-modified Silver Nanoparticles

Schiff base–naphthalene-2-ol (L) was synthesized by a coupling reaction between 2-hydroxy-1-naphthaldehyde and xylylenediamine in ethanol. The product was characterized by 1H NMR, 13C NMR, and mass spectroscopy. L was utilized as reducing and surface functionalizing agents in the synthesis of silver nanoparticles (AgNPs) which were then characterized by high-resolution transmission electron microscopy (HR-TEM) and UV–Visible spectroscopy. The colorimetric sensitivity and metal ion selectivity of L-modified AgNPs with various cations were examined using UV–Vis spectrophotometry. The presence of Fe2+ induced the aggregation of AgNPs through a cooperative metal–ligand interaction, resulting in a color change from bright yellow to dark yellow with a new band at 372 nm. The interference studies confirmed the high selectivity of Fe2+ sensing in presence of cations as well as anions by L-modified AgNPs. A linear relationship between the change of absorption at 372 nm and concentration Fe2+ ranging from 1.30 × 10−5 to 1.13 × 10−3 M was observed with a correlation coefficient of 0.9949. The detection limit of the developed method was 1.06 × 10−6 M. The proposed method has been successfully applied for determination of Fe2+ content in multivitamin tablet samples. The results were in good agreement with the label claim.

Interaction of cadmium sulfide quantum dots with jacalin for specific recognition of cancer cells

Surface functionalizations of quantum dots (QDs) are expected to improve their optoelectronic properties and advance their targeting nature, which is highly warranted for application in molecular imaging and biomedical diagnostics. Therefore, an understanding the interaction between surface functionalization agents and QDs is a prerequisite for their application. Herein, we investigated the interaction between cadmium sulfide (CdS) QDs and dietary T-antigen binding lectin (jacalin) isolated from Indian jack fruit seeds. Fluorescence spectroscopy study showed that CdS QDs effectively quenched the intrinsic fluorescence of jacalin. Analysis of fluorescence quenching at a different temperature indicated that the mechanism of interaction is static and a non-radiation energy transfer occurred within the molecules. The obtained binding constant, Ka value in the order of 104M−1 at the tested temperature range suggested that the binding affinity between jacalin and CdS QDs is in the same range as those obtained for the interaction of lectin with carbohydrate. Thermodynamic analysis of the binding data, ΔH0=−44.24±1.21kJmol−1, ΔS0=−60.92±4.10Jmol−1K−1 and ΔG0=−26.21±0.1kJmol−1 suggested that the binding reaction is enthalpy-driven spontaneous process. Hemagglutination activity of jacalin is well preserved even after binding to CdS QDs, indicating that the jacalin-CdS QDs complex can recognize T-antigens of the malignant tissues. To support the claim, we demonstrated selective fluorescence labeling of chronic myeloid leukemia cells, K562 with jacalin-CdS QDs complex.

Mechanically robust polyvinylidene fluoride (PVDF) based superhydrophobic coatings for self-cleaning applications

The demand for effective self-cleaning, water repellant coatings has been growing over the years. Achieving superhydrophobic coatings with good mechanical durability has always been a key challenge. In this work, superhydrophobic surface was created by introducing silica nanoparticles in a polyvinylidene fluoride matrix (PVDF). The combination of a fluorinated polymer matrix and inorganic particulate fillers (SiO2) and surface functionalizing agent aminopropyltriethoxysilane (APTES) produced coatings with improved mechanical properties and good adhesion with the substrate. The static contact angle (CA) of the composite coating with PVDF: SiO2 = 1: 1 by weight was found to be 154° with a sliding angle of <2°. The mechanical properties of the coating, particularly hardness and Young’s modulus, effect of accelerated erosion and coating adhesion have been studied in detail. The effect of UV weathering on the coated surfaces is also tested. A simple self-cleaning test based on spectrophotometry is applied to quantitatively measure the self-cleaning performance of the coatings. The described coating process is simple and can be effectively scaled up for large structure protection.

