1.9 Chemische und optische Sensorik
Filtern
Dokumenttyp
- Zeitschriftenartikel (99)
- Vortrag (71)
- Posterpräsentation (56)
- Beitrag zu einem Tagungsband (6)
- Sonstiges (1)
- Forschungsbericht (1)
Schlagworte
- Fluorescence (47)
- LIBS (29)
- Plasma modeling (26)
- Laser induced plasma (25)
- Plasma diagnostics (20)
- Core-shell particles (17)
- Microfluidics (14)
- Molecularly imprinted polymers (13)
- MIPs (12)
- Sialic acid (10)
- Spectroscopy (10)
- Additive manufacturing (8)
- Laser-induced plasma (8)
- Molecularly Imprinted Polymers (8)
- Roughness (8)
- Multiplexing (7)
- Rapid test (7)
- Cancer (6)
- Signal amplification (6)
- Smartphone (6)
- Vor-Ort-Analytik (6)
- BODIPY (5)
- Fluoreszenz (5)
- Glyphosate (5)
- Image processing (5)
- MamaLoCA (5)
- Molecular imprinting (5)
- Pyrethroids (5)
- Raman spectroscopy (5)
- Schnelltest (5)
- Sensor (5)
- Test strip (5)
- Thermography (5)
- Additive Manufacturing (4)
- Antibiotics (4)
- Antibodies (4)
- BODIPY dyes (4)
- Electron microscopy (4)
- Environment (4)
- Flow cytometry (4)
- Hybrid materials (4)
- Laser metal deposition (4)
- Mikrofluidik (4)
- Nanoparticles (4)
- Optical emission spectroscopy (4)
- Plasma (4)
- Rapid tests (4)
- Sensing (4)
- Tandem MS (4)
- Test strips (4)
- Teststreifen (4)
- Additive Fertigung (3)
- Affinity chromatography (3)
- Air quality (3)
- Analytical Sciences (3)
- Bead-based assay (3)
- Chemical vapor deposition (3)
- Core-Shell Particles (3)
- Core−shell particles (3)
- DPSS laser (3)
- Diclofenac (3)
- Embedded sensor (3)
- Explosives (3)
- Explosives detection (3)
- Fluorescent sensor (3)
- Lateral flow assay (3)
- MIP (3)
- Macrophages (3)
- Mass Spectrometry (3)
- Microfluidic (3)
- Multiplex (3)
- Oil (3)
- Optical sensor (3)
- PFAS (3)
- Plasma physics (3)
- Polyglycerol (3)
- Process control (3)
- Sensors (3)
- Spatial heterodyne spectroscopy (3)
- Thermographie (3)
- Water analysis (3)
- Adulteration (2)
- Air traffic (2)
- Ambient mass spectrometry (2)
- Analytical chemistry (2)
- Anion recognition (2)
- BODIPY dye (2)
- Biofouling (2)
- Biosensors (2)
- Calibration free LIBS (2)
- Charge transfer (2)
- Chemical reactors (2)
- Chlorine (2)
- Cocaine (2)
- Core–shell particles (2)
- Delivery system (2)
- Dip-stick assay (2)
- Direct Energy Deposition (2)
- Drogen (2)
- Electrochemical (2)
- Electron number density (2)
- Embedded system (2)
- Emission line profiles (2)
- Fluorescence sensing (2)
- Fluorescent Probes (2)
- Fluorometric sensing (2)
- Fungi (2)
- Gas sensing (2)
- Gesteuerte Freisetzung (2)
- Glutaraldehyde (2)
- Guanidinium Receptors (2)
- Human papillomavirus (2)
- Image analysis (2)
- Imaging (2)
- Immunoassay (2)
- Immunoassays (2)
- Indikatorfreisetzung (2)
- LMD (2)
- Lab-on-a-chip (2)
- Lab-on-chip (2)
- Laser induced dielectric breakdown (2)
- Laser-Induced Background Spectroscopy (2)
- Laser-Pulver-Auftragschweißen (2)
- Laser-induced breakdown spectroscopy (2)
- Laser-spark (2)
- Lateral Flow Assay (2)
- Lateral Flow Assays (2)
- Lateral flow test (2)
- Mass spectrometry (2)
- Mercury (2)
- Mesoporous materials (2)
- Modeling chemical reactions (2)
- Nerve agents (2)
- PCA (2)
- PH (2)
- Particle characterisation (2)
- Particles (2)
- Permethrin (2)
- Phosphorylated peptides (2)
- Plasma chemistry (2)
- Plasma enhanced chemical vapor deposition (2)
- Plasma processes (2)
- Plasma tomography (2)
- Process monitoring (2)
- Purification (2)
- Raid test (2)
- Reductive amination (2)
- SBA-15 (2)
- SHS (2)
- Sapphire (2)
- Scanning electron microscopy (2)
- Schnelltests (2)
- Sensorik (2)
- Sensorpartikel (2)
- Spatial heterodyne spectrometer (2)
- Spatial information (2)
- Spectrocube (2)
- Sugars (2)
- Temperatures (2)
- Test strip analysis (2)
- Thermal equilibrium (2)
- Thermografie (2)
- Toxic industrial chemicals (2)
- Underwater LIBS (2)
- Water (2)
- Water quality (2)
- Wireless mobile sensor device (2)
- 2,4-D (1)
- 3D image analysis (1)
- 3D-Mikrofluidik (1)
- 3D-printing (1)
- Acoustic Emission (1)
- Acoustic levitation (1)
- Adsorbed microgel particles (1)
- Advanced materials (1)
- Affinity extraction (1)
- Affinity support (1)
- Aggregates (1)
- Agricultural economy (1)
- Airborne (1)
- Aluminum oxide (1)
- Ambient Desorption/Ionization (1)
- Ambient desorption/ionization (1)
- Ambient ionization (1)
- Ambient pressure laser ionization (1)
- Amino acid analysis (1)
- Ammonia (1)
- Ammoniak (1)
- Ammunition (1)
- Amoxicillin (1)
- Amperometry (1)
- Amplification (1)
- Anilinopyridine (1)
- Anion receptors (1)
- Antibody (1)
- Antibody purification (1)
- Antibody-gated indicator delivery (1)
- Antibody-gated indicator delivery systems (1)
- Antibody-gated materials (1)
- Antifouling surface (1)
- Antikörper (1)
- Aptamere (1)
- Aromatic amino acid analysis AAAA (1)
- Aromatic amino acid analysis aaaa (1)
- Atomic (1)
- Autophagy (1)
- BODIPY Dyes (1)
- BODIPY probe (1)
- BODIPYs (1)
- BSA (1)
- BaF (1)
- Bacgteria (1)
- Bacteria (1)
- Batch analysis (1)
- Bead-based assays (1)
- Benzin (1)
- Benzoxadiazole dyes (1)
- Bio-gated hybrid materials (1)
- Biochemische Sensoren (1)
- Bioconjugation (1)
- Biofilm (1)
- Biomarker (1)
- Biosensor (1)
- Bioseparation (1)
- BornAgain simulation (1)
- Boron halides (1)
- Boronic acid (1)
- Bovine serum albumin (1)
- CF LIBS algorithms (1)
- CF-LIBS (1)
- CID (1)
- Caffeine (1)
- Calcite (1)
- Calibration-free LIBS (1)
- Cancer cells (1)
- Cannibal Drug (1)
- Carbamazepine (1)
- Carbon Nanodots (1)
- Carrier (1)
- Cellulose (1)
- Cement (1)
- Cement-based materials (1)
- Characterization (1)
