Open Access

Molecularly imprinted polymers (MIPs) containing fluorescent probe monomers or crosslinkers that are covalently polymerized into the MIP network are powerful tools for the direct indication of analytes in a sample or a sample extract [1]. This direct incorporation not only allows the use of the diverse formats in which MIPs can be prepared for analytical applications but also allows the use of MIPs for real-time signal readout as well as for enrichment and readout, depending on the design of the assay. In addition, the presence of a dye in each step of the preparation process, starting with the prepolymerization mixture, provides a useful tool for monitoring the synthetic procedure to determine whether the intended complexes are being imprinted and/or whether unexpected or undesirable events are occurring during preparation. Naturally, in addition to the general requirement that such a functional dye must survive the polymerization process, the intended application and desired format must also take various factors into account before a specific dye scaffold is selected, i.e., the wavelength range of operation, the type of signal changes to be measured, possible internal referencing as well as possible multiplexing. Based on our experience in the development of fluorescent probe monomers and crosslinkers [2–5], this contribution offers (young) researchers a guide to selecting the appropriate dye for their MIP.

Reactive extrusion (REx) is emerging as a powerful technology for the continuous and solventless production of modified lignins. However, the optimization of REx-based processes for modifying lignin relies on offline lignin analytics, which are time-consuming and heavily influenced by sample preparation. This study integrated near- infrared (NIR) spectroscopy into a twin-screw extruder to monitor in real time the modification of softwood kraft lignin via esterification with octenyl succinic anhydride (OSA). The NIR data was processed by means of chemometric methods. Temperature and screw configuration were found to influence the esterification of lignin. Combining these results with offline lignin analytics, 120 ◦ C was selected as the optimal temperature in conjunction with the integration of kneading elements into the screw profile, to yield OSA-lignin esters with ≥ 50% degree of modification. The product output was successfully scaled up sevenfold while using NIR spectroscopy to monitor the extrusion. In addition, the broader applicability of this inline monitoring method was demonstrated by using a biorefinery lignin from hardwood. The target degree of modification was achieved with minimal recalibration of process parameters. A space–time yield of up to 7 x 10 •day was realized, indicating the potential of this REx process for industrial adoption. Overall, this work provides a foundation for the development of a process analytical technology for monitoring lignin modification during REx that can be expanded to other lignin chemistries, thus providing scalable and adaptable solutions for adding value to lignin.

Over the past three decades, luminescent nanocrystals have evolved from a scientific curiosity into a versatile class of functional materials with applications spanning photonics, bioimaging, sensing, energy conversion, and quantum technologies. Throughout this development, Markus Haase has played a defining role in shaping the field through his pioneering contributions to colloidal semiconductor quantum dots and, in particular, lanthanide-doped upconverting nanocrystals. His work established fundamental synthetic strategies, provided mechanistic insight into particle formation and optical processes, and set new standards for reproducibility, characterization, and scientific rigor. This commemorative lecture brings together the perspectives of colleagues, former doctoral researchers, collaborators, and long-standing friends from the scientific community to celebrate Markus Haase's remarkable career and lasting scientific legacy. Beyond highlighting key milestones and breakthroughs, the presentation reflects on the qualities that have distinguished his work: intellectual curiosity, creativity, uncompromising scientific integrity, and the willingness to pursue challenging and unconventional research directions. Equally important, it acknowledges the personal values that have inspired generations of researchers—his honesty, loyalty, commitment, passion for science, and distinctive sense of humor. Together, these contributions have not only advanced the field of luminescent nanocrystals but have also left a lasting impact on the people and collaborations that continue to shape it.

The use of engineered nanoparticles of different size, shape, and composition is continuously increasing in life and materials sciences. This calls for methods and reference materials enabling the reliable and accurate determination of nanoparticle size, particle size distribution, shape, number concentration, degree of aggregation and agglomeration in different environments as well as for nanoparticle dispersibility and stability. We are currently building up and exploring a platform of lanthanide-based nanocrystals (LnNCs) and other functional nanoparticles with application-specifically tuned size, shape, composition, architecture, optical properties, and surface chemistry for emerging applications in life sciences and as reference and test materials. As a prerequisite for the broad applicability of these nanomaterials, we assess simple, robust, and easily up-scaleable synthesis protocols for LnNCs with defined morphologies and tunable optical properties [1], and the short-term and long-term stability of LnNCs with selected surface coatings in aqueous environments under different application-relevant conditions.[2] In addition to sensing and encoding applications, we are currently exploring the applicability of our LnNCs which can be prepared in large amounts in different shapes,. i.e., as spheres, bypyramids, or rods with excellent control of size and size distribution, as reference material candidates for sizing methods such as electron microscopy and small-angle X-ray scattering (SAXS) as well as for determination of particle number concentration. For spherical NPs, particle size can be easily determined from measurements of the diameter of by electron microscopy providing 2D information on a large number of dried nanoparticles deposited in vacuo on a solid substrate. However, for NPs with a different shape, this 2D-projection can be misleading. Here, new correlative approaches are needed for the complete 3D characterization for particles with a more complex shape [3] and non-spherical reference particles for establishing such methods and the implementation and validation of the respective data fitting routine. In this context, we are currently exploring the potential of differently sized functional nanoparticles as test and reference materials for size and particle number concentration (PNC) by SAXS and interlaboratory comparisons involving different SAXS expert groups.[4]

Luminescent particles such as spectrally shifting lanthanide-based nanocrystals (LnNCs) like NaYF4: Yb, Er, semiconductor quantum dots, and luminophore-labelled or doped silica and polymer particles are broadly applied in the life and material sciences. The identification of optimum particle architectures and surface chemistries for photonic applications requires quantitative spectroscopic studies of the application-relevant optical properties and simple methods for the determination of surface functionalities. In this context, photoluminescence studies of different luminescent nanocrystals are presented with focus on LnNCs. Also, methods for the determination of particle brightness and photoluminescence quantum yield are presented as well as examples for the determination of surface functionalities with optical assays.