Biocompatible Temperature Nanosensors Based on Titanium Dioxide

The measurement of temperature is of fundamental importance in a huge scale of applications, from nanomedicine, where the early detection of tumorous cells is an essential requirement, to microelectronics and microcircuits. Optical sensors with a micro/nano-spatial resolution can be used for temperature determination within a biological frame. Within this context, Raman spectroscopy is particularly interesting: the inelastic scattering of light has the advantage of a contactless measurement and exploits the temperature-dependence of intensities in the spectrum by observing the intensity ratio of anti-Stokes and Stokes signals. Titanium dioxide can be regarded as a potential optical material for temperature detection in biological samples, thanks to its high biocompatibility, already demonstrated in literature, and to its strong Raman scattering signal. The aim of the present work is the realization of biocompatible optical thermometers, with a sub-micrometric spatial resolution, made of titanium dioxide. Raman measurements have been performed on anatase powder using 514.5, 568.2 and 647.1 nm excitation lines of the CW Ar/Kr ion laser. The laser beam was focalized through a microscope on the sample, kept at defined temperature using a temperature controller. The Stokes and anti-Stokes scattered light was analyzed through a triple monochromator and detected by a liquid nitrogen-cooled CCD camera. Raw data were analyzed with Matlab and Raman spectrum parameters—such as area, intensity, frequency position and width of the peak—were calculated using a Lorentz fitting curve. Preliminary results showed that good reliable temperatures can be obtained.

MAX-DOAS NO2 profile retrieval over Minsk: 3 years of observation

<p>For NO<sub>2</sub> monitoring by MAX-DOAS method, the automated instrument MARS-B based on the spectrograph ORIEL MS257 with a Peltier-cooled CCD-array detector Andor Technology DV-420 OE (number of active pixels is 1024×256, working temperature is -40 ºC) has been employed. The MARS-B instrument records the spectra of scattered sunlight in the range of elevation angles 0º – 90º within vertical angle aperture of 1.3º in spectral range 340-400 nm with FWHM = 0.32 nm and is operating without mechanical shutter. Radiation input system is working without optical fiber and spectrograph unit has open-air design, spectrograph unit is temperature-stabilized at level 40 ± 0.5 ºC. The MARS-B instrument successfully took part in MAD-CAT (2013) and CINDI-2 (2016) international inter-comparison campaigns.</p><p>Since 2017 MARS-B instrument is performing spectra registering over Minsk (National Ozone Monitoring Research and Education Centre, Minsk, Belarus) using multi-axis geometry of observations during daytime and zenith geometry in twilights. More than 4.5 millions of day-time spectra aiming to retrieve differential slant columns of ozone, nitrogen dioxide and oxygen dimer have been processed by DOAS method. Total nitrogen dioxide columns have been retrieved by PriAM algorithm which is based on optimal estimation method.</p><p>Continuous 3-year MAX-DOAS measurements (nitrogen dioxide vertical column, near-surface nitrogen dioxide concentrations, aerosol optical depth) over Minsk in period of 2017 - 2019 will be presented, compared with data of impact gas analyzers and satellite data, analyzed and discussed. Also, zenith twilights measurements will be processed aiming to retrieve stratospheric nitrogen dioxide and ozone columns for comparison with different parameters of solar activity.</p>

Miniature Spatial Heterodyne Raman Spectrometer with a Cell Phone Camera Detector

A spatial heterodyne Raman spectrometer (SHRS) with millimeter-sized optics has been coupled with a standard cell phone camera as a detector for Raman measurements. The SHRS is a dispersive-based interferometer with no moving parts and the design is amenable to miniaturization while maintaining high resolution and large spectral range. In this paper, a SHRS with 2.5 mm diffraction gratings has been developed with 17.5 cm−1 theoretical spectral resolution. The footprint of the SHRS is orders of magnitude smaller than the footprint of charge-coupled device (CCD) detectors typically employed in Raman spectrometers, thus smaller detectors are being explored to shrink the entire spectrometer package. This paper describes the performance of a SHRS with 2.5 mm wide diffraction gratings and a cell phone camera detector, using only the cell phone’s built-in optics to couple the output of the SHRS to the sensor. Raman spectra of a variety of samples measured with the cell phone are compared to measurements made using the same miniature SHRS with high-quality imaging optics and a high-quality, scientific-grade, thermoelectrically cooled CCD.

Optical Odor Imaging by Fluorescence Probes

Odor gas detection is important for the detection of explosives, environmental sensing, biometrics, foodstuffs and a comfortable life. Such odor-source localizations is an active research area for robotics. In this study, we tried to detect odor chemicals with an optical method that can be applied for the spatiotemporal detection of odor. We used four types of fluorescence dyes; tryptophan, quinine sulfate, acridine orange, and 1-anilinonaphthalene-8-sulfonate (ANS). As analyses, we measured the following four odor chemicals, 2-furaldehyde, vanillin, acetophenone, and benzaldehyde. The fluorescence-quenching mechanism of PET (Photoinduced Electron Transfer) or FRET (Fluorescence Resonance Electron Transfer), which occur between fluorescence dyes and odor compounds, could prevent unintended detection of various odorants that is caused by their unspecific adsorption onto the detecting materials. The fluorescence changes were then observed. Thus, we could detect the odor substances through fluorescent quenching by using the fluorescence dyes. Odor information could be obtained by response patterns across all the fluorescence dyes. Moreover, we captured odor images with a cooled CCD camera. Shapes of the targets that emitted odor could be roughly recognized by the odor-shape images. From the spatiotemporal images of odors, twodimensional odor expanse could be obtained.