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Over the last few years, there has been a growing interest to apply spectroscopic methods to the agricultural field for better understanding of soil properties and for efficient, sustainable management of arable land. Within the project I4S (intelligence for soil), funded by the BMBF, an integrated system for site-specific soil fertility management is developed, consisting of different sensors like X-Ray fluorescence analysis (XRF), near-infrared spectroscopy (NIR) and laser-induced breakdown spectroscopy (LIBS). LIBS provides a fast and simultaneous multi-element analysis with little to no sample preparation, which makes it a suitable method for real-time analysis on the field.
The quantification of macro and micro nutrients in soils with LIBS is challenging due to matrix effects, different levels of moisture content and varying grain sizes. First studies revealed that the problems with matrix effects can be overcome by using well characterised soils as reference materials and chemometric tools like Partial Least Squares Regression (PLSR) for calibration.
The next step was to investigate the influence of moisture and grain sizes on the LIBS signal, which is a big issue when measuring directly on the field. The results showed that the LIBS signal decreases exponentially with increasing moisture content, as most of the laser energy is used for vaporising the water. With moisture contents of 30 % or higher almost no signal can be detected. This decrease is more severe for sandy soils than for clay soils. First tests of different grain size distributions indicate that the variation of the LIBS signal increases with growing amounts of larger grains. This results in a higher standard deviation, because of a poorer reproducibility of the plasma formation and plasma characteristic. With the help of chemometric tools the influence of moisture and grain sizes should be implemented in the calibration model for accurate analysis of nutrient composition in agricultural soils.
Over the last few years, there has been a growing interest to apply spectroscopic methods to the agricultural field for better understanding of soil properties and for efficient, sustainable management of arable land. Within the project I4S (intelligence for soil), funded by the BMBF, an integrated system for site-specific soil fertility management is developed, consisting of different sensors like X-Ray fluorescence analysis (XRF), near-infrared spectroscopy (NIR) and laser-induced breakdown spectroscopy (LIBS). LIBS provides a fast and simultaneous multi-element analysis with little to no sample preparation, which makes it a suitable method for real-time analysis on the field.
The quantification of macro and micro nutrients in soils with LIBS is challenging due to matrix effects, different levels of moisture content and varying grain sizes. First studies revealed that the problems with matrix effects can be overcome by using well characterised soils as reference materials and chemometric tools like Partial Least Squares Regression (PLSR) for calibration.
The next step was to investigate the influence of moisture and grain sizes on the LIBS signal, which is a big issue when measuring directly on the field. The results showed that the LIBS signal decreases exponentially with increasing moisture content, as most of the laser energy is used for vaporising the water. With moisture contents of 30 % or higher almost no signal can be detected. This decrease is more severe for sandy soils than for clay soils. First tests of different grain size distributions indicate that the variation of the LIBS signal increases with growing amounts of larger grains. This results in a higher standard deviation, because of a poorer reproducibility of the plasma formation and plasma characteristic. With the help of chemometric tools the influence of moisture and grain sizes should be implemented in the calibration model for accurate analysis of nutrient composition in agricultural soils.
Over the last few years, there has been a growing interest to apply spectroscopic methods to the agricultural field for better understanding of soil properties and for efficient, sustainable management of arable land. Within the project I4S (intelligence for soil), funded by the BMBF, an integrated system for site-specific soil fertility management is developed, consisting of different sensors like X-Ray fluorescence analysis (XRF), near-infrared spectroscopy (NIR) and laser-induced breakdown spectroscopy (LIBS). LIBS provides a fast and simultaneous multi-element analysis with little to no sample preparation, which makes it a suitable method for real-time analysis on the field.
The quantification of macro and micro nutrients in soils with LIBS is challenging due to matrix effects, different levels of moisture content and varying grain sizes. First studies revealed that the problems with matrix effects can be overcome by using well characterised soils as reference materials and chemometric tools like Partial Least Squares Regression (PLSR) for calibration.
