High Monodispersity Research Articles

A facile synthesis of mesoporous Pd[sbnd]ZnO nanocomposites as efficient chemical sensor

Mesoporous ZnO was synthesized through the sol-gel method in the presence of triblock co-polymer Pluronic (F-127) template as the structure directing agent. Palladium nanoparticles were photochemically reduced and deposited onto mesoporous ZnO to obtain 1 wt.% Pd/ZnO nanocomposite. Structural and morphological analysis revealed high homogeneity and monodispersity of Pd nanoclusters with small particle sizes ∼ 2–5 nm onto mesoporous ZnO. The electrochemical detection of ethanol in aqueous solutions was conducted at the newly developed Pd/ZnO modified glassy carbon electrode (GCE) by the current-potential (IV) and cyclic voltammetry (CV) techniques and compared with bare GCE or pure ZnO. The presence of Pd dopant greatly enhances the sensitivity of ZnO, and the obtained mesoporous Pd/ZnO sensor has an excellent performance for precision detection of ethanol in aqueous solution with low concentration. The sensitivity was found to be 33.08 μAcm−2 mM−1 at lower concentration zone (0.05–0.8 mM) and 2.13 μAcm−2 mM−1 at higher concentration zone (0.8–12 mM), with a limit of detection (LOD) 19.2 μM. The kinetics study of ethanol oxidation revealed a characteristic feature for a mixed surface and diffusion-controlled process. These excellent sensing characteristics make the mesoporous Pd/ZnO nanocomposite a good candidate for the production of high-performance electrochemical sensors at low ethanol concentration in aqueous solution.

Microfluidic synthesis of monodisperse pectin hydrogel microspheres based on in situ gelation and settling collection

AbstractBACKGROUNDGeneration of monodisperse hydrogel microspheres is needed to make exquisite microenvironments, provide effective delivery system, and obtain reliable results. In this work, we present a simple microfluidic approach for the preparation of monodisperse pectin hydrogel microspheres because of efficient collection and shape of hydrogel.RESULTSBased on the mechanism of in situ gelation and efficient collection, aqueous droplets of pectin polysaccharides are continuously generated in an immiscible continuous phase dissolving divalent metal ions, such as calcium. Under in situ gelation conditions, calcium ions are diffused into the interface between the continuous phase and the aqueous droplets, which triggers gelation of the pectin polysaccharides. The settling collection method, which involves dropping consecutive hydrogels from the outlet hole, is able to maintain the shape of the soft pectin hydrogels. Thus, pectin microspheres produced show high monodispersity (a coefficient of variation of 3.5%). In addition, the stiffness of the pectin hydrogels produced can be manipulated by a simple change of the concentration of pectin in the aqueous phase. The control of the mechanical properties can also be confirmed by measurement of the deformation of the pectin hydrogels using the micropipette aspiration method. Furthermore, the versatility of this approach enables the preparation of monodisperse pectin hydrogels with the capability to encapsulate or release nanoparticles on demand under mild conditions. The pectin microspheres are freely manipulated by the control of magnetic fields.CONCLUSIONWe believe that the in situ microfluidic synthesis method combined with settling collection provides an efficient approach for the preparation of soft, monodisperse hydrogel microspheres. © 2016 Society of Chemical Industry

Pepetide Dendron-Functionalized Mesoporous Silica Nanoparticle-Based Nanohybrid: Biocompatibility and Its Potential as Imaging Probe.

