The enhancement of optical processes near rough surface of metals

Last decades the enhancement of optical transitions near metal surface was observed under study the optical processes (luminescence, Raman scattering, IR absorption). The effect consists in an essential increase of the intensity of transition (for example, an effective cross-section increases by factor 10⁵…10¹¹ for Raman scattering and 10…10⁴ for IR absorption) or efficiency of the processes near metal surface (e.g. generation of second harmonic). We have analyzed a various experimental techniques that made it possible to achieve an enhancement in surface enhanced infrared absorption (SEIRA), surface enhanced Raman scattering (SERS), metal-enhanced fluorescence. Under the conditions of our experiment and according to literature data, there was observed enhancement factor which equal to 3…20 for vibrations of various molecular groups in SEIRA. Peculiarity of another optical amplifier, namely, colloidal gold nanoparticles, which were effectively used for enhancement of signal in IR absorption and Raman scattering, metal-enhanced fluorescence, has been studied also. Different roughness of gold surface leads to changes in an enhancement factor. The structural features of bovine serum albumine (BSA) – colloidal gold system and enhancement of guanine that obtained in SEIRA experiment are discussed. Atom force microscopy (AFM) technique was applied to test the roughness of the metal surface. We made an attempt to model the factor of enhancement of electrical field and its frequency dependence for different metal surfaces, and ascertained that silver, gold and copper are the best

Carbon Nanotubes Based Black Absorbing Coatings for Pyroelectric and Other Thermal Detector Application

The study of optical and thermophysical characteristics of the absorbing coatings (AC) for sensitive elements of pyroelectric detectors of radiation based on carbon nanotubes paste (CNTP-black) is performed in comparison with those AC formed from gold disperse layer (Au-black) and dielectric lacquer paint (DLP-black). The spectral dependences of reflectance and absorbance of CNTP-black, Au-black and DLP-black in IR-spectrum range 2.5—25 μm are presented. By photothermomodulation method, the frequency spectra of pyroelectric response amplitude and phase are obtained. The estimation of thermal diffusivity values of the investigated blacks as AC for sensitive elements of pyroelectric detectors is performed in situ. Prospects of using CNTP-black based AC for pyroelectric and other thermal detector applications are shown.Виконано порівняльні дослідження оптичних і теплофізичних характеристик вбирних покриттів (ВП) для чутливих елементів піроелектричних приймачів випромінення на основі пасти з вуглецевих нанорурок (ВНР- пасти), золотої черні (Au-черні) і діелектричної лакофарбової черні (ДЛФ-черні). Представлено спектральні залежності ІЧ-відбивання і вбирання ВНР-черні, Au-черні і ДЛФ-черні в інтервалі довжин хвиль 2,5—25 мкм. За допомогою фототермомодуляційнної методи одержано частотні спектри амплітуди і фази піроелектричного відгуку. Визначено «у місці знаходження» величини температуропровідности досліджуваних типів черні як ВП для чутливих елементів піроелектричних приймачів випромінен- ня. Показано перспективність використання ВП на основі черні з ВНР- пасти для піроелектричних й інших теплових приймачів випромінення.Проведены сравнительные исследования оптических и теплофизических характеристик поглощающих покрытий (ПП) для чувствительных элементов пироэлектрических приемников излучения на основе пасты из углеродных нанотрубок (УНТ-пасты), золотой черни (Au-черни) и диэлектрической лакокрасочной черни (ДЛК-черни). Представлены спектральные зависимости ИК-отражения и поглощения УНТ-черни, Au- черни и ДЛК-черни в интервале длин волн 2,5—25 мкм. С помощью фототермомодуляционного метода получены частотные спектры амплитуды и фазы пироэлектрического отклика. Проведено определение «в месте нахождения» величины температуропроводности исследуемых типов черни как ПП для чувствительных элементов пироэлектрических приемников излучения. Показана перспективность использования ПП на основе черни из УНТ-пасты для пироэлектрических и других тепловых приемников излучения