The next step was to investigate the influence of moisture and grain sizes on the LIBS signal, which is a big issue when measuring directly on the field. The results showed that the LIBS signal decreases exponentially with increasing moisture content, as most of the laser energy is used for vaporising the water. With moisture contents of 30 % or higher almost no signal can be detected. This decrease is more severe for sandy soils than for clay soils. First tests of different grain size distributions indicate that the variation of the LIBS signal increases with growing amounts of larger grains. This results in a higher standard deviation, because of a poorer reproducibility of the plasma formation and plasma characteristic. With the help of chemometric tools the influence of moisture and grain sizes should be implemented in the calibration model for accurate analysis of nutrient composition in agricultural soils.
In den letzten Jahrzehnten ist die Nachfrage nach kostengünstigen und flächendeckenden Kartierungsmöglichkeiten im Hinblick auf eine ertragssteigernde und umweltfreundlichere Bewirtschaftung von landwirtschaftlichen Nutzflächen stark gestiegen. Hierfür eignen sich spektroskopische Methoden wie die Röntgenfluoreszenzanalyse (RFA), Raman- und Gammaspektroskopie sowie die laserinduzierte Plasmaspektroskopie (LIBS). In Abhängigkeit von der Funktionsweise der jeweiligen Methoden werden Informationen zu verschiedensten Bodeneigenschaften wie Nährelementgehalt, Textur und pH-Wert erhalten.
Ziel dieser Arbeit ist die Entwicklung eines Online-LIBS-Verfahrens zur Nährelementbestimmmung und Kartierung von Ackerflächen. Die LIBS ist eine schnelle und simultane Multielementanalyse bei der durch das Fokussieren eines hochenergetischen Laserpulses Probenmaterial von der Probenoberfläche ablatiert wird und in ein Plasma überführt wird. Beim Abkühlen des Plasmas wird Strahlung emittiert, welche Rückschlüsse über die elementare Zusammensetzung der Probe gibt. Diese Arbeit ist im Teilprojekt I4S (Intelligenz für Böden) im Forschungsprogramm BonaRes (Boden als nachhaltige Ressource für die Bioökonomie) des Bundesministerium für Bildung und Forschung (BMBF) entstanden. Es wurden insgesamt 651 Bodenproben von verschiedenen Test-Agrarflächen unterschiedlichster Standorte Deutschlands gemessen, ausgewertet und zu Validierungszwecken mit entsprechender Referenzanalytik wie die Optische Emissionsspektroskopie mittels induktiv gekoppeltem Plasma (ICP-OES) und die wellenlängendispersive Röntgenfluoreszenzanalyse (WDRFA) charakterisiert.
Für die Quantifizierung wurden zunächst die Messparameter des LIBS-Systems auf die Bodenmatrix optimiert und für die Elemente geeignete Linien ausgewählt sowie deren Nachweisgrenzen bestimmt. Es hat sich gezeigt, dass eine absolute Quantifizierung basierend auf einem univariaten Ansatz aufgrund der starken Matrixeffekte und der schlechten Reproduzierbarkeit des Plasmas nur eingeschränkt möglich ist. Bei Verwendung eines multivariaten Ansatz wie der Partial Least Squares Regression (PLSR) für die Kalibrierung konnten für die Nährelemente im Vergleich zur univariaten Variante Analyseergebnisse mit höherer Güte und geringeren Messunsicherheiten ermittelt werden. Die Untersuchungen haben gezeigt, dass das multivariate Modell weiter verbessert werden kann, indem mit einer Vielzahl von gut analysierten Böden verschiedener Standorte, Bodenarten und einem breiten Gehaltsbereich kalibriert wird. Mithilfe der Hauptkomponentenanalyse (PCA) wurde eine Klassifizierung der Böden nach der Textur realisiert. Weiterhin wurde auch eine Kalibrierung mit losem Bodenmaterial erstellt. Trotz der Signalabnahme konnten für die verschiedenen Nährelemente Kalibriergeraden mit ausreichender, analytischer Güte erstellt werden.
