Project description:Composite nanostructures (approximately 200 nm wide and several micrometers long) of metal and polyaniline (PANI) in two new variations of core-shell (PANI-Au) and segmented (Au-PANI and Ni-Au-PANI) architectures were fabricated electrochemically within anodized aluminum oxide (AAO) membranes. Control over the structure of these composites (including the length of the gold shells in the core-shell structures) was accomplished by adjusting the time and rate of electrodeposition and the pH of the solution from which the materials were grown. Exposure of the core-shell structures to oxygen plasma removed the PANI and yielded aligned gold nanotubes. In the segmented structures, a self-assembled monolayer (SAM) of thioaniline nucleated the growth of PANI on top of metal nanorods and acted as an adhesion layer between the metal and PANI components.
Project description:Zein composite particles coated with caseinate-pectin electrostatic complexes (zein-caseinate-pectin particles) were fabricated using an electrostatic deposition and liquid-liquid dispersion method without heating treatment. Compared to zein particles coated only with caseinate, the acidic stability of zein-caseinate-pectin particles was greatly improved, and the particle aggregation was suppressed at pH 3-6, especially at pH values near the isoelectric point of caseinate (pH 4-5). Besides, desirable long-term storage stability and re-dispersibility were observed. Under different zein to curcumin (Cur) feeding ratios (10:1, 20:1, 30:1 and 40:1, w/w), the Cur-loaded zein-caseinate-pectin particles had a spherical shape with an average diameter ranging from 358.37 to 369.20 nm, a narrow size distribution (polydispersity index < 0.2) and a negative surface charge ranging from -18.87 to -19.53 mV. The relatively high encapsulation efficiencies of Cur (81.27% to 94.00%) and desirable re-dispersibility were also achieved. Fluorescence spectroscopy indicated that the encapsulated Cur interacted with carrier materials mainly through hydrophobic interactions. The in-vitro release profile showed a sustained release of Cur from zein-caseinate-pectin particles in acidic aqueous environment (pH 4) up to 24 h, without any burst effect. In addition, the encapsulation retained more ABTS•+ radical scavenging capacity of Cur during 4 weeks of storage. These results suggest that zein-caseinate-pectin particles may be used as a potential delivery system for lipophilic nutrients in acidic beverages.
Project description:Interest in uniform multifunctional magnetic particles is driven by potential applications in biomedical and materials science. Here we demonstrate the fabrication of highly tailored nanoscale and microscale magneto-polymer composite particles using a template based approach. Regiospecific surface functionalization of the particles was performed by chemical grafting and evaporative Pt deposition. Manipulation of the particles by an applied magnetic field was demonstrated in water and hydrogen peroxide.
Project description:Colloidal lithography is a cost-efficient method to produce large-scale nanostructured arrays on surfaces. Typically, colloidal particles are assembled into hexagonal close-packed monolayers at liquid interfaces and deposited onto a solid substrate. Many applications, however, require non close-packed monolayers, which are more difficult to fabricate. Preassembly at the oil/water interface provides non close-packed colloidal assemblies but these are difficult to transfer to a solid substrate without compromising the ordering due to capillary forces acting upon drying. Alternatively, plasma etching can reduce a close-packed monolayer into a non close-packed arrangement, however, with limited interparticle distance and compromised particle shape. Here, we present a simple alternative approach toward non close-packed colloidal monolayers with tailored interparticle distance, high order, and retained spherical particle shape. We preassemble poly(N-isopropylacrylamide)-silica (SiO2@PNiPAm) core-shell particles at the air/water interface, transfer the interfacial spacer to a solid substrate, and use the polymer shell as a sacrificial layer that can be thermally removed to leave a non close-packed silica monolayer. The shell thickness, cross-linking density, and the phase behavior upon compression of these complex particles at the air/water interface provide parameters to precisely control the lattice spacing in these surface nanostructures. We achieve hexagonal non close-packed arrays of silica spheres with interparticle distances between 400 and 1280 nm, up to 8 times their diameter. The retained spherical shape is advantageous for surface nanostructuring, which we demonstrate by the fabrication of gold nanocrescent arrays via colloidal lithography and silicon nanopillar arrays via metal-assisted chemical etching.
Project description:Owing to the advantages of cellulose such as exceptional biocompatibility and biodegradability, we synthesized cellulose-grafted bisindolyl methane (BIM) (1. Cell) composite. This biobased smart material was used as an effective colorimetric and fluorescent sensor for hypochlorite in the aqueous medium with a detection limit of 0.02 μM. Interestingly, cellulose exhibited inherent clusteroluminescence in solution, which was further intensified by the probe acting as a dopant. Both the boronic acid and bisindole groups in probe 1 are essential for this enhanced fluorescence, as boronic acid enables boronate ester formation with cellulose, while the bisindole groups facilitate additional hydrogen bonding interactions. This unique dual functionality produces a strong, solution-phase clusteroluminescent effect, creating a rigid microenvironment that promotes long-range exciton migration and an amplified fluorescence response. Furthermore, the 1. Cell exhibited ∼2.8-fold quenching, while probe 1 alone exhibited negligible fluorescence change in the presence of hypochlorite. Mechanistic investigation reveals that the probe formed a boronate ester via the interaction with cellulose, which was subsequently cleaved in the presence of hypochlorite. The differences in the response might be attributed to the distinct nature of their self-assemblies; 1. Cell could form long-range highly ordered aggregates, while probe 1 alone in the aqueous medium resulted in spontaneous random aggregates. Additionally, we employed cellulose paper strips to explore the practicability of the probe as a paper-based sensor. The chemically modified paper strips, grafted with probe molecules, were found to be stable for a week and could effectively detect hypochlorite in the presence of interfering analytes via the naked eye and fluorescent color-changing response.
