TY - CONF A1 - Rurack, Knut T1 - Reaction-based BODIPY dyes as powerful tools in fluorescence sensing applications N2 - The reversible analyte-induced switching between a colourless leuco form of a dye and its coloured all-π-conjugated form is one of the oldest concepts in probe- or indicator-based optical analysis,1 constituting so-called “one-color indicators”.2 In contrast to colour changes in the visible region, for which usually a bond-forming or a non-covalent interaction between a functional group on an indicator and an analyte is responsible, the extraordinarily large shifts of 150–250 nm seen for leuco-to-all-π-conjugated transformation are only possible when the reaction takes place directly at a site that is an intrinsic part of a dye’s π-system; the classic case are triphenylmethane dyes.3 Despite its obvious potential, this approach has not been a very popular area of scientific research for decades, perhaps because it is much more difficult to implement selectivity than by modifying terminal functional groups. However, in recent years, reaction-based fluorescence probes have attracted increasing attention by virtue of their superior sensitivity.4,5 Nowadays, rhodamines and fluoresceins are by far the most prominent groups of reaction-based indicators.5 They are usually switched between a colourless and non-fluorescent and a greenish-yellowish absorbing and yellowish-reddish emitting form. Typically, the coloured and fluorescent form is ionic, while the colourless form is neutral, reactions having mainly be designed to occur at the end groups of the xanthenoid π-system. BODIPY dyes, with their favourable spectroscopic and chemical properties as well as facile wavelength tunability features have only very recently been explored into this direction.6,7 Reaction at the core dipyrrin framework of these dyes led to strong colour and fluorescence modulations with potential applications in materials sciences6 and cell imaging.7 The present contribution will highlight the mechanisms at play and the sensing performance realized so far, and will compare core-reactive approaches to reaction-based signalling that involves π-extension of BODIPYs.8,9 T2 - 11th International Conference on Porphyrins and Phthalocyanines (ICPP-11) CY - Online meeting DA - 26.06.2021 KW - Indicators KW - Fluorescence KW - Sensing KW - BODIPY Dyes PY - 2021 AN - OPUS4-54001 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Tobias, Charlie T1 - Dip-stick coated with Polystyrene-Silica Core-Shell particles for the detection of microbiological fuel contamination N2 - The microbial contamination of fuels by fungi or bacteria presents risks such as corrosion and fuel system fouling, which can produce critical problems in refineries and distribution systems and has a significant economic impact at every phase of the process. Many factors have been cited as responsible for microbial growth, like the presence of water in the storage tanks. Indeed, only 1 % water in a storage system is enough for the growth of microorganisms like bacteria or yeasts, as well as for the development of fungal biomass at the oil/water interface.1 In this work, a rapid test for the accurate determination of genomic DNA from aqueous fuel extracts is presented. The detection is based on the employment of polystyrene-mesoporous silica core-shell particles, on which modified fluorescent molecular beacons are covalently grafted. Those beacons incorporate in the hairpin loop a target sequence highly conserved in all bacteria, corresponding to a fragment of the 16S ribosomal RNA subunit. The designed single-stranded molecular beacon contained fluorescein as an internal indicator and a quencher in its proximity when not hybridized. Upon hybridization in presence of the target sequence, the indicator and the quencher are spatially separated, resulting in fluorescence enhancement. To perform the assay the designed particles were disposed on different glass fiber strips to try to achieve a portable and sensitive rapid test. Assays showed that presence of genomic DNA extracts from bacteria down to 50–70 μg L-1 induces a fluorescence response. The optical read-out was adapted for on-site monitoring by adapting a 3D-printed case on a conventional smartphone, taking advantages of the CMOS detector sensitivity.2 Such embedded assembly allowed to detect genomic DNA in aqueous extracts down to the mg L-1 range and presents an interesting step toward on-site monitoring of fuel contamination. T2 - Europtrode 2021 CY - Warsaw, Poland DA - 28.11.2021 KW - Bacgteria KW - Fungi KW - Rapid test KW - Fluorescence KW - Smartphone KW - Biofouling PY - 2021 AN - OPUS4-53867 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sun, Yijuan A1 - Pérez-Padilla, Víctor A1 - Valderrey, Virginia A1 - Bell, Jérémy A1 - Gawlitza, Kornelia A1 - Rurack, Knut T1 - Fluorescence Detection of Perfluoroalkyl Carboxylic Acids with a Miniaturised Assay N2 - Per- and polyfluoroalkyl substances (PFAS) are a class of man-made organo-fluorine chemicals that have become environmental contaminants of emerging concern, originating from a variety of materials such as adhesive, stain- and oil-resistant coatings, firefighting foams, etc. The high strength of this C-F bond makes PFAS thermodynamically stable and resistant to (bio)degradation, thus retaining them in the environment over time. Perfluoroalkyl carboxylic acids (PFCAs), one category of the most used PFAS, consist of a fully fluorinated carbon backbone and a charged carboxylic acid headgroup, and have been classified as Substances of Very High Concern (SVHC) and added to the REACH Candidate List due to their persistence in the environment, non-biodegradability and toxicological effects.[1-2] Traditional techniques for the analysis of PFCAs include GC-MS, HRMS and HPLC-based approaches, which are laborious, not portable, costly and require trained personnel. In contrast, fluorescence assays can be designed as easy-to-operate, portable and cost-effective methods with high sensitivity and fast response. Integration of fluorescent probes with an adequately miniaturized assay enables a promising alternative for PFCAs analysis. Here, a novel guanidine fluorescent probe has been synthesized and fully characterized for the detection of PFCAs in a biphasic extract-&-detect assay. The fluorescent probe was then incorporated into polymeric matrices supported by a red dye-doped SiO2 nanoparticle to construct a dual-emission sensing platform. Such a system allows precise and selective detection of PFCAs, reducing the interference of competitors, matrix effects and other factors except for the PFCAs. The system was then employed in a droplet-based microfluidic setup which offers a portable and easy to operate detection platform. T2 - IMA 2023 CY - Chania, Greece DA - 18.09.2023 KW - PFAS KW - MIP KW - Fluorescence KW - Microfluidics KW - Fluorezsenz KW - Mikrofluidik PY - 2023 AN - OPUS4-58527 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rurack, Knut T1 - PFAS Sensors N2 - This contribution provides an introduction to the development of sensors for PFAS analysis, presents the most common approaches, and describes the opto-microfluidic strategy in combination with polymerizable indicators and detection matrices currently being pursued by the Chemical and Optical Sensing Division at BAM. T2 - Advancements of Analytical Techniques for Per- and Polyfluoroalkyl Substances (PFAS) – Second Workshop 2023 CY - Berlin, Germany DA - 19.09.2023 KW - PFAS KW - Sensors KW - Molecularly imprinted polymers KW - Microfluidics KW - Fluorescence PY - 2023 AN - OPUS4-58533 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rurack, Knut T1 - Development of a Lab-on-a-Chip for the Detection of Nerve Agents with a Handheld Device N2 - The development of a Lab-on-a-Chip (LoC) is presented, which can detect reactive phosphorous compounds in the gas phase in combination with an optochemical hand-held sensor. The LoC prototype contains three pairs of sensing materials containing fluorescent indicator dyes in various carrier materials. By measuring the fluorescence response to phosphoryl chloride, a surrogate compound, the detection of chemical warfare agents (CWAs) in gas phase becomes possible within seconds, introducing a novel approach to CWA detection. T2 - IEEE Sensors Conference CY - Vienna, Austria DA - 29.10.2023 KW - Chemical warfare agents KW - Lab-on-a-chip KW - Handheld sensors KW - Toxic industrial chemicals KW - Fluorescence PY - 2023 AN - OPUS4-58815 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Buchholz, Michelle T1 - Dual Fluorescent Molecularly Imprinted Polymers (MIPs) for Detection of the Prevalent Anti-Inflammatory Drug Diclofenac N2 - Ensuring the purity of air and water is essential for the overall well-being of life on earth and the sustainability of the planet's diverse ecosystems. To achieve the goal of zero pollution, as outlined in the 2020 European Green Deal by the European Commission,[1] significant efforts are in progress. A key aspect of this commitment involves advancing more efficient and economically viable methods for treating wastewater. This includes the systematic monitoring of harmful pollutants such as heavy metals, microplastics, pesticides, and pharmaceuticals. One example is the presence of the anti-inflammatory drug diclofenac in water systems, primarily originating from its use as a gel or lotion for joint pain treatment. Diclofenac contamination in surface waters has been detected at approximately 10 μg L-1 (0.03 μM)[2] which is not solely due to widespread usage but also because of the drug's resistance to microbial degradation. Conventional wastewater treatment plants (WWTPs), which rely on biodegradation, sludge sorption, ozone oxidation, and powdered activated carbon treatment, struggle to efficiently remove diclofenac from wastewater.