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We present the results of work on a hybrid material composed of a tellurite glass rod doped with nanodiamonds containing nitrogen-vacancy-nitrogen and paramagnetic nitrogen-vacancy color centers. The reported results include details on tellurite glass and cane fabrication, confocal and wide-field imaging of the nanodiamond distribution in their volume, as well as on the spectroscopic characterization of their fluorescence and Optically Detected Magnetic Resonance measurements of magnetic fields and temperatures. Magnetic fields up to 50 G were examined with a sensitivity of 10$^{-5}$ T Hz$^{-1/2}$ whereas temperature measurements were simultaneously performed with a sensitivity of 74 kHz K$^{-1}$ within the 8 Kelvin range at room temperature. In that way, we demonstrate the suitability of such systems for fiber magneto- and thermometry with a reasonable performance already in the form of glass rods. At the same time, the rods constitute an interesting starting point for further processing into photonic components such as microstructured fibers or fiber tapers for the realization of specialized sensing modalities., Comment: 16 pages, 3 figures

Integration of optically-active nanodiamonds with glass fibers is a powerful method of scaling of diamond magnetic sensing functionality. We propose a novel approach for integration of nanodiamonds containing nitrogen-vacancy centers directly into the fiber core. The core is fabricated using nanostructurization, that is by stacking the preform from 790 soft glass canes, drawn from a single rod dip-coated with nanodiamonds suspended in isopropyl alcohol. This enables manual control over distribution of nanoscale features, here - the nanodiamonds across and along the fiber core. We verify this by mapping the nanodiamond distribution in the core using confocal microscopy. The nanodiamonds are separated longitudinally either by 15 microns or 24 microns, while in the transverse plane separation of approximately 1 micron is observed, corresponding to the individual cane diameter in the final fiber, without significant agglomeration. Filtered, red fluorescence is observed with naked eye uniformly along the fiber. Its magnetic sensitivity is confirmed by in optically detected magnetic resonance recorded with a coiled, 60-cm-long fiber sample with readout contrast limited mainly by microwave antenna coverage. NV fluorescence intensity in 0 to 35 mT magnetic field is also demonstrated, allowing magnetometry applications with a large B-field dynamic range in absence of microwaves., Comment: 12 pages, 7 figures, 1 table

Additive manufacturing, called 3D printing, starts to play an unprecedented role in developing many applications in industrial or personalized products. The conductive composite structures require additional treatment to achieve an electroactive surface useful for electrochemical devices. In this paper, the surfaces of carbon black/poly(lactic acid) CB-PLA printouts were activated by electrolysis or enzymatic digestion with proteinase K, or a simultaneous combination of both. Proposed modification protocols allowed for tailoring electrochemically active surface area and electron transfer kinetics determined by electrochemical techniques (CV, EIS) with [Fe(CN)6]4-/3- redox probe. The X-ray photon spectroscopy and SEM imaging were applied to determine the delivered surface chemistry. The CB-PLA hydrolysis in alkaline conditions and under anodic polarization greatly impacts the charge transfer kinetics. The enzymatic hydrolysis of PLA with proteinase K has led to highly efficient results yet requiring an unsatisfactory prolonged activation duration of 72 h, efficiently reduced by the electrolysis carried out in the presence of the enzyme. Our studies hint that the activation protocol originates from surface electropolymerization rather than synergistic interaction between electrolysis and enzymatic hydrolysis. The detailed mechanism of CB-PLA hydrolysis supported by electrolysis has been elaborated since it pawed a new route towards a time-efficient and environmentally-friendly activation procedure., Comment: 23 pages, 8 figures

The fused deposition modeling is one of the most rapidly developing 3D printing techniques, with numerous applications, also in the field of applied electrochemistry. Here, utilization of conductive polylactic acid (C-PLA) for 3D printouts is the most promising, due to its biodegradability, commercial availability, and ease of processing. To use C-PLA as an electrode material, an activation process must be performed, removing the polymer matrix and uncovering the electroactive filler. The most popular chemical or electrochemical activation routes are done in solvents. In this manuscript, we present a novel, alternative approach towards C-PLA activation with Nd:YAG (lambda = 1064 nm) laser ablation. We present and discuss the activation efficiency based on various laser source operating conditions, and the gas matrix. The XPS, contact angle, and Raman analyses were performed for evaluation of the surface chemistry and to discuss the mechanism of the activation process. The ablation process carried out in the inert gas matrix (helium) delivers a highly electroactive C-PLA electrode surface, while the resultant charge transfer process is hindered when activated in the air. This is due to thermally induced oxide layers formation. The electroanalytical performance of laser-treated C-PLA in He atmosphere was confirmed through caffeine detection, offering detection limits of 0.49 and 0.40 microM (S/N = 3) based on CV and DPV studies, respectively.

In this paper, we describe the modification of Nanoscale Impedance Microscopy (NIM), namely, a combination of contact-mode atomic force microscopy with local impedance measurements. The postulated approach is based on the application of multifrequency voltage perturbation instead of standard frequency-by-frequency analysis, which among others offers more time-efficient and accurate determination of the resultant impedance spectra with high spatial resolution. Based on the impedance spectra analysis with an appropriate electric equivalent circuit, it was possible to map surface resistance and contact capacitance. Polycrystalline heavy boron-doped diamond (BDD) electrodes were the research object. Recent studies have shown that the exposure of such electrodes to oxidizing environment may result in the modification of termination type, and thus it is a key factor in describing the electric and electrochemical properties of BDD. We have successfully applied multifrequency NIM, which allowed us to prove that the modification of termination type is selective and occurs with different propensity on the grains having specific crystallographic orientation. Furthermore, our approach enabled the detection of even subtle submicroscopic surface heterogeneities, created as a result of various oxidation treatments and to distinguish them from the surface heterogeneity related to the local distribution of boron at the grain boundaries., Comment: 26 pages, 11 figures