Mateusz Brodowski

Herein, highly crystalline Zr_xN_y and Zr_xN_yO_z coatings are achieved by the deposition via high‐power impulse magnetron sputtering. Various N₂ and N₂/O₂ gas mixtures with argon are investigated. The chemical composition and, as a result, mechanical properties of the deposited layer can be tailored along with morphological and crystallographic structural changes. The corrosion resistance behavior is studied by potentiodynamic measurements and electrochemical impedance spectroscopy in a sample of synthetic wastewater designed to imitate real‐life domestic wastewater. The corrosion current density of the Zr_xN_yO_z coating is in the range of 33–70 μA cm⁻², whereas for the zirconium nitride layers, values below 1.0 μA cm⁻² are achieved. The highest corrosion resistance of 64 nm year⁻¹ is observed for the Zr_xN_y coating deposited with 1.00% N₂ content in the gas mixture with a corrosion potential of −0.41 V Ag/AgCl.

The interest of phosphorene as 2D material is high due to its excellent mechanical, electrical and optical properties [1]. However, the possibility of its application in the area of biosensors is a result of low cytotoxic cell-viability effects and excellent cytocompatibility [2]. Phosphorene has much higher surface to volume ratio compared to graphene and transition metal dichalcogenides. This due to its “puckered” lattice structure. These properties are advantages in sensing applications [3]. But puckered layer is quite reactive to oxygen and water adsorbed on the surface of phosphorene [4]. One way to change it and improve the ambient stability of layered black phosphorus is to modify the surface so that covalently or non-covalently attached chemical compounds passivate the surface to prevent damage [4, 5]. The biosensing device consists of chemical part and biological unit with unique specifities towards corresponding analytes for example proteins. In this work the biosensor of bacteria has been prepared in several steps: phosphorene preparation, functionalization with 4-azidobenzoic acid, followed by coating with an antibody layer. Phosphorene (few layered black phosphorus, FLBP) was prepared from pre-crushed black phosphorus (BP) dispersed in anhydrous dimethylformamide or toluene under an argon atmosphere by the liquid exfoliation. Afterwards, the resultant suspension was centrifuged to remove the residual un-exfoliated particles, yielding supernatant. We functionalized few layered black phosphorus (FLBP) by direct bonding of the phosphorus atom bearing lone electron pair with nitrogen during reaction with 4-azidobenzoic acid, leading to the formation of P=N double bonds, which passivate the reactive FLBP effectively. A covalent combining few-layered black phosphorus (FLBP) with 4-azidobenzoic acid can function as a bridge between FLBP and biomolecules. The functionalized phosphorene (f-FLBP) results in the possibility of using it as a biosensor platform for the detection of Heamophillus Influenza - one of the most common bacteria that cause infections in humans [6, 7]. It is very important to determine the presence of a given bacterial strain, because nowadays strains resistant to numerous antibiotics are more and more often observed. In the US alone, antibiotic-resistant bacteria cause at least 2 million infections and 23,000 deaths per year, which cause losses of 55-70 billion dollars a year [8]. The efficient functionalization of BP flakes was revealed by infrared spectroscopy. The cyclic voltammetry and electrochemical impedance spectroscopy measurements were carried out in Na₂SO₄ solution containing reference redox systems: [Fe(CN)₆]^3−/4−. Heamophillus Influenza bacteria were detected by the impedimetric method. The changes of the charge transfer resistance (R_ct) can be attributed to the selective protein binding on the surface of the electrode. This was preceded by the attachment of antibodies to f-FLBP and obtaining a stable sensory surface. The procedure is shown in Figure 1. Consequently: - the benzoic groups enhance electric conductivity delivering fast direct electron transfer. - antibody-coated functionalized phosphorene were used to detect a bacteria (Haemophilus influenzae). - modified FLBP can work as surface for determination of organic molecules, e.g., nucleic acid bases or peptides and proteins, while it offers the