Search

This paper aims to develop a selective molecularly imprinted polymer (MIP) layer combined with quartz crystal microbalance sensor for the detection of 3-Carene, a significant aroma compound of mango. The proposed sensor is prepared from the co-polymer of methacrylic acid and divinylbenzene, and it is imprinted with 3-Carene. The MIP template was synthesized and deposited onto the quartz crystal microbalance platform by proper functionalizing the gold electrode using 2-propene 1- thiol. The developed MIP material is characterized by fourier transform infra-red, scanning electron microscope, and atomic force microscope techniques. The sensor offers very good selectivity and sensitivity (1–1000 ppm) of 0.11 Hz/ppm to 3-Carene from its structural analogies. The limit of detection and the limit of quantitation of the sensor are found to be 0.8 and 1.4 ppm, respectively. The performance of the sensor offers satisfactory reproducibility and repeatability to 3-Carene. Moreover, the response of the sensor has been correlated to the standard gas- chromatography-mass spectrometry data to detect 3-Carene in Langda and Chausa mango.

Chiral recognition is the fundamental property of many biological molecules and is a quite important field in pharmaceutical analysis because of the pharmacologically different activities of enantiomers in living systems. Enantio-differentiating signal of the sensor requires specific interaction between the chiral compounds (one or a mixture of enantiomers) in question and the selector. This type of interaction is controlled normally by at least three binding centers, whose mutual arrangement and interacting characteristics with one of the enantiomers effectively control the selectivity of recognition. Molecular imprinting technology provides a unique opportunity for the creation of three-dimensional cavities with tailored recognition properties. Over the past decade, this field has expanded considerably across the variety of disciplines, leading to novel transduction approaches and many potential applications. The state-of-art of molecularly imprinted polymer-based chiral recognition might set an exotic trend toward the development of chiral sensors. The objective of this review is to provide comprehensive knowledge and information to all researchers who are interested in exploiting molecular imprinting technology toward the rational design of chiral sensors operating on different transduction principles, ranging from electrochemical to piezoelectric, being used for the detection of chiral compounds as they pose significant impact on the understanding of the origin of life and all processes that occur in living organisms.

This work describes the development of an electrochemical sensor based on a new molecularly imprinted polymer for the detection of γ-amino butyric acid at ultra-trace level. This is comprised of a thin imprinted film exploiting an abrasive immobilization of functionalized multi-walled carbon nanotubes on the tip of a pencil graphite electrode. For the reason that γ-aminobutyric acid is an electro-inactive species, its o-pthalaldehyde/sulphite derivative was used as a template for imprinting polymer made from a typical functional monomer (5-fluorouracil-N-acetylacrylamide) and cross-linking agent (ethylene glycol dimethacrylate) in the porogen, dimethyl sulphoxide. The electrodics of the template was explored using various techniques, viz., cyclic voltammetry, differential pulse anodic stripping voltammetry, and chronocoulometry. The template detection, in terms of γ-aminobutyric acid, at stringent limits of clinical settings was feasible by differential pulse anodic stripping voltammetry technique in the linear concentration range, 0.75–205.19 ng mL −1 (correlation coefficients 0.999, detection limits 0.28 ng mL −1 ), without any cross-reactivity and false positives in aqueous, human serum, and cerebrospinal fluid.

Carbon-nanotubes play a pivotal role in molecularly imprinted polymer technology for inculcating conducting property, high surface to volume ratio, and maximum porosity in the film texture. Contrary to the non-covalent heterogeneous dispersion of pure (unmodified) multiwalled carbon nanotubes in the imprinted polymer film, the homogeneous distribution of their functionalized derivative was found more effective to augment the sensitivity of the measurement. This could be made feasible using multiwalled carbon nanotubes bearing terminal monomeric unit (termed as “CNT-mer”) for the polymerization (one CNT-mer in each repeating unit). In this work, the CNT-mer entails a N -hydroxyphenyl maleimide functionality to be utilized in the chain propagation with simultaneous imprinting of epinephrine in the polymeric network. This system, when casted on the tip of a pencil graphite electrode, responded a highly sensitive and selective response for epinephrine, prevalent in aqueous and real samples at ultratrace level (linear range 0.09–5.90 ng mL −1 , limit of detection 0.02 ng mL −1 , S / N =3), without any cross-reactivity and matrix effects. The proposed sensor is advantageous in obtaining enhanced differential pulse anodic stripping voltammetric current vis-a-vis the corresponding imprinted sensor modified with randomly dispersed flocculated multiwalled carbon nanotubes bundles. While the latter might restrict the interlayer diffusion of analyte in the film, the former sensor facilitated high diffusivity with the channelized electron transport to respond higher current. The CNT-mer dispersed sensor was found to be stable and rugged against mechanical stress and can be used, after regeneration, for more than hundred consecutive experiments in clinical settings.