- Charge Transfer (1)
- Charged dyes (1)
- Chemical derivatization (1)
- Chemical warfare agents (1)
- Chemical-hydrodynamic modeling (1)
- Chlor (1)
- Chlorofluorosilanes (1)
- Chlorogenic acid (1)
- Cobaloxime complex (1)
- Cocaine detection (1)
- Collision-induced dissociation (1)
- Colorimetric Test (1)
- Concentration mapping (1)
- Concrete (1)
- Corundum (1)
- Cucurbituril (1)
- Cyanide (1)
- Cyanide detection (1)
- Cyclometalated iridium (III) complexes (1)
- Cytometry (1)
- Cytotoxicity (1)
- DNA (1)
- DOTA (1)
- DPSS-laser (1)
- Dendrimer (1)
- Deuterium (1)
- Deuterium enriched water (1)
- Device embedding (1)
- Devices (1)
- Diesel (1)
- Digital holographic cytometry (1)
- Digital holographic microscopy (1)
- Double-pulse laserinduced breakdown spectroscopy (1)
- Downstream processing (1)
- Drogenanalytik (1)
- Droplets (1)
- Drug delivery (1)
- Dual-color labeling glycan (1)
- Dual-pulse (1)
- Durchflusszytometrie (1)
- Dye loading optimisation (1)
- Dye monomers (1)
- Dye release (1)
- Dyes (1)
- Dyes/pigments (1)
- E. coli (1)
- ELISA (1)
- ESEM (1)
- Electrochemiluminiscence (1)
- Elektrochemie (1)
- Elektrochemilumineszenz (1)
- Emerging pollutants (1)
- Emission spectroscopy (1)
- Emmbedded sensor (1)
- Environmental monitoring (1)
- Equilibrium chemical modeling (1)
- Etofenprox (1)
- Excimers (1)
- Explosiven (1)
- Explosives determination (1)
- Faecal contamination (1)
- Farbstoffe (1)
- Fast Fourier Transform (1)
- Fiber-optic laser-induced breakdown spectroscopy (FO-LIBS) (1)
- Field test (1)
- Fluorescence detection (1)
- Fluorescence sensor (1)
- Fluorescent MIPs (1)
- Fluorescent Urea Receptors (1)
- Fluorescent dye (1)
- Fluorescent dyes (1)
- Fluorescent probes (1)
- Fluorescent sensors (1)
- Fluorezsenz (1)
- Fluorides (1)
- Fluorophores (1)
- Forsterite (1)
- Fourier transform spectroscopy (1)
- Fragmentation (1)
- Fragmentation activation (1)
- Fuel adulteration (1)
- Functional monomers (1)
- Gamma-hydroxybutyric acid (1)
- Gas analysis (1)
- Gas sensor (1)
- Gasoline (1)
- Gated delivery systems (1)
- Gated hybrid material (1)
- Gated hybrid materials (1)
- Gated materials (1)
- Gesteuerten Nanopartikeln (1)
- Glycan (1)
- Glycans (1)
- Grain size (1)
- Grazing incidence small-angle neutron scattering (1)
- Group profile (1)
- Guanidine benzoxadiazole (1)
- Guanidine receptor (1)
- Guanidinium receptors (1)
- HCD (1)
- Hand-held (1)
- Handheld device (1)
- Handheld sensors (1)
- Heat-transfer Measurements (1)
- Heterologous hapten (1)
- High repetition rate (1)
- High repetition-rate (1)
- Holographic microscopy (1)
- Human plasma (1)
- Hydrodynamic model (1)
- Hydrogen reduction (1)
- Hyperbranched polymer (1)
- ICP MS (1)
- IR-Spektroskopie (1)
- IR-spectroscopy (1)
- Igg (1)
- Immunassay (1)
- Immunochemical response optimization (1)
- Immunoglobulins (1)
- Immunoprecipitation (1)
- Immunosensor (1)
- Imprinting (1)
- Indicator displacement assay (1)
- Indicators (1)
- Inductively coupled plasma (1)
- Infrared Thermography (1)
- Insecticide (1)
- Interferometric spectroscopy (1)
- Ion mobility (1)
- Ionmobility spectrometry (1)
- Iron Complex (1)
- Kerosene (1)
- Kokain (1)
- Lab-on-a-Chip (1)
- Lanthanide (1)
- Laser (1)
- Laser ablation (1)
- Laser induced breakdown (1)
- Laser induced dielectric breakdown, Hydrogen reduction (1)
- Laser induced plasma deposition (1)
- Laser metal deposition (LMD) (1)
- Laser-Induced Breakdown Spectroscopy (LIBS) (1)
- Laser-Induced Plasma (1)
- Laser-Pulver-Auftragschweißen (LPA) (1)
- Laser-spark ionization (1)
- Laserauftragschweißen (1)
- Lasers (1)
- Lateral flow assays (1)
- Lateral flow tests (1)
- Linker (1)
- Luminescent lifetime (1)
- Lysosome (1)
- MC-LIBS (1)
- Magnetic Particles (1)
- Magnetic beads (1)
- Magnetophoresis (1)
- MamaLoCa (1)
- Mesoporous particles (1)
- Mesoporous silica (1)
- Metal complexes (1)
- Metal labeling (1)
- Micro-Hydrocyclone (1)
- Microbial (1)
- Microfluidic Chip (1)
- Mikrobiell (1)
- Mikroskopie (1)
- Mixed surface (1)
- Modeling (1)
- Molecular Imprinting (1)
- Molecular analysis (1)
- Molecular dynamics simulations (1)
- Molecular emission (1)
- Molecularly Imprinted Polymer (1)
- Molybdenum (1)
- Molybdenum carbide (1)
- Monitoring (1)
- Multigassensorik (1)
- Multiplexed assay (1)
- Multiplexing detection (1)
- Munition (1)
- NDT (1)
- Nanoparticle formation (1)
- Neutral dyes (1)
- Neutron reflectometry (1)
- Nomaterials (1)
- Nonspecific binding (NSB) (1)
- Oil analysis (1)
- Oil spills (1)
- Oligonucleotide (1)
- Optical Emission Spectroscopy (1)
- Optical detection (1)
- Optical sensing (1)
- Optically active surfaces (1)
- Optics (1)
- Optische Emissionsspektroskopie (1)
- Optische Emissionsspektroskopie (OES) (1)
- Organic-inorganic hybrid composites (1)
- PFOA (1)
- Parameter optimization (1)
- Particle Characterization (1)
- Particle characterization (1)
- Particle size (1)
- Partikeln (1)
- Penicillin (1)
- Perfluorooctanoic Acid (PFOA) (1)
- Periodate oxidation (1)
- Pesticide (1)
- Pesticides (1)
- Pestizid (1)
- Petrol (1)
- Petroleum (1)
- Phenothrin (1)
- Phospholipids (1)
- Phosphonic acids (1)
- Phosphorylated Tyrosine (1)
- Photoinduced Electron Transfer (1)
- Photophysics (1)
- Photopolymerization (1)
- Plasma chemical reactor (1)
- Plasma expansion (1)
- Plasma imaging (1)
- Plasma induced luminescence (1)
- Plasma-induced luminescence (1)
- Pollutant (1)
- Polymer nanolayers (1)
- Polymerwissenschaften (1)
- Portable (1)
- ProMoAM (1)
- Proinflammatory cytokines (1)
- Protein (1)
- Protein a (1)
- Protein hydrolysis (1)
