Electrochemical Aptasensor for Detection of Dopamine

This work presents a proof of concept of a novel, simple, and sensitive method of detection of dopamine, a neurotransmitter within the human brain. We propose a simple electrochemical method for the detection of dopamine using a dopamine-specific aptamer labeled with an electrochemically active ferrocene tag. Aptamers immobilized on the surface of gold screen-printed gold electrodes via thiol groups can change their secondary structure by wrapping around the target molecule. As a result, the ferrocene labels move closer to the electrode surface and subsequently increase the electron transfer. The cyclic voltammograms and impedance spectra recorded on electrodes in buffer solutions containing different concentration of dopamine showed, respectively, the increase in both the anodic and cathodic currents and decrease in the double layer resistance upon increasing the concentration of dopamine from 0.1 to 10 nM L-1. The high affinity of aptamer-dopamine binding (KD ≈ 5 nM) was found by the analysis of the binding kinetics. The occurrence of aptamer-dopamine binding was directly confirmed with spectroscopic ellipsometry measurements

Humidity effect on real-time response of tetranitro-oxacalix[4] arene-based surface plasmon resonance (SPR) acetone sensor at room temperature

We report the effect of humidity on the acetone sensitivity of nano-sized thin films obtained by spin coating the oxacalix[4]arenes(1,3) molecules on suitable substrates in this work. The surface morphologies and volatile organic compound (VOC) sensor properties of spin-coated thin films were examined using atomic force microscopy (AFM) and surface plasmon resonance (SPR), respectively. It was determined that the sensitivities calculated from the measurements performed using a mixture of acetone and water vapor were 14% and 11% incorrect for the 1 and 3 thin film sensors, respectively, compared to those performed with dry air and acetone mixture

Metal sulfide sub-nanometer clusters formed within calix(8)arene Langmuir-Blodgett films

This work describes the construction of layered Langmuir-Blodgett (LB) films of a calixarene and the use of these as matrices for the synthesis of a range of metal sulfide nanoparticles. CuS, CdS, HgS, and PbS nano-clusters were formed within LB films of an octa-tertbutyl-calix(8)arene substituted with carboxylic acid groups deposited on different substrates (glass, quartz, and silicon) from either: (i) aqueous sub-phases containing 0.5 mM of the respective metal chloride salt (e.g. CuCl2, CdCl2, HgCl2, PbCl2), or (ii) by soaking the LB films in 10 mM solutions of the above salts for 1 h. The formation of metal-sulfide (MeS) nanoparticles was then achieved by exposing samples to H2S gas for 10–12 h. Deposition from salt containing subphases was more reliable and resulted in stoichiometric metal sulfides (CdS, HgS, PbS) being formed within LB films of the calix(8)arene carboxylic acid whereas Cu tended to form polysulfides. UV–vis absorption spectroscopy showed the presence of multiple absorption bands corresponding to electron transitions between energy levels in nanoclusters formed as result of quantum confinement of electrons and holes. The MeS clusters obtained by this process are amongst the smallest reported for LB films, being of the range 0.6–1.2 nm

<i>N</i>,<i>N</i>′-Bis(<scp>l</scp>-alanine <i>tert</i>-butylester)-3,4:9,10-perylene diimide molecule for volatile organic vapor detection

Langmuir–Blodgett (LB) thin films were prepared using an N,N′-bis(l-alanine tert-butylester)-3,4:9,10-perylene diimide derivative to determine the optimum thin film forming conditions and their sensing properties towards volatile organic vapors.</p

Organic vapor sensing properties and characterization of alpha-naphthylmethacrylate LB thin films