In this study, we designed and fabricated a nanohybrid of mesoporous silica nanoparticles (MSNs) functionalized with peptide dendrons and evaluated its potential biocompatibility. The nanohybrid was prepared by combining azido-MSNs with alkynyl peptide dendrons via click chemistry to improve graft ratio. By modifying the azido-MSNs through the addition of the alkynyl peptide dendrons, we amplified and broadened the scope of their applications. After labeling with Cy5.5 dye, the nanohybrid was characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), nitrogen adsorption-desorption isotherms, dynamic light scattering (DLS) and zeta potential. The resulting nanohybrid showed high mono-dispersivity with a spherical diameter of 60 nm, negative surface charge and aqueous environment stability. Finally, a systematic assessment was conducted to evaluate the biocompatibility of the MSN-dendron-Cy5.5-based nanohybrid, both in vitro and in vivo. Cytotoxicity measurements, body weight shifts, histological analysis, and routine blood tests with mice demonstrated that the nanohybrid had good biocompatibility. Hemocompatibility evaluations demonstrated that the nanohybrid had improved blood safety compared to bare MSNs. Healthy nude mice were used to analyze the in vivo optical fluorescence images. Ex vivo fluorescence images of the major organs were studied to further evaluate the in vivo biodistribution of the nanohybrid, with results suggesting that the MSN-dendron-Cy5.5-based nanohybrid provided promise in biomedical applications. Overall, we provided a preliminary but important research piece on the safety and efficiency of MSN-dendron-Cy5.5-based nanohybrid as an in vivo functional vehicle used in diagnosis and therapy.

A novel technology: microfluidic devices for microbubble ultrasound contrast agent generation.

Microbubbles are used as ultrasound contrast agents, which enhance ultrasound imaging techniques. In addition, microbubbles currently show promise in disease therapeutics. Microfluidic devices have increased the ability to produce microbubbles with precise size, and high monodispersity compared to microbubbles created using traditional methods. This paper will review several variations in microfluidic device structures used to produce microbubbles as ultrasound contrast agents. Microfluidic device structures include T-junction, and axisymmetric and asymmetric flow-focusing. These devices have made it possible to produce microbubbles that can enter the vascular space; these microbubbles must be less than 10μm in diameter and have high monodispersity. For different demands of microbubbles production rate, asymmetric flow-focusing devices were divided into individual and integrated devices. In addition, asymmetric flow-focusing devices can produce double layer and multilayer microbubbles loaded with drug or biological components. Details on the mechanisms of both bubble formation and device structures are provided. Finally, microfluidically produced microbubble acoustic responses, microbubble stability, and microbubble use in ultrasound imaging are discussed.

Highly fluorescent Zn-doped carbon dots as Fenton reaction-based bio-sensors: an integrative experimental–theoretical consideration

Heteroatom doped carbon dots (CDs), with high photoluminescence quantum yield (PLQY), are of keen interest in various applications such as chemical sensors, bio-imaging, electronics, and photovoltaics. Zinc, an important element assisting the electron-transfer process and an essential trace element for cells, is a promising metal dopant for CDs, which could potentially lead to multifunctional CDs. In this contribution, we report a single-step, high efficiency, hydrothermal method to synthesize Zn-doped carbon dots (Zn-CDs) with a superior PLQY. The PLQY and luminescence characteristic of Zn-CDs can be tuned by controlling the precursor ratio, and the surface oxidation in the CDs. Though a few studies have reported metal doped CDs with good PLQY, the as prepared Zn-Cds in the present method exhibited a PLQY up to 32.3%. To the best of our knowledge, there is no report regarding the facile preparation of single metal-doped CDs with a QY more than 30%. Another unique attribute of the Zn-CDs is the high monodispersity and the resultant highly robust excitation-independent luminescence that is stable over a broad range of pH values. Spectroscopic investigations indicated that the superior PLQY and luminescence of Zn-CDs are due to the heteroatom directed, oxidized carbon-based surface passivation. Furthermore, we developed a novel and sensitive biosensor for the detection of hydrogen peroxide and glucose leveraging the robust fluorescence properties of Zn-CDs. Under optimal conditions, Zn-CDs demonstrated high sensitivity and response to hydrogen peroxide and glucose over a wide range of concentrations, with a linear range of 10-80 μM and 5-100 μM, respectively, indicating their great potential as a fluorescent probe for chemical sensing.

