Polyphosphazenes have a highly flexible backbone comprised of nitrogen and phosphorus atoms with two organic groups on each phosphorus. Materials in this class are inherently thermo-oxidatively stable, soluble, and chemically resistant especially when a variety of fluorinated organic groups are attached to the backbone. Several solution based side group exchange reactions have been examined previously that have profound effects on the surface topology, but may present problems for large scale production. We have utilized a high-throughput process for surface functionalization of polyphosphazenes to yield films with excellent chemical properties that can be tuned by surface treatment with plasma gases.

Films of the poly[bis(2,2,2-trifluoroethoxy)phosphazene] were surface functionalized with plasmas of methane, oxygen, or nitrogen gases. An environmental plasma head was used to treat the spuncast films with free radicals in the treatment gases. These surface treatments were characterized by XPS and water contact angle methods to determine the modified surface structure of the films and the effect on surface properties. More than 90° changes in water contact angle are possible, depending on the plasma used and the density of surface functionalization. Tuning of the water contact angle was also possible from the native 101° static contact angle of poly[bis(2,2,2-trifluoroethoxy)phosphazene] to approximately 70°, 40°, or 4° with appropriate treatment using methane, nitrogen, or oxygen plasmas. Using XPS surface surveys we found that the fluorine concentration on the surface was higher than in the bulk material. Significant changes in the carbon, oxygen, and nitrogen 1s binding energies of the samples were also detected that varied with plasma treatment.

This process allows polyphosphazene polymers or copolymers to be surface functionalized as an alternative to other processes where delamination or differences in thermal or chemical properties would preclude a traditional two polymer composite approach. Printing of controlled patterns with a cover mask are also possible to create a surface with several distinct regions of hydrophobicity or hydrophilicity or of functional groups all of which may be applicable in microfluidics, printing, adhesion, or sensor arrays.

This work focuses on the development of biological analysis tools using zinc selenide quantum dots (ZnSe QDs). Conjugating water-dispersible ZnSe QDs with oligonucleotides of increasing length was found to increase their photoluminescence (PL) intensity monotonically up to a certain length. Varying the sequence of the oligonucleotide without changing its length does not produce any measurable PL intensity change. The stability of QDs in water was significantly enhanced after conjugation with oligonucleotides. DNA hybridization was studied using QDs functionalized with complementary oligonucleotides. Hybridization of complementary QD-oligonucleotide complexes causes significant PL intensity amplification and a measurable red shift of the PL emission peak. The QD-oligo complexes are very stable in water under ambient dark conditions. Finally, a size-dependent optimal dilution of free QDs was discovered, corresponding to an optimal inter-QD-spacing that results in the highest PL emission intensity from as-prepared QD dispersions. Ongoing experiments in our laboratory aim to develop multiplexed DNA probes and immunoassays by employing luminescent QDs emitting at different wavelengths.

In this work, different set-ups as well as different transducer materials have been investigated in order to develop a hydrogen peroxide (H2O2) sensor for the gas phase. The sensor is based on a combined physical/chemical transduction mechanism and should be able to detect high H2O2 concentrations up to 10 Vol.%. Different sensor arrangements are presented that are based on a “three sensor” cell and a diffusion cell. As transducer materials manganese oxide and copper alloys have been investigated. For the reference part of the sensor set-up, Teflon and enamel have been tested as passivating material.

We have demonstrated surface-enhanced Raman spectroscopy on arrays of Au nanorods aligned in line by a dynamic oblique deposition technique. For the light polarized along the major axis of the nanorods, the plasma resonance of the Au nanorods has been tuned to a wavelength suitable for Raman spectroscopy. The Raman scattering on the discrete nanorods is enhanced significantly compared with that on semi continuous Au films. Since the preparation process is physically bottom-up, it is robust in its selection of the materials and is useful in providing the SERS sensors at low cost.

The application of gold nanowire arrays for neuronal recording and stimulation is explored. The process of electrochemical anodization is utilized to grow an aluminum oxide template consisting of an array of closely packed cylindrical pores with diameters in the range of nanometers and micron scale depth. The method of electrodeposition is used to deposit gold within the pores forming a nanowire array. By means of micro and nanoscale fabrication processes, this array is integrated at one end with microscale gold electrodes. At the other end, neuron cells are cultured. Such nanowire-array structures will eventually be used to record and stimulate neuronal activity.

