Acid dissociation and the subsequent solvation of the charged fragments at ultracold temperatures in nanoenvironments, as distinct from ambient bulk water, are relevant to atmospheric and interstellar chemistry but remain poorly understood. Here we report the experimental observation of a nanoscopic aqueous droplet of acid formed within a superfluid helium cluster at 0.37 kelvin. High-resolution mass-selective infrared laser spectroscopy reveals that successive aggregation of the acid HCl with water molecules, HCl(H2O)n, readily results in the formation of hydronium at n = 4. Accompanying ab initio simulations show that undissociated clusters assemble by stepwise water molecule addition in electrostatic steering arrangements up to n = 3. Adding a fourth water molecule to the ringlike undissociated HCl(H2O)3 then spontaneously yields the compact dissociated H3O+(H2O)3Cl- ion pair. This aggregation mechanism bypasses deep local energy minima on the n = 4 potential energy surface and offers a general paradigm for reactivity at ultracold temperatures.
This tutorial review focuses on the recent development of diverse synthetic approaches and possibilities for chemical tuning of the size, shape, and morphology, as well as properties such as luminescence, of rare earth tungstate and molybdate materials. The use of rare earth tungstate and molybdate nano- and micromaterials as single materials for the generation of white light is reviewed. Additionally, the use of these materials as red phosphors in phosphor-converted white light emitting diodes (pc-WLEDs) when employing GaN or InGaN chips as the primary light source is explored.
Covalent Organic Frameworks (COFs), an emerging class of crystalline porous materials,are proposed as anew type of support for grafting lanthanide ions (Ln 3+ )a nd employing these hybrid materials as ratiometric luminescent thermometers.ATpBpy-COF-prepared from 1,3,5-triformylphloroglucinol (Tp) and 2,2'-bipyridine-5,5'-diamine (Bpy) grafted with Eu/Tb and Dy acetylacetone (acac) complexes can be successfully used as al uminescent thermometer in the 10-360 K( Eu) and 280-440 K( Tb) ranges with good sensing properties (thermal sensitivity up to 1.403 %K À1 ,t emperature uncertainty dT < 1Kabove110 K). Forthe Eu/Tb systems,we observe an unusual and rarely reported behavior,t hat is,n o thermal quenching of the Tb 3+ emission, aresult of the absence of ion-to-ligand/host energy back-transfer.T he LnCOF materials proposed here could be anew class of materials employed for temperature-sensing applications following up on the wellknownluminescent metal-organic framework thermometers.
Recently, covalent organic frameworks (COFs) have emerged as an interesting class of porous materials, featuring tunable porosity and fluorescence properties based on reticular construction principles. Some COFs display highly emissive monocolored luminescence, but attaining white-light emission from COFs is difficult as it must account for a wide wavelength range. White-light emission is highly desired for solid-state lighting applications, and obtaining it usually demands the combination of red-, green-, and blue-light components. Hence, to achieve the targeted white-light emission, we report for the first time grafting of lanthanides (Eu 3+ /Tb 3+ ) on a two-dimensional imine COF (TTA-DFP-COF). We studied the luminescence properties of the hybrid materials prepared by anchoring Eu 3+ (red light) and Tb 3+ (green light) β-diketonate complexes onto the TTA-DFP-COF. Reticular construction is exploited to design strong coordination of Eu 3+ and Tb 3+ ions into nitrogen-rich pockets of the imine COF. Mixed Eu 3+ /Tb 3+ materials are then prepared to incorporate red and green components along with the inherent blue light from the organic moieties of the COF to produce white-light emission. We show that COFs have the potential for hosting Eu 3+ and Tb 3+ complexes, which can be tuned to obtain desired excitations for applications in the field of optoelectronics, microscopy, optical sensing, and bioassay.
A computational study using the B3LYP/6-31G(d) level of theory shows that the chemisorptions of one and two hydrogen atoms on the external surface of (3,3), (4,4), (5,5), and (6,6) armchair single-walled carbon nanotubes (SWNTs) are exothermic processes. Our results clearly indicate that two hydrogen atoms favor binding at adjacent positions rather than at alternate carbon sites. This is different from the results reported on zigzag nanotubes (Yang et al. J. Phys. Chem. B 2006, 110, 6236). In general, the exothermicity of hydrogen chemisorption decreases as the diameter of the armchair nanotubes increases, which is in contrast to the observation for zigzag-type structures. The chemisorptions of one and two hydrogen atoms significantly alter the C−C bond lengths of the nanotube in the vicinity of hydrogen addition as a result of a change in hybridization of the carbon atom(s) at the chemisorption site(s) from sp2 to sp3. The effect of increasing the length of the SWNTs on the geometries and the reaction energies of hydrogen chemisorption has also been explored.