A General Synthetic Approach for Integrated Nanocatalysts of Metal-Silica@ZIFs

Integration of different nanocomponents into a greater assemblage or object for applications poses a significant challenge to materials chemists. At present, it still remains extremely difficult to achieve high monodispersivity for such assembled products. To gain better synthetic controllability, ideally, an integration of this type should be done in a stepwise manner. Herein, we report a versatile stepwise approach for preparation of integrated nanocatalysts of metal-mSiO2@ZIFs (metal = Pt, Pd, Ru, Ag, and Pt53Ru47; mSiO2 = mesoporous silica; and ZIFs = ZIF-8 and ZIF-67). Starting with uniform solid Stober silica spheres in submicrometer scale, mesoporous channels with desired length and diameter can be created for silica which serves as a support. With measurements of amino-modification of mesopores and selection of metal precursors applied, subsequently, ultrafine metal nanoparticles (2–5 nm) can be deposited evenly onto the inner walls of silica channels. Resultant metal-mSiO2 spheres are then modifi...

Preparation of mesopourous Fe3O4 nanoparticle with template reagent: Tannic acid and the catalytic performance

We report a one-pot hydrothermal method for novel mesoporous Fe3O4 nanoparticles (NPs) preparation based on the reduction of ferric chloride with bifunctional agent: tannic acid (TA). TA acted both as template agent to obtain the mesoporous structure and functional agent to modify Fe3O4 NPs. The facile controlled process resulted in a relatively high surface area (99.5 m2 g−1) and good monodispersity with average diameter ∼200 nm of the synthetic nanoparticles. The high saturation magnetization (54.7 emu g−1) of the nanoparticles made it can be separated quickly from solution media via a magnet. The unique mesoporous structure of the Fe3O4 nanoparticles possessed high active site, and this was proved by studying the catalytic properties through Fenton catalytic degradation with hydrogen peroxide as a model reaction system. As a result, the tannic acid templated mesoporous Fe3O4 NPs (TA–Fe3O4 NPs) showed the very efficient catalytic properties for the degradation of methylene blue (MB) accelerated by the functionalization of TA.

Magnetic iron oxide nanoparticles as MRI contrast agents -- a comprehensive physical and theoretical study

Magnetite nanoparticles, especially superparamagnetic iron oxide nanoparticles, are established contrast agents for magnetic resonance imaging. Magnetosomes, which are magnetite nanoparticles of biological origin, have been shown to have better contrast properties than current formulations possibly because of their larger size and high monodispersity. Here, we present an integrated study of magnetosomes and synthetic magnetite nanoparticles of varying size, hence, magnetic properties. We investigate not only the relaxation times as a measure for the contrast properties of these particles, but also their cytotoxicity and demonstrate the higher contrast of the larger particles. A theoretical model is presented that enables us to simulate the R2=R1 ratio of a contrast agent and con�rm that larger particles offer higher contrast. The results from this study illustrate the possibility to obtain colloidal stability of large magnetic nanoparticles for magnetic resonance imaging applications and serve as an impetus for a more quantitative description of the contrast effect as a function of the size.

Preparation of potato starch-based carbon particles by low-temperature carbonization in oil

Abstract Potato starch-based carbon particles were prepared by low-temperature carbonization in methyl silicone oil at 220 °C for 15 h and subsequent carbonization at 600 °C for 1 hour under nitrogen. The as-prepared carbon particles were molded, and then heat-treated. The results confirmed that carbon particles could keep the original shape of the potato starch and exhibit high monodispersity with smooth surfaces. The size distribution of carbon particles ranged from 10 to 100 μm and the blocks molded from the carbon particles exhibited relatively superior mechanical strength with a flexural strength of 85.7 MPa. Additionally, it was found that the low-temperature carbonization in oil is crucial in the preparation of this kind of carbon particle.