- Protein immobilization (1)
- Protein quantification (1)
- Prozessmonitoring (1)
- Pyrethroid (1)
- Pyrethroids detection (1)
- Quartz (1)
- RF ICP discharge (1)
- Radon reconstruction (1)
- Radon transformation (1)
- Rapid prototyping (1)
- Rapid testing (1)
- Rapid testing methods (1)
- Rare-Earth elements (Tm3+) (1)
- Ratiometric measurement (1)
- Rational design (1)
- Real-time imaging (1)
- Reduction of MoF6 (1)
- Reduction of volatile chlorides and fluorides by hydrogen (1)
- Ring fusion (1)
- SA conjugates (1)
- SAFIA (1)
- SBA-16 (1)
- SDS-PAGE (1)
- SEM (1)
- SEM tilting (1)
- Schallemission (1)
- Schallemissionsanalyse (SEA) (1)
- Scientific communication (1)
- Scientific method (1)
- Scientific rigour (1)
- Scopolamine (1)
- Self-absorption coefficient (1)
- Self-assembled monolayer (SAM) (1)
- Self-assembled monolayers (SAM) (1)
- Sensor Materials (1)
- Sensoren (1)
- Sensory particles (1)
- Shadowgraphy (1)
- Silica (1)
- Silicon halides (1)
- Smartphone readout (1)
- Smartphone readout device (1)
- Sol-gel process (1)
- Solid phase (1)
- Solid-phase extraction (SPE) (1)
- Spatial Heterodyne Spectrometer (1)
- Spatial Heterodyne Spectroscopy (1)
- Spectral enhancement (1)
- Speichel (1)
- Splitting (1)
- Start-up (1)
- Stimulated Raman Spectroscopy (1)
- Sulfide sensing (1)
- Supramolecular Chemistry (1)
- Surface area control (1)
- Surface coating (1)
- Surface group quantification (1)
- Surfactants (1)
- Suspension Array (1)
- TATP (1)
- TEM (1)
- TNT (1)
- Tandem-MS (1)
- Test Streifen (1)
- Test Strip analysis (1)
- Test gas generation (1)
- Thermal model (1)
- Thermodynamic (1)
- Thin films (1)
- Tilting (1)
- Time-of-flight secondary ion mass spectrometry (1)
- Titanium dioxide (1)
- ToF-SIMS (1)
- Trace analysis (1)
- Trace detection (1)
- Type-I pyrethroids (1)
- Tyrosine (1)
- UV/vis spectroscopy (1)
- Ultrasonic acoustic resonator (1)
- Ultrasonic levitation (1)
- Ultrasound (1)
- Urin (1)
- Vacuum Ultraviolet (1)
- Vacuum ultraviolet (VUV) light (1)
- Velocimetry (1)
- Wasser (1)
- X-ray photoelectron spectroscopy (1)
- Zellanalytik (1)
- Zellulose (1)
- agricultural economy (1)
- embedded sensor (1)
- environment (1)
- fluorescence (1)
- gas analysis (1)
- ion optics (1)
- spectroscopy (1)
- transmission mode (1)
- µJ-DPSS laser (1)
- Öl (1)
Organisationseinheit der BAM
- 1 Analytische Chemie; Referenzmaterialien (234)
- 1.9 Chemische und optische Sensorik (234)
- 8 Zerstörungsfreie Prüfung (29)
- 6 Materialchemie (21)
- 8.1 Sensorik, mess- und prüftechnische Verfahren (17)
- 1.5 Proteinanalytik (16)
- 1.8 Umweltanalytik (12)
- P Präsident (12)
- 8.0 Abteilungsleitung und andere (11)
- 9 Komponentensicherheit (11)
Paper des Monats
- ja (3)
Eingeladener Vortrag
- nein (71)
Fluorometric sensing is a versatile approach for trace analysis outside of the laboratory, requiring suitable sensor materials and their integration into sensing devices. The versatility of fluorophores as probes, especially in terms of the possibility to tailor their optical as well as their recognition properties by synthetic modifications in a wide range, renders them as superior active component for the preparation of optical sensor devices. Recent works at BAM in this field include, for example, the detection of nerve gas agents,illustrating impressively the aforementioned benefits of fluorophores in optical sensing applications.
In the interdisciplinary approach presented here, we target hazardous gases such as ammonia, benzene, and hydrogen sulfide, next to others, which pose a major threat to human health and environmental safety and for which the availability of a sensitive and reliable detection method is highly desirable.
The dyes presented follow a “turn-on” fluorescence schematic, which allows for the selective and sensitive detection of the respective gaseous analyte. The immobilization of the probe in polymeric matrices is then the next step toward the fabrication of a prototype device for molecular sensing. Further steps in the project include the assembly of instruments for test-atmosphere generation, the referencing of the sensor system, development and implementation of an optical setup, and the testing of the prototype device under laboratory conditions and in the field.
In this presentation, we give an overview over the recent developments on this topic in our groups, including fluorophore designs investigated for the detection of benzene, ammonia, and hydrogen sulfide as well as approaches for the design of the sensing device.
Molecularly Imprinted Polymers with Integrated Fluorescence as Versatile Biomimetic Sensing Matrices
(2018)
Molecularly imprinted polymers (MIPs) are an established, versatile and high-performance matrix for the selective separation or enrichment of (bio)chemical species, especially small molecules of biochemical or environmental relevance. MIPs are prepared through the polymerization of a mixture of functional monomers and cross-linkers in the presence of the template with subsequent extraction of the latter. Conceptionally, this process can be seen as mimicking in a strongly accelerated, though single-step manner a biological process such as antibody formation. Because the resulting 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, these polymers are frequently termed “artificial antibodies”. Compared to natural antibodies, they are chemically and physically much more robust. Regarding sensitivity and selectivity, however, there is still a gap to bridge before MIPs can fully compete with antibodies.