Gold and colloidal gold surface influence on dna conformational change

DNA conformational changes caused by gold and colloidal gold surface have been studied by surface enhanced infrared spectroscopy (SEIRA), spectroscopy of plasmon resonance (SPR), atomic force microscopy (AFM) and principal component analysis. Experimental data have shown that DNA conformation is slightly influenced by gold surface, while it is strongly altered by colloidal gold. Spectroscopic features of DNA-colloidal gold system have shown that the intensity of the asymmetric PO₂– band at 1240 cm⁻¹ decreases by two times, and that of symmetric band at 1090 cm⁻¹ decreases by 2.4 times whereas the halfwidth of phosphate bands increases by 35–40 cm⁻¹; a frequency shift of asymmetric band position from 1240 to 1246 cm⁻¹ and a symmetric band from 1090 to 1106 cm⁻¹ has been observed. It was shown that intensity variation and shift of DNA base vibrations together with the broadening of OH, NH, and CH stretching vibrations occur due to DNA conformational changes and the redistribution of the H-bonding network. A supposition about DNA condensation by colloidal gold was made. SEIRA and AFM data have showed major DNA structural changes occurred on gold colloidal particles. It was found that all the spectral features are more prominent for DNA–colloidal gold system deposited on gold substrate than on CaF₂ substrate

Microwave-induced optical non-linearity of amino acid crystals

Changes (ΔR) of amino acid crystals infrared (IR) reflectance (R) induced by simultaneous irradiation of IR and microwaves (MW) or extremely high frequency (EHF) radiation have been observed. It was shown that under the microwave action, components of dielectric permeability tensor, εij, which is responsible for the alteration of the R, are changed. Square dependence of ΔR/R on power of EHF radiation has been observed. An attempt for explanation of the observed effect as non-linear phenomenon with participation of two EHF photons (Ωm) and one IR photon (ωi) was made. The estimation shows that the third order non-linear polarizability coefficient, χ⁽³⁾(Ωm,-Ωm, ωi), reaches the gigantic value - 10 сm/erg for α-Gly single crystal

Study of DNA interaction with carbon nanotubes

Structural characterisation of two different forms of carbon - graphite and single-walled carbon nanotubes (SWCNT) has been done with Raman and FTIR spectroscopy. Interaction of nucleic acids with graphite powder and SWCNT was studied with Surface Enhanced Infrared Absorption (SEIRA) spectroscopy. Analysis of DNA-SWCNT complex vibration modes has shown that the numerous structural changes in DNA have been connected with appearance of new sugar and bases conformations, changes in phosphate vibrations and could be interpreted as A-B conformation transition and stabilisation of structure in some DNA fragments. Only very slight graphite influence on DNA structure have been registered. We have proposed the model of DNA interaction with SWCNT based on wrapping of nucleic acid molecules around carbon nanotubes. The similar situation seems to occur in chromosome during DNA assembling by histones

Surface enhanced imaging and IR spectroscopy of the biological cells on the nanostructured gold film

New approach for optical imaging, structural study and cell cultivation based on the effect of the enhancement of optical signals from biomolecules and biological cells near nanostructured rough gold surface is proposed. The surface enhanced IR absorption (SEIRA) spectroscopy and confocal microscopy experiments were made using the culture of SPEV (porcine embryonic kidney epithelium transplantable line) and fibroblast cells, cultivated and/or adsorbed on the gold substrate. The SEIRA spectra registered from monolayer of the SPEV cells cultivated on the rough gold showed a low frequency shift of about 2 to 7 cm 1 for the most characteristic IR vibrations, compared with those adsorbed from suspension on the same substrate. An enhancement factor of 15…30 was obtained for different molecular vibrations. The confocal microscopy contrast images of the SPEV cells on rough gold substrate were obtained in laser fluorescence mode. This approach opens new possibilities for visualization of the living cells in vivo without staining. The fluorescence of the rough gold surfaces and effects responsible for our findings have been discussed

Carbon Nanotubes Based Black Absorbing Coatings for Pyroelectric and Other Thermal Detector Application