Magnetic Nanoparticles: Synthesis and Properties

The discovery of novel materials, processes, and phenomena at the nanoscale and the development of new experimental and theoretical techniques for research provide fresh opportunities for the development of innovative nanosystems and nanostructured materials. Nanomaterials with tailored unique properties have limitless possibilities in materials science. The most widely used synthesis routes for iron oxide nanoparticles are based on precipitation from solution. Most of the nanoparticles available to date have been prepared using chemical route. Physical processes have also been recently developed to produce high quality monodisperse and monocrystalline iron oxide nanoparticles. Magnetite has recently attracted attention because bulk Fe3O4has a high Curie temperature of 850 K and nearly full spin polarization at room temperature, and due to its wide range of applications in almost all branches of science and technology. Clearly, nanoscale magnetite offers potential for creation of novel technology in multiple fields of study. Opportunities for magnetite nanoparticles to be effectively incorporated into environmental contaminant removal and cell separation magnetically guided drug delivery, imaging of tissue and organs, magnetocytolysis, sealing agents (liquid O-rings), dampening and cooling mechanisms in loudspeakers, high gradient magnetic separation (HGMS) techniques and contrasting agents for magnetic resonance imaging (MRI). Advancement of synthesis and stabilization procedures towards production of uniformly sized, dispersed (potentially embedded) magnetite nanoparticles has clearly inspired creative imagination and application in various fields.

Green synthesis of carbon dots from prawn shells for highly selective and sensitive detection of copper ions

A facile, economical and effective green method was developed for synthesis of fluorescent carbon dots (C-dots) from prawn shells. The results showed that these C-dots (with an average diameter of 4nm) possess many excellent features such as to eliminate blue fluorescence under UV light (λ=365nm), with high monodispersity, good stability, excellent water solubility and high quantum yield (9%). We further explored these C-dots as effective sensing probes for Cu2+ detection and found that they exhibit excellent selectivity and sensitivity toward Cu2+ with a low detection limit of 5nM. We further demonstrated this novel sensing platform on Cu2+ ions analysis from seawater samples. This method is extremely rapid, low cost, ecofriendly, highly selective and sensitive for Cu2+ ions sensing from various sources of environment such as drinking water, river water and sea water.

Environmentally adaptable pathway to emulsion polymerization for monodisperse polymer nanoparticle synthesis

An environmentally adaptable method is proposed for emulsion polymerization to produce monodisperse polymer nanoparticles at surfactant concentrations much lower than conventional emulsion polymerization. The present method is based on an idea of employing a surfactant with a low critical micelle concentration (CMC) to generate a large number of polymer particles in the presence of micelles at low surfactant concentrations and to cease the particle generation by the micelle disappearance in early reaction stage for attainment of high monodispersity of particles. A hydrophobic monomer of styrene (St) and a less hydrophobic monomer of methyl methacrylate (MMA) were used in the present emulsion polymerization at a total monomer concentration of 0.3 M with an initiator of ammonium persulfate (APS) and a long alkyl chain surfactant of sodium octadecyl sulfate (SOS). The polymerization was conducted at a high APS concentration of 20 mM that gave the CMC as low as 0.085 mM for SOS. An increase in the monomer mole fraction of MMA increased the number of polymer particles, while the high monomer mole fraction of MMA failed to stabilize the dispersion of particles. The polymerization for a monomer ratio of St/MMA = 1/1 could produce monodisperse polymer particles of 33 nm at a surfactant concentration of 1 mM that was higher than its CMC (0.085 mM) but much lower than several ten mM of surfactant concentrations in conventional emulsion polymerization.

Monodisperse Copper Chalcogenide Nanocrystals: Controllable Synthesis and the Pinning of Plasmonic Resonance Absorption.