Another favorable aspect that distinguishes MIPs from antibodies is that they can be endowed with an explicit function, allowing the use of MIPs in applications that require more than only an efficient binder. For instance, if specifically designed and polymerizable fluorescent indicators are integrated as functional monomers into a MIP, direct fluorescence sensing can be accomplished. Because MIPs can be prepared in a variety of different formats, their combination with miniaturized or other specific analytical techniques or sensory devices is possible, especially when the transduction mode is light. This presentation will introduce basic design considerations, challenges, limitations and the potential that lies with such sensor materials with some recent examples of our group, targeting various organic oxoanions as analytes.
The detection of potential contaminants as early as possible and as close to their point of emission as well as immission is becoming increasingly important in contemporary environmental analytical chemistry. In addition, real-time monitoring of important chemical parameters for process control is strongly gaining relevance within the context of Industry 4.0. Not only is the development of powerful optical probes thus necessary but also their integration into a matrix and/or device that allows for the application of such systems in realistic measurement scenarios. Integrating fluorescent probes with sensing matrices, however, presents a major challenge because usually, when confined in a rather rigid matrix, fluorophores tend to behave completely different than for instance in the molecular state in solution. The present contribution will highlight recent examples of successful integration of BODIPY (boron–dipyrromethene) based probes with devices that have been developed in our group.
A simple system utilizing a test strip for direct readout with a conventional miniaturized camera as for instance routinely used in smartphones was recently devised by us for the determination of organophosphate nerve or chemical warfare agents (CWAs) Sarin (GB), Soman (GD), and Tabun (GA) in aqueous environments. Here, we coupled a reactive BODIPY to the inner and outer surface of mesoporous silica nanoparticles. In the presence of CWAs, the reactive BODIPY dye with an optimally positioned hydroxyl group undergoes an acylation reaction, yielding a bicyclic product that is non-emissive. The strong fluorescence quenching response allows reaching LODs in the pM range in natural waters.
Steric embedding, again relying on test strip analysis in combination with a smartphone-based readout and data processing, was sufficient to create a reusable optical pH stick. The family of pH-responsive fluorescent BODIPY probes used for this purpose has been designed in a rational manner with the aid of quantum chemistry tools. All the probes display very similar spectroscopic properties with ON−OFF fluorescence switching responses, being retained after embedding of the probes into hydrogel sensor spots on a plastic strip.
Dispensing with a matrix yet invoking microfluidic chips finally permits to use a highly sensitive boronic acid-functionalized BODIPY probe for in-line sugar analysis for instance in the beverage industry. Placement of an amino group in direct neighbourhood of the boronic acid moiety yielded a broad working range at neutral pH while meeting the desired sensitivity in the micro-molar range due to a pronounced analyte-induced fluorescence increase, guaranteeing the straightforward detection of sugar in (coloured) sodas without sample clean-up.
Supramolecular chemistry, fluorescence detection, hybrid (nano)materials and device miniaturization are in themselves highly interesting areas of research, yet especially their combination paves the way to (bio)chemical analysis systems that show outstanding performance. The lecture gives an overview of the toolbox of single components developed in BAM’s Chemical and Optical Sensing Division over the years, and how their combination can result in powerful sensors, quick tests and assays. While at the core of a development is the analytical problem, that is, the determination of a certain analyte in a sample of interest with the required sensitivity and selectivity by a specific end user in a given setting, signaling mechanisms, recognition elements, signal transduction modes, materials functionalization, device design and system integration are adequately chosen, tailored and adapted. Examples including molecularly imprinted polymers, hybrid mesoporous nanomaterials, gated indicator release systems, microfluidic devices, test strips and smartphone-based analysis will be presented.
We introduce herein boron-dipyrromethene (BODIPY) dyes as a new class of fluorophores for the design of reporter dyes for supramolecular host–guest complex formation with cucurbit[7]uril (CB7). The BODIPYs contain a protonatable aniline nitrogen in the meso-position of the BODIPY chromophore, which was functionalized with known binding motifs for CB7. The unprotonated dyes show low fluorescence due to photoinduced electron transfer (PET), whereas the protonated dyes are highly fluorescent. Encapsulation of the binding motif inside CB7 positions the aniline nitrogen at the carbonyl rim of CB7, which affects the pKa value, and leads to a host-induced protonation and thus to a fluorescence increase. The possibility to tune binding affinities and pKa values
is demonstrated and it is shown that, in combination with the beneficial photophysical properties of BODIPYs, several new applications of host–dye reporter pairs can be implemented. This includes indicator displacement assays with favourable absorption and
emission wavelengths in the visible spectral region, fluorescence correlation spectroscopy, and noncovalent surface functionalization
with fluorophores.
Contamination of natural bodies of water with oil and lubricants (or generally, hydrocarbon derivatives such as petrol, fuel and others) is a commonly found phenomenon around the world due to the extensive production, transfer and use of fossil fuels. The timely identification of these contaminants is of utmost importance, since they directly affect water quality and represent a risk for wildlife and human health even in trace amounts.
In this work, we develop a simple system for the on-field detection of total petroleum hydrocarbons (TPH) in water and soil, the "Spectrocube". The test is based on the measurement of the fluorescence signal emitted by the molecular rotor 4-DNS-OH dye. This dye is embedded in a hydrophobic polymeric matrix (PVDF), avoiding interactions of water with the dye and providing a robust support for use in test-strip fashion. The test-strip’s fluorescence intensity increases linearly at low concentrations of TPH, reaching a saturation value at higher concentrations.
For excitation and evaluation of the test-strip fluorescence, a simple miniature optical system was designed. The system works semi-quantitatively as solvent-free TPH detection kit, as well as quantitatively when using a simple cyclopentane extraction step. To simplify the fluorescence read-out, the device is coupled to a tablet computer via Bluetooth, running a self-programmed software ("app").
Contamination of natural bodies of water with oil and lubricants (or generally, hydrocarbon derivatives such as petrol, fuel and others) is a commonly found phenomenon around the world due to the extensive production, transfer and use of fossil fuels. In this work, we develop a simple system for the on-field detection of total petroleum hydrocarbons (TPH) in water and soil. The test is based on fluorescence emission of a 4-dimethylamino-4′-nitrostilbene derivative (4-DNS-OH). This fluorescent molecular rotor is embedded in a hydrophobic polymeric matrix (PVDF), avoiding interactions with water and providing a robust support for use in test-strip fashion. For the fluorescence detection a portable sensor device was developed, featuring two excitation LEDs, a micro-spectrometer and Bluetooth control. A limit of detection of at least 6 ppm of TPH in water was demonstrated.
Application of pesticides is ubiquitous to better manage agricultural production. However, most of these compounds are harmful or toxic for humans and highly persistent in the environment, even in the crops themselves. Therefore, the rapid and reliable monitoring of pesticide residues is a very important area of environmental analysis. If conducted directly in the field, the use of fluorescence sensing methods is particularly attractive, because they allow for sensitive and rapid analyses while being very versatile. Recently, molecularly imprinted polymers (MIPs) have emerged as promising candidates for the primary sensing phase. Their robustness, low price and tunability render them an attractive alternative to more conventional biosensors based on antibodies.
