Jesús Javier Ojeda

• PhD - Surface Science (University of Sheffield)
• Professor (Associate) at Swansea University

Minerals stabilize organic carbon (OC) in sediments, thereby directly affecting global climate at multiple scales, but how they do it is far from understood. Here we show that manganese oxide (Mn oxide) in a water treatment works filter bed traps dissolved OC as coatings build up in layers around clean sand grains at 3%w/wC. Using spectroscopic and...

Microplastics (<5 mm) have been documented in environmental samples on a global scale. While these pollutants may enter aquatic environments via wastewater treatment facilities, the abundance of microplastics in these matrices has not been investigated. Although efficient methods for the analysis of microplastics in sediment samples and marine orga...

A rapid and inexpensive method to characterise chemical cell properties and identify the functional groups present in the cell wall is Fourier transform infrared spectroscopy (FTIR). Infrared spectroscopy is a well-established technique to identify functional groups in organic molecules based on their vibration modes at different infrared wave numb...

Fenton’s reagent was used to isolate microplastics from organic-rich wastewater. The catalytic reaction did not affect microplastic chemistry or size, enabling its use as a pre-treatment method for focal plane array-based micro-FT-IR imaging. Compared with previously described microplastic treatment methods, Fenton’s reagent offers a considerable r...

Aquabacterium commune, a predominant member of European drinking water biofilms, was chosen as a model bacterium to study the role of functional groups on the cell surface that control the changes in the chemical cell surface properties in aqueous electrolyte solutions at different pH values. Cell surface properties of A. commune were examined by p...

The ability of different microbes to form biofilms on materials found in aviation fuel systems was assessed using both individual isolates and complex microbial communities. Biofilm formation by the Gram-negative bacterium, Pseudomonas putida, the fungus Amorphotheca resinae and the yeast, Candida tropicalis, was influenced by material surface prop...

Avoiding microbial contamination and biofilm formation on the surfaces of aircraft fuel tanks is a major challenge in the aviation industry. The inevitable presence of water in fuel systems and nutrients provided by the fuel makes an ideal environment for bacteria, fungi, and yeast to grow. Understanding how microbes grow on different fuel tank mat...

Avoiding microbial contamination and biofilm formation on the surfaces of aircraft fuel tanks is a major challenge in the aviation industry. The inevitable presence of water in fuel systems and nutrients provided by the fuel makes an ideal environment for bacteria, fungi, and yeast to grow. Understanding how microbes grow on different fuel tank mat...

Deep Geological Repository (DGR) is the preferred option for the final disposal of high-level radioactive waste. Microorganisms could affect the safety of the DGR by altering the mineralogical properties of the compacted bentonite or inducing the corrosion of the metal canisters. In this work, the impact of physicochemical parameters (bentonite dry...

Introduction: Industrial activities related with the uranium industry are known to generate hazardous waste which must be managed adequately. Amongst the remediation activities available, eco-friendly strategies based on microbial activity have been investigated in depth in the last decades and biomineralization-based methods, mediated by microbial...

Microplastics are a globally-ubiquitous aquatic pollutant and have been heavily studied over the last decade. Of particular interest are the interactions between microplastics and microorganisms, especially the pursuit to discover a plastic-specific biome, the so-called plastisphere. To follow this up, a year-long microcosm experimental setup was d...

The importance of lithium in modern industry is proven by a staggering triplication of the market for Li-based batteries, valued at $30b in 2017 and expected to reach $100b by 2025. Lithium is used as nanoparticles, particularly for batteries and electronics applications. Presently, lithium nanoparticles are manufactured using induction thermal pla...

Clinical applications of resin-based composite (RBC) generate environmental pollution in the form of microparticulate waste. Methods: SEM, particle size and specific surface area analysis, FT-IR and potentiometric titrations were used to characterise microparticles arising from grinding commercial and control RBCs as a function of time, at time of...

Plastic pollution is an increasing environmental concern, with an estimated 8 million tons of plastic accumulating in the world’s oceans annually. While large pieces of plastic are a well-known problem and can cause entanglement and injuries from ingestion to marine life, smaller (<5mm) particles of plastic, known as microplastics, are less visible...