We report on a novel, non-destructive, in-situ approach toward connecting and electrically contacting vertically aligned zinc oxide nanowire arrays using conductive gold nanoparticles. A chemical gas-sensing device was constructed and tested using this nano-architecture. Well-aligned, single-crystalline zinc oxide nanowires were grown through a direct thermal evaporation process at 550 °C on gold catalyst layers. Electrical contact to the top of the NW array was established by creating a contiguous nanoparticle film through electrostatic attachment of conductive gold nanoparticles exclusively onto the tips of nanowires. The gas-sensing device fabricated through this approach was found to be sensitive to both reducing (methanol) and oxidizing (nitrous oxides) gases. This assembly approach is amenable to any array of one-dimensional nanostructures for which a top contact electrode is needed.

Water dispersable and potentially biocompatible L-cysteine-capped CdSe nanoparticles with a narrow size distribution and blue fluoresence have been synthesized by a facile method without using any additional stabilizer. FTIR study shows that CdSe nanoparticles are capped through mercapto-group of the amino acid cysteine whilst its free amino and carboxylate groups make it amenable to bio-conjugation establishing the possibility of using these as fluorescent biomarkers.

The functionality of microfluidic and microassay devices could be enhanced through further development of porous engineered microstructures. New structural elements fabricated with porous nanostructured thin films deposited by the glancing angle deposition (GLAD) technique have been developed for these devices, and are reviewed here. With the GLAD technique, engineered structures such as vertical posts, slanted posts, helices, and square spirals can be directly grown inside microfluidic channels. A high surface area channel (517cm2/cm2) was made by depositing a silicon oxide porous film in glass microchannels (up to 4.5μm deep and 50μm wide). Similar channels were also fabricated by patterning channels in a photoresist-coated porous film. Self-sealed microchambers and channels were made by growing a SiO2 porous film on 14μm high silicon mesas (2.5×2.5μm, 7×7μm, and 25×25μm) and lines (2.5 to 50μm wide). Devices with channels containing periodic arrays of Si pillars with controllable porosity and architecture were fabricated with only one lithography and deposition cycle. The entire device was made by depositing a single GLAD porous film with areas of different porosity defining the channels. The channels, 200μm wide and 10.5μm deep, contained helical pillars with pore sizes ranging from 100nm-2μm, while a more dense nanofibrous helical film made up the remainder of the device. Fluid flow activated by negative pressure was demonstrated in this device, using both a dye solution and a 50nm microsphere solution. Material selection is not limited to silicon or silicon oxide, but may include a wide range of semiconductors, insulators and metals. A GLAD film was used to separate a test dye solution, demonstrating its potential for use in thin layer chromatography. The reported elements are suitable for a range of applications, including – but not limited to – chromatography, nano-assays and capillary electrophoresis.

High surface area nanosheet TiO2 with mesoporous structure were synthesized by hydrothermal method at 130 °C for 12 h. The samples characterized by XRD, SEM, TEM, SAED, and BET surface area. The nanosheet structure was slightly curved and approximately 50-100 nm in width and several nanometers in thickness. The as-synthesized nanosheet TiO2 had average pore diameter about 3-4 nm. The BET surface area and pore volume of the sample were about 642 m2/g and 0.774 cm3/g, respectively. The solar energy conversion efficiency (η) of the cell using nanorods/nanoparticles TiO2 (from the nanosheet calcined at 450 °C for 2 h) with mesoporous structure was about 7.08 % with Jsc of 16.35 mA/cm2, Voc of 0.703 V and ff of 0.627; while η of the cell using P-25 reached 5.82 % with Jsc of 12.74 mA/cm2, Voc of 0.704V and ff of 0.649.

Anodized aluminum oxide (AAO) membranes consist of locally highly ordered nanopores. The pore diameter (20-200 nm) and pore-to-pore distance are controlled through the anodizing voltage and the choice of etching solution. High aspect ratio over 1,000 can easily be achieved which makes AAO membranes the ideal templates for making nanowires and nanotubes. In this work, the early stage of nanopore formation was studied in-situ with the use of small angle x-ray scattering (SAXS) and glazing incidence GISAXS techniques. The nanopores were found to grow as a function of the square root of growth time. The resulting short nanopores or nanowells with length below 200 nm were further characterized with use of SEM and AFM. These AAO nanowells showed interference color. Their reflectance UV-Vis spectra indicated strong angular dependence and can be understood with a simple single layer (nanoporous alumina over aluminum) model. These spectra are influenced by the nanowells thickness and diameter. Therefore, large array of interferometric AAO nanowells sensors are possible. When these nanowells are coated with Ag or Au thin films, in addition to enhanced interference color, highly sensitive surface enhanced Raman scattering (SERS) effect has been observed. These results will be presented.