At present, a number of MIP formats are available besides the initial bulk polymer monoliths. Core/shell micro- and nanoparticles are especially suitable for sensor applications. A thin shell provides many advantages compared to a bulk polymer, such as fast diffusion of analyte, homogeneity of binding cavities and a higher number of binding sites closer to the surface. A strategy for sensory MIP synthesis is to introduce the fluorophore covalently into the polymer layer. The fluorescent probe monomer may thus consist of a fluorophore unit, a polymerizable unit and a recognition unit.
One of the issues in targeting acidic pesticides such as 2,4-D is the fact that usually their deprotonated form is used for imprinting in organic solvents, commonly as the tetraalkylammonium salt. This approach harbours drawbacks when it comes to analytical rebinding, because real samples seldom contain such counterions. In our group, we have thus developed a new fluorescent probe monomer containing the 2-aminopyridine moiety, which forms strong enough intermolecular hydrogen bonds with the carboxylic acid group of neat 2,4-D. During a titration of the probe monomer with the analyte, hydrogen bond formation is indicated by spectral shifts and fluorescence enhancement. Crystallography studies verified complex formation. The higher fluorometric response of the core-shell MIP compared to a non-imprinted control polymer proved successful imprinting.
Here, we will discuss the pros and cons of neutral molecule vs. salt imprinting, potentially expanding the possibilities of fluorescent sensory MIPs.
Sialic acid (SA) is a cell surface glycan, which has a strong role in many cell activities including differentiation, proliferation, and the immune response. The amount of SA has been found to be correlated with cancer, with an upregulation on more aggressive cancers. Therefore, there is great interest in developing methods for detection of SA on cancer cells. We are screening SA on cancer cell lines by using fluorescent molecularly imprinted polymers, SA-MIPs.Macrophages, which evolve from mono-cytes, are well known for their extraordinary ability to phagocytose foreign objects. This could lead to the hypothesis that the SA-MIPs can be recognized by macrophages as foreign object; thus leading to internalization and potential degradation. We have discovered that SA-MIPs can be detected after incubation with the RAW macrophage cells, with increasing fluorescence over time. The microscopy analysis shows that the RAW cells ingest the SA-MIP particles. This information is important when planning to use SA-MIPs in future in vivo applications.
Sialic acid (SA) is a cell surface glycan, which has a decisive role in many cell activities including differentiation, proliferation, and the immune response. The amount of SA has been found to correlate with cancer, with an upregulation on more aggressive cancers. Therefore, there is a great interest in developing methods for detection of SA on cancer cells. We are screening SA on cancer cell lines by using fluorescent molecularly imprinted polymers, SA-MIPs. Macrophages, which evolve from mono-cytes, are well known for their extraordinary ability to phagocytose foreign objects. This could lead to the hypothesis that the SA-MIPs can be recognized by macrophages as foreign object; thus leading to internalization and potentially degradation.
We have demonstrated that SA-MIPs can be detected after incubation with the RAW macrophage cells, with increasing fluorescence over time. The microscopy analysis shows that the RAW cells ingest the SA-MIP particles. This information is important when planning to use SA-MIPs in future in vivo applications.
Cancer is a leading cause of death worldwide, and its early detection and resultant treatment contributes significantly to patient recovery and survival. Detection is currently based on magnetic resonance imaging and computed tomography, methods that are expensive, while processing of the results is time consuming. There is a need for low-cost cancer-detection techniques that give conclusive results in the shortest time possible. Molecularly imprinted polymers (MIPs) targeting tumor markers on cancerous cells may provide a cheaper solution for cancer detection. Thin MIP layers immobilized on particle platforms are known to give faster response times and increased selectivity in comparison to bulk MIPs. It has been reported that a fluorescent monomer can be incorporated into the MIP layer, allowing for faster detection of the target group, thus significantly shortening the turn-around time for biopsies.
Changes in sialylation patterns of cell surface glycoproteins indicate malignancy. Here, we present the development of MIPs that target sialic acid-terminated glycoproteins (SA MIPs), prepared as a thin layer on a silica nanoparticle platform. A fluorescent monomer is incorporated into the MIP layer, and upon binding of the target group to the specific binding pockets in the MIP, the fluorescence signal is enhanced. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are used for structural characterization. To validate the specificity, fluorescence changes of MIPs in the presence and absence of template are compared to their corresponding non-imprinted polymer particles (NIP). Initial binding experiments with tumor cells using fluorescence microscopy demonstrate that the presented technique shows promise as a cheaper alternative to current detection methods, while allowing for relatively shorter analysis of biopsy results.
Small-molecule oxoanions are often imprinted noncovalently as carboxylates into molecularly imprinted polymers (MIPs), requiring the use of an organic counterion. Popular species are either pentamethylpiperidine (PMP) as a protonatable cation or tetraalkylammonium (TXA) ions as permanent cations. The present work explores the influence of the TXA as a function of their alkyl chain length, from methyl to octyl, using UV/vis absorption, fluorescence titrations, and HPLC as well as MD simulations. Protected phenylalanines (Z-L/D-Phe) served as templates/analytes. While the influence of the counterion on the complex stability constants and anion-induced spectral changes shows a monotonous trend with increasing alkyl chain length at the prepolymerization stage, the cross-imprinting/rebinding studies showed a unique pattern that suggested the presence of adaptive cavities in the MIP matrix, related to the concept of induced fit of enzyme−substrate interaction. Larger cavities formed in the presence of larger counterions can take up pairs of Z-X-Phe and smaller TXA, eventually escaping spectroscopic detection. Correlation of the experimental data with the MD simulations revealed that counterion mobility, the relative distances between the three partners, and the hydrogen bond lifetimes are more decisive for the response features observed than actual distances between interacting atoms in a complex or the orientation of binding moieties. TBA has been found to yield the highest imprinting factor, also showing a unique dual behavior regarding the interaction with template and fluorescent monomer. Finally, interesting differences between both enantiomers have been observed in both theory and experiment, suggesting true control of enantioselectivity. The contribution concludes with suggestions for translating the findings into actual MIP development.
Probe 1, which contains an anilinopyridine chromophore and an azaoxa macrocyclic subunit, presented an absorption band centered at 340 nm in acetonitrile. Addition of Fe(III), Cr(III) and Hg(II) induced the growth of a new absorption band at 430 nm (with color change from colorless to yellow), whereas in the presence of Cu(II), Zn(II) and Pb(II), less marked changes were observed. The color changes observed upon addition of Fe(III), Cr(III) and Hg(II) were ascribed to the formation of 1:1 stoichiometry complexes with probe 1. Coordination of Fe(III), Cr(III) and Hg(II) with the pyridine fragment of 1 induced an enhancement of the charge transfer character accompanied with a marked bathochromic shift that was reflected in a color change from colorless to yellow. The strength of the interaction between probe 1 and Fe(III) cation was modulated upon interaction with anions. Of all the anions tested, only cyanide was able to induce the bleaching of the yellow 1·Fe(III) complex solution. This bleaching was ascribed to
the formation of 1·Fe(III)-CN complex that restored, to some extent, the optical features of the free probe allowing the chromogenic sensing of cyanide. Besides, 1·Fe(III) complex was used to detect
cyanide in acetonitrile-water 90:10 v/v mixtures with good recoveries.
