Category: Articles

Electrochemical modified Pt nanoflower @ rGO for non- enzymatic electrochemical sensing of glucose

Saravanan Gengan, R.M. Gnanamuthu, Sanjay Sankaranarayanan, Venumbaka Maneesh Reddy, Bhanu Chandra Marepally, Ravi Kumar Biroju

Sensors and Actuators A: Physical, Volume 353, (2023)


Since lower danger of biorecognition element degradation, enzymes-less glucose have the potential for more reliable in vivo activity, but it suffers due to lack of linear response and poor selectivity. We made attempt to improve selectivity, linear response and stability, environmentally benign electrochemical method adopted to fabricate Pt nanoflowers (PtNF) anchored on rGO modified GCE (PtNF-rGO/GCE). The PtNF-rGO/GCE electrode demonstrated good glucose electrooxidation in alkaline solution, with a linear range, sensitivity and detection limit are up to 3.5 mM, 335.5 μA mM−1 cm−1 and 53 μM (S/N = 3) respectively. The PtNF-rGO/GCE electrode is not only selective also inhibit interfering molecules like uric, dopamine, ascorbic acid. This allows for broadly sensitive, work at low-potential, stable, and quick glucose current detection, which is capable for the expansion of non-enzymatic glucose detectors.

Defective Graphene/Plasmonic Nanoparticle Hybrids for Surface-Enhanced Raman Scattering Sensors

Biroju Ravi K., Marepally Bhanu Chandra, Malik Pariksha, Dhara Soumen, Gengan Saravanan, Maity Dipak, Narayanan Tharangattu N., Giri Pravat K.

In: ACS Omega 2023, 8, 4, 4344–4356, (2023)


Two-dimensional–zero-dimensional plasmonic hybrids involving defective graphene and transition metals (DGR-TM) have drawn significant interest due to their near-field plasmonic effects in the wide range of the UV–vis–NIR spectrum. In the present work, we carried out extensive investigations on resonance Raman spectroscopy (RRS) and localized surface plasmon resonance (LSPR) from the various DGR-TM hybrids (Au, Ag, and Cu) using micro-Raman, spatial Raman mapping analysis, high-resolution transmission electron microscopy (HRTEM), and LSPR absorption measurements on defective CVD graphene layers. Further, electric field (E) mappings of samples were calculated using the finite domain time difference (FDTD) method to support the experimental findings. The spatial distribution of various in-plane and edge defects and defect-mediated interaction of plasmonic nanoparticles (NPs) with graphene were investigated on the basis of the RRS and LSPR and correlated with the quantitative analysis from HRTEM, excitation wavelength-dependent micro-Raman, and E-field enhancement features of defective graphene and defective graphene-Au hybrids before and after rapid thermal annealing (RTA). Excitation wavelength-dependent surface-enhanced Raman scattering (SERS) and LSPR-induced broadband absorption from DGR-Au plasmonic hybrids reveal the electron and phonon interaction on the graphene surface, which leads to the charge transfer from TM NPs to graphene. This is believed to be responsible for the reduction in the SERS signal, which was observed from the wavelength-dependent Raman spectroscopy/mappings. We implemented defective graphene and DGR-Au plasmonic hybrids as efficient SERS sensors to detect the Fluorescein and Rhodamine 6G molecules with a detection limit down to 10–9 M. Defective graphene and Au plasmonic hybrids showed an impressive Raman enhancement in the order of 108, which is significant for its practical application.

Correlated reflectance and Raman spectroscopy in substrates with coherent transparent layers

VANČO, Ľubomír – KOTLÁR, Mário – VRETENÁR, Viliam – KADLEČÍKOVÁ, Magdaléna – VOJS, Marian – VOGRINČIČ, Peter

In Surfaces and Interfaces. Vol. 34, (2022)


Intensity of Raman bands in substrates covered with transparent overlayers can be enhanced due to optical interference, leading to incorrect quantitative interpretation of Raman signals. If thickness and optical properties of the overlayer are known, correction can be done using appropriate models. We theoretically discuss and experimentally evaluate a model where thickness and refractive index of the overlayer remain unknown and determination of enhancement factor is possible via linear relationship to reflectance-related response of the whole structure. Correct interpretation of the spectra is then possible since refractive index and thickness of the transparent layer are implicitly introduced in the measured reflectance. For experimental evidence we exploit SiNx/Si and SiO2/Si structures to find a significant correspondence with the model, aiming toward correlative reflectance and Raman spectroscopy.

Synthesis of Sulfide Perovskites by Sulfurization with Boron Sulfides

BYSTRICKÝ, Roman – TIWARI, Sameer K. – HUTÁR, Peter – VANČO, Ľubomír – SÝKORA, Milan.