We present a nanocomposite material based on functionalized silica nanoparticles in a methacrylate matrix. The nanocomposite material is synthesized without addition of a co-solvent, which enables the spin-coating of thick and defect-free layers of several tens of micrometers with smooth surfaces. SEM analysis indicates uniform distribution of the nanoparticles in the methacrylate matrix, and pinhole-free surfaces suitable for applications in optics. For optical characterization, the refractive index of the material for different silica concentrations is reported, and propagation losses in the UV/VIS range discussed. The tuning of the refractive indices can be applied towards the realization of low-loss passive optical waveguides. As a first step towards this goal, the processibility of the nanocomposite material for microfluidic applications, and the realization of a planar optical waveguide are demonstrated.

β-Ga2O3 nanostructures including nanowires, nanorods, nano and micro-pillars, nanosheets and nanobelts were successfully fabricated by simple and efficient thermal evaporation and condensation technique under argon flow.. The structures have been investigated by the electron microscope, XRD and EDX techniques and shown that nanostructures are predominatly β-Ga2O3 without other crystallographic phases. Cathodouminescence of as-grown nanostructures was investigated in the 10-300 K temperature range and exhibit luminescence band centered at 485 nm at 300 K due to donor-acceptor pair recombination. A new luminescence band centered at 387 nm developes at temperature below 150 K due to self-trapped exciton recombination.

The scheelite-type LiEuW2O8 (LEW) nanoparticles of ∼50 nm in diameter were synthesized from lithium acetate, europium (III) acetate and phosphotungstic acid in 1,4-butylene glycol at 300°C for 2h by autoclave treatment. Post calcination treatment at 600°C for 2 h enhanced the photoluminescence at 465 nm due to the 4f - 4f transition excitation of Eu3+ by a factor of 24.4, and due to charge transfer (CT) excitation from either O2− or WO42− to Eu3+ by a factor of 5.8. Convergent beam electron diffractmetry and the compositional analysis revealed the non-stoichiometric structure of the scheelite-type LEW nanocrystals. Raman spectroscopy also detected the WO4 vibrational modes due to the tetragonal scheelite-type LEW. Solid-state 7Li single pulse excitation MAS NMR indicated the existence of at least three Li sites in the samples. We conclude that the following three factors are improved by calcination to increase the f-f transition probability of Eu3+: (i) a distribution of the Eu3+ – Eu3+ distance, (ii) the symmetry of Eu3+ polyhedra, (iii) the symmetry of tetrahedral WO4 units in the vicinity of Eu3+ polyhedra. Furthermore, oxygen is provided for non-stoichiometric LEW during calcination to enhance the CT probability.

The increasing importance of nanomaterial-related applications has given rise to concerns pertaining to their impact on human health. In vitro mammalian cell-based assays can provide a quick and simple estimate of the possible adverse effects of the nanomaterials. However, recent studies have questioned the efficacy of traditional assays such as the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, in evaluating cell-nanomaterial interactions, implying the need for alternate methods. We applied image analysis to enumerate the DAPI (2-[4-(Aminomethyl) phenyl]-1H-indole-6-carboximidamide, dihydrochloride) – stained cellular nuclei. Image analysis, being non-destructive, capable of automation, and applicable over a wide range of cell seeding densities, offers several advantages compared to older methods like the MTT assay and hemocytometry. Using image analysis, the impact of singlewalled carbon nanotubes (SWNT) on rat aortic smooth muscle cell (SMC) growth kinetics, were examined. Despite the carbon nanomaterial presence, the fluorescent signal from the nuclei was not noticeably impacted over the SWNT range examined (0.00-0.10 mg/ml). We anticipate that this method can also be applied to evaluate the biological impact of other nanomaterials.

Nanoporous structures play a promising role in the development of nanomechanical, nanoelectrical and biosensing devices. In addition, nanopores can be utilized as chemical and gas sensors. TiO2 is a semiconductor material, which can have a wide range of applications in nanopore-based sensors. In this study, TiO2 nanopores were prepared by electrochemical anodization. Titanium was used as the anode, while platinum was used as the cathode in an electrochemical cell filled with a hydrofluoric acid electrolyte solution. During the preparation process, titanium was converted to its oxide form. Nanostructures were synthesized under varying physical conditions, including HF concentrations of 0.5-10% and anodization times of 5-30 minutes. The resulting nanopore structures were characterized by scanning electron microscopy (SEM). With a progressive increase in HF concentration (from 0.5% to 10%), the diameter of the nanopores decreased, from approximately 100 nm in diameter to 50 nm. The nanopores showed a transformation from tube-like structures to pore networks with increased HF concentration or anodization time. The results show that the dimensions and morphology of the nanopores can be controlled by alteration of the anodization conditions.

