Showing papers by "Nanjing Tech University published in 2011"

Fluorescent and luminescent probes for detection of reactive oxygen and nitrogen species

Abstract: Oxidative and nitrosative stress induced by ROS/RNS play crucial roles in a wide range of physiological processes and are also implicated in various diseases, including cancer and neurodegenerative disorders. Sensitive and selective methods for the detection of ROS/RNS based on fluorescent and luminescent probes are of great use in monitoring the in vivo production of these species and elucidating their biological functions. This critical review highlights recent advances that have been made in the development of fluorescent and luminescent probes employed to monitor various ROS/RNS (132 references).

Versatile bifunctional magnetic-fluorescent responsive Janus supraballs towards the flexible bead display

Abstract: electrophoretic displays, [ 4 , 5 ] self-assembly of multidimensional ordered structures, [ 6 ] and sensors. [ 7 ] A variety of Janus particles with complex shapes, anisotropic nature, and diverse functionalities have been developed by using elegant methods including electrifi ed co-jetting, [ 8 ] the spinning disks technique, [ 9 ] surface modifi cation, [ 10 ] microcontact printing, [ 11 ] the microfl uidic technique, [ 12 ] and others. [ 13 ] Particularly, Janus particles with magnetic, electric, or optical characteristics have aroused special interest because of their ability to undergo switching in response to a stimulus (e.g., magnetic or electric fi elds or light). In this respect, Yang et al. developed a light-curing technology to generate magnetoresponsive Janus microparticles for remotecontrolled locomotion. [ 2 ] Doyle and co-workers reported the preparation of Janus hydrogel particles with anisotropic superparamagnetism and demonstrated that these particles could be aligned and assembled by an external magnetic fi eld. [ 14 ]

Disruption of Chlorella vulgaris Cells for the Release of Biodiesel-Producing Lipids: A Comparison of Grinding, Ultrasonication, Bead Milling, Enzymatic Lysis, and Microwaves

Abstract: A comparative evaluation of different cell disruption methods for the release of lipids from marine Chlorella vulgaris cells was investigated. The cell growth of C. vulgaris was observed. Lipid concentrations from different disruption methods were determined, and the fatty acid composition of the extracted lipids was analyzed. The results showed that average productivity of C. vulgaris biomass was 208 mg L⁻¹ day⁻¹. The lipid concentrations of C. vulgaris were 5%, 6%, 29%, 15%, 10%, 7%, 22%, 24%, and 18% when using grinding with quartz sand under wet condition, grinding with quartz sand under dehydrated condition, grinding in liquid nitrogen, ultrasonication, bead milling, enzymatic lysis by snailase, enzymatic lysis by lysozyme, enzymatic lysis by cellulose, and microwaves, respectively. The shortest disruption time was 2 min by grinding in liquid nitrogen. The unsaturated and saturated fatty acid contents of C. vulgaris were 71.76% and 28.24%, respectively. The extracted lipids displayed a suitable fatty acid profile for biodiesel [C16:0 (~23%), C16:1 (~23%), and C18:1 (~45%)]. Overall, grinding in liquid nitrogen was identified as the most effective method in terms of disruption efficiency and time.

Facile Synthesis of Nanocrystalline TiO2 Mesoporous Microspheres for Lithium-Ion Batteries

Abstract: TiO2 mesoporous nanocrystalline microspheres assembled from uniform nanoparticles were synthesized by a facile and template-free hydrolytic precipitation route in normal solvent media The phase structure, morphology, and pore nature were analyzed by X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and BET measurements The electrochemical properties were investigated by cyclic voltammetry, constant current discharge−charge tests, and electrochemical impedance techniques Microspheres with diameters ranging from 02 to 10 μm were assembled by aggregation of nanosized TiO2 crystallites (∼8−15 nm) and yielded a typical type-IV BET isotherm curve with a surface area of ∼1169 m2 g−1 and a pore size of ∼54 nm A simplified model was proposed to demonstrate the nanoparticle packing modes to form the mesoporous structure The initial discharge capacity reached 265 mAh g−1 at a rate of 006 C and 234 mAh g−1 at a rate of 012 C The samples demonstrated high rat

