Publications by authors named "Helmar Wiltsche"

Optical temperature sensors based on self-referenced readout schemes such as the emission ratio and the decay time are crucial for a wide range of applications, with the former often preferred due to simplicity of instrumentation. This work describes a new group of dually emitting dyes, platinum(II) pincer complexes, that can be used directly for ratiometric temperature sensing without an additional reference material. They consist of Pt(II) metal center surrounded by a pyridinedipyrrolide ligand (PDP) and a terminal ligand (benzonitrile, pyridine, 1-butylimidazol or carbon monoxide).

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  • Micropatterning MOFs with oriented pores is crucial for creating devices with specific directional properties, informed by their tunable chemical structure.* -
  • A patterned MOF film is developed using X-ray exposure and a photomask, allowing the film to decompose in certain areas while maintaining integrity elsewhere, functioning as both a resist and a porous material.* -
  • The resulting micropatterns, enhanced with fluorescent dyes, can be manipulated for various optical applications, such as creating diffraction gratings and controlling light responses, supporting advancements in microfabrication for photonic devices.*
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Sulfate groups on cellulose particles such as cellulose nanocrystals (CNCs) provide colloidal stability credit to electrostatic repulsion between the like-charged particles. The introduction of sodium counter cations on the sulfate groups enables drying of the CNC suspensions without irreversible aggregation. Less is known about the effect of other counter cations than sodium on extending the properties of the CNC particles.

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Glycosaminoglycans (GAGs) are biomacromolecules necessary for the regulation of different biological functions. In medicine, GAGs are important commercial therapeutics widely used for the treatment of thrombosis, inflammation, osteoarthritis and wound healing. However, protocols for the encapsulation of GAGs in MOFs carriers are not yet available.

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Acid digestion is usually required for metal determination in food samples. However, this step is usually performed in batch mode which is time consuming, labor intensive, and may lead to sample contamination. Flow digestion can overcome these limitations.

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  • The study examined how biodegradable magnesium (Mg) and its alloys (Mg2Ag and Mg10Gd) affect the growth and properties of MC3T3-E1 cells when they come into contact with the materials.
  • It was found that surface changes due to corrosion, especially crystal formation on Pure Mg and Mg2Ag after 8 days, negatively impact cell viability, while non-corroded surfaces allow for better cell survival.
  • Notably, Mg10Gd showed improved expression of collagen I and Runx2 markers for cell differentiation after 8 to 12 days, suggesting its potential benefits for orthopedic applications by enhancing osteointegration.
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An innovative interface between the torch and the entrance optics for inductively coupled plasma optical emission spectrometry (ICP-OES) is proposed. This system is capable of collecting all argon which was initially supplied to the torch, cooling and cleaning it and feeding most of the argon back to the outer gas port of the torch. Thereby, the total argon consumption could be reduced from 14 to 1.

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A low cost imaging set-up for optical chemical sensors based on NIR-emitting dyes is presented. It is based on a commercially available 2-CCD colour near infrared camera, LEDs and tailor-made optical sensing materials for oxygen and pH. The set-up extends common ratiometric RGB imaging based on the red, green and blue channels of colour cameras by an additional NIR channel.

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A novel automated liquid/liquid extraction system was developed for the determination of trace contaminants in unalloyed, alloyed and highly alloyed steels and super alloys. In the presented batch extraction system the aqueous phase and the non-water miscible organic phase were brought into close phase contact by high-speed stirring with a magnetic stir bar. Iodide complexes of Ag, Bi, Cd, Pb, Sb, Sn, Tl, and Zn were extracted from aqueous steel digests into 4-methylpentan-2-one (MIBK) containing 20 g L(-1) trioctylphosphine oxide.

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Femtosecond laser ablation inductively coupled plasma mass spectrometry was used for the quantification of 23 metallurgical relevant elements in unalloyed, alloyed and highly alloyed steels, and super alloys. It was shown that by using scanning mode ablation with large ablation spot diameters (250 μm), stable and representative sampling can be achieved for the majority of elements, except for bismuth and lead. For Bi and Pb up to 46%, temporal relative standard deviation (TRSD) was encountered, whereas for most other elements, the TRSDs were below 10%.

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To achieve separation of isobaric interferences and minimization of matrix related interferences for laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) electrothermal heating of laser generated aerosols was investigated by analyzing a range of solid samples: NIST SRM 610, MBH B26, BAM M381, BAM M601 and Tantalum. ICPMS measurements showed that individual elements can be removed from the laser-generated aerosol at characteristic temperatures for different solid materials. Signal reduction as high as 3 orders of magnitude were achieved for volatile elements, such as Ag and Cd when heating laser-generated aerosol of NIST SRM 610 silicate glass.

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