promising possibility for biosensing. ACKNOWLEDGEMENTS This work was supported by the Polish National Science Centre [2016/22/E/ST7/00102]; and the National Centre for Science and Development [347324/12/NCBR/2017]. The DS funds of the Faculty of Electronics, Telecommunications and Informatics of the Gdansk University of Technology are also acknowledged. References [1] Y. Yi, X. Yu, W. Zhou, J. Wang, P. K. Chu, Two-dimensional black phosphorus: Synthesis , modification, properties, and applications, Materials Science and Engineering: R: Reports, 120, 1–33 (2017); doi: 10.1016/j.mser.2017.08.001 [2] H. Fu, Z. Li, H. Xie, Z. Sun, B. Wang, H. Huang, G. Han, H. Wang, P. K. Chu, X-F. Yu, Different-sized black phosphorus nanosheets with good cytocompatibility and high photothermal performance, RSC Adv., 7, 14618-14624 (2017); doi: 10.1039/C7RA00160F [3] A. Yang, D. Wang, X. Wang, D. Zhang, N. Koratkar, M. Rong, Recent advances in phosphorene as a sensing material, Nano Today, 20, 58-73 (2018); doi: 10.1016/j.nantod.2018.04.001 [4] R. Gusmão, Z. Sofer, M. Pumera, Functional Protection of Exfoliated Black Phosphorus by Noncovalent Modification with Anthraquinone, ACS Nano, 12, 5666-5673 (2018), doi: 10.1021/acsnano.8b01474 [5] C. Joseph, Y. Togawa, N. Shindo, Bacterial and viral infections associated with influenza, Influenza and other Respiratory Viruses, 7, 105–113 (2013); doi: 10.1111/irv.12089 [6] S. K. Morris, W. J. Moss, N. Halsey, Haemophilus influenzae type b conjugate vaccine use and effectiveness, The Lancet Infectious Diseases, 8, 435-443 (2008); doi: 10.1016/S1473-3099(08)70152-X [8] B. Li, T. J. Webster, Bacteria Antibiotic Resistance: New Challenges and Opportunities for Implant-Associated Orthopaedic Infections, J Orthop. Res., 36, 22-32 (2017); doi: 10.1002/jor.2365 Figure 1

Haemophilus influenzae (Hi) is a gram-negative pathogenic bacterium. Type b bacteria (Hib) and non-enveloped strains are of greatest clinical importance. Hib causes systemic infections by hematopoietic dissemination from the respiratory system to distant sites such as meninges.Nowadays the most reliable method for Hib infections diagnosis is isolation in microbiological culture. A cerebrospinal fluid sample from a patient suspected of having meningitis is stained and microbiologically cultured. Isolation efficiency and quality depend on many factors also in addition, carrying out the complete test procedure is time consuming and expensive. Thus it is crucial to develop techniques that allow detecting pathogenic bacteria in fast and qualitative way before the first symptoms appear.In the following work the electrochemical impedance methods were used to detect Hi bacteria and specific protein (protein D) appearing on its surface. Hi immunosensor was developed on boron-doped carbon nanowall (B:CNW) electrodes modified with anti-protein D antibodies.The B:CNW modification steps included electrochemical reduction of the aminobenzoic acid diazonium salt and antibody binding via EDC/NHS chemistry. Many scientists deal with the topic of use bovine serum albumin (BSA) for the blockage of unmodified electrode. Here this step was abandoned due to high resistance occurring on the sample after the electrografting stage, which indicates a very effective modification of the electrode surface. An additional argument confirming the correctness of skipping the BSA stage are the results of the sensor's cross-reactivity with other pathogens. For the determination of the sensor selectivity, three non-target pathogens were selected: S. pyogenes, S. pneumoniae, B. parapertussis. For each pathogen used for the selectivity study, the impedimetric responses were significantly lower than for Hi at similar concentrations.Electrochemical impedance spectroscopy measurements were performed on anti-protein D antibodies (ap. D) for protein D (Fig. 1a) and Hi. Then calibration curve was constructed as a relative change in the electron transfer resistance (R_ct) (Fig. 1b). Since the calibration curve shows the logarithmic relationship of the antigen concentration to the impedimetric sensor response, linear regression cannot be used to calculate the LOD. It is therefore necessary to modify the calculation procedure so that it can be applied in the present case. This requires changing the equation's layout and then deriving the formula for the deviation of the logarithm of the concentration. The LOD value calculated in this way for Hi bacteria was 19.45 CFU/ml which is a reliable value.For the sensor's selectivity studies, the electrodes were prepared identically to the electrodes intended for Hi detection. The response of sensor for S. pyogenes (64750 CFU/ml) and B. parapertussis (17200 CFU/ml) were less than 5%, which are almost unnoticeable in comparison to the response for Hi at level of 50% (47910 CFU/ml).This work was supported by the National Centre for Research and Development TECHMATSTRATEG 1/347324/12/NCBR/ 2017