Zebrafish as a good vertebrate model for molecular imaging using fluorescent probes

Abstract: Fluorescent probes have been used extensively to monitor biomolecules and biologically relevant species in vitro and in vivo. A new trend in this area that has been stimulated by the desire to obtain more detailed information about the biological effects of analytes is the change from live cell to whole animal fluorescent imaging. Zebrafish has received great attention for live vertebrate imaging due to several noticeable advantages. In this tutorial review, recent advances in live zebrafish imaging using fluorescent probes, such as fluorescent proteins, synthetic fluorescent dyes and quantum dots, are highlighted.

Mesoporous amine-modified SiO2 aerogel: a potential CO2 sorbent

Abstract: An amine-modified SiO2 aerogel (AMSA) was prepared using the sol–gel method and supercritical drying technology. CO2 adsorption tests were conducted under different conditions. High adsorption capacities were achieved in the presence of water vapor, with the highest CO2 adsorption capacity of 6.97 mmol/g-sorbent at 25 °C. A novel adsorption mechanism associated with the CO2 sorption process is proposed. The test results indicate that AMSA is a promising CO2 adsorbent.

Synthesis of shape-controlled monodisperse wurtzite CuIn(x)Ga(1-x)S2 semiconductor nanocrystals with tunable band gap.

Abstract: Monodisperse wurtzite CuIn(x)Ga(1-x)S(2) nanocrystals have been synthesized over the entire composition range using a facile solution-based method. Depending on the chemical composition and synthesis conditions, the morphology of the nanocrystals can be controlled in the form of bullet-like, rod-like, and tadpole-like shapes. The band gap of the nanocrystals increases linearly with increasing Ga concentration, with band gap values for the end members being close to those observed in the bulk. Colloidal suspensions of the nanocrystals are attractive for use as inks for low-cost fabrication of thin film solar cells by spin or spray coating.

Step-by-step seeding procedure for preparing HKUST-1 membrane on porous α-alumina support.

Abstract: Metal−organic framework (MOF) membranes have attracted considerable attention because of their striking advantages in small-molecule separation. The preparation of an integrated MOF membrane is still a major challenge. Depositing a uniform seed layer on a support for secondary growth is a main route to obtaining an integrated MOF membrane. A novel seeding method to prepare HKUST-1 (known as Cu3(btc)2) membranes on porous α-alumina supports is reported. The in situ production of the seed layer was realized in step-by-step fashion via the coordination of H3btc and Cu2+ on an α-alumina support. The formation process of the seed layer was observed by ultraviolet−visible absorption spectroscopy and atomic force microscopy. An integrated HKUST-1 membrane could be synthesized by the secondary hydrothermal growth on the seeded support. The gas permeation performance of the membrane was evaluated.

Cosorption of Phenanthrene and Mercury(II) from Aqueous Solution by Soybean Stalk-Based Biochar

Abstract: Soybean [Glycine max (L.) Merr.] stalk-based biochar was prepared using oxygen-limited pyrolysis. We evaluated phenanthrene (PHE) and Hg(II) sorption, from single and binary component solutions, onto prepared biochar. We found that the prepared biochar efficiently removed PHE and Hg(II) from aqueous solutions. The isotherms for PHE and Hg(II) sorption could be described using linear and Toth models, respectively, both with high regression coefficients (R2 > 0.995). When PHE and Hg(II) coexisted in an aqueous solution, we observed direct competitive sorption, each one suppressing another. Our results provide insight into the recycling of agricultural residues, and also a new application for removal of polycyclic aromatic hydrocarbons and heavy metals from contaminated water utilizing biochar from agricultural residue.

