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Many physical and chemical properties of solids, such as strength, plasticity, dispersibility, solubility and dissolution are determined by defects in the crystal structure. The aim of this work is to study in situ dynamic, dispersion, chemical, biological and surface properties of lacosamide powder after a complete cycle of mechanical loading by laser scattering, electron microscopy, FR-IR and biopharmaceutical approaches. The SLS method demonstrated the spontaneous tendency toward surface-energy reduction due to aggregation during micronisation. DLS analysis showed conformational changes of colloidal particles as supramolecular complexes depending on the loading time on the solid. SEM analysis demonstrated the conglomeration of needle-like lacosamide particles after 60 min of milling time and the transition to a glassy state with isotropy of properties by the end of the tribochemistry cycle. The following dynamic properties of lacosamide were established: elastic and plastic deformation boundaries, region of inhomogeneous deformation and fracture point. The ratio of dissolution-rate constants in water of samples before and after a full cycle of loading was 2.4. The lacosamide sample, which underwent a full cycle of mechanical loading, showed improved kinetics of API release via analysis of dissolution profiles in 0.1 M HCl medium. The observed activation-energy values of the cell-death biosensor process in aqueous solutions of the lacosamide samples before and after the complete tribochemical cycle were 207 kJmol−1 and 145 kJmol−1, respectively. The equilibrium time of dissolution and activation of cell-biosensor death corresponding to 20 min of mechanical loading on a solid was determined. The current study may have important practical significance for the transformation and management of the properties of drug substances in solid form and in solutions and for increasing the strength of drug matrices by pre-strain hardening via structural rearrangements during mechanical loading. [ABSTRACT FROM AUTHOR]

The issues of assessing the measurement error using laser coordinate measuring systems (LCMS) of the geometric parameters of vibrating, and also vibrating objects are considered. At the same time, attention is focused on their time-average values. In a number of special cases, calculated relations are given to estimate the average errors in measuring the amplitude and frequency of vibrations of the objects under consideration, their geometric parameters, such as the distance to the laser tracker, coordinates of points on the surface, and other indicators. It is noted that these ratios were obtained for the first time, therefore, in order to increase their reliability, it is possible to introduce them into the corresponding dependences of correcting coefficients and functions.

In solar cells, hybrid halide perovskites operate under constant bias, thus their stability towards electric field-induced degradation is of key importance. Here we report on evidence of previously unidentified electric field-induced transitions and degradation path of CH3NH3PbI3 (MAPbI3) using elemental and phase mapping. Thin films of MAPbI3 were deposited onto 1–2 µm-pitch interdigitated electrodes and subjected to direct current (DC)-polarization. The MAPbI3 layer polarized with < 0.8 V/µm DC electric field undergoes pronounced ion redistribution to methylammonium-rich MAPbI3−y (y < 0.6) and iodine-rich MA1−xPbI3 (x < 0.3) regions. Polarization-induced loss of both methylammonium and iodine provokes degradation of MAPbI3. Using nanofocus grazing-incidence wide-angle X-ray scattering (GIWAXS), we unambiguously showed that the bias voltage induces the transformation of β-MAPbI3 to metastable δ-MAPbI3 polymorph via alignment of polar organic cation with the electric field. This transformation is partially reversible upon field removal. However, once formed, δ-MAPbI3 disrupts the morphology of pristine film and undergoes decomposition to β-MAPbI3 (β-MAPI) and PbI2. With the aforementioned compositional and phase changes, only MA-rich part serves as the charge separation layer, while the I-rich excitation is blocked with the PbI2 barrier serving as holes trapping layer. These observations reveal the intermediate steps in electric-field-driven degradation of halide perovskites and show the role of polar cations in the process, which is instructive for further material design with higher stability metrics. [ABSTRACT FROM AUTHOR]

We report on fully electrochemical flow-through synthesis of Prussian Blue based nanozymes defeating peroxidase in terms of more than 200 times higher catalytic rate constant (kcatapp = 6 x 104 s-1). Being reagentless, reproducible, simple and scalable, the proposed approach blazes new trails for the electrosynthesis of functional conductive and electroactive nanomaterials. [ABSTRACT FROM AUTHOR]