Plastic pollution is an increasing environmental concern, with millions of tons of plastic accumulating in the world’s oceans annually. While large pieces of plastic are a well-known problem and can cause entanglement and injuries from ingestion to marine life, smaller (<5mm) particles of plastic, known as microplastics, are less visible and may pr...

Microbial communities occurring in reference materials for artificial barriers (e.g., bentonites) in future deep geological repositories of radioactive waste can influence the migration behavior of radionuclides such as curium (Cm III). This study investigates the molecular interactions between Cm III and its inactive analogue europium (Eu III) wit...

Microbial bio-transformations of the essential trace element selenium are now recognized to occur among a wide variety of microorganisms. These transformations are used to convert this element into its assimilated form of selenocysteine, which is at the active center of a number of key enzymes, and to produce selenium nanoparticles, quantum dots, m...

While the presence of microplastics (MP) has been reported in aquatic habitats across the globe, the pathways through which they enter the environment are still poorly understood. Studies investigating the fate of MP in wastewater are gaining attention but are still scarce, despite the urgent need to understand the role of wastewater treatment plan...

Microplastics (<5 mm particles) occur within both engineered and natural freshwater ecosystems, including wastewater treatment plants, lakes, rivers, and estuaries. While a significant proportion of microplastic pollution is likely sequestered within freshwater environments, these habitats also constitute an important conduit of microscopic polymer...

A hybrid composite of non-aggregated lead sulfide (PbS) nanoparticles of average size 5.8 ± 1 nm embedded within a film of an octaalkyl substituted metal-free phthalocyanine (Compound 2) was prepared on interdigitated gold electrodes by mild acidic treatment of newly synthesised octasubstituted lead phthalocyanine analogue (Compound 1) in solid sta...

In this work, we report the synthesis of novel cationic phosphonium gold nanoparticles dispersible in water and dimethylsulfoxide (DMSO) for their potential use in biomedical applications. All the cationic-functionalising ligands currently reported in the literature are ammonium-based species. Here, the synthesis and characterisation of an alternat...

Two new triphenylarsonium alkylthiolate precursors, a thiosulfate zwitterion and a thioacetate salt, have been structurally characterised and their cytotoxicity evaluated against PC3 cells. The arsonium compounds have been used to prepare gold nanoparticles decorated with triphenylarsonium groups.

This study thoroughly explores the use of time-of-flight secondary ion mass spectrometry (ToF-SIMS) for determining the deposition sequence of fingermarks and ink on a porous paper surface. Our experimental work has demonstrated that mapping selected endogenous components present in natural fingermarks enables the observation of friction ridges on...

An optimized sol–gel process has been developed to produce homogeneous thin films of calcium aluminate binary (12CaO·7Al2O3) compound, on magnesium oxide substrates via spin coating. Fourier transform infrared and Raman spectroscopies have been employed to investigate the effect of annealing temperature and duration on the phase transformations in...

The effectiveness of latent fingerprint development techniques is heavily influenced by the physical and chemical properties of the deposition surface. The use of powder suspensions is increasing for development of prints on a range of surfaces. We demonstrate that carbon powder suspension development on polymers is detrimentally affected by the pr...

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) chemical mapping was used to investigate the order of deposition of natural latent fingerprints and laser printed ink on paper. This feasibility study shows that sodium, potassium and C(3)H(5) positive ions were particularly abundant endogenous components of the natural fingerprints and also...

Attachment of cationic groups to the surface of gold nanoparticles (AuNPs) is an attractive proposition for facilitating mitochondria-targeted therapeutics and diagnostics. With this in mind we have prepared and characterised AuNPs functionalised with phosphonium groups derived from either triarylphosphoniopropylthiosulfate zwitterions or ω-thioace...

The first analytical intercomparison of fingerprint residue using equivalent samples of latent fingerprint residue and characterized by a suite of relevant techniques is presented. This work has never been undertaken, presumably due to the perishable nature of fingerprint residue, the lack of fingerprint standards, and the intradonor variability, w...

Diamond‐like carbon (DLC), a thin amorphous carbon film, has many uses in tribological systems. Exploiting alternative substrates and interlayers can enable the control of the hardness and modulus of the multilayer system and improve wear or friction properties. We used XPS and atomic force microscopy to examine DLC that had been concurrently coate...