Haemophilus influenzae (HI) is a Gram-negative pathogenic bacterium whose infections occur worldwide and mainly affect unvaccinated children and those who have not completed the basic vaccination course. Type B of this bacterium (Hib) can cause sepsis, and other invasive diseases as dermatitis or arthritis but the most dangerous is pneumonia meningitis. The most reliable method for recognizing Hib infections is isolation in microbiological culture. Serological tests are also performed to diagnose Hib infections. They rely on the detection of the presence of bacterial antigens or antibodies which have the ability to bind to specific antigens. Detection of antibodies doesn’t mean disease but only indicate contact with a given bacterium in the past. Recognition of bacteria using presently known methods takes a long time and requires expensive equipment although fast and sensitive detection of Haemophilus influenzae is crucial l to start treatment early enough. In this work, we present electrochemical detection of HI on diamond-based pastes electrodes using binding specific antibodies (ap. D) with proteins occurring on the surface of bacteria (protein D). The measuring system consisted of a specially prepared printed circuit board (PCB) and diamond-based electrode, which was prepared by screen printing in special conditions. Places printed on it, served as a working electrode, counter electrode and reference. Ceramics was first used as a substrate, but it was quickly changed to Teflon, which showed better adhesion to diamond pastes. Better sample strength was also obtained, so it could be washed in an ultrasonic cleaner without fear of damage. Before detection, the electrode had to be modified by electrochemical reduction of the aminobenzoic acid diazonium salt, antibodies deposition via EDC / NHS and blocking the unmodified electrode sites by incubating in solution of Bovine Serum Albumin (BSA). The last step of modification prevents unspecific adsorption on electrode surface which would lead to false detection results. Electrochemical Impedance Spectroscopy Fig. 1) were used to bacteria detection. The electron transfer resistance rises with each step of electrode modification and increased bacterial concentration in solution. Then a calibration curve was constructed. Three pathogens were selected to check the biosensor selectivity: S. pyogenes, S. pneumoniae, B. parapertussis. For each pathogen responses were significantly lower than for HI at similar concentrations. For example, the response of sensor for S. pyogenes (67474,28 CFU/ml) and B. parapertussis (17819,27 CFU/ml) were less than 5%, which are much smaller in comparison to response at level of 30% for HI (47003,48 CFU/ml). Acknowledgments The authors gratefully acknowledge financial support from the National Centre for Science and Development Grant Techmatstrateg No. 347324 2015/16/T/ST7/00469. Figure 1

Electrochemical sensors have attracted increasing interest due to their low cost, high sensitivity of detected analytes, and the possibility of sensor miniaturization, which allows for portable and field applications. These devices provide information about the system composition in real-time by combining a chemically selective layer with an electrochemical transducer. Thereby, the chemical energy of the specific interaction between the chemical substances and the sensor is converted into an analytically useful signal. Herein we demonstrate the electrochemical sensor based on boron-doped diamond/graphene nanowall electrodes (B:DGNW). A B:DGNW electrode is a hybrid electrode, which combines the extraordinary features of boron-doped diamond and a graphene nanowall on the same surface. B:DGNW is a sp² -rich phase material with