Controllable synthesis of copper chalcogenide nanocrystals (NCs), including desired geometry, composition and surrounding environment, is of high significance for the modulation of their optoelectronic response and the corresponding applications. Herein, copper nitride nanoparticles have been used as "uncontaminated" copper precursors to synthesize copper chalcogenide NCs with high monodispersity through a one-pot strategy. In this protocol, the sizes and compositions of NCs can be readily controlled by varying the ratio of the precursors. For Cu(2-x)S NCs with different diameters, the size variations are all smaller than 5.6%. Furthermore, the plasmonic properties of the copper chalcogenide NCs are investigated under a steady state by tuning the plasmonic resonance absorption band to a limiting condition (denoted "pinning" phenomena). It is observed that the pinning frequency increases (from 1.09 to 1.23 eV) with the increment of the NC size (from 5.4 ± 0.3 to 11.1 ± 0.4 nm), explained by introducing surface scattering. Meanwhile, the frequencies of ternary alloyed copper sulfide selenide NCs blue-shift from 0.90 to 1.00 eV with the increase of selenium content from 11% to 66%, which is related to the effective mass of free carriers. Additionally, the plasmonic absorption bands of Cu(2-x)S NCs encapsulated by two single-layer graphene pin at 1525-1550 nm during the oxidation process, which is influenced by both the dielectric constant and redox potential of the surrounding environment. This study demonstrates the controllable synthesis and precise fundamental plasmonic properties of the copper chalcogenide NCs, ensuring the potential plasmonic-related techniques with high efficiency, accuracy and excellent spatial resolution.

From Cu2S nanocrystals to Cu doped CdS nanocrystals through cation exchange: controlled synthesis, optical properties and their p-type conductivity research

Heterovalent doping represents an effective method to control the optical and electronic properties of semiconductor nanocrystals (NCs), such as the luminescence and electronic impurities (p-, n-type doping). Considering the phase structure diversity, coordination varieties of Cu atoms in Cu2S NCs, and complexity of Cu doping in II-VI NCs, monodisperse Cu2S NCs with pure hexagonal phase were synthesized firstly. Then through cation exchange reaction between Cd ions and well-defined Cu2S NCs, dominant Cu(I) doped CdS NCs were produced successfully. The substitutional Cu(I) dopants with controllable concentrations were confirmed by local atom-specific fine structure from X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) spectroscopy, elemental analysis characterizations from X-ray photoelectron spectroscopy (XPS) and the electron spin resonance (ESR) measurement. The dominant and strong Cu(I) dopant fluorescence was verified by their absorption and photoluminescence (PL) spectra, and PL lifetime. Finally, the band positions and the p-type conductivities of the as-prepared Cu2S and Cu(I) doped CdS NCs were identified by ultraviolet photoelectron spectroscopy (UPS) measurements. The high monodispersity of NCs enables their strong film-scale self-assembly and will hasten their subsequent applications in devices.

Closed-loop feedback control of droplet formation in a T-junction microdroplet generator

To precisely control the size of monodisperse droplets for droplet microfluidics, we here establish a closed-loop control system with real-time feedback of droplet length during droplet generation. Particularly, the microvalves are integrated into the system to control the flow rates of the two immiscible fluids. From experimental measurements, we observe that the droplet length is a linear function of the flow-rate ratio for low capillary numbers (Ca≤0.1). More importantly, the coefficients of the linear relation are determined by the geometry of the microchannel, and independent of the viscosity of the fluids. Based on MATLAB Simulink, the deviation between the predicted and measured droplet length is quantitatively studied. By using a PI controller, both the response speed and control accuracy of the droplet length can be greatly improved for the closed-loop control system. As a result, high monodispersity and uniformity of droplet generation can be achieved in a T-junction microdroplet generator.

Room Temperature Synthesis of Highly Monodisperse and Sers-Active Glucose-Reduced Gold Nanoparticles

A novel method of synthesizing gold nanoparticles was developed through which glucose-coated nanospheres of high monodispersity were synthesized at room temperature. More than 85% of the nanoparticles showed a mean diameter of 8–9 nm. The nanoparticles were characterized through TEM, UV-Vis absorption spectroscopy, dynamic light scattering (DLS), and Zeta potential measurements and were found to be highly stable in colloidal form over time with a surface potential of –38.7 mV. The nanoparticles also showed a great Raman enhancing factor when they were tested as a surface-enhanced Raman scattering (SERS) substrate on various analytes such as rhodamine 6G, crystal violet chloride, cresyl violet chloride, rose bengal, and the Cu(II) 4-(2-pyridylazo)resorcinol complex at micromolar concentrations.