Synthetic microplastics (≤5-mm fragments) are globally distributed contaminants within coastal sediments that may transport organic pollutants and additives into food webs. Although micro-Fourier-transform infrared (micro-FT-IR) spectroscopy represents an ideal method for detecting microplastics in sediments, this technique lacks a standardized ope...

The stabilities of CaS:Eu2+ and SrS:Eu2+ phosphors have been studied when they are subjected to accelerated ageing under conditions of 80% relative humidity and temperatures in the range of 50-80°C. The stability of the CaS:Eu2+ phosphor with an ALD coating of Al 2O3 is also investigated.

Polycrystalline titania (TiO2) films were prepared by Formula minutes long annealing at Formula of TiO2 hydrates electrodeposited on the ultrasonically cleaned indium tin oxide (ITO) glass substrate from the chemical bath of titanyl sulphate at four different temperatures from 296 K to 353 K. The film grew in thickness monotonically from 53 nm to 1...

The main wood degraders in aerobic terrestrial ecosystems belong to the white- and brown-rot fungi, where their biomass can be created on wood decay only. However, total sulfur (S) concentration in wood is very low and only little is known about the different S compounds in wood today. S-starved brown-rot fungi Gloeophyllum trabeum and Oligoporus p...

We demonstrate alteration in diamond-like carbon (DLC) film structure, chemistry and adhesion on steel, related to variation in the argon plasma pretreatment stage of plasma enhanced chemical vapour deposition. We relate these changes to the alteration in substrate structure, crystallinity and chemistry due to application of an argon plasma process...

Surfaces of YO:Eu and YO S:Pr phosphors, as well as pure YO, showed evidence of reactions with the atmosphere. No evidence of such reactions was found on the surfaces of commercial phosphor samples protected with silica. Surfaces of samples of both in-house and commercial YAG:Ce showed no evidence of atmospheric reactions.

Surfaces of Y2O3:Eu and Y2O 2S:Pr phosphors, as well as pure Y2O3, showed evidence of reactions with the atmosphere. No evidence of such reactions was found on the surfaces of commercial phosphor samples protected with silica. Surfaces of samples of both in-house and commercial YAG:Ce showed no evidence of atmospheric reactions.

TiAlN/VN multilayer coatings exhibit excellent dry sliding wear resistance and low friction coefficient, reported to be associated with the formation of self-lubricating V2O5. To investigate this hypothesis, dry sliding ball-on-disc wear tests of TiAlN/VN coatings on flat stainless steel substrates were undertaken against Al2O3 at 25 °C, 300 °C and...

Reflectance micro-Fourier transform infrared (FT-IR) analysis has been applied to characterize biofilm formation of Aquabacterium commune, a common microorganism present on drinking water distribution systems, onto the increasingly popular pipe material stainless steel EN1.4307. The applicability of the reflectance micro-FT-IR technique for analyzi...

The attachment of microbial cells to solid substrata is a primary ecological strategy for the survival of species and the development of specific activity and function within communities. An hypothesis arising from a biological sciences perspective may be stated as follows: The attachment of microbes to interfaces is controlled by the macromolecula...

In situ flow-cell ATR-FTIR using a hematite-coated germanium crystal was used to investigate the chemical interactions between Pseudomonas putida and hematite in real time, when compared with cells not attached to the mineral surface. ATR-FTIR spectra of bacteria growing on hematite showed a shift in the carboxylate signal when compared to the samp...

Reciprocating (ball on flat) dry sliding wear tests of TiAlN/VN and CrN/NbN multilayer coatings were undertaken under ambient conditions with either an alumina or tungsten carbide counterface. Wear rates were found to be in the mild wear regime. Worn surfaces and wear debris were examined by using scanning electron microscopy (SEM) and Fourier tran...

Bacteria exist as aggregates or in biofilms to help with adaptation and protection from environmental stresses. The hypothesis that is tested in this paper is that the relative presence of glucose in the media, at the beginning of the growth phase, influences the surface chemistry of the cell, which as a consequence reduces the tendency for the cel...