Für den Einsatz auf dem Acker wurde außerdem der Einfluss von Korngröße und Feuchtigkeit auf das LIBS-Signal untersucht. Die unterschiedlichen Korngrößen haben nur einen geringen Einfluss auf das LIBS-Signal und das Kalibriermodell lässt sich durch entsprechende Proben leicht anpassen. Dagegen ist der Einfluss der Feuchtigkeit deutlich stärker und hängt stark von der Bodenart ab, sodass für jede Bodenart ein separates Kalibriermodell für verschiedene Feuchtigkeitsgehalte erstellt werden muss. Mithilfe der PCA kann der Feuchtigkeitsgehalt im Boden grob abgeschätzt werden und die entsprechende Kalibrierung ausgewählt werden.
Diese Arbeit liefert essentielle Informationen für eine Echtzeit-Analyse von Nährelementen auf dem Acker mittels LIBS und leistet einen wichtigen Beitrag zu einer fortschrittlichen und zukunftsfähigen Nutzung von Ackerflächen.
The development of quick and simple optical sensing technologies for Endocrine Disrupting Chemicals (EDCs) is needed to facilitate monitoring of these substances to ensure consumer safety. Optical sensing was achieved against phthalates acting as EDC that have host guest interaction with an intercalated Metal-organic framework (MOF), resulting in a fluorescence emission upon excitation. The fluorescent turn-on signal was generated by using a fluorophore with a structural component that has little fluorescence unless excimers are formed. Strategies to engineer functional MOF structures suitable for sensing EDC phthalates were developed, and the characterization of the MOFs with and without present phthalates was done by single crystal XRD, PXRD, RAMAN and Thermogravimetry. Extensive photo-physical characterization of host-guest complexes of different phthalates and the MOF as well as the resulting exciplex fluorescence was performed. Photo physical characterization revealed an analyte specific fluorescence fingerprint that allows discerning even minute changes in chemical structures of the analyte and therefore paving the way for sensing tools in real world analytical applications. The presented capability of MOFs to sense EDCs is envisioned to complement established methods from analytical chemistry such as mass spectrometry based methods which can’t be used on site and are often associated with infrastructural capacity constraints
Zeolitic imidazolate framework (ZIF) hybrid fluorescent nanoparticles and ZIF antibody conjugates have been synthesized, characterized, and employed in lateral-flow immunoassay (LFIA). The bright fluorescence of the conjugates and the possibility to tailor their mobility gives a huge potential for diagnostic assays. An enzyme-linked immunosorbent assay (ELISA) with horseradish peroxidase (HRP) as label, proved the integrity, stability, and dispersibility of the antibody conjugates, LC-MS/MS provided evidence that a covalent link was established between these metal-organic frameworks and lysine residues in IgG antibodies.
We present the optical sensing of phthalate Esters (PAEs), a group of endocrine-disrupting chemicals. The sensing takes place as changes in the fluorescence emission intensity of aminopyrene covalently bound to the organic ligands of the metal−organic framework compound ZIF-8. In the presence of PAEs, a quenching of the fluorescence emission is observed. We evaluated strategies to engineer colloidal size distribution of the sensing particles to optimize the sensory response to PAEs. A thorough characterization of the modified ZIF-8 nanoparticles included powder X-ray diffractometry, transmission electron microscopy, high-performance liquid chromatography, and photophysical characterization. The presented capability of the fluorophore-functionalized ZIF-8 to sense PAEs complements established methods such as chromatography-based procedures, which cannot be used on-site and paves the way for future developments such as hand-held quick sensing devices.