Fabricating a graphene oxide—bayberry tannin sponge for effective radionuclide removal

Bayberry tannin (BT)–reduced graphene oxide (rGO) sponges have been prepared by self–assembly, with bayberry tannin serving as both reductant and surface functionalization agent. The synthetic method is based on the self-assembly of graphene oxide (GO) sheets into porous hydrogel structures. By varying the weight ratio of GO to BT, a series of sorbents with different densities of organic molecules have been obtained and applied to remove Sr2+ from aqueous solutions. Adsorption isotherms (Langmuir and Freundlich) and kinetics (pseudo-first order and pseudo-second order) have been investigated to discuss the sorption performance of rGO/BT sponges. The rGO/BT (w/w 1:1) sponge shows excellent adsorption properties for Sr2+, with maximum capacities of 67.98 mg g−1. The adsorption capacity is much higher than those in classic Sr2+ adsorbents, such as hydrous manganese dioxide, Egyptian soils, Hydroxyapatite nanoparticles, sodium hexa-titanate nanofibers, Graphene oxide, artificially altered phlogopite(Ca–Phl), and PB/Fe3O4/GO. Adsorption mechanisms have been examined using the x-ray photoelectron spectra of sorbents before and after Sr2+ adsorption, and the results indicate that the sorption of Sr2+ on GO and GO/BT 1.0 is largely depended on oxygen functional groups. The results show that the GO/BT sponge is a promising candidate for adsorbing Sr2+ ion.

Facile synthesis of multifunctional silver nanoparticles using mangrove plant Excoecaria agallocha L. for its antibacterial, antioxidant and cytotoxic effects.

The current study describes a simple, rapid and eco-friendly method for the synthesis of silver nanoparticles (AgNPs) using Excoecaria agallocha (E. agallocha) leaf extract as stabilizer, bioreductant and capping agent. Synthesized AgNPs were characterized by UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX). Generation of AgNPs was initially confirmed with the color change from yellow to dark brown which produces intense absorbance spectra at 440nm in UV-Vis spectroscopy without any shifting of peaks. Further, XRD pattern confirms that the synthesized AgNPs was face centered cubic (fcc) crystalline in structure with an average size of 20nm. On the other hand, FTIR spectrum reveals that the active metabolites like water soluble phenolic compounds, flavonoids, methylene groups, amides and carboxylate groups. These active biocompounds plays a vital role in the reduction of Ag+ into their nanoscale values, it also acts as a stabilizing and surface functionalization agent. FESEM micrographs of synthesized AgNPs shows spherical and hexagonal shaped well dispersed particles in the dimension ranging between 23 and 42nm. EDAX confirms the presence of silver (Ag) as the major constituent element without any impurities; also substantiate the stability of generated AgNPs. The biomedical insights of nanoparticles (NPs) were assessed through radical scavenging and antibacterial properties. Additionally, synthesized AgNPs was also exhibits an excellent cytotoxic effect against human breast carcinoma cell lines (MCF-7). This study proves that synthesized AgNPs can be developed as a potential nano-drug formulation to combat pathogenic disease and also for the expansion of breast cancer therapy.

Comparative Study of TiO2/CuS Core/Shell and Composite Nanostructures for Efficient Visible Light Photocatalysis

An enduring impediment in the photocatalysis domain is the rapid recombination of photoinduced charge carriers. One viable strategy to realize efficient separation of photoinduced charge carriers is to design core/shell nanostructures. In this context, our work explains the substantial separation of photocarriers and enhanced light harvesting in TiO2 nanostructures following the realization of core/shell geometry with CuS. We demonstrate the design of the TiO2/CuS core/shell nanostructures, utilizing a surface-functionalizing agent, 3-mercaptopropionic acid, and offering commendable visible light driven photocatalytic performance for degradation of virulent organic pollutants of dye wastewater, like methylene blue (MB). To validate the merits of the TiO2/CuS core/shell nanostructures, we have also designed TiO2/CuS composite nanostructures under similar conditions (without utilizing the surface-functionalizing agent, 3-mercaptopropionic acid). Successful realization of TiO2/CuS nanostructures (core/shell ...

