K. G. Mikheev

Laser modification of optical properties of a carbon nanotube suspension in dimethylformamide

It is shown experimentally that a semitransparent suspension of multiwall carbon nanotubes (MWNTs) in N,N-dimethylformamide (DMF) is irreversibly bleached in a wide optical wavelength range in a field of nanosecond high-power laser radiation with a wavelength of 532 nm. The bleaching is accompanied by a sharp decrease in the nonlinear scattering; the suspension ceases to optically limit power. It is shown that the suspension is bleached due to light-induced chemical reactions between MWNTs and DMF molecules with formation of new hydrocarbon chemical bonds.

Thresholds of optical limiting in solutions of nanoscale compounds of zinc phthalocyanine with galactopyranosyl radicals

The optical limiting (OL) of nanosecond laser pulses in solutions of newly synthesized dyes in dimethyl sulfoxide (DMSO) has been investigated. These dyes are compounds of zinc phthalocyanine (ZnPc) with D-galactopyranosyl radicals (Gal) located in the peripheral (p-GalZnPc) and nonperipheral (n-GalZnPc) positions with respect to the ZnPc macrocycle. Experiments have been performed using laser radiation with a wavelength of 532 nm, at which the optical absorbance of solutions of ZnPc, p-GalZnPc and n-GalZnPc dyes is four orders of magnitude lower than the absorbance in the peaks at wavelengths of 671, 680, and 701 nm, respectively. It is established that solutions of p-GalZnPc and n-GalZnPc in DMSO have a much lower OL threshold in comparison with ZnPc solution; the nonlinearity of p-GalZnPc solutions exceeds that of n-GalZnPc solutions. OL thresholds for the dyes under study in a wide concentration range are determined.

Laser-induced diamagnetism in suspension of onion-like carbon particles

It is experimentally established that the bleached fraction of a suspension of onion-like carbon (OLC) particles in N,N-dimethylformamide (DMF), which is clarified under the action of high-power pulsed laser radiation at λ = 1064 nm, is pushed out from inhomogeneous magnetic field. By changing the spatial arrangement of a permanent magnet relative to the point of laser action on the suspension, it is possible to control the direction of motion of the bleached fraction. The observed behavior can be explained by laserstimulated chemical reactions between OLC and DMF, which lead to the formation of a new substance with pronounced diamagnetic properties.

Z-scanning under monochromatic laser pumping: a study of saturatable absorption in a suspension of multiwalled carbon nanotubes

A system has been developed and designed based on a single-mode single-frequency passive Q-switched pulsed YAG : Nd3+ laser to investigate with high accuracy the nonlinear optical properties of a liquid placed in an optical cell with uncoated input windows. The efficiency of this system is demonstrated by examples of studying the saturable absorption of an aqueous suspension of multiwalled carbon nanotubes and the nonlinear absorption of a colour glass filter ZhS18 at a wavelength of 532 nm.

Laser images recording on aerosol-synthesized single-walled carbon nanotube films

It is shown that images on semitransparent conducting films of aerosol-synthesized single-walled carbon nanotubes (SWCNTs) can be recorded using focused low-power radiation of a He–Ne laser operating at a wavelength of 632.8 nm. Both free-standing films and those deposited on glass or polymer substrates can be used. Laser recording of images on the polymer-supported films is possible due to their transparency increased as a result of chemical reactions between iron nanoparticles encapsulated in SWCNTs and the products of local thermal decomposition of the polymer. Recording on the free-standing SWCNT films and those supported on glass substrates was performed upon acid treatment of the film surface.

