Sensitive detection of endocrine disrupters using ionic liquid – single walled carbon nanotubes modified screen-printed based biosensors
Ana-Maria Gurban, Lucian Rotariu, Mihaela Baibarac, Ioan Baltog, Camelia Bala,
Talanta, Volume 85, Issue 4, 30 September 2011, Pages 2007-2013
Simple and low cost biosensor based on screen-printed electrode for sensitive detection of some alkylphenols was developed, by entrapment of HRP in a nanocomposite gel based on single-walled carbon nanotubes (SWCNTs) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) ionic liquid. Raman and FTIR spectroscopy, CV and EIS studies demonstrate the interaction between SWCNTs and ionic liquid. The nanocomposite gel, SWCNT–[BMIM][PF6] provides to the modified sensor a considerable enhanced electrocatalytic activity toward reduction. The HRP based biosensor exhibits high sensitivity and good stability, allowing a detection of the alkylphenols at an applied potential of −0.2 V vs. Ag/AgCl, in linear range from 5.5 to 97.7 μM for 4-t-hydrogen peroxideoctylphenol and respectively, between 5.5 and 140 μM for 4-n-nonylphenol, with a response time of about 5 s. The detection limit was 1.1 μM for 4-t-octylphenol, and respectively 0.4 μM for 4-n-nonylphenol (S/N = 3).
Mihail Secu, Marin Cernea, Corina Elisabeta Secu and Bogdan S. Vasile
Journal of Nanoparticle Research, Volume 13, Number 8, 3123-3128
Nanocrystalline Ho-doped BaTiO3, with average nanocrystals size of 20 nm, have been prepared using a sol–gel combustion technique. The structural and morphological properties of the powders have been investigated by X-ray powder diffraction and high resolution transmission electron microscopy. Chemical states of the holmium on the Ba0.97Ho0.03-TiO3 ceramic surface were analyzed using X-ray photoelectron spectroscopy. Furthermore, their photoluminescence properties were analyzed
Nanoparticles size effects in thermoluminescence of oxyfluoride glass-ceramics containing Sm3+ doped CaF2
J Nanopart Res (2011) 13:2727-273
Oxyfluoride glass-ceramic in the system SiO2–Al2O3–CaF2–SmF3 containing Sm3+-doped CaF2 nanocrystals in the range from 15 to 150 nm size were produced by using the controlled ceramization of the precursor glass. The incorporation of the Sm3+-dopant ion in the glass ceramic creates new electron-trapping centers and thermoluminescence (TL) method has been used in order to trace their evolution during glass ceramization. The 370 oC TL peak observed in precursor glass has been assigned to the recombination of the electrons released from the Sm2+-traps in the amorphous glass network. In the glass-ceramic sample containing nanocrystals with about 15 nm size the new weak TL peaks at 270, 290, and 310 oC were attributed to the recombination of the electrons released from the Sm2+-traps located mainly at the surface of the CaF2 nanocrystals. In the glass-ceramic sample containing nanocrystals with about 150 nm size, the new TL peaks at 232, 270, and 302 oC size have been assigned to the recombination of the electrons released from the Sm2+-traps located inside the CaF2 nanocrystals.
Electrochemical functionalisation of SWNTs with poly(3,4-ethylenedioxy thiophene) evidenced by anti-Stokes/Stokes Raman spectroscopy
Ioan Baltog, Mihaela Baibarac, Serge Lefrant, Jean Yves Mevellec
Journal of Raman Spectroscopy, Volume 42.Issue 3, pages 303-312, March 2011
The capability of anti-Stokes/Stokes Raman spectroscopy to evaluate chemical interactions at the interface of a conducting polymer/carbon nanotubes is demonstrated. Electrochemical polymerisation of the monomer 3,4-ethylenedioxythiophene (EDOT) on a Au support covered with a single-walled carbon nanotube (SWNT) film immersed in a LiClO4/CH3CN solution was carried out. At the resonant optical excitation, which occurs when the energy of the exciting light coincides with the energy of an electronic transition, poly(3,4-ethylenedioxythiophene) (PEDOT) deposited electrochemically as a thin film of nanometric thickness on a rough Au support presents an abnormally intense anti-Stokes Raman spectrum. The additional increase in Raman intensity in the anti-Stokes branch observed when PEDOT is deposited on SWNTs is interpreted as resulting from the excitation of plasmons in the metallic nanotubes. A covalent functionalisation of SWNTs with PEDOT both in un-doped and doped states takes place when the electropolymerisation of EDOT, with stopping at +1.6 V versus Ag/Ag+, is performed on a SWNT film deposited on a Au plate. The presence of PEDOT covalently functionalised SWNTs is rationalised by (1) a downshift by a few wavenumbers of the polymer Raman line associated with the symmetric CC stretching mode and (2) an upshift of the radial breathing modes of SWNTs, both variations revealing an interaction between SWNTs and the conjugated polymer. Raman studies performed at different excitation wavelengths indicate that the resonant optical excitation is the key condition to observe the abnormal anti-Stokes Raman effect. Copyright 2010 John Wiley & Sons, Ltd
Stokes and anti-Stokes Raman spectra of SWNTs at two excitation wavelengths 514.5 nm (top) and 676.4 nm (bottom). Red (dashed) curves show the anti-Stokes replica for a non-resonant Raman effect, which is calculated with the MB formula applied to the Stokes spectra,
Tailoring immobilization of immunoglobulin by excimer laser for biosensor applications
Felix Sima, Emanuel Axente, Carmen Ristoscu, Ion N. Mihailescu, Taras V. Kononenko,Ilya A. Nagovitsin, Galina Chudinova, Vitaly
Journal of Biomedical Materials Research Part A, Volume 96A, Issue 2, FEBRUARY 2011, Pages: 384-394
The sheltered transfer and immobilization of rabbit anti-human antiserum immunoglobulin G (IgG) by matrix assisted pulsed laser evaporation (MAPLE) are reported. The iced targets submitted to laser irradiation consisted of 0.2– 2 mg/mL IgG blended or not with lipid (L-a-phosphatidylcholine dipalmitoyl) dissolved in distilled water-based saline buffer. Thin IgG coatings were obtained at room temperature onto glass, fused silica, or silicon substrates. Ten thousand subsequent laser pulses of 0.33, 0.5, or 0.67 J/cm2 fluence were applied for the synthesis of each sample. Morphology and composition of the thin films were studied by optical, scanning, and atomic force microscopy and Fourier transformed infrared spectrometry. Optical labeling methods such as spectrofluorimetry and fluorescence microscopy were selected to verify the biosensor transduction principle because of their high sensitivity for detecting low amounts of antigen (IgG). Protein immobilization to the substrate surface was demonstrated for all obtained structures after immersion in the donkey anti-rabbit secondary antibody solution. The IgG transfer and immobilization onto substrates were improved by addition of lipid to MAPLE solutions.
AFM images of IgG structures obtained by MAPLE deposition on fused silica substrates from IgG dissolved in water and saline buffer without lipid at fluences of (A) 0.33 J/cm2 (I33), (B) 0.5 J/cm2 (I50), and (C) 0.67 J/cm2 (I67), respectively