Curcuma Longa Extract as a Sensitizer for Singlet Oxygen Generation

In this work, the spectral study of aqueous extract of Curcuma Longa (Turmeric) to determine the photodynamic properties. It is established that due to the absorption extract light of wavelength 400-450 nm and intensive fluorescence in the red region of the spectrum, this extract can be used as a sensitizer of singlet oxygen (1

Application of Raman spectroscopy to study the inactivation process of bacterial microorganisms

Raman spectroscopy (RS) is one of the promising approaches for structural and functional studies of various biological objects, including bacterial microorganisms. Both traditional biochemical tests and genetic methods which require expensive reagents, consumables and are time-consuming are used for bacterial analysis. Spectroscopic methods are positioned as noninvasive, highly sensitive, and requiring minimal sample preparation. In this work we investigated the possibility of using the RS method using optical sensors based on gold anisotropic nanoparticles. The applicability of the method was demonstrated by studying the effect of a broad-spectrum cephalosporin antibiotic and an extract of Viburnum opulus L (VO) on Escherichia coli (E. Coli) colonies. The studies were performed by Raman spectroscopy using a Virsa spectrometer (Renishaw). Raman signal amplification was carried out using two original optical sensors proposed by the authors. To create sensors, we used a chemical method of depositing gold nanostars on APTES-modified quartz glasses and a physical method for creating sensors based on anodizing titanium surfaces. The results of the study showed the high sensitivity and information content of the proposed method. The possibility of using the RS method for studying the inactivation of bacterial microorganisms is shown. Spectral Raman bands of E. Coli were determined and identified before and after exposure to VO extract and antibiotic as a control. A decrease in the intensity of spectral modes corresponding to amino acids and purine metabolites was found in the average Raman spectrum of E. Coli after exposure to VO extract. For the first time, a study of the antimicrobial effect of an aqueous extract of VO fruits was carried out by the method of Raman scattering. It has been shown that the use of plant extracts, including VO fruit extracts, to inactivate the vital activity of bacterial colonies is a promising approach to the search for new alternative antibacterial agents. The results obtained are in good agreement with the already known scientific studies and confirm the effectiveness of the proposed method

Refraction, fluorescence, and Raman spectroscopy of normal and glycated hemoglobin

In this study, the optical properties of glycated (HbA1c) and non-glycated (Hb) hemoglobin are compared using refractometry, fluorescence and Raman spectroscopy. The fluorescence measured at an excitation wavelength of 270 nm indicates differences in the molecular structure of hemoglobins. Analysis of the spectral shift of Raman spectra also showed variations indicating differences in their molecular structure. The refractive index measured in the visible and near IR regions for different temperatures allowed for quantification of mean values of temperature increment, which are quite different as dn/dT= –(1.03 ± 0.05)×10–4 °C–1 for Hb and – (1.37 ± 0.07)×10–4 °C–1for HbA1c.The data obtained in the work can serve as a basis for further study of the optical properties of glycated hemoglobin and other glycated proteins

Prospects for Raman spectroscopy in cardiology

Raman spectroscopy (RS) is a promising diagnostic method with high informative value and sensitivity. In addition, it is non-destructive and minimally invasive, and also requires minimal sample preparation, which opens up wide prospects for in vitro and in vivo use. There are some perspectives for this method in future cardiology practice. RS may allow to identify previously studied markers of cardiovascular disease, as well as to search for new ones. It is a sensitive method for the detection and biochemical assessment of early-stage atherosclerotic lesions and can be used in vivo. Of great interest is the possibility of using the RS to control the amount of eluted substance from drug-eluting stents to assess clinical efficacy. Study of platelet membranes using the RS technique revealed structural changes in patients with hypertension. This method makes it possible to assess myocardial viability in the border zone after myocardial infarction, and the obtained results correlate with the intraoperative data. More details about the prospects of using the RS will be described in the review

