Study of nonlinear optical phenomena in silicon nanowires

This work studies generation of second and third harmonics in arrays of vertically oriented silicon nanowires (SiNWs) encapsulated into a silicone membrane and separated from the growth substrate. The structures were produced by plasma-chemical etching of silicon substrate resulting in a formation of homogeneous arrays of SiNWs. Such SiNW-based membranes demonstrated efficient infrared-to-visible light conversion by generation of second and third harmonic signals visible by a naked eye. This study contributes to the development of technology of optical devices based on silicon and presents a new route for visualization of infrared radiation.

Processing and characterization of GaP nanowires encapsulated into a PDMS large-scale membrane for flexible optoelectronics

This paper presents the methods of fabricating arrays of semiconductor III-V nanowires transferred into a flexible polydimethylsiloxane membrane. Molecular beam epitaxy was used to synthesize GaP nanowires. The synthesized nanowire arrays were encapsulated into a silicone membrane by a heavy load swinging-bucket centrifuge. For optoelectronic applications, the nanowire/polydimethylsiloxane membranes were contacted with single-walled carbon nanotubes, peeled from the substrate, then the second carbon nanotubes contact was formed. For optical experiments, the nanowire/polydimethylsiloxane membranes were bonded to supporting polydimethylsiloxane films by oxygen plasma treatment, and then easily released from the substrate by unsticking. The obtained membranes have a high practical potential in flexible optoelectronics.

Light-emitting p-i-n GaP/GaPAs NW encapsulated in a flexible PDMS membrane

Our work is aimed at the method of fabricating arrays of semiconductor III-V NWs transferred into a flexible polymer membrane made of polydimethylsiloxane. GaP/GaPAs NWs with an axial p-i-n structure were synthesized by molecular beam epitaxy. The synthesized NW arrays on substrates were encapsulated into a silicone membrane by the G-coating method in a swinging-bucket centrifuge. After membranes were treated in a plasma mixture of O2/CF2 gases to open the NWs tops, which ensured the application of conductive transparent contacts - single-walled carbon nanotubes obtained by aerosol chemical method. At the last technological stage, the membranes were separated from substrates by peeling with a razor blade and the second carbon nanotubes contact was formed. The obtained LED NW/silicone membranes were characterized by I-V and the electroluminescence spectroscopy measurements.

Register of the human brain acoustic area spectrum

Last years, there were developed methods based on the human brain and body acoustic signals application. We consider human brain micro vibrations as an ancient, highly reliable, relatively rapid channel of the central nervous system with all the organism cells and structures. There is offered a method of the human brain acoustic area spectrum analysis and registration. Experimental sample “Register of the human brain micro vibrations spectrum is developed. The model of the human brain acoustic area generation is offered – neurovascular reflex and related with human brain blood vessels smooth muscularity nerve cells metabolism. In comparison with classical EEG, it is demonstrated that acoustic encephalogram also reflects human brain neuroreflex activity. Piezoelectric sensors, which feature in silicone membrane existence, are investigated. Such type of construction allowed to register human brain mechanical vibrations in the gamut from 0.1 up to 27 Hz. Spectral analysis is specific in that signal integration time is 160 seconds. Meanwhile, 12600 spectral harmonics of the human brain reticular activating system were reliably extracted. For convenience, all the acoustic area spectrum of the human brain was shrunk into segmental frame of reference which is frequency structured matrix of functional conditions multiplicity “multiple arousal” of 24х625 frequency cells size. All the developed technologies and device might be used for the organism adaptation estimations, psycho-emotional conditions estimations and functional-topical diagnosis of the internal parts of the human body.

Using autofluorescence for microplastic detection –Heat treatment increases the autofluorescence of microplastics 1

INTRODUCTION: More and more researchers are studying the effects of microplastics on the environment and the organisms living in it. Existing detection methods still require a heavy workload, complex sample preparation and high costs. In this study, autofluorescence of plastic was used as a new method for microplastic detection. MATERIAL AND METHODS: Particles of common plastics were incubated at various temperatures (21–230 °C) for different time periods to investigate the influence of these conditions on their autofluorescence using methods like fluorescence microscopy, and measurement of absorption and emission. To give an example of an autofluorescence application, ImageJ was used to determine the contamination of microplastic in sea salt samples. RESULTS: After treatment at 140 °C for 12 h the plastics ABS, PVC and PA showed a distinct increase in their fluorescence intensity. For PET higher temperatures were necessary to achieve higher fluorescence intensities. Using ImageJ, the particle contamination in sea salt samples was determined as 4903±2522 (aluminium membrane) / 5053±2167 (silicone membrane) particles in 10 g salt, which is a much higher number than counted in other publications. DISCUSSION: Probably the increase in fluorescence intensity is due to the movement of atomic bonds caused by the thermic energy during the heat treatment. The high number of counted particles by using ImageJ is most likely based on the smaller pore size of the used filter membranes and other contaminations like dust and fibers, which could be avoided by alternative sample treatment. CONCLUSION: Considering the outcomes of this study, heat treatment is a useful tool to make microplastic particles more visible in microscopic applications without readable destruction of their composition. The heat treatment of plastics for defined incubation times and temperatures can lead to a distinct increase in autofluorescence intensity of the plastics and therefore serve as an easy and cost-effective applicable method for microplastic detection.