In Inorganic Chemistry. Vol. 61, iss. 47 (2022)


Chalcogenide perovskites (CPs), with the general composition ABX3, where A and B are metals and X = S and Se, have recently emerged as promising materials for application in photovoltaics. However, the development of CPs and their applications has been hindered by the limitations of available preparation methods. Here we present a new approach for the synthesis of CPs, based on the sulfurization of ternary and binary oxides or carbonates with in situ formed boron sulfides. In contrast to the previously described approaches, the method presented here uses chemically stable starting materials and yields pure-phase crystalline CPs within several hours, under low hazard conditions. CP yields over 95% are obtained at temperatures as low as 600 °C. The generality of the approach is demonstrated by the preparation of CPs with compositions BaZrS3, β-SrZrS3, BaHfS3, SrHfS3, and EuHfS3. Mechanistic insights about the formation of CPs are discussed.

Raman spectroscopy of silicon with nanostructured surface

KADLEČÍKOVÁ, Magdaléna – VANČO, Ľubomír – BREZA, Juraj – MIKOLÁŠEK, Miroslav – HUŠEKOVÁ, Kristína – FRÖHLICH, Karol – PROCEL, Paul – ZEMAN, Miro – ISABELLA, Olindo

In Optik. Vol. 257, (2022)


We compared the morphology and Raman response of nanoscale shaped surfaces of Si substrates versus monocrystalline Si. Samples were structured by reactive ion etching, and four of them were covered by a RuO2-IrO2 layer. Raman bands, centred at approx. 520 cm–1, belonging to samples processed by etching the Si surface have intensities higher by approximately one order of magnitude than those of reference non-etched samples. For nanostructured samples, the rise in the Raman signal was 12–14 × , which is in agreement with the model of the electric field at the tips of Si due to their geometry. This phenomenon is related to the high absorption of excitation radiation. Nanostructured surfaces of samples containing a layer of RuO2-IrO2 give rise to the phenomenon of surface enhancement of the Raman response most likely due to the charge transfer at the interface between silicon and conductive oxides. The nanostructured surface of Si without a metal layer behaves as a SERS substrate and detects the analytes at a low concentration.

Mesoporous SnO2 Nanoparticle-Based Electron Transport Layer for Perovskite Solar Cells

ULLAH, Sami – FARAZ, Muhammad Ud Din – KHAN, Kasi Jafar – KHAN, Kasi Ajab – VÉGSÖ, Karol – KOTLÁR, Mário – MIČUŠÍK, Matej – JERGEL, Matej – NÁDAŽDY, Vojtech – ŠIFFALOVIČ, Peter – MAJKOVÁ, Eva – FAKHARUDDIN, Azhar

In ACS Applied Nano Materials. Vol. 5, iss. 6 (2022)


A perovskite solar cell (PSC) featuring a mesoporous architecture can facilitate perovskite layer formation over a large area via increasing the number of heterogeneous nucleation sites. The morphology of the electron transport layer (ETL) and its interface with the perovskite layer is one of the key factors to boost the performance of a PSC. Tin dioxide (SnO2) is considered as a promising ETL in PSCs owing to its high carrier mobility, good transmittance, deep conduction band level, and efficient photoelectron extraction. Generally, the mesoporous SnO2 (m-SnO2) ETL has a higher surface-to-volume ratio compared to a compact SnO2 layer. Herein, we report on an m-SnO2 ETL prepared by anodizing a metallic tin film on a fluorine-doped tin oxide (FTO) substrate in NaOH solution under an ambient atmosphere. In particular, we developed a bilayer architecture of the m-SnO2 ETL based on the fabrication of two consecutive m-SnO2 layers. The morphology of each layer was controlled by varying the anodization voltage and time at a constant solution concentration during the growth process. This unique approach enabled the deposition of an m-SnO2 ETL with sufficient coverage of the FTO substrate, which is difficult to achieve with a single layer of m-SnO2. In particular, the scanning electron and atomic force microscopy analyses confirmed that the m-SnO2 layer covers completely the FTO substrate. The device fabricated with this bilayer m-SnO2 ETL achieved a 27% improvement in power conversion efficiency compared to that with a single layer of m-SnO2.

Fe3O4-PEI Nanocomposites for Magnetic Harvesting of Chlorella vulgaris, Chlorella ellipsoidea, Microcystis aeruginosa, and Auxenochlorella protothecoides

GERULOVÁ, Kristína – KUCMANOVÁ, Alexandra – SANNY, Zuzana – GARAIOVÁ, Zuzana – SEILER, Eugen – ČAPLOVIČOVÁ, Mária – ČAPLOVIČ, Ľubomír – PALCUT, Marián

In Nanomaterials. Vol. 12, iss. 11 (2022)


Magnetic separation of microalgae using magnetite is a promising harvesting method as it is fast, reliable, low cost, energy-efficient, and environmentally friendly. In the present work, magnetic harvesting of three green algae (Chlorella vulgaris, Chlorella ellipsoidea, and Auxenochlorella protothecoides) and one cyanobacteria (Microcystis aeruginosa) has been studied. The biomass was flushed with clean air using a 0.22 μm filter and fed CO2 for accelerated growth and faster reach of the exponential growth phase. The microalgae were harvested with magnetite nanoparticles. The nanoparticles were prepared by controlled co-precipitation of Fe2+ and Fe3+ cations in ammonia at room temperature. Subsequently, the prepared Fe3O4 nanoparticles were coated with polyethyleneimine (PEI). The prepared materials were characterized by high-resolution transmission electron microscopy, X-ray diffraction, magnetometry, and zeta potential measurements. The prepared nanomaterials were used for magnetic harvesting of microalgae. The highest harvesting efficiencies were found for PEI-coated Fe3O4. The efficiency was pH-dependent. Higher harvesting efficiencies, up to 99%, were obtained in acidic solutions. The results show that magnetic harvesting can be significantly enhanced by PEI coating, as it increases the positive electrical charge of the nanoparticles. Most importantly, the flocculants can be prepared at room temperature, thereby reducing the production costs.

