ФОРМИРОВАНИЕ НАНОСТРУКТУР СЕРЕБРА МЕТОДОМ ИММЕРСИОННОГО ОСАЖДЕНИЯ НА ПОРИСТЫЙ КРЕМНИЙ И ИССЛЕДОВАНИЕ ИХ ОПТИЧЕСКИХ СВОЙСТВ

Nanostructures formed by immersion deposition of silver on porous silicon at different regimes for their application in surface enhanced Raman spectroscopy (SERS) has been presented. Porous silicon has been fabricated by anodization of monocrystalline silicon in water solution of isopropanol and hydrofluoric acid. Reflectance spectra of the obtained structures of silver/porous silicon have been studied. It has been revealed that the optimal regimes of SERS require using laser with wave length of 400-450 nm.Представлены результаты исследований наноструктур, изготовленных при различных режимах иммерсионного осаждения серебра на пористый кремний (ПК), для их применения в качестве активных субстратов в спектроскопии гигантского комбинационного рассеяния (ГКР). ПК был сформирован методом анодирования монокристаллического кремния в водно-спиртовом растворе фтористоводородной кислоты. Исследованы спектры отражения полученных наноструктур серебра на ПК. Выявлено, что для создания оптимальных условий ГКР-спектроскопии с использованием наноструктур серебра на ПК необходимо использовать возбуждающий лазер с длиной волны 400-450 нм

Trends of Career Development for Women in Physics and STEM in Belarus

In this paper, changes in the curricula of tertiary education and trends of career development for women in Physics/STEM in Belarus are reported. In particular, the ways that two reputative universities in Belarus have passed for the last decades to use women's potential in areas strongly dependent on knowledge and skills in Physics/STEM including microelectronics/nanotechnology and physics education were studied

Experimental study of the sensitivity of a porous silicon ring resonator sensor using continuous in-flow measurements

A highly sensitive photonic sensor based on a porous silicon ring resonator was developed and experimentally characterized. The photonic sensing structure was fabricated by exploiting a porous silicon double layer, where the top layer of a low porosity was used to form photonic elements by e-beam lithography and the bottom layer of a high porosity was used to confine light in the vertical direction. The sensing performance of the ring resonator sensor based on porous silicon was compared for the different resonances within the analyzed wavelength range both for transverse-electric and transverse-magnetic polarizations. We determined that a sensitivity up to 439 nm/RIU for low refractive index changes can be achieved depending on the optical field distribution given by each resonance/polarization

Shelf Life Improvement of SERS-Active Substrates Based on Copper and Porous Aluminum Oxide

Copper nanostructures demonstrating an activity in the surface-enhanced Raman scattering (SERS) spectroscopy were formed via electrochemical deposition of copper on porous aluminum oxide (PAO) and protected from oxidation by surface coverage with polyethylene glycol (PEG) and silver. The SERS measurements of 10−6−6-M 4-mercaptophenylboronic acid (MPBA) molecules adsorbed on fresh Cu-coated samples, Cu–PEG and Cu–PEG–Ag nanocomposites after 5, 10, 15, 60, 180 and 300min of storage in air indicated the effectiveness of the proposed approach in protection from oxidation

Label-Free Nanosensing Platform for Breast Cancer Exosome Profiling

Breast cancer accounts for 11.6% of all cancer cases in both genders. Even though several diagnostic techniques have been developed, the mostly used are invasive, complex, time-consuming, and cannot guarantee an early diagnosis, significantly constraining the tumor treatment success rate. Exosomes are extracellular vesicles that carry biomolecules from tissues to the peripheral circulation, representing an emerging noninvasive source of markers for early cancer diagnosis. Current techniques for exosomes analysis are frequently complex, time-consuming, and expensive. Raman spectroscopy interest has risen lately, because of its nondestructive analysis and little to no sample preparation, while having very low analyte concentration/volume, because of surface enhancement signal (SERS) possibility. However, active SERS substrates are needed, and commercially available substrates come with a high cost and low shelf life. In this work, composites of commercial nata de coco to produce bacterial nanocellulose and in-situ-synthesized silver nanoparticles are tested as SERS substrates, with a low cost and green approach. Enhancement factors from 104 to 105 were obtained, detecting Rhodamine 6G (R6G) concentrations as low as 10−11 M. Exosome samples coming from MCF-10A (nontumorigenic breast epithelium) and MDA-MB-231 (breast cancer) cell cultures were tested on the synthesized substrates, and the obtained Raman spectra were subjected to statistical principal component analysis (PCA). Combining PCA with Raman intravariability and intervariability in exosomal samples, data grouping with 95% confidence was possible, serving as a low-cost, green, and label-free diagnosis method, with promising applicability in clinical settings

Study of Diluted Meldonium Solutions by Surface Enhanced Raman Scattering Spectroscopy

Silvered porous silicon was utilized as an active substrate for a detection of small amounts of meldonium by surface enhanced Raman scattering (SERS) spectroscopy. We were able to detect the meldonium in its water solutions at the concentrations of 102–106 M. Immersion of the silvered porous silicon in the meldonium solutions at the 104M concentration and lower led to the dimers' formation. At the concentrations larger than 103 M, a greater contribution to the enhancement of the Raman intensity was caused by a chemical mechanism while the smaller amounts were detected mostly due to an electromagnetic mechanism

Bimetallic nanostructures on porous silicon with controllable surface plasmon resonance

The most intensive surface plasmon resonance (SPR) band is typical for the metallic particles of 10–150nm diameters. The SPR band of such nanoparticles is usually narrow and allows using just one laser (i.e. limited range of excitation wavelength) to achieve the maximal enhancement of electromagnetic field near metallic nanostructures caused by surface plasmon oscillations. It hinders usability of plasmonic nanostructures in some application including surface enhanced Raman scattering (SERS) spectroscopy. To overcome this hurdle enlarged metallic nanostructures are fabricated resulting in a broadening of the SPR band due to additional oscillation modes. However, the SPR bands of the enlarged particles are characterized by less intensity and weak enhancement at different wavelengths. In this paper, we proposed an alternative way for the SPR band broadening by use of bimetallic nanostructures on a sculptured template. Plasmonic substrates were fabricated by sequential copper electroplating and silver electroless deposition on porous silicon. Presented data implies that variation in morphology and ratio of the silver/copper nanostructures allow to control position of their SPR band from blue to near-infrared (IR) range. It is shown that SERS-spectroscopy with the fabricated nanostructures provide equal detection limits of rhodamine 6G under red and near-IR excitation wavelengths

Potent E. coli M‑17 Growth Inhibition by Ultrasonically Complexed Acetylsalicylic Acid−ZnO−Graphene Oxide Nanoparticles

A single-step ultrasonic method (20 kHz) is demonstrated for the complexation of acetylsalicylic acid (ASA)−ZnO− graphene oxide (GO) nanoparticles with an average size of <70 nm in aqueous solution. ASA−ZnO−GO more e ffi ciently inhibits the growth of probiotic Escherichia coli strain M-17 and exhibits enhanced antioxidant properties than free ASA and ASA−ZnO in neutralization of hydroxyl radicals in the electro-Fenton process. This improved function of ASA in the ASA −ZnO GO can be attributed to the well-de fi ned cone-shaped morphology, the surface structure containing hydroxyl and carboxylate groups of ZnO−GO nanoparticles, which facilitated the complexation with ASA