WOS: 000470430300001Determination of organic vapor sensing properties of alpha-Naphthylmethacrylate (alpha-NMA) monomer based Langmuir-Blodgett (LB) thin films was aimed in this study. LB thin film fabrication was performed on quartz glass and quartz crystal substrates in order to investigate the characterization and organic vapor properties of alpha-NMA materials by using UV-Visible, Atomic Force Microscopy (AFM) and Quartz Crystal Microbalance (QCM) techniques. pi-A isotherm graph was taken and a suitable surface pressure value were primarily determined as 13 mN m(-1) for successful alpha-NMA LB thin film fabrication. Transfer ratio value was found to be >= 0.93 for quartz glass and quartz crystal substrates. The typical frequency shift per layer was obtained as 16.93 Hz/layer and the deposited mass onto a quartz crystal was calculated as 271.30 ng/layer (1.02 ng mm(-2)). The sensing responses of alpha-NMA LB films against dichloromethane, chloroform, toluene and m-xylene were measured by QCM system. Dichloromethane created the maximum shift in the resonance frequency than other organic vapors used in this study. Results exhibited that alpha-NMA LB thin films were potential candidates for organic vapor sensing applications, especially high sensitive detection of dichloromethane at room temperature.Scientific and Technical Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [216Z080]The authors acknowledge The Scientific and Technical Research Council of Turkey (TUBITAK) for its financial support (Project No. 216Z080)

Electrochemical Aptasensor for Detection of Dopamine

This work presents a proof of concept of a novel, simple, and sensitive method of detection of dopamine, a neurotransmitter within the human brain. We propose a simple electrochemical method for the detection of dopamine using a dopamine-specific aptamer labeled with an electrochemically active ferrocene tag. Aptamers immobilized on the surface of gold screen-printed gold electrodes via thiol groups can change their secondary structure by wrapping around the target molecule. As a result, the ferrocene labels move closer to the electrode surface and subsequently increase the electron transfer. The cyclic voltammograms and impedance spectra recorded on electrodes in buffer solutions containing different concentration of dopamine showed, respectively, the increase in both the anodic and cathodic currents and decrease in the double layer resistance upon increasing the concentration of dopamine from 0.1 to 10 nM L−1. The high affinity of aptamer-dopamine binding (KD ≈ 5 nM) was found by the analysis of the binding kinetics. The occurrence of aptamer-dopamine binding was directly confirmed with spectroscopic ellipsometry measurements.</jats:p

Preparation of Zinc (II) phthalocyanine-based LB thin film: Experimental characterization, the determination of some optical properties and the investigation of the optical sensing ability

Zinc(II) phthalocyanine (Zn(II)Pc) molecule was the first time prepared onto three different substrates utilizing Langmuir-Blodgett (LB) deposition technique to investigate its vapor sensing abilities and some optical properties. We utilized five different and well-known techniques to control monolayer quality of Zn(II)Pc LB film. The obtained the thickness and refractive index values for Zn(II)Pc LB film with coated at different layers vary from 3.2 to 10.9 nm and from 1.42 to 1.71, respectively. The sensing properties were investigated by exposing the Zn(II)Pc-based mass or optical sensor to some organic vapors. Kinetic results presented that this Zn(II)Pc material is a good candidate as a sensor element with a fast and reversible response for dichloromethane sensing devices

Synthesis, characterization and chemical sensor properties of a novel Zn(II) phthalocyanine containing 15-membered dioxa-dithia macrocycle moiety

The issue of utilizing organic materials in chemical sensing devices has recently received considerable critical attention. Phthalocyanines (Pcs) and metal phthalocyanines (MPcs) have been identified as promising materials thanks to their outstanding properties reported in this study. A novel zinc(II) phthalocyanine containing four 15membered dioxa-dithia macrocyclic moieties was synthesized via the reaction of anhydrous Zn(II) acetate and 13,14-dihydro-6H,12H,20H-tribenzo[f,j,n][1,5]dioxa[9,12] dithiacyclopenta-decine-2,3-dicarbonitrile which was prepared from 1,3-di(2-thio-methylphenoxy) propane and 4,5-dichloropthalonitrile. In order to synthesize and characterize this novel compound, elemental analysis, MS, FT-IR, 1H, 13C NMR, and UV-vis spectral techniques were utilized. To create a Quartz Crystal Microbalance (QCM) sensor, zinc(II) phthalocyanine-based macrocyclic molecules were deposited onto a quartz crystal using the Langmuir-Blodgett (LB) thin film technique. The sensing ability of this chemical sensor was examined by recording the interaction between this novel material as a QCM-sensor and selected chemical vapors such as carbon tetrachloride, chloroform, benzene and toluene. The interaction results for this zinc(II) phthalocyanine based macrocyclic material indicated that this material can be used as a QCM chemical sensor element for chloroform sensing devices with a low detection limit, fast response and recovery times, selectivity, and high sensitivity