High-yield synthesis of uniform Ag nanowires with high aspect ratios by introducing the long-chain PVP in an improved polyol process

Abstract: Polyvinyl pyrrolidone (PVP) with different molecular weights was used as capping agent to synthesize silver nanowires through a polyol process. The results indicated that the yields and aspect ratios of silver nanowires were controlled by the chain length of PVP and increased with increasing the molecular weight (MW) of PVP. When the long-chain PVP-K90 (MW= 800,000) was used, the product was uniform in size and was dominated by nanowires with high aspect ratios. The growth mechanism of the nanowires was studied. It is proposed that the chemical adsorption of Ag+ on the PVP chains at the initial stage promotes the growth of Ag nanowires.

Micro-lotus constructed by Fe-doped ZnO hierarchically porous nanosheets: Preparation, characterization and gas sensing property

Abstract: Preparation of micro-lotus constructed by hierarchically porous Fe-doped ZnO nanosheets via a facile hydrothermal method is reported here. The products have been analyzed by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and high resolution transmission electron microscope (HRTEM). Results showed that the morphology of the sample did not change with the Fe doping amount. The photoluminescence (PL) spectra revealed the existence of oxygen vacancies in the Fe-doped ZnO porous nanosheets, which is beneficial to the adsorption of oxygen and gas response, resulting in the improved performances in the later gas sensing experiments towards several reductive gases. The effect of Fe doping percentage on the gas response has also been investigated. We found that ZnO sample with Fe doping atomic percentage of 1% showed the highest gas sensing performance, while excessive Fe doping in ZnO suppressed the gas sensing response. A possible mechanism of how Fe-doped ZnO-based sensor responses to the target gas is also proposed.

An enhanced CdS/TiO2 photocatalyst with high stability and activity: Effect of mesoporous substrate and bifunctional linking molecule

Abstract: To accomplish the more effective coupling of cadmium sulfide quantum dots (CdS QDs), the mesoporous TiO2 substrate and bifunctional linker, mercaptopropionic acid (MPA), were used to disperse and stabilize the CdS QDs. Due to the porous nano-architecture on the TiO2 substrate with large surface area and high crystallinity, the efficiency of degradation of organic compounds in aqueous solution under visible light irradiation is greatly enhanced, compared to CdS loaded anatase TiO2 without porous structure and common commercial P25. Furthermore, the bifunctional linking molecule, MPA, could effectively disperse and stabilize CdS nanoparticles. CdS/TiO2 with the linking molecule CdS-MPA-TiO2(m) exhibits much more stability and activity than CdS-TiO2(m) which is prepared by direct deposition. After 3 cycling tests of degradation of MB (methylene blue), the loss ratio of CdS on CdS-TiO2(m) is 70.6%, much larger than that of 17.8% on CdS-MPA-TiO2(m). This work may give ideas for the synthesis of other stable and active supported catalysts in many fields.

An emerging pore-making strategy: confined swelling-induced pore generation in block copolymer materials.

Abstract: Block copolymers (BCPs) composed of two or more thermodynamically incompatible homopolymers self-assemble into periodic microdomains. Exposing self-assembled BCPs with solvents selective to one block causes a swelling of the domains composed of this block. Strong swelling in the confinement imposed by the matrix of the other glassy block leads to well-defined porous structures via morphology reconstruction. This confined swelling-induced pore-making process has emerged recently as a new strategy to produce porous materials due to synergic advantages that include extreme simplicity, high pore regularity, involvement of no chemical reactions, no weight loss, reversibility of the pore forming process, etc. The mechanism, kinetics, morphology, and governing parameters of the confined swelling-induced pore-making process in BCP thin films are discussed, and the main applications of nanoporous thin films in the fields of template synthesis, surface patterning, and guidance for the areal arrangements of nanomaterials and biomolecules are summarized. Recent, promising results of extending this mechanism to produce BCP nanofibers or nanotubes and bulk materials with well-defined porosity, which makes this strategy also attractive to researchers outside the nanocommunity, are also presented.