Lignin is a highly aromatic low value biomass residue, which can be utilized for chemicals, fuels and materials production. In recent years, significant attention has focused on adsorber materials based on lignin. However, only 5% of the available lignin is exploited worldwide, thus significant opportunities for materials development still exist. Lignin has been vastly utilized as a feedstock for the synthesis of adsorbers for the removal of dyes and toxic organic molecules . To improve adsorption capacity, lignin can be chemically modified with oxygen-, nitrogen-, or sulfur-containing functional groups. Most frequently the phenolic groups of lignin were modified. In order to extend the application of lignin as adsorbers, we are especially interested in the chemical modification of this natural resource with a bio-based linear difluoro oligomers LOx (di- or monofunctional) or a heterocyclic monomer (Figure).
The development of new fluorescent organic probes effective in the NIR-II region is currently a fast-growing field and represents a challenge in the domain of medical imaging. In this study, we have designed and synthesized an innovative series of aza-boron dipyrromethenes emitting in the NIR-II region. We have investigated the effect of different water-solubilizing groups not only on the photophysical properties of the compounds but also on their in vitro and in vivo performance after bioconjugation to the antibody trastuzumab. Remarkably, we discovered that the most lipophilic compound unexpectedly displayed the most favorable in vivo properties after bioconjugation. This underlines the profound influence that the fluorophore functionalization approach can have on the efficiency of the resulting imaging agent.
Optical Thermometry is popular among researchers because of its non-contact, high sensitivity, and fast measurement properties. In the present experiment, Er3+/Yb3+/K+ co-doped NaYF4 nanoparticles with different K+ concentrations were synthesized by solvothermal method, and the samples showed bright upconversion green emission under the excitation of a 980 nm laser. The powder X-ray diffractometer and transmission electron microscope were used to characterize the crystal structure and its surface morphology, respectively. The spectral characteristics of nanoparticles with K+ doping concentration from 10% to 30% (Molar ratio) were investigated by fluorescence spectroscopy, and it was observed that the fluorescence intensity reached the maximum at the K+ concentration of 20%, after which the intensity weakened when the K+ content continued to increase. According to the dependence between the luminescence intensity of the sample and the laser power density and fluorescence lifetime, the intrinsic mechanism was carefully investigated. Temperature-dependent spectra of the samples were recorded in the temperature range of 315–495 K, and the maximum values of absolute sensitivity (Sa) and relative sensitivity (Sr) were measured at 0.0041 K−1 (455 K) and 0.9220%K−1 (315 K). The experimental results show that K+/Er3+/Yb3+ triple-doped NaYF4 green fluorescent nanoparticles (GFNs) have good prospects for applications in display devices, temperature sensing, and other fields.
DNA origami nanostructures provide a platform where dye molecules can be arranged with nanoscale accuracy allowing to assemble multiple fluorophores without dye−dye aggregation. Aiming to develop a bright and sensitive ratiometric sensor system, we systematically studied the optical properties of nanoarrays of dyes built on DNA Origami platforms using a DNA template that provides a high versatility of label choice at minimum cost. The dyes are arranged at distances, at which they efficiently interact by Förster resonance energy transfer (FRET). To optimize array brightness, the FRET efficiencies between the donor fluorescein (FAM) and the acceptor cyanine 3 were determined for different sizes of the array and for different arrangements of the dye molecules within the array. By utilizing nanoarrays providing optimum FRET efficiency and brightness, we subsequently designed a ratiometric pH nanosensor using coumarin 343 as a pH-inert FRET donor and FAM as a pHresponsive acceptor. Our results indicate that the sensitivity of a ratiometric sensor can be improved simply by arranging the dyes into a well-defined array. The dyes used here can be easily replaced by other analyte-responsive dyes, demonstrating the huge potential of DNA nanotechnology for light harvesting, signal enhancement, and sensing schemes in life sciences.
