Design and Fabrication of Fiber-Optic Nanoprobes for Optical Sensing

This paper describes the design and fabrication of fiber-optic nanoprobes developed for optical detection in single living cells. It is critical to fabricate probes with well-controlled nanoapertures for optimized spatial resolution and optical transmission. The detection sensitivity of fiber-optic nanoprobe depends mainly on the extremely small excitation volume that is determined by the aperture sizes and penetration depths. We investigate the angle dependence of the aperture in shadow evaporation of the metal coating onto the tip wall. It was found that nanoaperture diameters of approximately 50 nm can be achieved using a 25° tilt angle. On the other hand, the aperture size is sensitive to the subtle change of the metal evaporation angle and could be blocked by irregular metal grains. Through focused ion beam (FIB) milling, optical nanoprobes with well-defined aperture size as small as 200 nm can be obtained. Finally, we illustrate the use of the nanoprobes by detecting a fluorescent species, benzo[a]pyrene tetrol (BPT), in single living cells. A quantitative estimation of the numbers of BPT molecules detected using fiber-optic nanoprobes for BPT solutions shows that the limit of detection was approximately 100 molecules

Motivation factors for online buying: the price driver

Price is often argued to be the determining factor for online (eBusiness) purchasing. The idea that buying online provides both asking and hidden cost savings is an assumption that has been promoted by IT advocates of the commercial opportunity. In this research Price (attribute) is to be investigated as a contributor to customer motivations for online purchasing. The investigation is to begin with a literature search for other factors that are claimed to influence online purchasing and studies others have published in the focus area. Previously research has been carried out by others to understand the changes brought by internet and ecommerce to our lives and business opportunities. It has been found that behavioural characteristics like shopping convenience, information seeking, immediate possession, social interaction, and variety affects the consumer behaviour towards shopping on the internet (Rohm, 2004). There are other factors such as privacy and security affecting consumer attitude towards shopping online (Shergill, 2005). In this research the factors identified from the literature are listed in priority order and the top two used to explain the relationship to price. This approach is taken to limit the cost (financial and time) of the survey and yet to still contribute valuable knowledge regarding price and other factors affecting online purchasing behaviour. The ability to collect price information and make comparisons between the different product and offerings from various providers is argued to be defining for competitive advantage in ecommerce (Jiang, 2002). The research is started by asserting an initial model that suggests price is a moderating factor for other factors when customers purchase online. This model is a “straw man” to be tested. The resource limitations of this short study are managed by selecting only two of the possible constructs affecting online buying motivations. The research is operationalised by submitting banks of potential questions to experts, a pilot study, and reliability testing and then surveying a stratified random sample of online purchasers. Structural equation modelling method is chosen for data analysis and the appropriate approach for confirming (or otherwise) a mediation role for price in online customer purchasing. A metric and a path model were constructed from the empirical data and compared with the initial model. It was found that Price was the dominant motivating factor for those in the sample for transacting online. The initial model was not the best fit for the empirical data and other relationships were explored. Best fit was found by removing the hypothesised relationship from trust to price and establishing the relationship between trust and security. The best fit model hence showed that Price and intention to buy was a very strong relationship

Visualization 4.mpg

Behavior of the D-EAP membrane — with the silver nanoparticles drop-coated on the passive segment in between the electrodes — on the application and subsequent removal of the actuating voltage

Numerical investigation of plasmonic bowtie nanorings with embedded nanoantennas for achieving high SEIRA enhancement factors

This paper presents the numerical investigation of several complex plasmonic nanostructures — bowtie nanoring and crossed-bowtie nanoring nanoantennas with embedded bowtie nanoantennas and crossed-bowtie nanoantennas — for surface enhanced infrared absorption (SEIRA) spectroscopy-based substrates. The proposed nanostructures exhibit substantially large SEIRA enhancement factor (∼8.1 × 10 ^5 ) compared to previously reported enhancement factor values for bowtie nanoantennas or nanoring antennas. The plasmonic properties of the proposed nanostructures have been studied by the numerical evaluation of the near-field electromagnetic enhancement at resonant plasmon mode excitation wavelengths in the mid-IR spectral regime. The highest SEIRA enhancement of ∼8.1 × 10 ^5 occurs at a wavelength of ∼6800 nm (6.8 μ m). A substantial electric field enhancement as large as ∼375, corresponding to SEIRA EF of ∼1.4 × 10 ^5 is noted even when the minimum gaps between the plasmonic nanostructures is as large as 10 nm, which can easily be fabricated using the conventional nanolithography techniques. The occurrence of several electric field hotspots due to the presence of plasmonic nanoantennas embedded inside the nanorings was observed, as the electric fields are enhanced in the vicinity of the plasmonic nanostructures being proposed. The multiple electric field hotspots in the proposed nanostructures can lead to larger average electric field enhancement as well as the average SEIRA enhancement for these substrates. Moreover, by embedding plasmonic nanoantenna structures inside the bowtie nanorings and crossed-bowtie nanorings, large spectral tunability of plasmon resonance wavelengths is achieved in the spectral regime from 4 μ m to 8 μ m. This is done by varying a larger number of spectral parameters that are present in these complex nanostructures. This paper also reports a novel configuration of crossed-bowtie nanoring plasmonic structure exhibiting less polarization dependence of the SEIRA enhancement factor. This structure also exhibits tunability of hotspot positions when the direction of the polarization of the incident light is rotated. The proposed structures in this paper can be fabricated by the state-of-the-art nanofabrication technologies. The proposed structures could find potential applications in chemical and biological sensing and biochemical detection of analyte molecules

PAN-based activated carbon fibres: Production, characterization and applications

222-235<span style="font-size:14.0pt;line-height: 115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:="" hi"="" lang="EN-IN">Use of activated carbon fibres (ACF) as selective molecular adsorbents presents many advantages over granulated activated carbons (GAC) on account of their greater adsorption rate and larger adsorption capacity. These properties increase the efficiency of adsorption bed and lead to simplified plant designs used for environmental pollution control. In this paper, various methods of activation for the production of ACF from PAN-based precursors have been discussed. Different adsorption techniques used for measuring the porosity (micropore &lt;0.6 nm, mesopore &gt; 1.6 nm and macropore &gt; 200 nm), surface area and surface functional groups have been critically analysed. Specific applications of ACF in air and water purification, medicine and catalysis have been highlighted.</span

Electronic textiles and their potential

170-176Textile materials are generally lightweight, flexible and unique in many ways compared to other materials. Most importantly, they are omnipresent in our lives. Textiles are necessary next to our skin as well as in our environment. They are used for comfort and protection as well as fashion. In the near future, almost all textile products including what we wear and walk on seem destined to be transformed from their present to multifunctional, adaptive and responsive systems. The functions may include communication, computation and entertainment, as well as health care and threat detection. Textiles used in non-apparel applications may perform surveillance and detection functions. Some of the concepts being explored currently may revolutionize our understanding and appreciation of fiber-textile products. This paper reports the developments in the field of electronic textiles, focusing on the current state-of-the-art of electrotextile products and the research being carried out in this field

Surface plasmon resonance imaging (SPRI) sensor biochips based on gold and silver nano- and microstructures

présenté par Vo-Din