[3],[4] For instance, to enable WWTPs to efficiently monitor and optimize their processes, it would be advantageous to develop on-site detection and extraction methods for persistent pharmaceutical residues in aqueous samples. In this work, a sol-gel process was used to prepare Nile blue-doped silica nanoparticles (dSiO2-NPs) with a diameter of ca. 30 nm that were further functionalized to enable reversible-addition-fragmentation chain-transfer (RAFT) polymerization. To achieve fluorescence detection, a fluorescent monomer was used as a probe for diclofenac in ethyl acetate, generating stable complexes through hydrogen bond formation. The diclofenac/fluorescent monomer complexes were imprinted into thin molecularly imprinted polymer (MIP) shells on the surface of the dSiO2-NPs. Thus, the MIP binding behaviour could be easily evaluated by fluorescence titrations to monitor the spectral changes upon addition of the analyte. Doping the core substrate with Nile blue generates effective dual fluorescent signal transduction. This approach does not solely depend on a single fluorescence emission band in response to analyte recognition. Instead, it enables the fluorescent core to function as an internal reference, minimizing analyte-independent factors such as background fluorescence, instrumental fluctuation, and operational parameters.[5] Rebinding studies showed that the MIP particles have excellent selectivity towards the imprinted template and good discrimination against the competitor ibuprofen, with a discrimination factor of 2.5. Additionally, the limit of detection was determined to be 0.6 μM. Thus, with further optimization of the MIP, there is potential for the development of a MIP-based biphasic extract-&-detect fluorescence assay for simple, sensitive and specific sensing of diclofenac in aqueous samples down to the required concentrations of 0.03 μM. T2 - MIP2024: The 12th International Conference on Molecular Imprinting CY - Verona, Italy DA - 18.06.2024 KW - Sensor KW - Diclofenac KW - Molecularly Imprinted Polymers KW - Fluorescence KW - Pollutant PY - 2024 AN - OPUS4-60439 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rurack, Knut T1 - Sensitive and multiplexed assays for point-of-need applications: innovations for robust, reliable, and user-friendly diagnostics N2 - The development of portable analytical assays, particularly during the SARS-CoV-2 pandemic, has revolutionized diagnostics and expanded their use to areas such as food safety, environmental monitoring and forensics. These assays offer the advantage of rapid on-site decision making without the need for laboratory facilities. The omnipresence of mobile devices with advanced cameras and processing power further increases their usability. However, most current assays are limited to detecting single parameters. The challenge now is to develop robust multiplexed assays that can simultaneously detect multiple parameters with high sensitivity. This lecture will present generic approaches developed at BAM with a focus on supramolecular chemistry, luminescence detection, nanomaterials and miniaturization of devices. Examples include mesoporous nanomaterials, gated indicator systems, imprinted polymers, microfluidic devices, test strips and smartphone-based analysis. T2 - Kolloquium Optische Technologien der FH Münster CY - Steinfurt, Germany DA - 18.12.2024 KW - Rapid testing KW - Fluorescence KW - Explosives KW - Environmental contaminants KW - Multiplexing PY - 2024 AN - OPUS4-62322 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Biyikal, Mustafa T1 - Development of a handheld device for the trace detection of explosives N2 - This presentation introduces a new explosives trace detector (ETD), a handheld device developed by True Detection Systems (TDS). Addressing the limitations of current handheld detectors—such as unreliable measurements and cumbersome operation— the new ETD XT-1 integrates advanced sensor technology, including a Lab-on-a-Chip, to deliver high sensitivity and accuracy. Capable of detecting trace levels of substances like TNT, TATP, and ammonium nitrate, the device offers rapid, user-friendly detection through AI/ML-enhanced algorithms. These algorithms enable precise substance identification by analyzing absorption and desorption rates, significantly reducing false positives. The XT-1 has broad applications in security, hazardous material detection, and environmental monitoring. T2 - Photonics Days Berlin Brandenburg CY - Berlin, Germany DA - 09.10.2024 KW - Explosives KW - Trace detection KW - Handheld device KW - Lab-on-a-chip KW - Fluorescence PY - 2024 AN - OPUS4-61433 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Prakash, Swayam T1 - Development of a Rapid and Sensitive Fluorometric Detection Method for Urobilin Analysis for On-site Water Quality Assessment N2 - The W.H.O. estimated that globally at least 2 billion people use drinking water sources contaminated with faeces and according to UNICEF, most of these faecal contaminants detection methods are expensive, time-consuming (18–24 h time to result), and, with few exceptions, not suited for on-site analysis. Hence, there is an urgent need for the development of rapid analytical methods that allow to unequivocally assess drinking water quality directly on-site. Our approach exploits the weak fluorescence of faecal biomarkers such as urobilin (UB), which is enhanced through complexation with Zn2+ in alcoholic media and is the basis of their detection/estimation, known as Schlesinger’s test.3 However, this method is associated with limitations, as the fluorescence of Zn2+ complexes of UB in water is weak, shows time dependent loss of emission intensity and has strong interference from humic substances that naturally present in surface waters. , To circumvent these issues and achieve the rapid and sensitive on-site detection of FPs, silane-functionalized glass fibre paper test strips were developed following the ‘drop-&-detect’ concept. Drop casting of water samples containing faecal contaminants like UB on specifically functionalized test strips allowed the sensitive detection with a smartphone coupled to a 3D printed optical setup. A series of silanes were used to functionalize glass fibre paper and tune its hydrophobicity, exploiting the influence of matrix tailoring to enhance binding of the Zn2+ salt used as co-reagent to bind UB for optimal fluorometric response. A detection spot was designed by the combination of hydrophilic and hydrophobic silanes with ZnCl2-impregnated test strips. This developed analytical method showed sensitive (nano- and sub-nanomolar concentration) response for UB detection. Furthermore, it can be successfully applied to the analysis of real water samples, allowing for the first time to test for faecal contamination in fresh water directly on-site using a smartphone in only a few minutes, instead of >10 h required for the current standard, i.e., lab-based bacterial tests. T2 - 14th International Conference on Instrumental Methods of Analysis: Modern Trends and Applications CY - Kefalonia, Greece DA - 14.09.2025 KW - Faecal contamination KW - Fluorescence KW - Metal complexes KW - Water analysis KW - Optical and chemical sensing KW - Spectroscopy KW - Onsite analysis KW - Rapid testing PY - 2025 AN - OPUS4-64270 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gawlitza, Kornelia T1 - Using Dual Fluorescent Molecularly Imprinted Particles Coupled with a Miniaturized Opto-Microfluidic Platform for On-Site Detection of Perfluoroalkyl Carboxylic Acids N2 - Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic organofluorine chemicals widely used in the production of various materials, including firefighting foams, adhesives, and coatings that resist stains and oil. In recent years, PFAS have gained attention as emerging environmental contaminants, with particular emphasis on perfluoroalkyl carboxylic acids (PFCAs), the most common type of PFAS. PFCAs are defined by a fully fluorinated carbon chain and a charged carboxylic acid group. They have been classified as Substances of Very High Concern and included in the REACH Candidate List due to their persistence, resistance to biodegradation, and toxicological impacts. Traditional methods for analyzing PFCAs, like GC-MS, HRMS, and HPLC-based techniques, are time-consuming, non-portable, expensive, and require specialized expertise. On the other hand, fluorescence assays offer a user-friendly, portable, and cost-effective alternative with high sensitivity and quick results, particularly when the binding of the analyte causes a specific increase in the probe’s fluorescence. Combining these probes with a carrier platform and a miniaturized optofluidic device presents a promising approach for PFCA monitoring. In this study, a new guanidine BODIPY fluorescent indicator monomer was synthesized, characterized, and incorporated into a molecularly imprinted polymer (MIP) designed for the specific detection of perfluorooctanoic acid (PFOA). The MIP layer was formed on silica core nanoparticles doped with tris(bipyridine)ruthenium(II) chloride, serving as an optical internal reference for calibration-free assays. In combination with an extraction step prior to sample analysis, this system enables selective and reliable detection of PFCAs in surface water samples, minimizing interference from competing substances, matrix effects, and other factors. When integrated into an