We report the single‐step fabrication of advanced electrochemical biosensors upon drop‐casting of "artificial peroxidase", that is, oxidase‐containing mixtures. Compared to bienzyme biosensors, we substitute peroxidase with more active and stable nanozymes based on catalytically synthesized Prussian Blue. The electroactivity of nanozymes in the sensing membrane was facilitated with carbon black nanoparticles, which resulted in record sensitivity of the H2O2 transducer exceeding 1.1 A M−1 ⋅ cm−2. Both glucose and lactate oxidases were co‐immobilized with nanozymes in alkoxysilane or perfluorosulfonated ionomer membranes. The proposed drop‐casting approach results in biosensors that are advantageous over those conventionally produced upon layer‐by‐layer immobilization in terms of i) almost an order of magnitude increased sensitivity, ii) unsurpassed biosensor‐to‐transducer sensitivity ratio reaching the value of 0.3, and iii) three times extended operational lifetime. [ABSTRACT FROM AUTHOR]

• Advantageous sensitivity of the flow-through (bio)sensors upon power generation. • Up to 3 times increased signal-to-noise ratio compared to three-electrode setup. • Potentiostat-free operation, simplicity of read-out. We report on advanced Prussian Blue (PB) based flow-through (bio)sensors operated in power generation mode. The performance of such (bio)sensors in wall-jet cell is significantly improved with respect to three-electrode regime in terms of up to 1.5 times higher sensitivity probably due to the enhanced mass transport compared to it in batch cell upon stirring. Most importantly, potentiostat-free operation upon short-circuiting PB modified electrode with Ag|AgCl reference through an ammeter drastically decreases noises, which results in up to 3 times increased signal-to-noise ratio compared to conventional three-electrode flow-through systems. These findings, as well as the simplicity of the proposed approach, are encouraging for the high throughput robust sensing and open new horizons for elaboration of electrochemical analyzers. [ABSTRACT FROM AUTHOR]

Abstract: We report on microsensor for direct detection of microorganisms in aerosol. Microsensor is based on interdigitated ultramicroelectrodes modified with electropolymerized 3‐aminophenylboronic acid (3‐APBA). Appearance of Penicillium chrysogenum in aerosol as well as further increase of its concentration lead to poly(3‐APBA) conductivity increase found by impedance spectroscopy. According to Raman spectroscopy data, the presence of microorganism affects polymer conductivity similarly to binding of glucose to polymer which results in self‐doping phenomenon. The elaborated detection technique is 100 times faster comparing to agar plate cultivation: it requires less than 20 minutes for analysis. Dynamic range of microsensor includes the upper limit for non‐contaminated air in Russian hygienic standard (500 colony‐forming units per cubic meter). The first reported reagentless detection of Penicillium chrysogenum in aerosol by conductivity increase reveals a prospect for creation of a promising alternative to conventional techniques for detection of microorganisms. [ABSTRACT FROM AUTHOR]

Abstract: We report on Prussian Blue based (bio)sensors displaying advantageous analytical performance characteristics when operated both in conventional three‐electrode regime powered by potentiostat and in power generation mode. ‘Self‐powered’ sensors are commonly aimed to produce sufficient energy for signalling and, thus, being energetically autonomous. In order to generate maximum energy output, the electrodes with high potential difference are preferable. In contrast, we propose the systems with the lowest potential difference between the working and the counter electrodes. Short‐circuiting the Prussian Blue modified working and the Ag|AgCl reference electrode, working electrode potential is adjusted to 0.00 V without potentiostat. The efficiency of the (bio)sensors in power generation mode is achieved due to high catalytic activity of Prussian Blue at 0.00 V versus Ag|AgCl reference. Here we discuss the benefits of the Prussian Blue based (bio)sensors operated through power generation in a short‐circuit regime without potentiostat, including an order of magnitude decreased noise and simplified readout. The multimodality of the sensors would provide their versatile functionality for the electroanalysis and elaboration of miniature highly sensitive wearable devices. [ABSTRACT FROM AUTHOR]