Template-free synthesis and photocatalytic properties of flower-like ZnOHF nanostructures

A facile one-step solution-based method with the assistance of N,N-dimethylformamide (DMF) has been developed to prepare well-dispersed hierarchical flower-like ZnOHF nanostructures, in which DMF acts not only as solvent but also as surface-functionalizing agent. The prepared ZnOHF are characterized for the structural and morphological properties by XRD, SEM and TEM. The SEM and TEM results indicate that the hierarchical ZnOHF nanoflowers are assembled by numerous nanowires. The amount of DMF and reaction time play crucial roles in the formation of hierarchical nanowires-assembled ZnOHF nanoflowers. After calcination, the ZnOHF is completely transformed into ZnO while the flower structures are perfectly retained. The hierarchical ZnOHF and ZnO nanoflowers exhibit specific surface areas up to 48.8m2/g and 71.2m2/g, respectively. The as-obtained ZnOHF and ZnO nanoflowers exhibit excellent UV light photocatalytic activity for photodegradation of Rhodamine B.

Composition and hydrophilicity control of Mn-doped ferrite (MnxFe3-xO4) nanoparticles induced by polyol differentiation.

Manganese doped ferrite (MnxFe3-xO4) nanoparticles with x = 0.29-0.77 were prepared under solvothermal conditions in the presence solely of a polyol using the trivalent manganese and iron acetylacetonates as precursors. In this facile approach, a variety of polyols such as polyethylene glycol (PEG 8000), tetraethylene glycol (TEG), propylene glycol (PG) and a mixture of TEG and PG (1 : 1) were utilized in a triple role as a solvent, a reducing agent and a surface-functionalizing agent. The composition of the fine cubic-spinel structures was found to be related to the reductive ability of each polyol, while determination of structural characteristics plus the inversion parameter (i = 0.18-0.38) were provided by X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy at both the Fe and Mn K-edges. The saturation magnetization increased up to 80 emu g(-1) when x = 0.35 and i = 0.22. In addition, the as-prepared nanocrystals coated with PEG, PG and PG&TEG showed excellent colloidal stability in water, while the TEG-coated particles were not water dispersible and converted to hydrophilic when were extra PEGylated. Measurements of the (1)H NMR relaxation in water were carried out and the nanoprobes were evaluated as potential contrast agents.

Use of 3-aminopropyltriethoxysilane deposited from aqueous solution for surface modification of III-V materials

Focal plane arrays of strained layer superlattices (SLSs) composed of InAs/GaSb are excellent candidates for infrared imaging, but one key factor limiting their utility is the lack of a surface passivation technique capable of protecting the mesa sidewall from degradation. Along these lines, we demonstrate the use of aqueous 3-aminopropyl triethoxysilane (APTES) deposited as a surface functionalizing agent for subsequent polymer passivation on InAs and GaSb surfaces following a HCl/citric acid procedure to remove the conductive oxide In2O3. Using atomic force microscopy, variable angle spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and modeling with density functional theory (DFT), we demonstrate that APTES films can successfully be deposited on III-V substrates by spin coating and directly compare these films to those deposited on silicon substrates. The HCl/citric acid surface preparation treatment is particularly effective at removing In2O3 without the surface segregation of In oxides observed from use of HCl alone. However, HCl/citric acid surface treatment method does result in heavy oxidation of both Ga and Sb, accompanied by segregation of Ga oxide to the surface. Deposited APTES layer thickness did not depend on the substrate choice, and thicknesses between 1 and 20nm were obtained for APTES solution concentrations ranging from 0.1 to 2.5 vol%. XPS results for the N1s band of APTES showed that the content of ionic nitrogen was high (∼50%) for the thinnest films (∼1nm), and decreased with increasing film thickness. These results indicate that APTES can indeed be used to form a silane surface layer to cover III-V materials substrates. Such APTES silane layers may prove useful in surface passivation of these materials alone, or as surface functionalizing agents for subsequent covalent binding with polymer overlayers like polyimide.