This study describes the synthesis of a new class of substrate-selective molecularly imprinted polymer. This involved tetraethylene glycol 3-morpholin propionate acrylate (functional monomer) and bovine serum albumin (template) for polymerization in aqueous condition, using “ surface grafting-from ” approach directly on a vinyl exposed multiwalled carbon nanotubes-ceramic electrode. The analyte recapture at pH 6.8 in aqueous environment simultaneously involved hydrophobically driven hydrogen bonds and ionic interactions between negatively charged bovine serum albumin and positively charged imprinted nanofilm. The selectively encapsulated bovine serum albumin first gets reduced at −0.9 V and then oxidized within the cavity, without getting stripped off, to respond a differential pulse voltammetry signal. The limit of detection [0.42 ng mL −1 (3 σ , RSD≤1.02%)] obtained was free from any cross-reactivity and matrix complications in aqueous, pharmaceutical, serum, and liquid milk samples. The proposed sensor can be used as a practical sensor for ultra-trace analysis of bovine serum albumin in clinical settings.

Thin films of Ge–As–Se chalcogenide glasses have been deposited by thermal evaporation from bulk material and submitted to thermal treatments. The linear refractive index and optical band-gap for as-deposited and annealed films have been analyzed as function of the deposition parameters, chemical composition and mean coordination number (MCN). The chemical composition of the films was found to be directly affected by deposition rate, with low rates producing films with elevated Ge and reduced As content, whilst at high rates the Ge content was generally reduced and As levels increased compared with the bulk starting material. As a result films with close to the same stoichiometry as the bulk glass could be obtained by choosing appropriate deposition conditions. As-deposited films with MCN in between 2.44 and 2.55 showed refractive indices and optical band-gaps very close to those of the bulk glass whereas outside this range the film indices were higher and the optical gaps lower than those of the bulk glass. Upon annealing at close to their glass transition temperature, high MCN films evolved such that their indices and band-gaps approached the bulk glass values whereas at low MCN films resulted in no changes to the film properties.

Ge x As y Se100−x−y (33 ≤ x ≤ 39 and 12 ≤ y ≤16) glasses were prepared, and their structure and optical properties were studied by Raman and UV–Vis-IR spectroscopic techniques. Ge-tetrahedrons [GeSe4] dominated in the structural units, and ‘defect’ bonds, such as Ge–Ge, Ge–As and As–As bonds, also occurred in the glasses. A structural model for calculation of the optical band gap energy (E g ) of Ge–As–Se glasses was proposed, and the calculated values are consistent with experimental results. Increasing germanium and decreasing selenium content can reduce both the mean bond energies and optical band gap energies, enhancing the photo-sensitivity of the glasses.

A simple hyphenation approach was adopted to obtain a new molecularly imprinted micro solid-phase extraction fiber (as a selective extraction tool) and complementary molecularly imprinted polymer coated pencil graphite electrode (as a detection tool) for the selective and sensitive analysis of epinephrine, which is a disease biomarker prevalent at ultra trace level in biological fluids. In both extraction and detection processes, the functionalized multiwalled carbon nanotubes (CNT-mers) were preferred to multiwalled carbon nanotubes (unmodified) in order to obtain a stable homogeneously dispersed imprinted polymer matrix of better electroconductivity and adsorptive characteristics. The hyphenation of both tools helped dual pre-concentration of epinephrine so as to achieve the stringent limit [limit of detection: 0.002 ng mL(-1), S/N=3] of clinical detection, without any problems of non-specific contributions and cross-reactivity.

A novel molecularly imprinted polymer, selective for human hemoglobin, was immobilized on the surface of CdS quantum dots-multiwalled carbon nanotubes nanoconjugate-modified pencil graphite electrode. The fabricated sensor was found to be water-compatible and biologically benign, since the molecular imprinting was exclusively carried out in water, without any protein denaturation and electrode fouling. Notably, the pencil graphite electrode modified with merely a nanoconjugate matrix might involve the onset possibilities of electrode passivation and protein denaturation. However, a polymer coating onto the nanoconjugate obviated such obstacle while evaluating human hemoglobin in an aqueous environment (pH 4.2). The quantification of the hemoglobin in the dilute whole blood samples varied in the linear range 27.8–444.0 ng mL−1; and the detection limit was obtained as 6.73 ng mL−1 (S/N=3), without any cross-reactivity and false-positives. The proposed sensor can be used as a cost effective sensor for hemoglobin, in clinical settings.

We report the properties of dispersion-engineered nanowire waveguides fabricated in Ge11.5As24Se64.5chalcogenide glass with ? ranging from ?25,000-150,000W-1km-1. These waveguides are capable of generating broadband super-continuum when pumped with ps pulses with peak power ?20W.

I discuss our work to optimize of the properties of highly nonlinear Ge x As y Se 1-x-y chalcogenide glasses for all-optical signal processing.