In contrast to "self-powered" (bio)sensors aiming to generate maximum energy output, we propose the systems with the lowest potential difference between the working and the counter electrodes, which in galvanic mode would provide achievement of the best analytical performance characteristics. Prussian Blue based (bio)sensors known to operate at 0.00 V versus Ag|AgCl reference, in the short-circuit regime generate the current proportional to analyte concentration. Sensitivity and dynamic range of Prussian Blue based (bio)sensors in power generation mode are, respectively, even slightly higher and wider compared to the same (bio)sensors operated in the conventional three-electrode regime powered by a potentiostat. Selectivity of the (bio)sensors in power generation mode is similarly high relative to both oxygen, allowing H2O2 detection by its reduction, and reductants. Among the most important advantages of the proposed power generation mode is an order of magnitude decreased noise compared to performance in a conventional three-electrode setup powered by a potentiostat. Noiseless performances of Prussian Blue based (bio)sensors would open new horizons for electrochemical analysis. [ABSTRACT FROM AUTHOR]

We report on the novel reagentless and label-free detection principle allowing discrimination of specific binding over non-specific interactions. Unlike majority of impedimetric and conductometric (bio)sensors, which specific and unspecific signals are directed in the same way (resistance increase), making doubtful their real applications, the response of the reported system results in resistance decrease, which is directed oppositely to the background. The mechanism of the resistance decrease is the polyaniline self-doping, i.e. as an alternative to proton doping, an appearance of the negatively charged aromatic ring substituents in polymer chain. Negative charge at boronic ring substituent appears as a result of complex formation with di- and triols, i.e. specific binding. Thermodynamic data on interaction of the electropolymerized aminophenylboronic acids with saccharides and hydroxy acids indicate that the observed resistance decrease is due to polymer interaction with polyols. A possibility to detect microorganisms ( Penicillum chrysogenum) on the basis of interdigitated electrodes modified with boronate substituted polyaniline is also shown. The first reported conductivity increase as a specific signal opens new horizons for reagentless affinity sensors. [ABSTRACT FROM AUTHOR]

We report on the novel reagendess and label-free detection principle based on electroactive (conducting) polymers considering sensors for polyols, particularly, saccharides and hydroxy acids. Unlike the majority of impedimetric and conductometric (bio)sensors, which specific and unspecific signals are directed in the same way (resistance increase), making doubtful their real applications, the response of the reported system results in resistance decrease, which is directed oppositely to the background. The mechanism of the resistance decrease is the polyaniline self-doping, i.e., as an alternative to proton doping, an appearance of the negatively charged aromatic ring substituents in polymer chain. Negative charge "freezing" at the boron atom is indeed a result of complex formation with di- and polyols, specific binding. Changes in Raman spectra of boronate-substituted polyaniline after addition of glucose are similar to those caused by proton doping of the polymer. Thermodynamic data on interaction of the electropolymerized 3-aminophenylboronic acid with saccharides and hydroxy acids also confirm that the observed resistance decrease is due to polymer interaction with polyols. The first reported conductivity increase as a specific signal opens new horizons for reagentless affinity sensors, allowing the discrimination of specific affinity bindings from nonspecific interactions. [ABSTRACT FROM AUTHOR]

The ability of Prussian Blue, ferric hexacyanoferrate (FeHCF), to sensitively and selectively detect hydrogen peroxide by its reduction in the presence of oxygen is of high importance for analytical chemistry. Success with Prussian Blue (PB) provided an appearance of contradictory reports concerning electrocatalysis of the other transition metal hexacyanoferrates (HCFs) in H2O2 reduction. Investigating thermodynamics of the catalyzed reactions as well as electrochemical properties of the hexacyanoferrates, we are able to conclude that the noniron hexacyanoferrates themselves are completely electrocataryrically inactive, except for a minor electrocatalysis in the opposite reaction, hydrogen peroxide oxidation, registered for NiHCF. Concerning the most important reaction, H2O2 reduction, the observed electrocatalytic activity (by the way, 100 times decreased compared to PB) is due to the presence of FeHCF (Prussian Blue) as defects in the structure of noniron hexacyanoferrates. This finding, considering other unique properties of transition metal HCFs, will provide a systematic search for sensing materials with improved analytical performance characteristics. [ABSTRACT FROM AUTHOR]