Small Molecule-Initiated Light-Activated Semiconducting Polymer Dots: An Integrated Nanoplatform for Targeted Photodynamic Therapy and Imaging of Cancer Cells

Photodynamic therapy (PDT) is a noninvasive and light-activated method for cancer treatment. Two of the vital parameters that govern the efficiency of PDT are the light irradiation to the photosensitizer and visual detection of the selective accumulation of the photosensitizer in malignant cells. Herein, we prepared an integrated nanoplatform for targeted PDT and imaging of cancer cells using folic acid and horseradish peroxidase (HRP)-bifunctionalized semiconducting polymer dots (FH-Pdots). In the FH-Pdots, meta-tetra(hydroxyphenyl)-chlorin (m-THPC) was used as photosensitizer to produce cytotoxic reactive oxygen species (ROS); fluorescent semiconducting polymer poly[2-methoxy-5-((2-ethylhexyl)oxy)-p-phenylenevinylene] was used as light antenna and hydrophobic matrix for incorporating m-THPC, and amphiphilic Janus dendrimer was used as a surface functionalization agent to conjugate HRP and aminated folic acid onto the surface of FH-Pdots. Results indicated that the doped m-THPC can be simultaneously excited by the on-site luminol-H2O2-HRP chemiluminescence system through two paths. One is directly through chemiluminescence resonance energy transfer (CRET), and the other is through CRET and subsequent fluorescence resonance energy transfer. In vitro PDT and specificity studies of FH-Pdots using a standard transcriptional and translational assay against MCF-7 breast cancer cells, C6 glioma cells, and NIH 3T3 fibroblast cells demonstrated that cell viability decreased with increasing concentration of FH-Pdots. At the same concentration of FH-Pdots, the decrease in cell viability was positively relevant with increasing folate receptor expression. Results from in vitro fluorescence imaging exhibited that more FH-Pdots were internalized by cancerous MCF-7 and C6 cells than by noncancerous NIH 3T3 cells. All the results demonstrate that the designed semiconducting FH-Pdots can be used as an integrated nanoplatform for targeted PDT and on-site imaging of cancer cells.

Synthesis, characterization and photocatalytic properties of nanobelt-assembled flower-like Zn3(OH)2V2O7·2H2O microcrystals

3D hierarchical flower-like Zn3(OH)2V2O7·2H2O microcrystals have been fabricated in a high yield via a simple hydrothermal process in the presence of l-aspartic acid (l-Asp). The purity, crystalline phase and morphologies of the products were characterized by XRD, TEM and SEM. The SEM results indicate that the microflowers are self-assembled by numerous nanobelts with mean diameter of 100nm. During the process, l-Asp is chosen as the complexing and surface-functionalizing agent. It is found that the amount of l-Asp and reaction time have significant effects on the morphology of the Zn3(OH)2V2O7·2H2O micro/nanostructures. The photocatalytic properties of Zn3(OH)2V2O7·2H2O were investigated by the decomposition of RhB under UV light irradiation and exhibit good photocatalytic activities.

Green synthesis of self assembled silver nanowire decorated reduced graphene oxide for efficient nitroarene reduction

We have developed a facile and green route to prepare reduced graphene oxide (rGO) from graphene oxide (GO) and decorated its surface edges with self assembled Ag Nanowires (Ag NWs). This was carried out by a novel approach using vegetable extract (Abelmoschus esculentus) as a reducing and stabilizing agent. Currently seed mediated and polyol methods are most common in the preparation of any metallic nanowires. These methods would generally be carried out in two steps, whereas in the present study we have developed Ag NWs on a rGO surface (Ag NWs–rGO) in a one step process. Here, the vegetable extract acts as a reductant, functionalizing and capping agent in the reduction of GO followed by the effective functionalization of the rGO surface which in turn in the presence of Ag+ ions, permits the growth of self assembled Ag NWs on the edges of the rGO. The as-prepared Ag NWs–rGO was characterized by UV-visible spectroscopy, XRD, FE-SEM, FT-IR, Raman spectroscopy and elemental analyses. The resultant Ag NWs–rGO exhibits excellent catalytic activity towards the reduction of toxic nitroarene substrates. Importantly, this study could open an avenue for environmentally friendly, simple and cost effective methods in the surface functionalization and generation of self assembled Ag NWs on the edges of rGO nanosheets. Eventually, the unique green reductant used in this work has been proved to be the better reductant and surface functionalizing agent in synthesizing Ag NWs–rGO nanosheets compared to any hazardous chemical reductants.