Chalcogenide glasses, which contain the chalcogen elements S, Se and Te covalently bonded with network forming elements such as Ge, As, Sb, etc, possess a higher third order (Kerr) optical nonlinearity at telecommunications wavelengths than any other known glass. Their high linear index and low optical absorption also makes it practical to use them to fabricate nanowire waveguides. In particular the third order nonlinear response of these materials displays a pure refractive nonlinearity with negligible two-photon absorption and a complete absence of free carrier effects. As a result we have been able to demonstrate all optical signal processing of telecommunications signals at speeds up to 640Gb/s [1] and RF spectral analysis with ≈3THz bandwidth [2] using waveguides made from As 2 S 3 chalcogenide glass with nonlinear parameters up to ≈10,000W−1km−1. However, in order to reduce power requirements higher values of the nonlinear parameter are desirable. Here we describe our first results using a new waveguide material: Ge 11 As 22 Se 67 whose nonlinearity is about 4 times larger than As 2 S 3 [3] and which has allowed us to achieve nonlinear parameters in air-clad rib waveguides in excess of 26000W−1km−1. Rib waveguides were fabricated by dry etching 340nm deep into 680nm thick glass films deposited by thermal evaporation onto an oxidized silicon wafer. Waveguides 3µm and 4µm wide were used in these experiments and these had nonlinear parameters (γ=2πn 2 /A eff γ) of 33000W−1km−1 and 26000W−1km−1 respectively - record values for a glass waveguide. This enhanced nonlinear response along with dispersion control leads to strong effects such as supercontinuum generation (Fig. 1(a)) and broad-band four wave mixing with large gain (Fig. 1(b)) using pulses with peak powers of 10–30W. The nonlinear response is also sufficient to allow nonlinear processing using CW powers in the 100mW range. This talk will describe the properties of Ge 11 As 22 Se 67 waveguides and their nonlinear properties at telecommunications wavelengths.

Chalcogenide glasses are an important class or amorphous materials with applications that include phase-change optical memories, solar cells, and optical waveguides. Particularly interesting for optical applications is their good transparency in the mid-infrared combined with their high linear and nonlinear refractive indices. This last property has motivated interest in the use of chalcogenide waveguides for all-optical processing of high-speed telecommunications signals [1].

We present a systematic study of Ge(x)As(y)Se(1-x-y) bulk chalcogenide glasses to determine the best composition for fabricating all-optical devices. The dependence of physical parameters such as the band-gap, glass transition temperature and third order optical nonlinearity (n(2)) on composition has been studied and a relation between the bond-structure and elevated linear loss levels in high Germanium glasses has been identified. It is found that glasses with 11

This research focuses on several aspects of chalcogenide all-optical processors. This study has chosen glasses in the Ge-As-Se system with the aim of optimising glass composition to obtain low loss, high nonlinearity and glass stability, whilst complementary efforts are focussed on the production, optimisation and application of chalcogenide waveguide devices to all-optical of high-speed telecommunication signals. Devices have been characterised in realistic telecommunications conditions with the eventual aim being to validate performance at rates up to 640 Gb/s.

GexAsySe100-x-y glasses with 0les xles40 and 12lesyles40 have been characterized for properties of bulk material as well as thermally deposited films. The effect of phase separation on film properties is studied.

The optical and structural properties of Ge-As-Se glasses have been studied using Raman, UV-Vis-IR, Z-scan and DSC techniques, and the effect of composition on structural transition, optical band gap and nonlinearity is described.

Chalcogenide glasses, which contain S, Se or Te atoms combined with network forming elements such as Ge, As, Sb have the largest third order optical nonlinearity of any inorganic glass. As a result they are attractive candidates for fibre and waveguide devices for all-optical signal processing in the telecommunications bands. In this talk I will review our recent progress in all-optical devices such as regenerators, wavelength converters and other devices in chalcogenide glasses.

Optical properties of chalcogenide glasses, GexAsySe100-x-y (33les x les39 and 12les y les16) were studied by using Raman, UV-vis-IR and PDS spectroscopic techniques, and the relationships between structure, composition and optical property were discussed.

We review the fabrication processes and properties of waveguides that have been made from chalcogenide glasses including highly nonlinear waveguides developed for all-optical processing.

This research was partly supported by the Australian Research Council through its Centres of Excellence and Federation Fellow Programs.

In this study GeXAsySe100x+y glasses with 0lesx 0.1 dB/cm for Ge > 33% (Ge33As12Se55) at 1550 nm. A modified Z-Scan technique was developed to measure the nonlinear refractive index (n2) at 1500 nm. The conventional closed aperture is replaced by an InGaAs camera to image the output beam. Image analysis is done using Lab VIEW software and the on axis transmission is measured and extracted as a Z-scan.

Chalcogenide glasses are important amorphous semiconductors used for phase-change memories, solar cells and in photonics. Here I will review their photonic applications with an emphasis on new glasses for high speed all-optical signal processing.