The study of optical and thermophysical characteristics of the absorbing coatings (AC) for sensitive elements of pyroelectric detectors of radiation based on carbon nanotubes paste (CNTP-black) is performed in comparison with those AC formed from gold disperse layer (Au-black) and dielectric lacquer paint (DLP-black). The spectral dependences of reflectance and absorbance of CNTP-black, Au-black and DLP-black in IR-spectrum range 2.5—25 μm are presented. By photothermomodulation method, the frequency spectra of pyroelectric response amplitude and phase are obtained. The estimation of thermal diffusivity values of the investigated blacks as AC for sensitive elements of pyroelectric detectors is performed in situ. Prospects of using CNTP-black based AC for pyroelectric and other thermal detector applications are shown.Виконано порівняльні дослідження оптичних і теплофізичних характе- ристик вбирних покриттів (ВП) для чутливих елементів піроелектричних приймачів випромінення на основі пасти з вуглецевих нанорурок (ВНР- пасти), золотої черні (Au-черні) і діелектричної лакофарбової черні (ДЛФ- черні). Представлено спектральні залежності ІЧ-відбивання і вбирання ВНР-черні, Au-черні і ДЛФ-черні в інтервалі довжин хвиль 2,5—25 мкм. За допомогою фототермомодуляційнної методи одержано частотні спектри амплітуди і фази піроелектричного відгуку. Визначено «у місці знаходження» величини температуропровідности досліджуваних типів черні як ВП для чутливих елементів піроелектричних приймачів випромінення. Показано перспективність використання ВП на основі черні з ВНР-пасти для піроелектричних й інших теплових приймачів випромінення.Проведены сравнительные исследования оптических и теплофизических характеристик поглощающих покрытий (ПП) для чувствительных элементов пироэлектрических приемников излучения на основе пасты из углеродных нанотрубок (УНТ-пасты), золотой черни (Au-черни) и диэлектрической лакокрасочной черни (ДЛК-черни). Представлены спектральные зависимости ИК-отражения и поглощения УНТ-черни, Au-черни и ДЛК-черни в интервале длин волн 2,5–25 мкм. С помощью фототермомодуляционного метода получены частотные спектры амплитуды и фазы пироэлектрического отклика. Проведено определение «в месте нахождения» величины температуропроводности исследуемых типов черни как ПП для чувствительных элементов пироэлектрических приемников излучения. Показана перспективность использования ПП на основе черни из УНТ-пасты для пироэлектрических и других тепловых приемников излучения

SPR-spectroscopy of protein molecules adsorbed in microwave field

A possibility to use surface plasmon resonance (SPR) in the investigations of the microwave radiation influence upon proteins in the process of their adsorption on the gold surface and their interaction with other proteins. For the first time, this method is applied to experimental study of physical parameters of the biological molecules under the action of the weak (from 1 to 10 mW/ cm²) electromagnetic fields in real-time regime. The changes in the process of adsorption of protein on the gold at different stages of the absorption as well as the changes in the reaction of antigen-antibody were introduced under the action of microwave field. More dense layers of protein was obtained in the microwave fields resulting in the decreased contribution of non-specific and specific interactions between proteins

Synthesis, properties and electrocatalytic application of g-C3N4 for oxygen electrodes of fuel cells

AbstractA new type of metal-free oxygen electrode has been proposed. Its distinguishing feature is applying as an active layer nanodispersed graphitic carbon nitride with electrocatalytic properties controlled by synthesis conditions. Optimal conditions of thermochemical synthesis of g-C3N4 by a heat treatment of a solid mixture of melamine precursor and nitrogen-rich urea additive have been defined. The obtained layered g-C3N4 has been characterized by XRD, selected area electron diffraction, TEM and FTIR. An investigation of the electrocatalytic characteristics of oxygen electrodes has been carried out in a fuel half-cell with alkaline electrolyte. The electrochemical characteristics of the obtained g-C3N4 material with melamine-to-urea ratio 1:2 have been shown to be close to those of platinum electrodes. Electrochemical studies have shown that the obtained carbon nitride is a promising material as metal-free catalyst for oxygen electrodes of fuel cells The long-term testing of produced materials confirmed that they were stable over six months