Silver nanoparticles based selective colorimetric sensor for Cd2+, Hg2+ and Pb2+ ions: Tuning sensitivity and selectivity using co-stabilizing agents

N-(2-hydroxybenzyl)-valine (VP) and N-(2-hydroxybenzyl)-isoleucine (ILP) organic ligands have been utilized as reducing and surface functionalizing agents in the synthesis of silver nanoparticles (AgNPs) with metal ion interacting functionality. VP and ILP metal interacting ligands functionalized AgNPs exhibited selective colorimetric sensing of toxic Cd2+, Hg2+ and Pb2+ metal ions in aqueous solution at ppm level. The colorimetric sensitivity and metal ion selectivity of VP- and ILP-AgNPs were modulated by incorporating co-stabilizing agents. Importantly, ILP functionalized AgNPs selectively detected Cd2+ ions in the polluted ground water samples also.

Controlled Synthesis of Amine-Capped γ-Fe2O3 Nanoparticles by a One-Step Process

Amine-capped γ-Fe2O3 nanoparticles were prepared by a simple one-step chemical solution method. By changing the type of iron salts, the phase composition and morphology of the samples were adjusted. The resultant products were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy. The magnetic properties were also studied. Triethanolamine (TEA) plays an important role in the formation of magnetic structures. It can act as a precipitator, structure-directing agent, and surface-functionalizing agent. Successful attachment of amine groups to the surface of the magnetic nanoparticles was characterized.

Gold-titania interface toughening and thermal conductance enhancement using an organophosphonate nanolayer

We demonstrate that a mercaptan-terminated organophosphonate nanolayer at gold-titania interfaces can give rise to two- to three-fold enhancement in the interfacial fracture toughness and thermal conductance. Electron spectroscopy reveals that interfacial delamination occurs at the metal-molecule interface near the gold-sulfur bonds, consistent with density functional theory calculations of bond energies. Qualitative correlation between interfacial fracture toughness and bond energies suggest that organophosphonate nanolayers are resilient to humidity-induced degradation. These results, and the versatility of organophosphonates as surface functionalization agents for technologically relevant materials, unlock uncharted avenues for molecular engineering of interfaces in materials and devices for a variety of applications.

Band Gap Tuning of ZnO/In2S3 Core/Shell Nanorod Arrays for Enhanced Visible-Light-Driven Photocatalysis

We report an efficient and environmentally benign one-dimensional ZnO/In2S3 core/shell nanostructure to be used as a photocatalyst to overcome the drawback of low photocatalytic efficiency brought by electron–hole recombination and narrow photoresponse range. In2S3 nanoparticles were successfully grown on the ZnO nanorods by the surface functionalization method using citric acid as a surface-functionalizing agent. The photocatalytic activity under visible light to degrade rhodamine B (RhB) was enhanced by these core/shell nanostructures due to the formation of heterojunctions, which prolong the separation of photogenerated electrons and holes. The photocatalytic degradation of RhB dye was found to be 83.7, 2.7, and 35.0% for the ZnO/In2S3 core/shell nanorod arrays, ZnO nanorods, and In2S3 nanoparticles, respectively, under visible light irradiation. Photoconductivity studies showed a 6-fold enhancement in photocurrent (compared to the dark current) for the core/shell nanorod arrays. Moreover, these core/s...

