Abstract: Detection of antigenic biomarkers present in trace amounts is of crucial importance for medical diagnosis. A parasitic disease, human toxocariasis, lacks an adequate diagnostic method despite its worldwide occurrence. The currently used serology tests may stay positive even years after a possibly unnoticed infection, whereas the direct detection of a re-infection or a still active infection remains a diagnostic challenge due to the low concentration of circulating parasitic antigens. We report a time-efficient sandwich immunosensor using small recombinant single-domain antibodies (nanobodies) derived from camelid heavy-chain antibodies specific to Toxocara canis antigens. An enhanced sensitivity to pg/mL levels is achieved by using a redox cycle consisting of a photocatalytic oxidation and electrochemical reduction steps. The photocatalytic oxidation is achieved by a photosensitizer generating singlet oxygen (1O2) that, in turn, readily reacts with p-nitrophenol enzymatically produced under alkaline conditions. The photooxidation produces benzoquinone that is electrochemically reduced to hydroquinone, generating an amperometric response. The light-driven process could be easily separated from the background, thus making amperometric detection more reliable. The proposed method for detection of the toxocariasis antigen marker shows superior performances compared to other detection schemes with the same nanobodies and outperforms by at least two orders of magnitude the assays based on regular antibodies, thus suggesting new opportunities for electrochemical immunoassays of challenging low levels of antigens.

Abstract: Despite its widespread application in the fields of ophthalmology, orthopedics and dentistry and the stringent need for polymer packagings that induce in vivo tissue integration, the full potential of poly(methyl methacrylate) (PMMA) and its derivatives as medical device packaging material has not been explored yet. We therefore elaborated on the development of a universal coating for methacrylate-based materials which ideally should reveal cell-interactivity irrespective of the polymer substrate bulk properties. Within this perspective, the present work reports on the UV-induced synthesis of PMMA and its more flexible poly(ethyleneglycol) (PEG)-based derivative (PMMAPEG) and its subsequent surface decoration using polydopamine (PDA) as well as PDA combined with gelatin B (Gel B). Successful application of both layers was confirmed by multiple surface characterization techniques. The cell interactivity of the materials was studied by performing live-dead assays and immunostainings of the cytoskeletal components of fibroblasts. It can be concluded that only the combination of PDA and Gel B yields materials posessing similar cell interactivities, irrespective of the physicochemical properties of the underlying substrate. The proposed coating outperforms both the PDA functionalized and the pristine polymer surfaces. A universal cell-interactive coating for methacrylate-based medical device packaging materials has thus been realized.

Abstract: Das rote Pigment α-HgS neigt in Gegenwart von Licht und Chloridionen zur Schwärzung. Als Grund für die Zersetzung und Entfärbung werden die Bildung von (schwarzem) β-HgS oder Quecksilbermetall vermutet, doch diese Substanzen wurden noch nicht auf natürlich oder künstlich zersetzter HgS-Farbe nachgewiesen. Elektrochemische Experimente belegen nun die Bildung von Quecksilbermetall in Gegenwart von Licht und Chloridionen.

Abstract: Daily and seasonal variations in dry and wet atmospheric nitrogen fluxes have been studied during four campaigns between 2004 and 2006 at a coastal site of the Southern North Sea at De Haan (Belgium) located at coordinates of 51.1723° N and 3.0369° E. Concentrations of inorganic N-compounds were determined in the gaseous phase, size-segregated aerosol (coarse, medium, and fine), and rainwater samples. Dissolved organic nitrogen (DON) was quantified in rainwater. The daily variations in N-fluxes of compounds were evaluated with air-mass backward trajectories, classified into the main air-masses arriving at the sampling site (i.e., continental, North Sea, and Atlantic/UK/Channel). The three, non-episodic campaigns showed broadly consistent fluxes, but during the late summer campaign exceptionally high episodic N-deposition was observed. The average dry and wet fluxes for non-episodic campaigns amounted to 2.6 and 4.0 mg N m−2 d−1, respectively, whereas during the episodic late summer period these fluxes were as high as 5.2 and 6.2 mg N m−2 d−1, respectively. Non-episodic seasons/campaigns experienced average aerosol fluxes of 0.91.4 mg N m−2 d−1. Generally, the contribution of aerosol NH4+ was more significant in the medium and fine particulate fractions than that of aerosol NO3−, whereas the latter contributed more in the coarse fraction, especially in continental air-masses. During the dry mid-summer campaign, the DON contributed considerably (15%) to the total N-budget. Exceptionally high episodic aerosol-N inputs have been observed for the late summer campaign, with especially high deposition rates of 3.6 and 2.9 mg N m−2 d−1 for Atlantic/UK/Channel and North Sea-continental (mixed) air-masses, respectively. During this pollution episode, the flux of NH4+ was dominating in each aerosol fraction/air-mass, except for coarse continental aerosols. High deposition of gaseous-N was also observed in this campaign with an average total N-flux of 22.5-times higher than in other campaigns.