multilayered graphene walls oriented vertically to the substrate. Moreover, the presence of the boron-doped diamond phase enhances the electrochemical performance and kinetics of the electrode surface when compared with typical carbon nanowalls. The electrodes were fabricated in a one-step growth process using chemical vapor deposition without any additional modifications (thin films were grown on (100)-oriented silicon substrates). Two different sensing platforms will be presented: i) impedimetric biosensor for detection of pathogenic bacteria (e.g., Haemophilus influenzae), and ii) voltammetric sensor for determination of important nitroaromatic explosive compounds (2,4,6-trinitrotoluene (TNT), 2,4,6-trinitroanisole (TNA), 4,4',5,5'-tetranitro-1H,1'H-2,2'-biimidazole (TNBI)). The proposed B:DGNW electrodes were revealed to have a high electroactive area towards the voltammetric detection of various nitroaromatic compounds. The biosensor platform was obtained by B:DGNW surface functionalization firstly by electrografting of diazonium salt and secondly by the attachment of antibodies. The electrochemical biosensor shows high sensitivity and selectivity towards Haemophilus influenzae. The measurements were conducted in the presence of three non-target pathogens S. pyogenes, S. pneumoniae, and B. parapertussis. The proposed B:DGNW nonmodified carbon electrodes were revealed to have a high electroactive area towards the voltammetric determination of various nitroaromatic compounds, thus appearing to be an attractive nanocarbon surface for further applications. The B:DGNW electrode exhibits high sensing performance for TNT detection with linearity between 0.05 to 2 ppm and 4 to 15 ppm, and a limit of detection (LOD) of 73 ppb. The LOD for 2,4,6-trinitroanisole, in turn, is equal to 0.27 ppm, whereas the limit of detection of TNBI is equal to 0.52 ppm. To the authors' knowledge, this is the first time B:DGNW has been used to detect the nitroaromatic compounds electrochemically [1]. Acknowledgment This work was supported by the Science for Peace Programme of NATO [Grant no. G5147], Polish National Science Centre [2016/22/E/ST7/00102], and the National Centre for Science and Development [347324/12/NCBR/2017]. The DS funds of the Faculty of Electronics, Telecommunications, and Informatics of the Gdansk University of Technology are also acknowledged. Reference: [1] A. Dettlaff et al., J. Hazard. Mater [In press]. Doi: 10.1016/j.jhazmat.2019.121672.

The selection of efficient corrosion inhibitors requires detailed knowledge regarding the interaction mechanism, which depends on the type and amount of functional groups within the inhibitor molecule. The position of functional groups between different isomers is often overlooked, but is no less important, since factors like steric hinderance may significantly affect the adsorption mechanism. In this study, we have presented how different dihydroxybenzene isomers interact with aluminum alloy 5754 surface, reducing its corrosion rate in bicarbonate buffer (pH = 11). We show that the highest inhibition efficiency among tested compounds belongs to catechol at 10 mM concentration, although the differences were moderate. Utilization of novel impedance approach to adsorption isotherm determination made it possible to confirm that while resorcinol chemisorbs on aluminum surface, catechol and quinol follows the ligand exchange model of adsorption. Unlike catechol and quinol, the protection mechanism of resorcinol is bound to interaction with insoluble aluminum corrosion products layer and was only found efficient at concentration of 100 mM (98.7%). The aforementioned studies were confirmed with Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy analyses. There is a significant increase in the corrosion resistance offered by catechol at 10 mM after 24 h exposure in electrolyte: from 63 to 98%, with only negligible changes in inhibitor efficiency observed for resorcinol at the same time. However, in the case of resorcinol a change in electrolyte color was observed. We have revealed that the differentiating factor is the keto-enol tautomerism. The Nuclear Magnetic Resonance (NMR) studies of resorcinol indicate the keto form in structure in presence of NaOH, while the chemical structure of catechol does not change significantly in alkaline environment.