We report on a novel electroanalytical system for hydrogen peroxide (H2O2) detection in humidity or droplets of aerosol, formed by air bubbling through a washing chamber; the resulting flow mimics the exhaled human breath. The system is based on a planar three-electrode structure (with a Prussian Blue based H2O2 transducer modified working electrode) bridged by a solid salt-saturated filament material (filter paper, cotton textile). Respective to the hydrogen peroxide content in the washing valve, the response of the aerosol-sensing system is linear in the concentration range of 0.1-10 μM, which overlaps the generally accepted H2O2 content in exhaled breath condensate (EBC), with the sensitivity of 8 A M-1 cm-2. The response to the upper limit of the calibration range is stable for more than 50 injection cycles recorded within 3 days. Both the stability and the suitable calibration range allow one to consider the reported aerosol-sensing system as a prototype for a simple (avoiding intermediate EBC collection) noninvasive diagnostic tool for pulmonary patients. [ABSTRACT FROM AUTHOR]

Self-powered sensors are among promising candidates for wake-up device elaboration. Generally, such sensors are designed to generate superior energy output to the detriment of analytical performance. Here we report on power output of Prussian Blue (PB) based (bio)sensors retaining advanced analytical performance in power generation mode. The maximum power density is linearly proportional to analyte concentration: the slopes for hydrogen peroxide sensor and glucose biosensor are of 37 mW M−1 cm−2 and 3 mW M−1 cm−2, respectively. The cells consisted of power generating (bio)sensors are able to switch on a light-emitting diode (LED) at threshold concentration of 0.6 mM H 2 O 2 or 8 mM glucose that is suitable for naked-eye semiquantitative analysis. The presented prototype of signaling device is expected to have significant impact on the development of autonomous wake-up sensors for medical, industrial or environmental monitoring. • Prussian Blue (PB) based (bio)sensors power output is a function of analyte content. • The galvanic cells were made of PB based (bio)sensors. • The cells connected to a LED can be utilized as wake-up signaling devices. • Threshold level for sensor-based wake-up device is 0.6 mM of H 2 O 2. • Threshold level for biosensor-based wake-up device is 8 mM of glucose. [ABSTRACT FROM AUTHOR]

This letter introduces the pre-steady-state kinetic approach, which is traditional for evaluation of elementary constants in molecular (enzyme) catalysis, for nanozymes. Apparently, the most active peroxidase-mimicking nanozyme based on catalytically synthesized Prussian Blue nanoparticles has been chosen. The elementary constants ( k 1 ) linearly decays with an increase of the substrate redox potential (cotangent value ≈125 mV). On the contrary, for the largest nanozymes with a diameter above 150 nm, k 1 ) linearly decays with an increase of the substrate redox potential (cotangent value ≈125 mV). On the contrary, for the largest nanozymes with a diameter above 150 nm, k 1 is almost independent of it. Moreover, for the substrate with the lowest redox potential (K 4 [Fe(CN) 6 ]), the rate constant under discussion ( k 1 ) is almost independent of the nanozymes' size. Perhaps, the rate of the intrananozyme electron transfer causing bleaching becomes comparative or even lower than that of the nanoparticle interaction with the fastest substrate. Anyway, the elementary constant of nanozyme reduction with potassium ferrocyanide ( k 1 ) reaches the value of 1 × 10 10 M -1 s -1 , which is 3-4 orders of magnitude faster than for enzymes peroxidases. The obtained results obviously demonstrate that the pre-steady-state kinetic approach is able to discover novel advantages of nanozymes from both fundamental and practical points of view.

Catalytic current of pyrroloquinoline quinone (PQQ)-glucose dehydrogenase (PQQ-GDH) immobilized over electropolymerized methylene green (MG) is increased only five times after the addition of the freely diffusing mediator. This value, being an efficiency criterion for bioelectrocatalysis, is several (three to six) times lower than that for the best reagentless glucose electrodes reported for this enzyme. Thermodynamics of the polyMG|PQQ-GDH electrode is determined by the enzyme-catalyzed reaction pointing to the direct bioelectrocatalysis. PQQ-GDH immobilized over polyMG displays the current plateau region from 0.0 to 0.2 V in the presence of glucose; at 0.00 V, being the optimal potential for biosensing applications, the catalytic current of the polyMG|PQQ-GDH electrode is 700-fold higher than that for the enzyme on a blank electrode. Successful glucose detection in human sweat by means of the corresponding enzyme electrode confirms that the reported bioelectrocatalytic system is attractive for advanced biosensors, as well as for biofuel cells.