Abstract: Cultural heritage represents the vehicle of our cultural identity, handed over from past to future generations throughout human history. As a repository of fundamental cultural and social values, the preservation of all forms of cultural heritage is a responsibility of every society and of humankind as a whole. When it comes to tangible cultural heritage, preservation of heritage translates into preservation of objects and, therefore, of the materials they are constituted of. This crucial task relies heavily on the application of scientific analytical methods to answer material and conservation-related questions. ​ ​ The fundamental contribution of this analytical approach led, in the past decades, to an ever-deepening understanding of the factors governing the degradation of cultural heritage. However, the extreme complexity of the heritage object-environment system results in a massive research field, which inevitably presents relevant open questions. This is where the present PhD work comes into play, attempting to fill knowledge gaps in literature by starting from specific case studies and un-answered research questions. ​ ​ The multianalytical research conducted during this PhD unraveled fundamental information on the properties governing the reactivity and long-term behavior of different classes of materials, from α-brass in an indoor environment to artists’ pigments in the presence of light, moisture and soluble particulate matter (PM). The paramount importance of the synthesis conditions on the composition, physical properties and reactivity of heritage materials was also demonstrated, in particular for stable lead pyroantimonate and unstable Geranium lake artists’ pigments. Moreover, the study and characterization of specific heritage objects, namely a series of 16th century reliquary altarpieces and the painting L’Arlesienne, by Vincent Van Gogh, allowed to obtain relevant insights into their composition and on potential risks for their conservation. The challenging nature of the samples considered, created the perfect opportunity to test an innovative spectroscopic technique, optical photo-thermal IR (O-PTIR), for the characterization of heritage materials. Striking results were obtained, highlighting a great potential for the application of this non-destructive sub-micron molecular spectroscopy to the analysis of cultural heritage. Finally, in the last section of this work, strategies to implement the continuous monitoring of PM levels in indoor environmental quality studies were also considered, with a particular focus on the identification of environmental hazards for the collections housed in specific conservation environments (War Heritage Institute in Brussels and St. Martin’s church in Aalst, BE).

Abstract: Controllable chemical doping of graphene has already proven very useful for electronic applications, but when turning to optical and photonic applications, the additional requirement of having both a high transparency and a low surface roughness has, to our knowledge, not yet been fulfilled by any chemical dopant system reported so far. In this work, a new method that meets for the first time this opticalquality requirement while also providing efficient, controllable doping is presented. The method relies on F4-TCNQ dissolved in methyl ethyl ketone (MEK) yielding a uniform deposition after spin coating because of an extraordinary charge transfer interaction between the F4-TCNQ and MEK molecules. The formed F4-TCNQ/MEK layer exhibits a very high surface quality and optical transparency over the visible-infrared wavelength range between 550 and 1900 nm. By varying the dopant concentration of F4-TCNQ from 2.5 to 40 mg ml1 MEK, the doping effect can be controlled between Dn ¼ +5.73 1012 cm2 and +1.09 1013 cm2 for initially strongly p-type hydrogen-intercalated graphene grown on 6Hsilicon- carbide substrates, and between Dn ¼ +5.56 1012 cm2 and +1.04 1013 cm2 for initially weakly p-type graphene transferred on silicon samples. This is the first time that truly optical-quality chemical doping of graphene is demonstrated, and the obtained doping values exceed those reported before for F4-TCNQ-based graphene doping by as much as 50%.