An improved algorithm for calibration-free laser induced breakdown spectroscopy (CF LIBS) is presented which includes several novel features in comparison with previously proposed similar algorithms. In particular, it allows using spectral lines with arbitrary optical thickness for the construction of Saha-Boltzmann plots, retrieves the absorption path length (plasma diameter) directly from a spectrum, replaces the Lorentzian line profile function by the Voigt function, and allows for self-absorption correction using pre-calculated and tabulated data rather than approximating functions. The tabulated data embody the solutions of the radiative transfer equation for numerous combinations of optical thicknesses and line widths. The algorithm is thoroughly verified with synthetic spectra.
Laser-induced plasmas are widely used in many areas of science and technology; examples include spectrochemical analysis, thin film deposition, material processing, and even jet propulsion. Several topics will be addressed. First, general phenomenology of laser-induced plasmas will be discussed. Then, a chemical model will be presented based on a coupled solution of Navier-Stokes, state, radiative transfer, material transport, and chemical (Guldberg-Waage) equations. Results of computer simulations for several chemical systems will be shown and compared to experimental observations obtained by optical imaging, spectroscopy, and tomography. The latter diagnostic tools will also be briefly discussed. Finally, a prospective application of laser-induced plasma and plasma modeling will be illustrated on the example of calibration-free MC LIBS (Monte Carlo Laser Induced Breakdown Spectroscopy), in which concentrations of elements in materials are found by fitting model-generated and experimental spectra.
Accuracy of calibration-free (CF) methods in laser-induced breakdown spectroscopy (LIBS) depends on experimental conditions and instrumental parameters that must match a CF LIBS model. Here, the numerical study is performed to investigate effects of various factors, such as the optical density, plasma uniformity, line overlap, noise, spectral resolution, electron density and path length on the results of CF-LIBS analyses. The effects are examined one-by-one using synthetic spectra of steel slag samples that fully comply with the mathematical model of the method. Also, the algorithm includes several new features in comparison with previously proposed CF algorithms. In particular, it removes limits on the optical thickness of spectral lines that are used for the construction of the Saha-Boltzmann plot; it retrieves the absorption path length (Plasma diameter) directly from spectral lines; it uses the more realistic Voigt line profile function instead of the Lorentzian function; and it employs the pre-calculated and tabulated thin-to-thick line ratios instead of approximating functions for selfabsorption correction.
Die Bundesanstalt für Materialforschung und -prüfung (BAM) ist eine Ressortforschungseinrichtung, die zum Schutz von Mensch, Umwelt und Sachgüter, forscht, prüft und berät. Im Fokus aller Tätigkeiten in der Materialwissenschaft, der Werkstofftechnik und der Chemie steht dabei die technische Sicherheit von Produkten und Prozessen. Dazu werden Substanzen, Werkstoffe, Bauteile, Komponenten und Anlagen sowie natürliche und technische Systeme erforscht und auf sicheren Umgang oder Betrieb geprüft und bewertet. Schwerpunkt des Vortrages sind multimodale Polymeranalytik, nanoskalige Sensormaterialien und die Charakterisierung von technischen Eigenschaften von Polymeren sowie ihre Alterung und Umweltrelevanz.
A novel technique based on laser induced plasma imaging is proposed to measure residual pressure in sealed containers with transparent walls, e.g. high voltage vacuum interrupter in this paper. The images of plasma plumes induced on a copper target at pressure of ambient air between 10−2Pa and 105Pa were acquired at delay times of 200ns, 400ns, 600ns and 800ns. All the plasma images at specific pressures and delay times showed a good repeatability. It was found that ambient gas pressure significantly affects plasma shape, plasma integral intensities and expansion dynamics. A subsection characteristic method was proposed to extract pressure values from plasma images. The method employed three metrics for identification of high, intermediate and low pressures: the distance between the target and plume center, the integral intensity of the plume, and the lateral size of the plume, correspondingly. The accuracy of the method was estimated to be within 15% of nominal values in the entire pressure range between 10−2Pa and 105Pa. The pressure values can be easily extracted from plasma images in the whole pressure range, thus making laser induced plasma imaging a promising technique for gauge-free pressure detection.
Laser induced plasma (LIP) is a dynamic, short living event which presents significant difficulty for modeling. In this report, a collisional-dominated chemical model developed earlier* is expanded by the inclusion of a new method for calculation of chemical reactions. The model consists of the coupled Navier-Stokes, state, radiative transfer, material transport, and chemical equations. The latter are written in terms of atomic and molecular partition functions rather than reaction rates. Typically, a solution of such the system of chemical equations is difficult for the entire range of plasma temperatures and densities because reaction constants may vary by hundreds orders of magnitude owing to extreme plasma conditions. No numerical solver of non-linear systems of equations handles this situation with ease. We resolve the problem by using a hierarchical approach. First, we rank the reactions according to their ascendancy. Second, we exploit either the contraction or Newton-Raphson algorithms to solve the system of chemical equations. We illustrate the approach by performing a series of calculations for reacting species Si, C, N, Ca, Cl and their molecules in laser induced plasmas.
This course will provide an introduction to plasma diagnostic techniques. The major focus of the course will be on the discussions of the practical procedures as well as the underlying physical principles for the measurements of plasma fundamental characteristics (e.g., temperatures, thermodynamic properties, and electron number density). Particular emphasis will be placed on inductively coupled plasma–atomic emission spectrometry, but other analytical plasmas will also be used as examples when appropriate. Selected examples on how one can manipulate the operating conditions of the plasma source, based on the results of plasma diagnostic measurements, to improve its performance used for spectrochemical analysis will also be covered. Topics to be covered include thermal equilibrium, line profiles, temperatures, electron densities, excitation processes, microreactions, pump and probe diagnostics, tomography, temporal and spatial resolution. Basis of plasma computer modeling will be presented.
2,4-D ist ein in der Landwirtschaft weitverbreitetes Pflanzenschutzmittel, das Grundwasser kontaminiert, sich innerhalb der Nahrungskette anreichert und Umwelt- und Gesundheitsprobleme verursachen kann. Hier stellen die Autoren ein mikrofluidisches Nachweissystem für die Echtzeitdetektion von 2,4-D in Grund- oder Oberflächenwasser vor. Es basiert auf der Kombination 2,4-D-selektiver, fluoreszierender, molekular geprägter Polymer-(MIP-)Mikropartikel mit einem 3D-mikrofluidischen Extraktions- und Detektionssystem. Messungen vor Ort sollen damit künftig möglich sein.