Synthesis and deposition of ultrafine Pt nanoparticles within high aspect ratio TiO2 nanotube arrays: application to the photocatalytic reduction of carbon dioxide

Abstract: Using a rapid microwave-assisted solvothermal approach ultrafine Pt nanoparticles are synthesized and deposited in situ within high aspect ratio nanotube arrays. Adjusting the initial concentration of metal ion precursor inside the nanotube support controls the resulting Pt nanoparticle sizes. The Pt-nanoparticle/TiO2 nanotube composite is shown to greatly promote the photocatalytic conversion of carbon dioxide and water vapor into methane, a behavior attributed to the homogeneous distribution of metal co-catalyst nanoparticles over the TiO2 nanotube array surface providing a large number of active reduction sites. The novelty and flexibility of the technique, described herein, could prove useful for the deposition of metal, metal alloy, or metal oxide nanoparticles within a variety of nanotubular or nanoporous material systems with the resulting nanocomposites useful in catalysis, photocatalysis, photovoltaic, and photoelectrochemical applications.

Enhanced photocatalytic activity of hierarchical ZnO nanoplate-nanowire architecture as environmentally safe and facilely recyclable photocatalyst

Abstract: A hierarchical ZnO nanoplate-nanowire (ZNP-ZNW) architecture immobilized onto a substrate via a facile two-step synthesis strategy was used as an environmentally safe and recyclable photocatalyst It showed greatly enhanced photocatalytic activity compared with a monomorphological ZnO nanoplate structure in the degradation of methyl orange (MO) The higher content of surface oxygen defects, which can capture the photogenerated electrons and holes separately and make them available for decomposing organic contaminants, is considered to play an important role in the degradation of MO and makes a major contribution to the enhanced photocatalysis Increasing the surface-to-volume (S/V) ratio without limit cannot benefit the photocatalytic activity significantly if there are not enough defects to separate additional photogenerated charges caused by a larger S/V ratio A detailed photocatalytic mechanism related to surface defects of the hierarchical architecture was clearly demonstrated The present study provides a new paradigm for further understanding the photocatalytic mechanism and suggests a new direction to design high-efficiency photocatalysts based on increasing the number of surface defects of nanostructures

Research progress and materials selection guidelines on mixed conducting perovskite-type ceramic membranes for oxygen production

Abstract: Oxygen production by air separation is of great importance in both environmental and industrial processes as most large scale clean energy technologies require oxygen as feed gas. Currently the conventional cryogenic air separation unit is a major economic impediment to the deployment of these clean energy technologies with carbon capture (i.e. oxy-fuel combustion). Dense ceramic perovskite membranes are envisaged to replace the cryogenics and reduce O2 production costs by 35% or more; which can significantly cut the energy penalty by 50% when integrated in oxy-fuel power plant for CO2 capture. This paper reviews the current progress in the development of dense ceramic membranes for oxygen production. The principles, advantages or disadvantages, and the crucial problems of all kinds of membranes are discussed. Materials development, optimisation guidelines and suggestions for future research direction are also included. Some areas already previously reviewed are treated with less attention.

Fabrication of gold nanoparticles on bilayer graphene for glucose electrochemical biosensing

Abstract: The hydrophilic and carboxyl group functionalized graphene–gold nanoparticles (AuNPs) hybrid has been synthesized in situ. AuNPs can be scattered well on the graphene bilayer, and the loading amount of AuNPs can be controlled. Glucose oxidase (GOD) was successfully bound to the surface of the hybrid through a condensation reaction between terminal amino groups on the lysine residues of GOD and carboxyl groups on the AuNPs. The hybrid provided a suitable microenvironment for GOD to retain its biological activity. The direct and reversible electron transfer process between GOD and the hybrid electrode was realized without any supporting film or electron mediator. A novel model of the glucose biosensor based on the hybrid electrode was fabricated. Blood sugar concentrations measured in human serum samples by the glucose biosensor were in good agreement with the values provided by the Nanjing University hospital, and the average relative standard deviation was 3.2% for six successive measurements. Three constructed biosensors showed good stability, and all of them retained 80% of their initial signals after they were stored at 4 °C for four months. It is promising that the model of the glucose biosensor can be used as an effective candidate for the detection of blood sugar concentration in clinical diagnoses.