Abstract: Composition of the prehistoric pigments (from Carriqueo rock shelter, Rio Negro province, Argentina) has been analysed by means of molecular spectroscopy (Fourier transform infrared (FTIR) and micro-Raman) and scanning electron microscopy (SEM) coupled to an energy-dispersive X-ray spectrometer (EDS). Red and yellow pigments were recognized as red and yellow ochre. The matrix of the pigments is composed of one or more substances. According to the matrix composition yellow and red pigments were also divided into two groupsi.e. those containing kaolinite or sulphates. Green pigment was detected as green earth, made up of celadonite as a chromophore.

Abstract: Combined mu-XRF, mu-XAFS, and mu-XRD investigations of a uranium-rich tertiary sediment, from a nuclear repository natural analogue site, and a fractured granite bore core section after a column tracer experiment using a Np(V) containing cocktail have been performed. Most mu-XRF/mu-XAFS measurements are recorded in a confocal geometry to provide added depth information. The U-rich sediment results show uranium to be present as a tetravalent phosphate and that U(IV) is associated with As(V). Arsenic present is either As(V) or As(0). The As(0) form thin coatings on the surface of pyrite nodules. A hypothesis for the mechanism of uranium immobilization is proposed, where arsenopyrite acted as reductant of ground water dissolved U(VI) leading to precipitation of less soluble U(IV) and thereby forming As(V). Results for the granite sample show the immobilized Np to be tetravalent and associated with facture material.

Abstract: Colors in many paintings of great art historical value have changed over time, due to the combined effects of natural ageing, accumulated surface grime, and materials added during later conservation treatments. The physical restoration of the colors in such paintings is not possible. This article describes one part of work done to digitally restore the colors of Van Gogh's painting Field with Irises near Arles, dating from May 1888. We have used multispectral reflectance data to estimate absorption K and backscattering S parameters of Kubelka-Munk 2-constant theory. This was done for all 13 pigments known to have been used by Van Gogh in this painting, and based on this the concentration maps for each of these pigments were calculated. We validated the calculated concentration maps in several ways. For some pigments, we were able to predict spots on the painting where the pigment is expected to occur in unmixed form based on visual examination. For several other pigments, the concentration maps could be shown to agree with XRF data. Finally, for some other pigments the concentration maps were supported by additional evidence from microscopic examinations, remarks in Van Gogh's letters and from early color reproductions. For the 1.7 million pixels for which multispectral data is available, the average color difference between the calculated and measured spectral reflectance curves is CIEDE2000 = 1.05. This further confirms that the Kubelka-Munk calculations are well suited to describe the variety of spectral reflectance on the painting.

Abstract: Co-adsorption of norfloxacin (Nor) and Cu(II) on montmorillonite at pH 4.5, 7.0 and 9.0 was studied by integrated batch adsorption experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy. Under such pH conditions the dominant species of Nor are cation (Nor+), zwitterion (Nor±), and anion (Nor−), respectively. Results indicated that Nor sorption decreased with an increase of solution pH. The presence of Cu(II) slightly suppressed the Nor+ sorption at pH 4.5, while increased Nor± and Nor−sorption on montmorillonite at pH 7.0 and 9.0, respectively. In contrast, Nor increased Cu(II) adsorption at pH 4.5, but had little effect on the adsorption of Cu(II) on montmorillonite at pH 7.0 and 9.0. Spectroscopic results showed that, at pH 4.5, Nor+ was sorbed on montmorillonite by the formation of outer-sphere montmorilloniteNorCu(II) ternary surface complex. At pH 7.0, montmorilloniteNorCu(II) and montmorilloniteCu(II)Nor ternary surface complexes co-exist. At pH 9.0, montmorilloniteCu(II)Nor ternary surface complex was likely formed, which was different to Cu(II)(Nor)2 precipitate of the solution.

Abstract: Chromium and silicon are determined simultaneously in steel by 14-MeV neutron activation analysis. The activities of 52V(Eγ=1.43 MeV,TView the MathML source=3.76 min) from 52Cr(n,p)52V and 28Al (Eγ=1.78 MeV; TView the MathML source=2.24 min) from 28Si(n,p)28Al are evaluated by mixed γ-ray spectrometry. The influence of manganese and phosphorus, the main interfering elements, is negligible for most stainless steels. The count rate should be limited, to avoid 52V pulse pile-up effects interfering in the 28Al energy region. Precisions in the 2-10% range are reached, depending on the concentrations, for a 10-min analysis time. Results for a series of steel samples are compared with industrial analyses.