Tandem MS techniques are widely used for both, structure and sequence elucidation of biopolymers. Thereby, fragmentation activation is realized by various methods, for example with lasers or collisions with neutral gases. In this study, we present a new Tandem MS system using a commercially available vacuum ultraviolet lamp. On the one hand, this approach provides efficient fragmentation in both ionization modes, positive as well as negative. On the other hand, it enables an additional previously not achieved post ionization of the fragments. While the first results in atypical fragment patterns and, thus provides orthogonal information, the second is crucial especially to identify low abundant ions.
The development and enhancement of new ionization techniques for mass spectrometry often needs to be custom-tailored for specific sampling approaches. Here, a direct sampling ionization technique is presented for ambient mass spectrometry. Ambient mass spectrometry based techniques are typically used to analyze samples in their native states without sample pretreatment. This new design is based on a quasi-continuous airborne plasma which is ignited inside the particulate air via a focused laser irradiation. Desorption and ionization of the analyte molecules are achieved by the laser plasma without reaching the plasma. The ionization process is induced by interaction with nascent ionic fragments, electrons and ultraviolet photons in the plasma vicinity. Previously, this method was solely used for the characterization of solid and gaseous analytes. The sample introduction was occurred via thermal desorption and headspace analysis. This study focuses on the potential applicability of liquid samples. In comparison to previous approaches, the usage of liquid samples has an impact on the stability of typically used plasma of 532 nm. It was necessary to realize an alternative plasma using light of the fundamental wavelength of 1064 nm. That new plasma resulted in a significant more stable and bright plasma and the first laser plasma ionization spectrum was recorded for an analyte in the condensed phase with a mass spectrometer of type LCQ DecaXP.
A versatile ionization scheme for atmospheric pressure MS is presented. It is based on a quasi-continuous laser-induced plasma (LIP), generated by a 26 kHz pulsed DPSS-laser, which is ignited in front of the MS inlet. Analytes are determined with different sampling regimes, comprising either an ambient desorption/ionization mechanism, a liquid-phase or gas-phase sample introduction.
The MS signal closely resembles the ionization behavior of APCI-like plasma-based sources, such as DBD or DART. Though LIPs are known to efficiently atomize/ionize any sample material, mass spectra of intact molecular ions are recorded, exhibiting low fragment-ion content. To understand this contradictory behavior, the plasma properties are investigated that lead to the formation of molecular ions. Comprehensive studies include optical emission spectroscopy, shadowgraph imaging and mass spectrometry diagnostics.
The results show that the ionization of analyte does not occur in the plasma itself, but in the cold adjacent gas layer. The pulsed character of LIPs induces an expanding shockwave, which concentrically expands around the plasma core and sweeps the molecules toward the plasma edges, where they are ionized either directly by the self-emission of the hot core or via interaction with secondary reactants. However, this unidirectional transport causes a rarefaction inside the plasma center, which leads to a decrease in plasma intensity and number density. Thus, a restoration of the former gaseous medium by other dynamically equilibrated diffusion processes would be favorable. Besides gas replenishing, we demonstrate the beneficial use of an acoustical standing wave inside an ultrasonic resonator on the performance of the LIP.
Mass spectrometry is applied as a tool for the elucidation of molecular structures. This premises that gas-phase structures reflect the original geometry of the analytes, while it requires a thorough understanding and investigation of the forces controlling and affecting the gas-phase structures. However, only little is known about conformational changes of oligonucleotides in the gas phase. In this study, a series of multiply charged DNA oligonucleotides (n¼15–40) has been subjected to a comprehensive tandem mass spectrometric study to unravel transitions between different ionic gas-phase structures. The nucleobase sequence and the chain length were varied to gain insights into their influence on the geometrical oligonucleotide organization. Altogether, 23 oligonucleotides were analyzed using collision-induced fragmentation. All sequences showed comparable correlation regarding the characteristic collision energy. This value that is also a measure for stability, strongly correlates with the net charge density of the precursor ions. With decreasing charge of the oligonucleotides, an increase in the fragmentation energy was observed. At a distinct charge density, a deviation from linearity was observed for all studied species, indicating a structural reorganization. To corroborate the proposed geometrical change, collisional cross-sections of the oligonucleotides at different charge states were determined using ion mobility-mass spectrometry. The results clearly indicate that an increase in charge density and thus Coulomb repulsion results in the transition from a folded, compact form to elongated structures of the precursor ions. Our data show this structural transition to depend mainly on the charge density, whereas sequence and size do not have an influence.
Rationale: The most commonly used fragmentation methods in tandem mass spectrometry (MS/MS) are collision‐induced dissociation (CID) and higher energy collisional dissociation (HCD). While in CID the preselected ions in the trap are resonantly (and m/z exclusively) excited, in HCD the entire m/z range experiences the dissociative acceleration. The different excitation is reflected in different fragment distributions. Methods: As a test‐bed for particularly pronounced fragmentation specificity, here MS/MS experiments on several 4‐mer oligonucleotides were conducted employing both collision methods and the results were thoroughly compared. Oligonucleotides are shown to be sensitive probes to subtle changes, especially in the negative ion mode. A detailed analysis of these differences reveals insight into the dissociation mechanics. Results: Thedifferencesarerepresentedinheat‐maps,whichallowforadirectvisualinspection oflargeamountsofdata.Inthesefalsecolourrepresentationsthe,sometimessubtle,changesinthe individual dissociation product distributions become distinct. Another advantage of these graphic plots can be found in the formation of systematic patterns. These patterns reflect trends in dissociation specificity which allow for the formulation of general rules in fragmentation behavior. Conclusions: Instruments equipped with two different excitation schemes for MS/MS are today widely available. Nonetheless, direct comparisons between the individual results are scarcely made. Such comparative studies bear a powerful analytical potential to elucidate fragmentation reaction mechanism.
We found cascade IR generation in Al laser induced plasma. This generation includes doublet transitions 3s25s 2S1∕2→ 3s24p 2P1∕2,3∕2 → 3s24s 2S1∕2; corresponding to strong lines at 2110 and 2117 nm, and much weaker lines at 1312–1315 nm. The 3s25s2S 1∕2 starting IR generation level is directly pumped from the 3s23p 2P3∕2 ground level. The starting level for UV generation at 396.2 nm (transitions 3s24s 2S1∕2 → 4p 2P3∕2) is populated due to the fast collisional processes in the plasma plume. These differences led to different time and special dependences on the lasing in the IR and UV spectral range within the aluminum laser induced plasma.