We successfully measured the mechanoluminesence (ML) from a single ML nanoparticle at the first time. In order to measure the weak light emission from a single nanoparticle induced by applying a micro force, we developed an AFM-based new apparatus with a photomultiplier. Interestingly, the emission (ML) intensity from a nanoparticle was approximately proportional to the load, the phenomena is similar to the macroscopic ML emission properties.

A BioFET array can be fabricated by post-processing of a standard CMOS chip if temperatures are kept below 450 ° and radiation or ion-bombardment damage is minimized. The processing starts with encapsulation by deposition of a low stress, electrolyte-impermeable silicon nitride layer by PECVD at 375 °C. Anisotropic reactive ion etching with an inductively coupled plasma using C4F8 and Ar was used to remove the silicon nitride and oxide layers above the poly-silicon gates. The poly-silicon was then etched off using a selective wet etch. The effect of the processing was characterized by making current-voltage and capacitance-voltage measurements with MOS capacitor structures at each stage of processing and results showed that trapped charges or interface states could be annealed out at low temperatures. Scanning electron microscopy was used to examine the cross-section of the gate areas after the etching. The results of current-voltage measurements with a Ag/AgCl reference electrode on devices in electrolyte solutions were compared to the results of charge-sheet model calculations including the effect of amphoteric charging sites on the oxide and the potential drops in the electrolyte. Measurements showing the threshold shifts subsequently produced by DNA probe attachment and hybridization will also be presented.

Monodisperse smooth carbon nanospheres were synthesized via preparation and complex subsequent multistage pyrolysis of spherical melamine formaldehyde copolymer microparticles. The diameters of optained carbon spheres were located between several tens to several hundreds nanometers depending on the size of used initial copolymer particles. During the conversion of copolymer to carbon, the spheres pass strong shrinking of more than 80 % without any deformation. They meet the high quality standards of common prepared and used polymer and silica spheres and are therefore a promising material with great potential. Carbon nanoparticles could be used in a wide range of applications, such as for gas storage, fuel cells, sensing, catalyst support, separation and purification, supercapacitors or lithium-ion batteries, and photonic bandgap materials. Especially for the last mentioned usage monodispersity and a perfect spherical shape are very important. So-called synthetic opals from carbon spheres have been grown by sonic-supported sedimentation and a photonic bandgap in the infrared region has been found. Due to their high thermal resistance under non-oxidizing conditions carbon opals are also suitable as template for inverse opals. The structure of the spheres has been studied during different stages of carbonization by scanning electron microscopy, nuclear magnetic resonance and fourier transform infrared spectroscopy.

It is important to develop flexible transparent polymer films having high gas barrier properties and abrasion resistance because new applications involving transparent polymer films for flat panel displays require these properties. We report on organic-inorganic hybrid coatings of polyvinylalcohol (PVA)/polyacrylicacid (PAA)-silica, which have high gas barrier properties almost equivalent to those achieved by the dry coating process. The hybrid coatings were prepared by the sol-gel reaction of alkoxysilane in a PVA/PAA aqueous solution. In order to obtain transparent coating films, 3-aminopropyltrimethoxysilane (APTMOS) was used as a compatibilizer in the sol-gel reaction of tetramethoxysilane (TMOS). No structure could be seen in the TEM of the cross-sectional coating layer, indicating that polymers and silica were mixed homogeneously. PVA/PAA-silica hybrid coatings were shown to have excellent abrasion resistance based on the ΔHaze index. O2 permeability of PVA/PAA-silica hybrid coatings evaluated by MOCON under the conditions of 23°C, 90% RH was lower than that of PVA/PAA polymer coating, which suggests that silica affects the barrier property of the hybrid coating in humid conditions. Furthermore, O2 permeability decreased as silica content increased in the coatings. Unexpectedly, high gas barrier properties appeared when the silica content exceeded 50 wt%. From the result of element distribution analysis measured by EF-TEM, it was confirmed that phase separation occurred between PVA/PAA and silica on a nanometer scale and silica forms continuous structures, which are considered to suppress O2 permeability.

Germanium dioxide nanowires have gained significant interest lately due to the the bandgap of 2.44 eV, and high index of refraction, n=1.63. In this paper we aim at investigating the lateral growth of high density metal-catalyzed germanium dioxide nanowires between electrodes. The gaps between two electrodes varied. The catalyst metal was placed on the electrodes, followed by a thermal annealing process, resulting in lateral growth of germanium dioxide whiskers with several microns length and eventually the formation of bridge-like nanostructures. These whiskers have certain unique properties, such as a high surface-to-volume ratio and the capability of connecting two electrodes. Because of these properties, the growth of whiskers from the electrodes has the potential to be developed as electronic devices such as nanosensors. These products are characterized by scanning electron microscopy (SEM), as well as X-Ray diffraction (XRD).