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This contribution reports the development of a polymerizable BODIPY-type fluorescent probe targeting small-molecule carboxylates for incorporation into molecularly imprinted polymers (MIPs). The design of the probe crosslinker includes a urea recognition site p-conjugated to the 3-position of the BODIPY core and two methacrylate moieties. Titration experiments with a carboxylate-expressing antibiotic, levofloxacin (LEVO), showed a blue shift of the absorption band as well as a broadening and decrease in emission, attributed to hydrogen bonding between the probe’s urea group and the carboxylate group of the antibiotic. Using this probe crosslinker, core–shell particles with a silica core and a thin MIP shell were prepared for the detection of LEVO. The MIP exhibited highly selective recognition of LEVO, with an imprinting factor of 18.1 compared to the non-imprinted polymer. Transmission electron microscopy confirmed the core–shell structure and spectroscopic studies revealed that the receptor’s positioning leads to a unique perturbation of the polymethinic character of the BODIPY chromophore, entailing the favourable responses. These features are fully preserved in the MIP, whereas no such response was observed for competitors such as ampicillin. The sensory particles allowed to detect LEVO down to submicromolar concentrations in dioxane. We have developed here for the first time a BODIPY probe for organic carboxylates and incorporated it into polymers using the imprinting technique, paving the way for BODIPY-type fluorescent MIP sensors.
VIS-Spectroscopy of Aztec colors. Possible application of a non-destructive analytical method
(2020)
VIS-spectrometry is a rapid, non- invasive, mobile method that offers a first overview of possible colorants used for painting. This is worked out in detail for European paintings and applied for artefacts and illuminated manuscripts. Manuscripts from Asia for example show colorful decoration identified to be mostly prepared with mineral pigments such as cinnabar, azurite, malachite or orpiment, which can be well confirmed by elemental analyses due to their color-giving metal ions. This is not the case for the colorants used in pictorial manuscripts from pre-Hispanic America, painted mainly with organic dyes from plants. The palette of colors used by the Aztecs is very rich due to their extensive empire and long- distance communication with vassal states liable to tributes including dyes of high quality. These include for example red cochineal, yellow zacatlaxcalli, tagetes, safflower, and achiotl, as well as blue indigo, or matlalli.
The presented Humboldt Codices are from the early colonial period of Mexico and originate from different localities
1. typical indigen colors and mixtures:
cochineal (red), indigo (blue and green), carbon (black),
mangle, zacatlaxcalli, organic (brown, yellow)- critical!
2. colonial influence:
iron gall ink for writing
3. single fragments belong together:
are cut (fragments IX-XII),
from Mizquahuala distributed (VII, XIII, XIV, [XV]) (VII, XIII in Mexico, XIV in Paris)
Organic/inorganic mixtures were prepared from ordinary Portland cement (OPC), water (w/c 0.22), a fluorescent dye in aqueous solution (stable at alkaline pH; BAM-I), and two different comb shape polycarboxylates (PCEs), i.e., high charge (PCE-HC) and low charge (PCE-LC), respectively. Rheological and calorimetric measurements were performed prior to optical studies in order to select PCE concentrations. Absorption and fluorescence spectroscopy of the system OPC + BAM-I (CBAM-I) revealed maxima of dye BAM-I located at 645 nm and 663 nm, respectively. In presence of PCE-HC and PCE-LC, these mixtures displayed a small red shift in reflectance and a faster decrease in intensity compared to studies with CBAM-I; however, only slight differences were observed between the different PCEs. With time, all systems exhibited a decrease in intensity of BAM-I in absorption/reflectance and emission. This could be caused by dye adsorption and possibly decomposition when in contact with cement particles or hydration products.
Pigments and dyes
(2015)
The present volume is the main achievement of the Research Networking Programme ‘Comparative Oriental Manuscript Studies’, funded by the European Science Foundation in the years 2009–2014. It is the first attempt to introduce a wide audience to the entirety of the manuscript cultures of the Mediterranean East.
The chapters reflect the state of the art in such fields as codicology, palaeography, textual criticism and text editing, cataloguing, and manuscript conservation as applied to a wide array of language traditions including Arabic, Armenian, Avestan, Caucasian Albanian, Christian Palestinian Aramaic, Coptic, Ethiopic, Georgian, Greek, Hebrew, Persian, Slavonic, Syriac, and Turkish.
Seventy-seven scholars from twenty-one countries joined their efforts to produce the handbook. The resulting reference work can be recommended both to scholars and students of classical and oriental studies and to all those involved in manuscript research, digital humanities, and preservation of cultural heritage.
The volume includes maps, illustrations, indexes, and an extensive bibliography.
Besides their plasticizing effect, superplasticizers (SPs) are known to retard the hydration of inorganic systems such as cement. Despite their frequent use, the understanding of these highly complex systems is still limited and the relevant parameters, which control the interaction between SPs, and cement components and reaction products are in the focus of ongoing research activities.[1] Optical methods have been successfully used for the analysis and monitoring of the interactions between a broad variety of nanoscale and molecular systems like nanoparticles of various chemical composition and different types of organic ligands or biomolecules. The potential of these methods to study processes at the interface between (hydrated) particles and the fluid phase at a very early stage of concrete formation could reveal possible mechanisms of interaction.