This work presents a novel anticounterfeiting strategy based on a material changing its emission color in response to a change in the excitation sources—where a single ultraviolet (UV) or near‐infrared (NIR) light source are employed or simultaneously using two excitation sources (xenon lamp and NIR laser). Following this approach, various combinations of lanthanide (Ln3+)‐doped LiLuF4/LiYF4 core/shell nanoparticles are prepared, providing a promising route to design flexible nanomaterials, as well as already a small library of luminescent materials, which change color when varying the excitation source (UV, NIR or both UV and NIR). Aside from excitation source‐dependent color change, these materials additionally show excitation‐source power‐dependent color change. This work exploits the possibility of developing a new class of multimode anticounterfeit nanomaterials, with excellent performance, which would be almost impossible to mimic or replicate, providing a very high level of security.
Lanthanide-doped luminescent nanoparticles are an appealing system for nanothermometry with biomedical applications due to their sensitivity, reliability and minimally invasive thermal sensing properties. Here, we propose four unique hybrid organic-inorganic materials prepared by combining β-NaGdF4 and PMOs (Periodic Mesoporous Organosilica) or mSiO2 (mesoporous silica). PMO/mSiO2 materials are excellent candidates for biological/biomedical applications as they show high biocompatibility with the human body. On the other hand, the β-NaGdF4 matrix is an excellent host for doping lanthanide ions, even at very low concentrations with yet very efficient luminescence properties. We propose a new type of Er 3+ -Yb 3+ upconversion luminescence nanothermometers operating both in the visible and near infrared regime. Both spectral ranges permit promising thermometry performance even in aqueous environment. It is additionally confirmed that these hybrid materials are non-toxic to cells, which makes them very promising candidates for real biomedical thermometry applications. In several of these materials the presence of additional voids leaves space for future theranostic or combined thermometry and drug delivery applications in the hybrid nanostructures.
1 of 5) 1700258around the world in banknotes (lanthanide (Ln) luminescence in Euro banknotes) as well as documents such as passports, IDs, and birth certificates, to name a few. The unique luminescence properties of lanthanides (strong, sharp emission bands in the visible and near-infrared range, which are not dependent on the environment) make them ideal candidates for use for anti-counterfeit purposes.  Yet, because Ln 3+ ions have low extinction coefficients, chromophoric molecules (so-called "antennae") should be placed in close proximity to allow energy transfer from the sensitized chromophore to the lanthanides.  Due to the destructive nature of counterfeiting, new techniques that will show a higher security level from those existing are continuously and excessively searched for and developed.  In this highlight paper, we report a new conceptual approach for creating a multistage security technology, where one material simultaneously shows significant wavelength-and temperature-dependent luminescence properties when placed under a simple UV lamp. To the best of our knowledge, no such technology has been previously proposed; no materials based on temperature dependence in combination with wavelength dependence have been introduced for this application. To date, some of the most advanced materials and technologies reported for multistage anti-counterfeiting are based on upconversion. Yet, the use of lasers (needed as one of the excitation sources for these materials) is not very convenient in daily use.The strength of the reported concept lies in its simplicity; only one excitation source-a standard UV lamp-would be needed. For real applications the material would need to be incorporated into objects or printed on surfaces. The objects could then be slightly heated up (e.g., by 20 °C) with a widely available infrared lamp, or by rubbing the surface of a material intensely. Materials that show a change in emission color at temperatures below room temperature could, for example, be applied in products such as expensive champagne bottles, which are best stored at 7 °C. Overcoming the current limitations (one-stage security) would facilitate the fabrication of novel materials and their exploitation for security technologies. A visualization of the dual-mode behavior of the materials has been presented in Scheme 1 using materials that are discussed further in the paper.The choice of metal-organic frameworks (MOFs) as materials for this application is based on several factors: 1) their well-defined structures in terms of dimensionality, size, and shape; 2) high porosity, which provides an environment for Hybrid materials displaying multistage security behavior, where a single material shows both wavelength-and temperature-dependent luminescence properties, are reported. The materials consist of mixed-lanthanide β-diketonate complexes grafted into the pores of a nanosized 2,2′-bipyridine-5,5′-dicarboxylate-acid MOF. A very specific choice of lanthanides and their ratios, as well as β-diketonate ...
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