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“Blinking” behavior of fluorophores, being harmful for the majority of super-resolved techniques, turns into a key property for stochastic optical fluctuation imaging and its modifications, allowing one to look at the fluorophores already used in conventional microscopy, such as graphene quantum dots, from a completely new perspective. Here we discuss fluorescence of aggregated ensembles of graphene quantum dots structured at submicron scale. We study temperature dependence and stochastic character of emission. We show that considered quantum dots ensembles demonstrate rather complicated temperature-dependent intermittent emission, that is, “blinking” with a tendency to shorten “blinking” times with the increase of temperature. We verify “blinking” mechanism demonstrating hysteresis of the optical response under pulsed excitation timed to expected rates of dots transition to “dark” nonemitting states. Experimental results are well fitted by a simple qualitative model of transitions to the “dark” states. The obtained results suggest that this type of standardized quantum dots and even their submicron-size agglomerations can be useful as controlled fluorophores for super-resolution microscopy and, particularly, for SOFI-like microscopy.

Black silicon (bSi) refers to an etched silicon surface comprising arrays of microcones that effectively suppress reflection from UV to near-infrared (NIR) while simultaneously enhancing the scattering and absorption of light. This makes bSi covered with a nm-thin layer of plasmonic metal, i.e., gold, an attractive substrate material for sensing of bio-macromolecules and living cells using surface-enhanced Raman spectroscopy (SERS). The performed Raman measurements accompanied with finite element numerical simulation and density functional theory analysis revealed that at the 785 nm excitation wavelength, the SERS enhancement factor of the bSi/Au substrate is as high as 108due to a combination of electromagnetic and chemical mechanisms. This finding makes the SERS-active bSi/Au substrate suitable for detecting trace amounts of organic molecules. We demonstrate the outstanding performance of this substrate by highly sensitive and specific detection of a small organic molecule of 4-mercaptobenzoic acid and living C6 rat glioma cell nucleic acids/proteins/lipids. Specifically, the bSi/Au SERS-active substrate offers a unique opportunity to investigate the living cells’ malignant transformation using characteristic protein disulfide Raman bands as a marker. Our findings evidence that bSi/Au provides a pathway to the highly sensitive and selective, scalable, and low-cost substrate for lab-on-a-chip SERS biosensors that can be integrated into silicon-based photonics devices.

We demonstrate that predepositing a nanometrically thin nickel film on a dielectric surface is sufficient to transform an amorphous pyrolyzed photoresist film (PPF) into a graphitic film (GRF) enriched with nickel particles. The GRF shows 3 orders of magnitude higher carrier mobility than the amorphous PPF, whereas its electrical conductivity doubles after etching away the nickel remains. The pronounced 2D peak in the Raman spectrum, almost dispersionless absorbance in the spectral range of 750–2000 nm, and the saturable absorption coefficient indicate that GRF possesses a graphene-like band structure. The proposed cost-efficient and scalable synthesis route opens avenues toward fabrication of micron size patterned graphitic structures of any shape directly on a dielectric substrate. Having graphene-like transport and electrical properties at 20 times higher absorbance than the single-layer graphene, GRF is attractive for fabrication of fast modulators for optical radiation, bolometers, and other photonics and optoelectronic devices that require enhanced optical absorption.

The latest our results on triple polymer composites based on graphene nanoplatelets (GNP) covered by copper nanoparticles, iron oxide nanoparticles, and CdSe two-dimensional and spherical nanoparticles are presented and analyzed. It was found that GNP covered by copper nanoparticles results in higher conductivity and film stability increase in PEDOT:PSS than pure GNP. It was revealed that in magnetic field, composites based on GNP with iron oxide nanoparticles have metallic conductivity and form thin films with higher surface while thin films formed without magnetic field are dielectrics and have less surface. Luminescent composite based on CdSe nanoplatelets has been obtained. Two maxima in the luminescence spectra of CdSe nanoplatelets have been found and explained with a model based on efficient absorption of photons between neighbor nanoplatelets. Luminescence of active particles was different in different places of the sample and strongly depends on the graphene type. Stronger luminescence is observed in graphene with less amount of defects.

The latest our results on triple polymer composites based on graphene nanoplatelets (GNP) covered by copper nanoparticles, iron oxide nanoparticles, and CdSe two-dimensional and spherical nanoparticles are presented and analyzed. It was found that GNP covered by copper nanoparticles results in higher conductivity and film stability increase in PEDOT:PSS than pure GNP. It was revealed that in magnetic field, composites based on GNP with iron oxide nanoparticles have metallic conductivity and form thin films with higher surface while thin films formed without magnetic field are dielectrics and have less surface. Luminescent composite based on CdSe nanoplatelets has been obtained. Two maxima in the luminescence spectra of CdSe nanoplatelets have been found and explained with a model based on efficient absorption of photons between neighbor nanoplatelets. Luminescence of active particles was different in different places of the sample and strongly depends on the graphene type. Stronger luminescence is observed in graphene with less amount of defects.

Broadband dielectric properties of epoxy composites containing the different additions of manganese ferrite (MnFe2O4) with two spherical particle sizes (28 and 60 nm) are studied in the wide temperature range from 150 to 500 K. The percolation thresholds in such systems are 30 and 29.3 vol% for small and large MnFe2O4particles, respectively. The small difference in the percolation threshold value is related to a better distribution of larger nanoparticles. Composites above the percolation threshold are appropriate candidates for electromagnetic shielding applications. Above 380 K, the electrical conductivity is typical for all composites, both below and above the percolation thresholds due to the electrical transport in the polymer matrix. The activation energy strongly decreases with MnFe2O4concentration indicating that the electrical transport occurs simultaneously in both MnFe2O4and epoxy matrix subsystems. Broadband dielectric properties of epoxy composites containing manganese ferrite (MnFe2O4) additions with two spherical particle sizes (28 and 60 nm) are presented in the wide temperature range from 150 to 500 K. The percolation thresholds in such systems are 30 and 29.3 vol% for small and large particles, respectively. Composites are appropriate candidates for electromagnetic shielding applications.