Contribution of photocatalytic and Fenton-based processes in nanotwin structured anodic TiO2 nanotube layers modified by Ce and V

THIRUNAVUKKARASU,  Guru Karthikeyan – GOWRISANKARAN, Sridhar – ČAPLOVIČOVÁ, Mária – SATRAPINSKYY, Leonid – GREGOR, Maroš – LAVRIKOVA, Aleksandra Y. – GREGUŠ, Ján – HALKO, Radoslav – PLESCH, Gustav – MOTOLA, Martin – MONFORT, Olivier

In Dalton Transactions. Vol. 51, iss. 28 (2022)


In the present work, nanotwin structured TiO2 nanotube (TNT) layers are prepared by the electrochemical anodization technique to form the anatase phase and by surface modification via spin-coating of Ce and V precursors to form Ce-TNT and V-TNT, respectively. The surface and cross-sectional images by SEM revealed that the nanotubes have an average diameter of ∼130 nm and a length of ∼14 μm. In addition, the TEM images revealed the nanotwin structures of the nanotubes, especially the anatase (001) and (112) twin surfaces, that increase the transport of photogenerated charges. The photoinduced degradation of caffeine (CAF) by TNT, Ce-TNT, and V-TNT led to a degradation extent of 16%, 26% and 33%, respectively, whereas it increased to 26%, 38%, and 46% in the presence of H2O2, owing to the involvement of Fenton-based processes (in addition to photocatalysis). The effect of the Fenton-based processes accounts for about 10% of the total degradation extent of CAF. Finally, the mechanism of the photoinduced degradation of CAF was investigated. The main oxidative species were the hydroxyl radicals, and the better efficiency of V-TNT over Ce-TNT and TNT was ascribed to its negative surface, thus improving the interactions with CAF.

Ni-Fe Cathode Catalyst in Zero-Gap Alkaline Water Electrolysis

ZÁCHENSKÁ, Jana – JORÍK, Vladimír – VANČO, Ľubomír – MIČUŠÍK, Matej – ZEMANOVÁ, Matilda

In Electrocatalysis. Vol. 13, iss. 4 (2022)


Ni–Fe cathode catalyst for zero-gap alkaline water electrolysis was studied. Ni–Fe coatings on nickel foam were prepared by direct current (DC) and pulse current (PC) electrodeposition. The influence of different plating conditions and composition of the electrolyte on the morphology of the samples was studied. It was found that under DC electrodeposition, iron is dominant in the coating. Under PC plating conditions, Ni is the dominant element in Ni–Fe coatings. Ni–Fe coatings prepared under DC electrodeposition provide an effective catalyst in zero-gap electrolysis. Increasing Fe content in the coatings improves the catalytic activity of Ni–Fe catalyst. The study of convenient parameters of PC electrodeposition seems to be complex to reach a highly active surface area.

Microstructure, Mechanical and Tribological Properties of Advanced Layered WN/MeN (Me = Zr, Cr, Mo, Nb) Nanocomposite Coatings

Smyrnova K., Sahul M., Haršáni M., Pogrebnjak A., Ivashchenko V., Beresnev V., Stolbovoy V., Čaplovič L., Čaplovičová M., Vančo L., Kusý M., Kassymbaev A., Satrapinskyy L., Flock D.

Nanomaterials, 12 (3), art. no. 395


Due to the increased demands for drilling and cutting tools working at extreme machining conditions, protective coatings are extensively utilized to prolong the tool life and eliminate the need for lubricants. The present work reports on the effect of a second MeN (Me = Zr, Cr, Mo, Nb) layer in WN-based nanocomposite multilayers on microstructure, phase composition, and mechanical and tribological properties. The WN/MoN multilayers have not been studied yet, and cathodic-arc physical vapor deposition (CA-PVD) has been used to fabricate studied coating systems for the first time. Moreover, first-principles calculations were performed to gain more insight into the properties of deposited multilayers. Two types of coating microstructure with different kinds of lattices were observed: (i) face-centered cubic (fcc) on fcc-W2N (WN/CrN and WN/ZrN) and (ii) a combination of hexagonal and fcc on fcc-W2N (WN/MoN and WN/NbN). Among the four studied systems, the WN/NbN had superior properties: the lowest specific wear rate (1.7 × 10−6 mm3/Nm) and high hardness (36 GPa) and plasticity index H/E (0.93). Low surface roughness, high elastic strain to failure, Nb2O5 and WO3 tribofilms forming during sliding, ductile behavior of NbN, and nanocomposite structure contributed to high tribological performance. The results indicated the suitability of WN/NbN as a protective coating operating in challenging conditions.