Quantitative analysis of complex proteins is a challenging task in modern bioanalytical chemistry. Commonly available isotope labels are still suffering from limitations and drawbacks, whereas new metal labels open numerous possibilities in mass spectrometric analyses. In this work, we have developed a newmetal labeling strategy to tag glycan structures of proteins, more particularly antibodies. The oligosaccharide glycans were selectively trimmed to the last N-acetylglucosamine to which an artificial azide containing galactose residue was bound. This azide can be used for subsequent cycloaddition of an alkyne. Therefore, we developed a lanthanide-containing macrocyclic reagent to selectively connect to this azido galactose. In summary, the glycan structures of an antibody can be labeled with a metal functionality using this approach. Furthermore, the functionality of the antibodies can be fully maintained by labeling the Fc glycans instead of using labeling reagents that target amino or thiol groups. This approach enables the possibility of using elemental, besides molecular mass spectrometry, for quantitative analyses or imaging experiments of antibodies in complex biological samples.
Chemical functionalization for quantitative spectroscopic labeling on macroscopically flat surfaces
(2018)
This chapter highlights the application of chemical derivatization (CD) to facilitate the quantification of surface functional groups being an important issue for a wide field of applications. The selective attachment of a chemical label to a surface functional group being afterwards exclusively detectable by a highly sensitive technique overcomes the problem of characterizing low amounts of functional groups on macroscopically flat surfaces. The most frequently employed methods include CD X-ray photoelectron spectroscopy, ultraviolet/visible absorption, and fluorescence spectroscopy, as well as time-of-flight secondary ion mass spectrometry. Herein, the basic conditions for the different techniques regarding the specific surface functional group which need to be quantified are discussed. Additionally, the substrate highly influences the compatibility of the corresponding method. Because not just the quantification but also the preparation of the desired application is important, a summary of different preparation methods for glass, polymer and gold substrates is presented.
Optical elemental analysis in the gas phase typically relies on electrically driven plasmas. As an alternative approach, laser-induced plasmas (LIPs) have been suggested but have so far been only scarcely used.
Here, a novel signal enhancement strategy for laser-based airborne plasma optical Emission spectroscopy for gas phase analytics is presented. In contrast to an electrically driven plasma, in the laser-induced analogue dynamic matter transport equilibrium builds up. The latter results in a rarefied density regime in the plasma core itself, surrounded by an area of compressed matter. The central rarefaction leads to a decrease in plasma intensity and analyte number density, both of which are detrimental for analytical purposes. Since the repetitive ignition of LIPs is a transient process, a restoration of the former gaseous medium by other dynamically equilibrated diffusion processes would be favourable. The presented combination of an airborne LIP and an ultrasonic acoustic resonator yields a fourfold signal enhancement while the Background contribution of ubiquitous air is at the same time effectively suppressed. Since the entire enhancement effect occurs without contact, no additional sources for abrasive sample contamination are introduced.
Data processing in the calibration-free laser-induced breakdown spectroscopy (LIBS) is usually based on the solution of the radiative transfer equation along a particular line of sight through a plasma plume. The LIBS data processing is generalized to the case when the spectral data are collected from large portions of the plume. It is shown that by adjusting the optical depth and width of the lines the spectra obtained by collecting light from an entire spherical homogeneous plasma plume can be least-square fitted to a spectrum obtained by collecting the radiation just along a plume diameter with a relative error of 10 −11 or smaller (for the optical depth not exceeding 0.3) so that a mismatch of geometries of data processing and data collection cannot be detected by fitting. Despite the existence of such a perfect least-square fit, the errors in the line optical depth and width found by a data processing with an inappropriate geometry can be large. It is shown with analytic and numerical examples that the corresponding relative errors in the found elemental number densities and concentrations may be as high as 50% and 20%, respectively. Safe for a few found exceptions, these errors are impossible to eliminate from LIBS data processing unless a proper solution of the radiative transfer equation corresponding to the ray tracing in the spectral data collection is used.
Because of the globally increasing prevalence of diabetes, the need for accurate, efficient and at best miniaturized automated analytical systems for sugar detection in medical diagnostics and the food industry is still urgent. The development of molecular probes for sugars based on boronic acid receptors offers an excellent alternative to the kinetically slow enzyme-based sugar sensors. Moreover, by coupling such chelating units with dye scaffolds like BODIPYs (boron–dipyrromethenes), highly fluorescent sugar sensing schemes can be realized. In this work, a boronic acid-functionalized BODIPY probe was developed, which binds selectively to fructose’s adjacent diols to form cyclic boronate esters. Placement of an amino group in direct neighborhood of the boronic acid moiety allowed us to obtain a broad working range at neutral pH, which distinguishes the probe from the majority of systems working only at pH > 8, while still meeting the desired sensitivity in the micro-molar range due to a pronounced analyte-induced fluorescence increase. To enhance the applicability of the test in the sense described above, integration with a microfluidic chip was achieved. Here, fructose was selectively detected by fluorescence with similar sensitivity in real time on chip, and an assay for the straightforward detection of sugar in (colored) sodas without sample clean-up was established.
Highly emissive phenanthrene-fused boron–dipyrromethene (PBDP) dyes have been spectroscopically characterized in a series of solvents. The influence of different substituents (-H,
-I, -CN, -DMA or a 15C5-crown ether) in the para-position of a phenyl ring attached to the meso-position of the BODIPY core is discussed. This family of dyes has an intense emission at lambda > 630 nm, with fluorescence quantum yields between 0.7 and 1.0 in all solvents studied, except in the case of the dimethylamino-substituted
derivative, PBDP-DMA, which undergoes excited-state intramolecular charge transfer (CT), leading to broadband dual fluorescence in highly polar solvents. Introduction of a weaker electron donor such as a benzocrown to the meso-position is not able to trigger a second (charge or electron transfer) process and, interestingly, heavy atom (iodine, PBDP-I derivative) substitution at that moiety does also not have a relevant influence on the photophysics, i.e., enhanced intersystem crossing was not observed.
Electrochemical studies of PBDP-DMA complement the data reported and stress the fact that the decrease in fluorescence of PBDP-DMA in highly polar solvents is due to an excited-state CT process
rather than to a photoinduced electron transfer (PET).
Fluorescent sensory MIP (molecularly imprinted polymer) particles were combined with a droplet-based 3D microfluidic system for the selective determination of a prototype small-molecule analyte of environmental concern, 2,4-dichlorophenoxyacetic acid or 2,4-D, at nanomolar concentration directly in water samples. A tailor-made fluorescent indicator cross-linker was thus designed that translates the binding event directly into an enhanced fluorescence signal. The phenoxazinone-type cross-linker was co-polymerized into a thin MIP layer grafted from the surface of silica microparticles following a RAFT (reversible addition-fragmentation chain transfer) polymerization protocol. While the indicator cross-linker outperformed its corresponding monomer twin, establishment of a phase-transfer protocol was essential to guarantee that the hydrogen bond-mediated signalling mechanism between the urea binding site on the indicator cross-linker and the carboxylate group of the analyte was still operative upon real sample analysis. The latter was achieved by integration of the fluorescent core-shell MIP sensor particles into a modular microfluidic platform that allows for an in-line phasetransfer assay, extracting the analyte from aqueous sample droplets into the organic phase that contains the sensor particles. Real-time fluorescence determination of 2,4-D down to 20 nM was realized with the system and applied for the analysis of various surface water samples collected from different parts of the world.