We report on the nanoparticles composed of the catalytically synthesized Prussian Blue (PB) core stabilized with the nickel hexacyanoferrate (NiHCF) shell. Catalyzing hydrogen peroxide reduction, the resulting nanozymes (ø = 66 nm) display catalytic rate constants, which for pyrogallol or ferrocyanide are, respectively, 25 and 35 times higher than those for peroxidase enzyme. After more than half a year of storage at a room temperature, the core-shell PB-NiHCF nanozymes retain both their size and physicochemical properties; such stability is unreachable for the enzymes. Being immobilized, core-shell PB-NiHCF nanozymes (ø = 45 nm) result in a hydrogen peroxide sensor with a sensitivity similar to that of the sensor based on sole PB nanoparticles. However, whereas the latter response in hard inactivating conditions (25 min in 1 mM H 2 O 2 ) drops down to 7.5%, the PB-NiHCF nanozymes-based sensor retains >75% of initial sensitivity. Application of the core-shell PB-NiHCF nanozymes "artificial peroxidase" would obviously open new horizons in elaboration of anti-inflammatory drugs and (bio)sensors.

We report on the kinetic mechanism of the catalytically synthesized Prussian Blue nanoparticles denoted as "artificial peroxidase". In contrast to the enzyme, whose active site first interacts with hydrogen peroxide forming the so-called Compound I, in the case of the nanozymes, H 2 O 2 oxidizes their complex with reducing substrate. Slow release of the product (oxidized form of the latter) from the nanozymes has been registered. The interaction of substrates with the nanozymes is 100 times faster than with enzyme peroxidases, and the rate-limiting constant for the nanozymes is also 2 orders of magnitude greater: for pyrogallol k 2 = 1.3 ± 0.1 × 10 8 M -1 s -1 and for ferrocyanide k 2 = 1.9 ± 0.1 × 10 8 M -1 s -1 . Thus, the discovered novel advantage of nanozymes over the corresponding enzymes is the 100-fold greater bimolecular rate constants, resulting, most probably, from their uniformly accessible surface, avoiding the effect of rotation on the diffusion-controlled rate.

The ability of Prussian Blue, ferric hexacyanoferrate (FeHCF), to sensitively and selectively detect hydrogen peroxide by its reduction in the presence of oxygen is of high importance for analytical chemistry. Success with Prussian Blue (PB) provided an appearance of contradictory reports concerning electrocatalysis of the other transition metal hexacyanoferrates (HCFs) in H2O2 reduction. Investigating thermodynamics of the catalyzed reactions as well as electrochemical properties of the hexacyanoferrates, we are able to conclude that the noniron hexacyanoferrates themselves are completely electrocatalytically inactive, except for a minor electrocatalysis in the opposite reaction, hydrogen peroxide oxidation, registered for NiHCF. Concerning the most important reaction, H2O2 reduction, the observed electrocatalytic activity (by the way, 100 times decreased compared to PB) is due to the presence of FeHCF (Prussian Blue) as defects in the structure of noniron hexacyanoferrates. This finding, considering other unique properties of transition metal HCFs, will provide a systematic search for sensing materials with improved analytical performance characteristics.

We report here a way for improving the stability of ultramicroelectrodes (UME) based on hexacyanoferrate-modified metals for the detection of hydrogen peroxide. The most stable sensors were obtained by electrochemical deposition of six layers of hexacyanoferrates (HCF), more specifically, an alternating pattern of three layers of Prussian Blue and three layers of Ni-HCF. The microelectrodes modified with mixed layers were continuously monitored in 1 mM hydrogen peroxide and proved to be stable for more than 5 h under these conditions. The mixed layer microelectrodes exhibited a stability which is five times as high as the stability of conventional Prussian Blue-modified UMEs. The sensitivity of the mixed layer sensor was 0.32 A·M(-1)·cm(-2), and the detection limit was 10 µM. The mixed layer-based UMEs were used as sensors in scanning electrochemical microscopy (SECM) experiments for imaging of hydrogen peroxide evolution.