A one-step method to coat polystyrene particles with an organo-silica shell and their functionalization

A facile method of coating polystyrene (PS) particles with organo-silica and their functionalization was presented. By adding the organo-silane precursor into PS aqueous solution in presence of ammonia, an organo-silica shell could be coated on PS particles directly. This method has several characteristics. First, only one process, one precursor and one solvent were used. Second, the organic groups could be varied from methyl, propyl, vinyl, to mercaptopropyl. The third is the tunable shell thickness with a high monodispersity. The organo-silica shells are further functionalized. The PS@vinyl-SiO2 particles were used to assemble colloidal crystals, and further modified with bromine, resulting in tunable photonic band gaps. PS@mercaptopropyl-SiO2 particles allow the encapsulation of Au nanoparticles. The resulting 2.2 nm Au particles were stable at 550 °C and well-distributed in the whole SiO2 shell with a loading up to 20 wt%.

Monodispersed In2O3 mesoporous nanospheres: One-step facile synthesis and the improved gas-sensing performance

Mesoporous In2O3 nanospheres were successfully synthesized by a simple solvothermal route, which was performed without the assistance of any additives or templates. The obtained mesoporous In2O3 nanospheres show high monodispersity with average size about 90nm and pore size about 2–4nm. The optical absorption property of the In2O3 mesoporous spheres was investigated by UV–vis spectroscopy, which indicates that the In2O3 mesoporous spheres are semiconducting with a direct band gap of 3.1eV. The gas sensing performance of the as-prepared In2O3 mesoporous nanospheres was investigated towards a series of typical organic solvents and fuels. For 100ppm of butanol and ethanol, the mesoporous In2O3 demonstrates sensing responses of 59.6 and 29.6, respectively. These values are much higher than those of the reported In2O3-based gas sensors and the In2O3 powder sample with similar size, indicating the highly enhanced gas sensing performance of In2O3 mesoporous nanospheres. The obtained In2O3 mesoporous nanospheres appear to be a promising sensing material for environmental detection application and would also find applications in catalyst, electrode, or related fields.

Hydrothermal synthesis and electrochemical performance of nanoparticle Li2FeSiO4/C cathode materials for lithium ion batteries

Li2FeSiO4 nanoparticles are successfully synthesized via hydrothermal approach, with the hydrothermal process monitored in detail. Structural characterizations by XRD, FTIR, SEM and HRTEM measurements reveal that the Li2FeSiO4 nanoparticles have a high crystalline degree and monodisperse nanoparticle shape with a size around of 50–200nm. To further improve the electronic conductivity, the Li2FeSiO4 nanoparticles are coated by a carbon layer using in suit polymerization of dopamine. Moreover, the effect of carbon content for electrochemical performance of Li2FeSiO4/C is systemically investigated, and as a result, the composite with a ratio of Li2FeSiO4 and dopamine of 3:1 demonstrate the best electrochemical performance with a discharge specific capacity of 148mAhg−1 at a rate of 0.1C at room temperature. Furthermore, the electrochemical performance of Li2FeSiO4/C at high temperature of 55°C is also investigated, and it also exhibits a good performance with a discharge specific capacity of 240mAhg−1at a current rate of 0.2C.

Highly monodisperse, lanthanide‐containing polystyrene nanoparticles as potential standard reference materials for environmental “nano” fate analysis

ABSTRACTFor the safe commercialization of nanoparticle technology, there is a need for reference materials that can be used in studies related to the environmental fate of nanoparticles. This work produced metal‐containing polystyrene nanoparticles with target parameters such as high monodispersity, tailorable size range (33–193 nm), and variable surface charge. In addition, the combination of organic and inorganic components made them detectable by all of the main analytical techniques routinely used in nanoparticle characterization, e.g., TEM, DCS, DLS, and ICP‐MS (the latter when interfaced to chromatographic instrumentation). The lanthanides Gd, Dy, and Nd were investigated as the inorganic component because of their high response when analyzed by ICP‐MS, and because of their low environmental abundance. Particles were prepared by emulsion polymerization using one of two stabilizers: the nonionic surfactant Pluronic F68 or the anionic surfactant sodium dodecyl sulfate © 2015 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42061.