The DNA origami technique has great potential for the development of brighter and more sensitive reporters for fluorescence based detection schemes such as a microbead-based assay in diagnostic applications. The nanostructures can be programmed to include multiple dye molecules to enhance the measured signal as well as multiple probe strands to increase the binding strength of the target oligonucleotide to these nanostructures. Here we present a proof-of-concept study to quantify short oligonucleotides by developing a novel DNA origami based reporter system, combined with planar microbead assays. Analysis of the assays using the VideoScan digital imaging platform showed DNA origami to be a more suitable reporter candidate for quantification of the target oligonucleotides at lower concentrations than a conventional reporter that consists of one dye molecule attached to a single stranded DNA. Efforts have been made to conduct multiplexed analysis of different targets as well as to enhance fluorescence signals obtained from the reporters. We therefore believe that the quantification of short oligonucleotides that exist in low copy numbers is achieved in a better way with the DNA origami nanostructures as reporters.
DNA origami nanostructures provide a platform where dye molecules can be arranged with nanoscale accuracy allowing to assemble multiple fluorophores without dye–dye aggregation. Aiming to develop a bright and sensitive ratiometric sensor system, we systematically studied the optical properties of nanoarrays of dyes built on DNA origami platforms using a DNA template that provides a high versatility of label choice at minimum cost. The dyes are arranged at distances, at which they efficiently interact by Förster resonance energy transfer (FRET). To optimize array brightness, the FRET efficiencies between the donor fluorescein (FAM) and the acceptor cyanine 3 were determined for different sizes of the array and for different arrangements of the dye molecules within the array. By utilizing nanoarrays providing optimum FRET efficiency and brightness, we subsequently designed a ratiometric pH nanosensor using coumarin 343 as a pH-inert FRET donor and FAM as a pH-responsive acceptor. Our results indicate that the sensitivity of a ratiometric sensor can be improved simply by arranging the dyes into a well-defined array. The dyes used here can be easily replaced by other analyte-responsive dyes, demonstrating the huge potential of DNA nanotechnology for light harvesting, signal enhancement, and sensing schemes in life sciences.
Silver nanoparticles (AgNPs) nowadays appear in close to 24% of consumer products that contain engineered nanomaterials. Thus, they are expected to be released into the environment, where their fate and effect are still undetermined. Considering the evidenced efficacy of the single particle Inductively Coupled Plasma – Mass Spectrometry (sp ICP-MS) technique in the study of nanomaterials, this work reports on the use of sp ICP-MS along with an online dilution sample introduction system for the direct analysis of untreated and spiked seawater samples, as part of a larger scale experiment studying the fate of Ag (ionic and nanoparticles) in seawater mesocosm systems. Silver nanoparticles coated with branched polyethyleneimine (BPEI@AgNPs) or ionic silver (Ag+) were introduced gradually into the seawater mesocosm tanks at very low, environmentally relevant concentrations (50 ng Ag L− 1 per day, for 10 consecutive days, up to a total of 500 ng Ag L− 1 ), and samples were collected and analyzed daily, within a consistent time window. Using very low detector dwell time (75 μs) and specialized data treatment, information was obtained on the nanoparticles’ size distribution and particle number concentration, as well as the ionic silver content, of both the AgNPs and the Ag+ treated seawater mesocosm tanks. The results for the AgNP treated samples indicated the rapid degradation of the added silver particles, and the subsequent increase of ionic silver, with recoveries close to 100% for the first days of the experiment. On the other hand, particle formation was observed in the Ag+ treated seawater tanks, and even though the number concentration of silver-containing nanoparticles increased throughout the experiment, the amount of silver per particle remained relatively constant from the early days of the experiment. In addition, the online dilution sample introduction system for the ICP-MS proved capable of handling the untreated seawater matrix without significant contamination issues and downtime, while the low dwell time and data treatment procedure developed were shown to be suitable for the analysis of nanomaterials at the low nm-scale, despite the complex and heavy matrix introduced into the ICP-MS.
In the interest of exploring their potential in the field of single particle analysis, a Microdroplet Generator (MDG) was coupled to an ICP-ToF-MS. Isotopic Dilution Analysis was also incorporated for the size determination of three different Platinum nanoparticles samples (50, 63 and 70 nm). The performance of the technique was validated by comparison to traditional size characterization techniques (sp-ICP-ToF-MS, TEM), while the robustness of the technique was proven by incorporating NaCl in the samples’ matrix, up to 100 mg/L.