opto-microfluidic setup, the assay provided a compact, user-friendly detection system capable of detecting micromolar levels of PFOA in under 15 minutes from surface water samples. T2 - ANAKON2025 CY - Leipzig, Germany DA - 10.03.2025 KW - Perfluorooctanoic Acid (PFOA) KW - On-site detection KW - Fluorescence KW - Microfluidics KW - Molecularly Imprinted Polymers PY - 2025 AN - OPUS4-62712 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Prakash, Swayam T1 - Fluorescence Spectroscopy as an Analytical Tool for Rapid and Sensitive Faecal Pigments Detection: From Fundamentals to Onsite Applications N2 - W.H.O estimated that globally at least 2 billion people use drinking water sources contaminated with faeces [1] and according to UNICEF, most of these faecal detection methods are expensive, time-consuming (18–24 h time to result),[2] and, with few exceptions, not suited for on-site analysis.[3] Hence, there is an urgent need for the development of analytical methods that allow to unequivocally test for drinking water quality directly on-site. Today, microbial detection methods primarily targeting E. coli, the major faecal indicator bacteria, are still the prevalent methods for detecting faecal contamination of drinking and recreational waters. As an alternative, Schlesinger proposed the detection of urobilin (UB), a metabolic degradation product of haemoglobin occurring in all mammals, as faecal indicator pigment (FIP) through enhancement of its weak fluorescence by complexation with Zn2+ in alcoholic media already 120 years ago.[4] However, the major limitation of this method is the only weak enhancement of the intrinsically very weak UB fluorescence in aqueous media, requiring either the use of organic solvents or very sensitive instrumentation to reach the relevant detection limits, hampering the method’s use outside of a laboratory environment.[3] In the present work, we addressed the shortcomings relying on interfacial and supramolecular chemistry as well as materials functionalization, transforming Schlesinger’s approach into a fluorometric ‘drop and detect’ assay using a smartphone coupled to a 3D-printed optical setup as a simple and portable device. A series of silanes were used to functionalize glass fibre paper and tune its hydrophobicity, exploiting the influence of matrix tailoring to enhance binding of the Zn salt used as co-reagent to UB for optimal fluorescence response. Combination of bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane and N-octyltrimethoxysilane with ZnCl2-impregnated test strips showed the best response for sensitive (nano- and sub-nanomolar concentration) smartphone-based FIP detection. The obtained fluorescence sensing results were validated with a benchtop fluorometer. Furthermore, the developed analytical method was successfully applied to the analysis of real water samples, allowing for the first time to test for faecal water contamination directly on site in a very short time of few minutes. T2 - Anakon 2025 CY - Leipzig, Germany DA - 10.03.2025 KW - Faecal contamination KW - Fluorescence KW - Metal complexes KW - Water analysis KW - Optical and chemical sensing PY - 2025 AN - OPUS4-62795 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rurack, Knut T1 - Advanced Onsite Analysis for Point-of-Need Applications: Innovations for Robust, Reliable, and User-Friendly Detection N2 - The advancement of portable analytical assays has transformed onsite analysis in several areas, including food safety, environmental monitoring and forensics. The SARS-CoV-2 pandemic has fueled a need for rapid, onsite solutions that enable immediate decision making without the need for and use of laboratory infrastructure. The integration of mobile devices with advanced cameras and significant computing power improves the accessibility and usability of these tests. However, many current methods are limited to the detection of single parameters. The next challenge is to develop robust multiplexed assays that can analyze multiple parameters simultaneously with high sensitivity. In this lecture, innovative approaches developed at BAM will be presented with a focus on supramolecular chemistry, luminescence detection, nanomaterials and miniaturization of devices. Examples will include mesoporous nanomaterials, gated indicator systems, imprinted polymers, microfluidic devices, test strips and smartphone-based analytical tools, focusing on two use cases, i.e., the detection of contaminants in surface waters and immunoanalytical explosives detection. T2 - International Conference on Emergin Trends in Materials Chemistry CY - Coimbatore, India DA - 03.04.2025 KW - Onsite analysis KW - Rapid tests KW - Mobile devices KW - Supramolecular chemistry KW - Fluorescence PY - 2025 AN - OPUS4-65434 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -