Lanthanide grafted phenanthroline-polymer for physiological temperature range sensing

Accurate measurement of the temperature is crucial as it determines the dynamics of almost any system. Conventional contact thermometers are not well suited for small scale measurements. Temperature dependent luminescent materials, i.e. materials that emit light of different color at different temperature, are therefore of particular interest in the development of noncontact thermometers. Luminescent materials consisting of lanthanide ions feature high thermal sensitivity, high photostability and high quantum yields. These ions possess very interesting light emitting properties. By anchoring them onto different backbone materials, their light absorption is increased. The search for a backbone that allows the sensor to be active in a defined temperature range, with a high detection sensitivity is ongoing. This work reports the first insoluble phenanthroline-polymer (phen-polymer) backbone on which europium (Eu3+) and terbium (Tb3+) trifluoroacetylacetone (tfac) complexes are easily grafted in a 1 : 1 metal ratio in order to create a noncontact temperature sensor. Two clear, discriminable emission peaks were observed during the photoluminescence study at room temperature, demonstrating that this material can be used as a ratiometric thermometer. The characteristic emission peak correlated to Eu3+ transition is slightly stronger than the emission peak of Tb3+ transition, resulting in a yellow emission color. The maximum value of the relative temperature sensitivity was calculated to be 2.3404% K-1 (340 K), which indicated good thermometric behavior. The emission color of the designed phen-polymer@Eu,Tb_tfac changed from light green (260 K) to orange-red (460 K). The thermometer can therefore be used as a ratiometric noncontact temperature sensor in the broad physiological temperature range

Overview of N‐rich antennae investigated in lanthanide-based temperature sensing

The market share of noncontact temperature sensors is expending due to fast technological and medical evolutions. In the wide variety of noncontact sensors, lanthanide‐based temperature sensors stand out. They benefit from high photostability, relatively long decay times and high quantum yields. To circumvent their low molar light absorption, the incorporation of a light‐harvesting antenna is required. This review provides an overview of the nitrogen‐rich antennae in lanthanide‐based temperature sensors, emitting in the visible light spectrum, and discuss their temperature sensor ability. The N‐rich ligands are incorporated in many different platforms. The investigation of different antennae is required to develop temperature sensors with diverse optical properties and to create a diverse offer for the multiple application fields. First the molecular probes, consisting of small molecules, are discussed. Furthermore, the thermometer properties of ratiometric temperature sensors, based on di‐ and polynuclear complexes, metal‐organic‐frameworks, periodic mesoporous organosilicas and porous organic polymers, are summarized. The antenna mainly determines the application potential of the ratiometric thermometer. It can be observed that molecular probes are operational in the broad physiological range, metal‐organic‐frameworks are generally very useful in the cryogenic region, periodic mesoporous organosilica show temperature dependency in the physiological range and porous organic polymers are operative in the cryogenic to medium temperature range

Assessment of the trifluoromethyl ketone functionality as an alternative zinc-binding group for selective HDAC6 inhibition

Recent studies point towards the possible disadvantages of using hydroxamic acid-based zinc-binding groups in HDAC inhibitors due to e.g. mutagenicity issues. In this work, we elaborated on our previously developed Tubathian series, a class of highly selective thiaheterocyclic HDAC6 inhibitors, by replacing the benzohydroxamic acid function by an alternative zinc chelator, i.e., an aromatic trifluoromethyl ketone. Unfortunately, these compounds showed a reduced potency to inhibit HDAC6 as compared to their hydroxamic acid counterparts. In agreement, the most active trifluoromethyl ketone was unable to influence the growth of SK-OV-3 ovarian cancer cells nor to alter the acetylation status of tubulin and histone H3. These data suggest that replacement of the zinc-binding hydroxamic acid function with a trifluoromethyl ketone zinc-binding moiety within reported benzohydroxamic HDAC6 inhibitors should not be considered as a standard strategy in HDAC inhibitor development

Synthesis of nitrile-functionalized polydentate N-heterocycles as building blocks for covalent triazine frameworks

Covalent triazine frameworks (CTFs) based on polydentate ligands are highly promising supports to anchor catalytic metal complexes. The modular nature of CTFs allows to tailor the composition, structure, and function to its specific application. Access to a broad range of chelating building blocks is therefore essential. In this respect, we extended the current available set of CTF building blocks with new nitrile-functionalized N-heterocyclic ligands. This paper presents the synthesis of the six ligands which vary in the extent of the aromatic system and the denticity. The new building blocks may help in a rational design of enhanced support materials in catalysis

Dialdehyde carboxymethyl cellulose cross-linked chitosan for the recovery of palladium and platinum from aqueous solution

Platinum (Pt) and palladium (Pd) have widespread applications, such as in catalysts, jewelry, fuel cells, and electronics because of their favorable physical and chemical properties. Recovery of Pt and Pd from secondary sources is of great concern due to the increased market demand and limitation of the natural reserves of these precious metals. The aim of this research is to achieve recovery of Pt and Pd ions from dilute aqueous solution using dialdehyde of carboxymethyl cellulose (DCMC) crosslinked chitosan (Ch-DCMC). The DCMC was prepared by periodate oxidation of carboxymethyl cellulose (CMC). Both the DCMC and Ch-DCMC were characterized before and after Pt or Pd adsorption using Fourier-transformed infrared (FTIR) spectroscopy, X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM). The effect of cross-linking ratios of chitosan and DCMC (1:1, 1:0.8, 1:0.5, 1:0.25 and 1:0.1) on the Pt and Pd recovery was studied. The optimal cross-linking ratio was found to be 1:0.25 (chitosan: DCMC) with maximum adsorption capacity of 80.8 mg/g Pt and 89.4 mg/g Pd. High selectivity for Pt and Pd compared to base metals and common anions was achieved

N‐rich porous polymer with isolated Tb3+‐ions displays unique temperature dependent behavior through the absence of thermal quenching

The challenge of measuring fast moving or small scale samples is based on the absence of contact between sample and sensor. Grafting lanthanides onto hybrid materials arises as one of the most promising accurate techniques to obtain noninvasive thermometers. In this work, a novel bipyridine based porous organic polymer (bpyDAT POP) was investigated as temperature sensor after grafting with Eu(acac)(3)and Tb(acac)(3)complexes. The bpyDAT POP successfully showed temperature-dependent behavior in the 10-310 K range, proving the potential of amorphous, porous organic frameworks. We observed unique temperature dependent behavior. More intriguingly, instead of the standard observed change in emission as a result of a change in temperature for both Eu(3+)and Tb3+, the emission spectrum of Tb(3+)remained constant. This work provides framework- and energy-based explanations for the observed phenomenon. The conjugation in the bpyDAT POP framework is interrupted, creating energetically isolated Tb(3+)environments. Energy transfer from Tb(3+)to Eu(3+)is therefore absent, nor energy back transfer from Tb(3+)to bpyDAT POP ligand (i.e. no thermal quenching) is detected

Functionalized chitosan adsorbents allow recovery of palladium and platinum from acidic aqueous solutions

Platinum (Pt) and palladium (Pd) are precious metals considered critical in our society and are needed in a variety of sustainable technologies. Their scarcity urges the increase of recycling from secondary waste streams through new and efficient recovery techniques. Adsorption is an established recovery method for liquid streams, where chitosan shows promising results as a low-cost adsorbent, derived from biomass. This biopolymer is able to capture metals, but suffers from a low stability under acidic conditions and poor adsorbing properties. In this study, three new chitosan derivatives were synthesized and employed for Pd(II) and Pt(IV) recovery from acidic solutions. Specific and simple modifications were selected based on their known affinities for these metal ions and taking into account the principles of green chemistry. The prepared derivatives consist of 1,10-phenanthroline-2,9-dicarbaldehyde cross-linked chitosan (Ch-PDC), [2,2'-bipyridine]-5,5'-dicarbaldehyde cross-linked chitosan (Ch-BPDC) and glutaraldehyde cross-linked chitosan grafted with 8-hydroxyquinoline-2-carbaldehyde (Ch-GA-HQC). For all derivatives, the adsorption occurred fast and equilibrium reached within 30 min. The Langmuir isotherms revealed a maximum adsorption capacity for Pd(II) and Pt(IV) of respectively 262.6 mg g(-1) and 119.5 mg g(-1) for Ch-PDC, 154.7 mg g(-1) and 98.3 mg g(-1) for Ch-BPDC and 340.3 mg g(-1) and 203.9 mg g(-1) for Ch-GA-HQC. Such adsorption capacities are considerably higher compared to the biosorbents reported in the literature. Excellent physical properties in homo-and heterogeneous systems and high regeneration performances demonstrate that chitosan-based adsorbents are very promising for Pd(II) and Pt(IV) recovery from acidic solutions