Bio-panning is a common process involved in recombinant antibody selection against defined targets. The biopanning process aims to isolate specific antibodies against an antigen via affinity selection from a phage display library. In general, antigens are immobilized on solid surfaces such as polystyrene plastic, magnetic beads, and nitrocellulose. For high-throughput selection, semi-automated panning selection allows simul-taneous panning against multiple target antigens adapting automated particle processing systems such as the KingFisher Flex. The system setup allows for minimal human intervention for pre-and post-panning steps such as antigen immobilization, phage rescue, and amplification. In addition, the platform is also adaptable to perform polyclonal and monoclonal ELISA for the evaluation process. This chapter will detail the protocols involved from the selection stage until the monoclonal ELISA evaluation with important notes attached at the end of this chapter for optimization and troubleshooting purposes.
The spatial distribution and concentration of lanthanide activator and sensitizer dopant ions are of key importance for the luminescence color and efficiency of upconverting nanoparticles (UCNPs). Quantifying dopant ion distributions and intermixing, and correlating them with synthesis methods require suitable analytical techniques. Here, X-ray photoelectron spectroscopy depth-profiling with tender X-rays (2000–6000 eV), providing probe depths ideally matched to UCNP sizes, is used to measure the depth-dependent concentration ratios of Er3+ to Yb3+, [Er3+]/[Yb3+], in three types of UCNPs prepared using different reagents and synthesis methods. This is combined with data simulations and inductively coupled plasma-optical emission spectroscopy (ICP-OES) measurements of the lanthanide ion concentrations to construct models of the UCNPs’ dopant ion distributions. The UCNP sizes and architectures are chosen to demonstrate the potential of this approach. Core-only UCNPs synthesized with XCl3·6H2O precursors (β-phase) exhibit a homogeneous distribution of lanthanide ions, but a slightly surface-enhanced [Er3+]/[Yb3+] is observed for UCNPs prepared with trifluroacetate precursors (α-phase). Examination of Yb-core@Er-shell UCNPs reveals a co-doped, intermixed region between the single-doped core and shell. The impact of these different dopant ion distributions on the UCNP's optical properties is discussed to highlight their importance for UCNP functionality and the design of efficient UCNPs.
Rapid tests and assays to be used outside of a laboratory for non-trained personal and also at a point of need are becoming increasingly important in areas such as health, food, security, or the environment. Specially on that regard, paper-based sensors are emerging as a new class of devices because they fulfil the requisites of the "World Health Organization" to be ASSURED: affordable, sensitive, specific, user-friendly, rapid and robust, equipment free and deliverable to end-users. The physical, chemical and mechanical properties of cellulose or glass fiber paper in combination with the facility of preparation are making these materials of great interest while looking for cost-efficient and green alternatives for device production technologies. To improve the sensitivity of these systems, a particularly promising approach is the employment of gated indicator delivery systems using preorganized nanoscopic solid structures incorporated on paper strips to produce an exponential amplification of the detectable signal. Having in mind these concepts, several examples of (bio)gated materials incorporated into sensing membranes will be presented for the detection of small organic molecules, having fluorescence or electrochemiluminescence signal as output signal. Compared with fluorescence, it has been demonstrated that the non-optical excitation has significantly reduced the background signal, and with the help of a portable potentiostat in combination with a home-made 3D-printed case fitted onto a smartphone, the sensitivity of the sensing system has been improved tremendously, from the lower ppb range (fluorescence) to the lower ppt range. With this study, the applicability of ECL detection on paper strips in combination with gated indicator-releasing materials has been demonstrated for the first time, presenting a novel synergistic match. Considering the modularity of the system developed, the platform technology potential is obvious, promising expansion of the general concept to many other analytes, applications and scenarios.