This investigation focuses on the study of organic/inorganic mixtures consisting of cement (CEM) and cement phases (C3S and C3A) in the presence of polycarboxylate ether and organic dyes in aqueous solution (particularly alkali resistant dyes) at a water to powder ratio of 1. Diffuse reflectance as well as steady state and time resolved fluorescence spectroscopy of the above mentioned mixtures were evaluated. Based upon changes of the intensity of the reflectance and fluorescence signal and spectral changes of the dye, acting as optical reporter, a model for the interactions of dye, PCE and cement (including different cement phases) was derived which describes the very first stage of cement hydration.
Molecularly imprinted polymers (MIPs) are an established and powerful matrix for the selective enrichment and separation of chemical species, especially of small organic molecules. Because MIPs contain cavities in their matrix that are complementary in size, shape and electronic/electrostatic or hydrogen bonding demand to the imprinted target molecule or template, they are frequently termed “artificial antibodies”. Compared to natural antibodies, they are chemically and physically much more robust. MIP formation proceeds through the polymerization of a mixture of functional monomers and cross-linkers in the presence of the template with subsequent extraction of the latter. While this strategy has been successfully employed for separation MIPs since decades, the development of sensory MIPs has long been limited to the combination of a MIP as enrichment phase with a separate signalling element in a discontinuous fashion, being unsuitable for many sensing applications. Only very recently, the implementation of specifically designed fluorescent probes into MIPs has been successfully accomplished, fluorescence being one of the most versatile, sensitive and easily miniaturizable techniques. This presentation will introduce basic design considerations, challenges, limitations and the potential that lies with such sensor materials on the background of the work carried out in our group.
An ideal sensor system is a combination of a selective receptor, an effective transducer, and a sensitive detector. To utilize molecularly imprinted polymers (MIPs) as responsive recognition phases in sensors, the employment of fluorescent molecules or nanoparticles (NPs) that show prominent changes in their spectroscopic properties after binding of the target molecule in the MIP’s cavity is particularly attractive. Such fluorescent MIPs (fMIPs) act through target-induced quenching, enhancement, or spectral shifts of the fluorescence. This contribution introduces different strategies of incorporation of fluorescent dyes, probes, and NPs into fMIPs. In addition, various sensing mechanisms are reviewed, and depending on the application of the sensor, the different deployable formats, their advantages, drawbacks, and impact will be presented and discussed.
Since more than 20 years, optical spectroscopic techniques, in particular fluorescence-based methods, are on the rise in many different areas of chemical and biochemical analysis, with no end being in sight.1,2 Advances in miniaturization and remote applications on one hand and ground-breaking developments in microscopy and laser-based high-throughput instrumentation on the other hand have fuelled these developments substantially.3,4 At the core of utmost of these applications however is not only the instrument, but a small entity that is able to absorb and emit photons and thus to report on the actual (bio)chemistry that is going on in a particular sample of interest.5,6 Besides intense research on various types of luminescent particles (e.g., quantum dots and carbon dots) and proteins, dye chemistry has thus seen its revival and the number of publications dealing with the design, synthesis and application of new fluorescent dyes as probes, stains, labels or indicators is still continuing to grow.
Among the various classes of dyes available as bright fluorophores for a wavelength range that is compatible with many (bio)analytical applications and the respective instrumentation, in particular pyrrolic dyes that do not belong to the classical porphyrins or phthalocyanines have received strong attention recently. Starting perhaps with the revival of the traditional boron-dipyrromethene laser dye ca. 15 years ago,7 these so-called BODIPYs have developed into a colourful spectrum of different derivatives.8 However, the interest in expanding the range of pyrrole-containing π-systems beyond BODIPYs has also constantly increased and has brought about several other pyrrole-based ring systems such as diketopyrrolopyrroles9 or dipyrrolonaphthyridinediones which possess a favourable brightness and other interesting properties. The present contribution will give a critical overview of the field, pinpointing advantages and prospects as well as discussing potential aspects of improvement with an emphasis on the chemical sensing and the longer wavelength range.
Molecularly imprinted polymers (MIPs) are potent and established recognition phases in separation and enrichment applications. Because of their robustness, versatility and format adaptability, they also constitute very promising sensing phases, especially when the active sensing element is directly integrated into the MIP. Fluorescent MIPs incorporating fluorescent monomers are perhaps the best developed and most successful approach here. This article reviews the state of the art in this field, discussing the pros and cons of the use of fluorescent dye and probe derivatives as such monomers, the different molecular interaction forces for template complexation, signalling modes and a variety of related approaches that have been realized over the years, including Förster resonance energy transfer processes, covalent imprinting, postmodification attachment of fluorescent units and conjugated polymers as MIPs; other measurement schemes and sensing chemistries that use MIPs and fluorescence interrogation to solve analytical problems (fluorescent competitive assays, fluorescent analytes, etc.) are not covered here. Throughout the article, photophysical processes are discussed to facilitate understanding of the effects that can occur when one is planning for a fluorescence response to happen in a constrained polymer matrix. The article concludes with a concise assessment of the suitability of the different formats for sensor realization.