Project description:Electrically insulating graphite particles were prepared by coating graphite with electrically insulating materials via a two-step mechanical mixing process. Graphite particles were treated with a binder in the 1st mixing process and coated with an electrically insulating particle in the 2nd mixing process under high shear forces within a short processing time (below 1 min). Micron-sized graphite particles were successfully coated with various inorganic particles of appropriate particle diameter. Talc and boron nitride exhibited good affinities with graphite and formed effective coating layers to render reliable electrical insulation. Graphite coated with talc and boron nitride exhibited a high volume resistivity, greater than 109 Ω cm. The insulating property was retained even after compounding and moulding the coated graphite particles with a polymer. The two-step coating process under high shear forces is a promising method for production of coated graphite particles.
Project description:Nanostructuring organic polymers and organic/inorganic hybrid materials and controlling blend morphologies at the molecular level are the prerequisites for modern electronic devices including biological sensors, light emitting diodes, memory devices and solar cells. To achieve all-around high performance, multiple organic and inorganic entities, each designed for specific functions, are commonly incorporated into a single device. Accurate arrangement of these components is a crucial goal in order to achieve the overall synergistic effects. We describe here a facile methodology of nanostructuring conjugated polymers and inorganic quantum dots into well-ordered core/shell composite nanofibers through cooperation of several orthogonal non-covalent interactions including conjugated polymer crystallization, block copolymer self-assembly and coordination interactions. Our methods provide precise control on the spatial arrangements among the various building blocks that are otherwise incompatible with one another, and should find applications in modern organic electronic devices such as solar cells.
Project description:This work thoroughly investigates chemical solvent-particles interactions during the formation of composite particles by pulsed laser melting of α-Fe2O3. Two solvents, with different dielectric constants, such as ethyl acetate (εr = 6) and ethanol (εr = 24.6), were examined in terms of their effect on the morphology, size, and phase composition of iron oxide composites. We calculated the laser fluence curves using the heating-melting-evaporation approach to identify the critical particle size that undergoes the phase changes first. We assessed the temperature of the particles irradiated with 390 mJ/pulse.cm2 in both solvents, including the heat dissipation between the particles and the liquid. The phase diagram of the Fe-O-C-H system was calculated to determine the temperature-pressure relationship of the system in equilibrium. We also employed an in situ GC-MS analysis to identify the volatile products during irradiation. Based on our experimental results, we concluded that the final diameter of the composites increases from 400 to 600 nm, along with the decreasing dielectric constant of the solvent, which is related to the different polarization of the organic liquid and the degree of particle agglomeration. The reduction of hematite in ethanol proceeded much faster, ending up with Fe/FeCx, while in ethyl acetate, it ended up with Fe3O4. Among all the particles, those with a diameter of 200 nm have the highest temperature and undergo the phase transition first. The temperature of a 200 nm composite particle in ethanol is slightly lower than in ethyl acetate, i.e. 1870 K as compared to 1902 K. Phase equilibrium diagrams proved the existence of Fe, FeO, and Fe3O4 as the preferred phases at about 1900 K. Our research provides a new insight into the process of submicron particle formation during pulsed laser irradiation and allows proposing a mechanism for the growth of particles of different size and phase composition depending on the solvent.
Project description:Single crystalline Ni-Mn-Ga is well known as a prototype ferromagnetic shape memory alloy (FSMA) exhibiting a giant magnetic field-induced strain (MFIS), up to 12%, due to the magnetically driven twin boundary rearrangement. The large stroke and fast magnetomechanical response make it important for actuators and sensors. Polycrystalline Ni-Mn-Ga is inexpensive and technologically easy accessible, but constrains from the grain boundaries inhibit the twin boundary motion, whereby a very low MFIS is observed. Here, we have shown for the first time that a polycrystalline Ni-Mn-Ga can be split into the magnetostrain-active single grains which, being specially assembled in a silicone polymer matrix, caused large and fully reversible MFIS of the resulting composite. We termed the unique reversibility of a large MFIS of the composite as the magnetic field-induced rubber-like behavior. The magnetostrain of individual particles was explored by the X-ray μCT 3D imaging. The results suggest novel solutions for development of the low cost magnetic actuators and sensors for haptic applications.
Project description:In this work, a molecule "walking" along a single chain of a synthetic helical polymer, which is used as a rail on a substrate in an organic solvent at room temperature, is observed. The walking comprises the unidirectional processive movement of a short-chain molecule along a chiral helical chain in 3 nm steps, driven by Brownian motion and a tapping effect of the atomic force microscopy tip based on a flash ratchet mechanism. Furthermore, the rail consists of a long-chain substituted phenylacetylene polymer with pendant cholesteryl groups, along which the short-chain molecule can walk as a result of van der Waals interactions. The macromolecular motion is videoed using a fast-scanning atomic force microscope, and additionally, this phenomenon is also simulated by all-atom molecular dynamics calculations. On the basis of these results, we propose the principle of a polymer molecular motor. This is the first report of a synthetic walking machine of a chiral helical polymer driven by thermal fluctuation as an artificial life function.