Photon-drag in single-walled carbon nanotube and silver-palladium films: The effect of polarization

Abstract. Polarization influence on the photovoltaic current raised due to the photon-drag effect in the single-walled carbon nanotube (SWNT) films and nanostructured silver-palladium (Ag/Pd) resistive films is examined at the wavelengths of 532 and 1064 nm of nanosecond laser pulses. The SWNT films were synthesized by the aerosol chemical vapor deposition technique. Ag/Pd films, consisting of AgPd alloy and palladium oxide (PdO), were prepared by burning a special paste on a ceramic substrate. The films obtained were characterized by Raman spectroscopy. It is shown that the Ag/Pd films Raman spectra consist of PdO peak that moves from 650  cm−1 to 628  cm−1 as the excitation He-Ne laser power increases. The photocurrent was measured at the oblique incidence of the laser beam on the film in the direction perpendicular to the plane of incidence. It is found that the transverse photocurrent in the SWNT films at circular polarization is absent and does not depend on the direction of the electric field vector rotation (the sign of the circular polarization) of the incident irradiation. The photocurrent in the Ag/Pd films at circular polarized irradiation is significant and depends on the circular polarization sign. The results obtained demonstrate the potential applications of the Ag/Pd resistive films as a sensor of the circular polarization sign of the incident light pulse in a wide wavelength range.

Laser Bleaching of Carbon Nanotubes Suspension in N,N- Dimethylformamide

Laser Bleaching of Carbon Nanotubes Suspension in N,N- Dimethylformamide It is shown experimentally that the multiwall carbon nanotubes (MWNTs) suspension in N,N-dimethylformamide (DMF) irreversibly bleaches in a wide spectrum range under a pulsed nanosecond laser radiation at the wavelength of 532 nm. According to the data of the transmission electron microscopy (TEM), the Raman spectroscopy and the reflection infrared spectrometry the bleaching is shown to be caused by MWNTs degradation, with the formation of new chemical bonds which result from the laserinduced chemical reactions between MWNTs and DMF molecules.

Deposition of stoichiometric Bi2Se3 film by vacuum-thermal treatment of Se/Bi heterostructure

The possibility of obtaining a stoichiometric Bi2Se3 film by vacuum-thermal treatment of a Se/Bi heterostructure is demonstrated for the first time. It was found that a stoichiometric Bi2Se3 film can be only produced at a certain ratio of the Se and Bi film thicknesses (dSe/dBi = 3.13). X-ray-diffraction analysis and Raman spectroscopy were used to study the phase transformations in a Se(141 nm)/Bi(45 nm) heterostructure upon its thermal treatment in a vacuum. The phase transition temperatures at which various crystalline phases are formed were determined. It is shown that Bi2Se3 crystallizes in the Se(141 nm)/Bi(45 nm) heterostructure heated to 493 K in conformity with an exponential law, with a characteristic time in which the equilibrium state is attained equal to 20 min.

The influence of PdO content on circular photocurrent in resistive Ag/Pd films

We have studied the influence of PdO content in resistive Ag/Pd films (consisting of this oxide and Ag–Pd solid solution) on photocurrent dependent on the sign of circular polarization of the exciting radiation. The photocurrent was excited by nanosecond pulsed laser radiation with a 532 nm wavelength and measured in the direction perpendicular to the plane of laser beam incidence onto the film. The content of PdO in the film was varied by electrolytic reduction of Pd from PdO in sulfuric acid solution. Raman spectroscopy and X-ray diffraction measurements showed that reduced PdO content in the film leads to nonlinear decrease in the magnitude of photocurrent. It is established that photocurrent is also observed when PdO is fully absent on the film surface. The obtained results suggest that the nature of photocurrent in Ag/Pd films is related to the structure of Ag–Pd solid solution.

Optical limiting in suspension of detonation nanodiamonds in engine oil

Abstract. The optical limiting (OL) of detonation nanodiamond (DND) suspensions in engine oil was studied at a temperature range of 20°C to 100°C. Oil suspensions were prepared on the basis of the DNDs with an average nanoparticle cluster size in hydrosols (Daver) of 50 and 110 nm. Raman spectroscopy was used to characterize the samples. The OL investigation was carried out by the z-scan technique. The fundamental (1064 nm) and second (532 nm) harmonic radiations of YAG:Nd3+ laser with passive Q-switching as an excitation source were used. The OL thresholds for both suspensions at 532 and 1064 nm were determined. It is shown that a decrease in the average nanoparticle cluster size as well as an increase of the wavelength of the incident radiation leads to the OL threshold increase. It is established that the OL performance is not influenced by increasing the temperature from 20°C to 100°C. The results obtained show the possibility of using the DNDs suspensions in engine oil as an optical limiter in a wide temperature range.