Tuesday, November 3, 2015

Kulim Kht for functional nanoparticle deposition



Voltammetric sensors based on LB films
 
The use of quick, reliable and cheap sensors for the detection of chemical compounds represents an important need in the food industry. Antioxidants, in particular phenols, are among the analytes that must be monitored and measured in order to guarantee the quality of final products. Previous works have demonstrated that voltammetric electrodes chemically modified with electrocatalytic materials can be successfully used as sensors for the detection of antioxidants.

Electrodes can be prepared using a variety of techniques from simple Carbon Paste Electrodes (CPE) or Screen printed Electrodes (SPE) to extremely sophisticated nanostructured sensors prepared using the Langmuir-Blodgett (LB) or the electrostatic Layer-by-Layer (LbL) techniques. Nanostructured sensors have the advantage of the enhanced number of active sites producing an increase in the intensity. In this webinar we will get introduced to the field of voltammetric sensors based on LB films and especially LB films with functionalized nanoparticles. The excellent sensing properties of these sensors could be attributed to the electrocatalytic properties of the nanoparticles combined with the high surface to volume ratio and homogeneity provided by the LB technique used for the immobilization. Moreover, the LB technique also provided an accurate method to immobilize the gold nanoparticles giving rise to stable and reproducible sensors. Read more

Kulim Kht bionavis SPR.... Polymer collapse



 Polymer collapse due to pH or electric potential change monitored with MP-SPR
Conductive polymers (CP) are utilized in drug delivery systems, microelectronics, photonics and also for material in biomedical engineering. CP polymer poly (3,4-ethylenedioxythiophene) (PEDOT) was deposited on a sensor slide and above that Poly (acrylic acid) (PAA) brush which is a promising biointerface material.
Multi-Parametric Surface Plasmon resonance (MP-SPR) was utilized to follow PAA polymer brushes swelling and collapse caused by pH or electric potential change. MP-SPR with electrochemical cell was utilized to form potential change to the conductive sensor surface. Multi wavelength MP-SPR measures whole SPR curve with two different wavelength and this can be utilized to calculate deposited layer thickness (more detailed see AN#128).
On a sensor slide had 18 nm thick PBrEDOT layer and 15 nm thick PAA layer on top of that. BrEDOT-g-PAA revealed to be pH sensitive as expected. In acidic environment (pH4) PAA polymer brushes collapsed resulting a decrease in thickness of the layer and an increase in refractive index of brushes. Electric potential change seemed to cause PAA brushes conformational collapse also in basic environment due to conductive polymer oxidation.