Multiple Quantum Barrier Avalanche Photodiode Based on GaN/AlGaN Heterostructures for Long Wavelength Infrared Detection

A multiple quantum barrier (MQB) avalanche photodiode (APD) structure based on GaN/AlxGa $_{1{-}x}\text{N}$ material system has been proposed in this paper which is capable of detecting infrared (IR) signal up to $6.0~\mu \text{m}$ wavelength. A self-consistent quantum drift-diffusion (SCQDD) model developed by the authors, has been used to determine the current-voltage characteristics under dark and illuminated conditions, spectral response, excess noise properties, signal-to-noise ratio, time and frequency responses. Results show that the proposed MQB APD attains peak responsivity of 60 AW $^{-1}$ at $3.0\, \mu \text{m}$ wavelength. Incorporation of a dedicated thin $n$ -type GaN layer for avalanche multiplication in between the $p^{+}$ -GaN contact layer and MQB constant-field drift-layer ensures significantly low noise equivalent power under normal operating conditions at room temperature (300 K). Optical pulse response of the device reveals that special restriction over the charge multiplication able to supress the minor peaks of the current response and consequently significantly narrow pulse response can be achieved. Narrow pulse response leads to broad bandwidth of 274.5 GHz, which is significantly broader than the existing IR photo-detectors

Photonic properties of two-dimensional high-contrast periodic structures: Numerical calculations

The photon properties of two-dimensional periodic structures formed by infinite homogeneous dielectric cylinders packed in a square lattice have been investigated theoretically. Depending on the dielectric contrast between the cylinders and the surrounding medium, the photonic band structure, transmission spectra of crystals with a finite number of layers, and spectra of Mie scattering by an isolated cylinder have been calculated. The calculations have been performed for the TE polarization. The transformation of photonic stop-bands corresponding to Bragg and Mie resonances has been analyzed using the obtained data. The main effect consists in castling energy positions of the Bragg stop-bands and Mie stop-bands. For low-contrast photonic crystals, the low-frequency region of the energy spectrum is determined by Bragg stop-bands, and Mie stop-bands are located higher in energy. With an increase in the dielectric contrast, the energy of Mie stop-bands decreases, and they intersect the region of Bragg stop-bands weakly varying in the TE polarization and form the low-energy region of the spectrum. © 2014 Pleiades Publishing, Ltd

Optical properties of glycated and non-glycated hemoglobin – Raman/fluorescence spectroscopy and refractometry

In this study, the optical properties of glycated (HbA1c) and nonglycated (Hb) hemoglobin are compared using Surface-enhanced Raman spectroscopy (SERS), spectrofluorimetry, and refractometry. Analysis of the spectral shift of SERS spectra showed good discrimination between two hemoglobins indicating differences in their molecular structure. The fluorescence spectra measured at excitation wavelengths of 260, 270, and 280 nm also indicate differences in the molecular structure of these hemoglobins. For the first time refractive index temperature increments were measured for HbA1c in a wide wavelength range in the visible and NIR as –(1.35 ± 0.11) ´ 10–4 °C–1 and compared with normal hemoglobin (dn/dT = –(1.02 ± 0.12) ´ 10–4 °C–1). The comparison of temperature RI increments for hemoglobin obtained from the whole blood of healthy volunteers and diabetic patients is also done. The data obtained can serve as a basis for further study of the optical properties of glycated hemoglobin and other glycated proteins

Polarized plasmon resonance spectra of electrochemically modified titanium surfaces with gold nanoparticles

In this paper, the plasmon resonance on electrochemically modified titanium surfaces synthesized by anodic dissolution method has been studied in the presence with gold ablative nanoparticles. The permittivity functions and reflection coefficients of p- and s-polarized light spectra on the titanium oxide surface of various modification (roughness) have been analyzed. Spectral features of the negative refractive index in the area of surface plasmon generation on the rough titanium-oxide film interface have been also presented in this paper