Abstract: Chrome yellow refers to a group of synthetic inorganic pigments that became popular as an artists material from the second quarter of the 19th century. The color of the pigment, in which the chromate ion acts as a chromophore, is related to its chemical composition (PbCr1-xSxO4, with 0≤x≤0.8) and crystalline structure (monoclinic/orthorhombic). Their shades range from the yellow-orange to the paler yellow tones with increasing sulfate amount. These pigments show remarkable signs of degradation after limited time periods. Pure PbCrO4 (crocoite in its natural form) has a deep yellow color and is relatively stable, while the co-precipitate with lead sulfate (PbCr1-xSxO4) has a paler shade and seems to degrade faster. This degradation is assumed to be related to the reduction of Cr(VI) to Cr(III). We show that on increasing the sulfur(S)-content in chrome yellow, the band gap increases. Typically, when increasing the band gap, one might assume that a decrease in photo activity is the result. However, the photo activity relative to the Cr content, and thus Cr reduction, of sulfur-rich PbCr1-xSxO4 is found to be much higher compared to the sulfur-poor or non-doped lead chromates. This discrepancy can be explained by the evolution of the crystal and electronic structure as function of the sulfur content: first-principles density functional theory calculations show that both the absorption coefficient and reflection coefficients of the lead chromates change as a result of the sulfate doping in such a way that the generation of electron-hole pairs under illumination relative to the total Cr content increases. These changes in the material properties explain why paler shade yellow colors of this pigment are more prone to discoloration. The electronic structure calculations also demonstrate that lead chromate and its co-precipitates are p-type semiconductors, which explains the observed reduction reaction. As understanding this phenomenon is valuable in the field of cultural heritage, this study is the first joint action of photo-electrochemical measurements and first-principles calculations to approve the higher tendency of sulfur-rich lead chromates to darken.

Abstract: Children's exposure to air pollution requires a focus on air quality in places where they spend most time, e.g. in schools. Therefore, understanding how indoor elemental concentrations relate the outdoor ones is necessary to create healthy indoor school environment. The aims of this study were to examine the elemental composition of particulate matter (PM1, PM2.5, PM10) in the school and also to investigate to what degree indoor elemental concentrations are affected by outdoor air or generated inside the school. The measurements were performed inside and outside the public school building in the centre of the city. It was observed that concentrations of most elements were higher at school than outside. The dominant elements in PM1 both indoors and outdoors were S, Cl, K, and Zn. PM2.5 and PM10 fractions inside the school were clearly enriched in elements of mineral origin, additionally S, Zn, K and Cl were also present in high concentrations both indoors and outdoors. Results suggested that a significant contribution to indoor Zn, Pb and S concentrations in the PM2.5 fraction was from penetration of outdoor air. 88%, 80% and 90% of the observed total variations in indoor concentrations of Zn, Pb, and S were explained by the linear relationship between indoor and outdoor concentrations. The lack of correlation between indoor and outdoor concentrations obtained for Si, Ca, Ti, Sr indicated that these metals were more likely to originate from indoor sources. (C) 2013 Elsevier Ltd. All rights reserved.

Abstract: Chelation by oxine followed by adsorption on activated carbon results in the efficient collection of many trace metal ions, independent of the trace metal concentration and of high alkali and alkaline earth ion abundances. Preconcentration factors around 10000 are often achieved. When this preconcentration procedure is combined with energy-dispersive X-ray fluorescence, accurate and precise analysis can be carried out, as was proven in several experiments. The technique can also be applied for the determination of divalent ions in natural waters containing up to 10 ppm of humic substances. Trivalent ions can quantitatively be collected from natural water provided suKicient activated carbon is added. Omitting the oxine chelation prior to the activated carbon adsorption step still results in collection of a sometimes important fraction of the trace metal ions from natural waters. This is related to organically bound or colloidal forms of the trace metals.

Abstract: Cellulose powder with 2,2′-diaminodiethylamine (DEN) functional groups exhibits efficient complexation of transition metal cations. Collection yields above 85 % are obtained up to a chelation capacity of 1.5 meq per gram. Since a good collection is obtained for a pH up from 5, no pH adjustments have to be made for natural water samples. The cellulose-DEN powder is insensitive to abundant substances like alkali and alkaline earth ions, and humic matter. Some cations can be eluted efficiently in a small volume of HNO3. Blank concentration levels from the cellulose-DEN powder are reported.