Mussel-Inspired Synthesis of Polydopamine-Functionalized Graphene Hydrogel as Reusable Adsorbents for Water Purification

We present a one-step approach to polydopamine-modified graphene hydrogel, with dopamine serving as both reductant and surface functionalization agents. The synthetic method is based on the spontaneous polymerization of dopamine and the self-assembly of graphene nanosheets into porous hydrogel structures. Benefiting from the abundant functional groups of polydopamine and the high specific surface areas of graphene hydrogel with three-dimensional interconnected pores, the prepared material exhibits high adsorption capacities toward a wide spectrum of contaminants, including heavy metals, synthetic dyes, and aromatic pollutants. Importantly, the free-standing graphene hydrogel can be easily removed from water after adsorption process, and can be regenerated by altering the pH values of the solution for adsorbed heavy metals or using low-cost alcohols for synthetic dyes and aromatic molecules.

Surface controlled synthesis of MFe2O4(M = Mn, Fe, Co, Ni and Zn) nanoparticles and their magnetic characteristics

Engineered magnetic nanoparticles, MFe2O4 (where M = Mn, Fe, Co, Ni and Zn), of mean size 2–16 nm (standard deviation σ ≤ 15%) with controlled magnetic properties have been synthesized through a solventless thermolysis technique. In this ‘energy-efficient’ facile approach, a long-chain amine is utilized as the solvent, reducing and surface-functionalizing agent. The particle sizes between 2–9 nm are tuned by simple manipulation of the amine to precursor molar ratio while the larger sizes (12–16 nm) are attained by seed-mediated growth. The synthesized nanoparticles are magnetic and show cubic-spinel structure as characterized by HRTEM, SAED, XRD and Raman spectroscopy. The spin–orbit coupling, which induces larger magnetocrystalline anisotropy energy, leads to an increase of the blocking temperature in an order of Zn, Ni, Mn, Fe and Co. Additionally the saturation magnetization (magnetization at 2 T) of nanoparticle decreases in an order as per the periodic arrangement i.e. Mn > Fe > Co > Ni > Zn. This trend is better understood in terms of a cationic distribution of varying magnetic moments in these spinel oxides. For all the ferrites, the magnetization saturates to the bulk value at sizes ≥12 nm, indicating strict control over the dead layer thickness. The effect of surface coordination on the magnetic properties of the ferrite nanoparticles is analyzed. In contrast to trioctylphosphine oxide (TOPO) and oleic acid (OA) functionalized nanoparticles the saturation magnetization of amine protected nanoparticles is higher, which suggests a strong coupling of amine molecules to cations at the particle interface.

An effective and controllable approach to derive polymer corona on oxide nanoparticles to enhance their compatibility in polymeric nanocomposites

Barium titanate nanoparticles were surface-functionalized by a novel polymeric surface-functionalization agent, using a rotary coating technology combined with the post-treatment bonding process. Fourier transform infrared and transmission electron microscopy results display that the nanoparticle surfaces were successfully functionalized by nitrile groups, and surrounded with a polymer corona. This can effectively prevent nanoparticles from agglomeration, and also can greatly enhance their compatibility with polymer matrices through macromolecular chains entanglement. It is important to note that the thickness of polymer corona is controllable. Furthermore, it was found that this method is also applicable to numerous other oxide nanoparticles, such as SiO2, TiO2, Fe3O4, etc.

Synthesis, Characterization and Surface Functionalization of Novel Spindle-Like &amp;alpha;-Fe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Nanocrystals

We synthesized novel α-Fe2O3 nanocrystals (NFO-1) with single crystalline structure. In our synthetic strategy, the morphology and structure can be controlled simultaneously by the choice of inorganic salt (IS) and organic template (OT) in the extremely low precursor concentration reaction system. The evaporation-induced self-assembly (EISA) method was used to accelerate the reaction and to recover the synthesized α-Fe2O3 with high yields while preserving its favorable shape and structure. The morphologies and structures of the obtained α-Fe2O3 nanocrystals greatly influence their surface functionalization capability. The chemical interaction between NFO-1 and the surface functionalization agent (dopamine) was obviously enhanced because of its special spindle-like morphology. The synthesis method described in this paper is suitable for the synthesis of other transition metal oxide single nanocrystals as well and we expect that this new route will be useful for the synthesis of novel nanomaterials.