Currently, a student at the University of Warwick on the MSc Analytical Science going to proceed to do PhD research at completion of MSc. A member of Analytical Science Centre for Doctoral Training since September 2019. An alumnus of Coventry University and Chemical Vocational school no 3 in Cracow. The main interest in the application of a broad spectrum of analytical methods for R&D in the field of Energy Materials, especially Photovoltaics.
“Ultrathin metal film sensors”
Supervised by Dr Ross Hatton
Thin metal films of thickness 10-50 nm are widely applied in numerous devices including sensors. There are two main types of thin metal film sensors: chemiresistors and plasmonic sensors. Ultra-thin metal chemiresistors, are mostly made of gold, copper, platinum or other coinage metals, due to their stability and DC conductivity, and are types of sensors that are capable of detecting changes in the environment of the surface in terms of changes in resistance as a result of sorption and generation of new scattering cen-tres. These sensors are mainly applied in detecting chemical species including gases, such as hydrogen, harmful vapours, such as mercury, and even in developments of self-assembled monolayers (SAM). In this case, the crucial factors were identified to be sensitivity and selectivity. Sensitivity was found to be improved by using the optimal thickness of the thin metal film around 5-20nm set by maintaining the high surface to volume ratio while avoiding quantum size effects. The selectivity could be improved by the application of SAM as semipermeable filters. Moreover, numerous developments in fabrication (i.e. application of molecular adhesives) and characterisation (SEM and AFM) may catalyse the rediscovery of ultra-thin metal film chemiresistors and find their new applications in numerous lab-on-chip and microfluidic sensors in near future. Modern plasmonic sensors are mainly based on the localised surface plasmon resonances (LSPRs) which are collective oscillations of the conduction band electrons confined within the lateral dimensions of the nanofeature i.e. nanoparticle (NP) or nanohole (NH) arrays, of which the latter are discussed in the review. In this case, NHs imitate NPs similarly like holes imitate electrons in semiconductors. The biggest issue slowing down the commercialisation of NH-based LSPR sensors was identified to be the fabrication cost. Cost-cutting of the fabrication costs recently gained huge research interest resulting in advancements in large area fabrication (CL, IL and UV-nanoimprinting) and implementation of cheaper set-ups. Such plasmonic sensors find most of their applications in sensing biochemical or even biological species such as proteins, viruses (Dengue virus rupture), food pathogens, and biomarkers (Leukemic biomarkers) and bacteria (E. coli), point of care and medical applications.
“Investigation of the mechanism of passivation on TFSI-enhanced SiO2 layers on silicon wafers using x-ray photoelectron spectroscopy.”
Supervised by Dr John Murphy
It is essential to reduce the negative effect of surface recombination, which can significantly affect the efficiency of silicon solar cells. One of the most popular ways to tackle the surface recombination is the application of dielectric layers that passivate the surface by suppression of charge and/or by chemical modifications. A novel technique for ambient temperature solution-based organic oxidation was developed by Grant et al. (2017). The method involves the application of bis(trifluoromethanesulfonyl)-based chemicals, mainly bis(trifluoromethanesulfon)imide (TFSI), also known as bistriflimide acid, which possesses super acidic (SA) properties. This study aims to elucidate the interaction between TFSI and SiO2 layer, to clarify the mechanism of the passivation, and to understand the source of the decay and recovery of the passivation using the X-ray photoelectron spectroscopy. It is concluded that the TSFI may not directly modify the surface; instead, it might rather support the passivation process by most possibly termination of the immobilised radicals with hydrogen atoms.
BSc Analytical Chemistry and Forensic Science
“Sonochemically activated persulfate induced degradation of traces of tetracyclines in water samples”
Supervised by Dr Larysa Paniwnyk
Tetracyclines (including tetracycline and chlortetracycline), as broad-spectrum antibiotics, are commonly used in agriculture. However, traces of those pharmaceuticals can be detected in environmental samples such as surface waters. Although the antibiotic activity can be neglected in such low concentrations, about 1µg/L (Boxall et al. 2003) even the presence of traces of the pharmaceuticals might lead to major, long-term issues associated exempli gratia with bacterial antibiotic resistance. The objective of this project was to develop a simple, rugged and affordable method of removal and monitoring of tetracycline and chlortetracycline in environmental water samples.
Since the tetracyclines are known to be present in water samples in such low levels, the sample preparation involved pre-concentration on reverse phase C-18 (octadecylsilane) Solid Phase Extraction (SPE) cartridges. The method of removal of the antibiotics was proposed to be based on power ultrasound activated Advanced Oxidation Process (US|AOP) (Wacławek et al. 2017). Due to the high effectivity and reasonable cost the oxidation agent was chosen to be Peroxydisulfate (PDS ≡ S2O82-). The process (US|PDS) was monitored using the Reverse Phase Ultra-High-Performance Liquid Chromatography (RP-UHPLC) with end-capped octadecylsilane UHPLC column (Poroshell 120 EC-C18 2.1×50mm 1.9µ). The detection of the tetracycline and chlortetracycline took place at 357 and 367 nm respectively using a variable slit Diode Array Detector (DAD). The limits of detection (LOD) and quantitation (LOQ) were determined to be 0.5430 and 1.8101 mg/L for tetracycline, and 1.0258 and 3.4193 mg/L for chlortetracycline. The US|PDS resulted in 90.05% degradation efficiency just after 30min long sonication, however, most of the results from positive samples (sonicated) returned peak areas that were either below LOD or between the LOD and LOQ values.
As the LODs and LOQs were quite too high, an alternative method of sample preparation and monitoring should be proposed. The Hydrophilic-Lipophilic Balance (HLB) or Mix-Mode Cation-Exchange (MCX) SPE cartridges would be a better choice when dealing with antibiotics (Bečić et al. 2014, Meijer et al. 2019). According to Aguilera-Luiz et al., detection using tandem mass spectrometry (MS/MS) would give significantly better detection and quantitation limits varying from 1 to 4 µg/kg (Aguilera-Luiz et al. 2008). This method, however, is significantly more expensive and may not be affordable for most chromatographic laboratories.