A Luminescent Metal–Organic Framework Thermometer with Intrinsic Dual Emission from Organic Lumophores

A new mixed‐ligand metal–organic framework (MOF), ZnATZ‐BTB, has been constructed as a luminescent ratiometric thermometer by making use of the intrinsic dual emission at cryogenic temperatures. Its twofold interpenetrated network promotes the Dexter energy transfer (DET) between the mixed organic lumophores. The temperature‐dependent luminescent behavior arises from the thermal equilibrium between two separated excited states coupled by DET, which is confirmed by Boltzmann distribution fitting. The small excited‐state energy gap allows ZnATZ‐BTB to measure and visualize cryogenic temperatures (30–130 K) with significantly high relative sensitivity (up to 5.29 % K^?1 at 30 K). Moreover, it is the first example of a ratiometric MOF thermometer the dual emitting sources of which are widely applicable mixed organic ligands, opening up new opportunities for designing such devices.     

Multi-Channel Optical Device for Solar-Driven Bacterial Inactivation under Real-Time Temperature Feedback

Solar-driven photothermal antibacterial devices have attracted a lot of interest due to the fact that solar energy is one of the cleanest sources of energy in the world. However, conventional materials have a narrow absorbance band, resulting in deficient solar harvesting. In addition, lack of knowledge on temperature change in these devices during the photothermal process has also led to a waste of energy. Here, we presented an elegant multi-channel optical device with a multilayer structure to simultaneously address the above-mentioned issues in solar-driven antibacterial devices. In the photothermal channel, semiconductor IrO₂-nanoaggregates exhibited higher solar absorbance and photothermal conversion efficiency compared with nanoparticles. In the luminescence channel, thermal-sensitive Er-doped upconversion nanoparticles were utilized to reflect the microscale temperature in real-time. The bacteria were successfully inactivated during the photothermal effect under solar irradiation with temperature monitoring. This study could provide valuable insight for the development of smart photothermal devices for solar-driven photothermal bacterial inactivation in the future.     

Synthesis and Characterization of Newly Designed and Highly Solvatochromic Double Squaraine Dye for Sensitive and Selective Recognition towards Cu2+

Synthesis and characterization of a novel and zwitterionic double squaraine dye (DSQ) with a unique D-A-A-D structure is being reported. Contrary to the conventional mono and bis-squaraine dyes with D-A-D and D-A-D-A molecular frameworks reported so far, DSQ dye demonstrated strong solvatochromism allowing for the multiple ion sensing using a single probe by judicious selection of the suitable solvent system. The DSQ dye exhibited a large solvatochromic shift of about 200 nm with color changes from the visible to NIR region with metal ion sensitivity. Utilization of a binary solvent consisted of dimethylformamide and acetonitrile (1:99, v/v), highly selective detection of Cu²⁺ ions with the linearity range from 50 μM to 1 nM and a detection limit of 6.5 × 10⁻¹⁰ M has been successfully demonstrated. Results of the Benesi–Hildebrand and Jobs plot analysis revealed that DSQ and Cu²⁺ ions interact in the 2:1 molecular stoichiometry with appreciably good association constant of 2.32 × 10⁴ M⁻¹. Considering the allowed limit of Cu²⁺ ions intake by human body as recommended by WHO to be 30 μM, the proposed dye can be conveniently used for the simple and naked eye colorimetric monitoring of the drinking water quality.     

Polyethyleneimine Solubilized Luminescent Au(I)‐Thiolate Complexes for Highly Sensitive and Selective Cyanide Anion Sensing

Cyanide (CN^?) is a highly toxic anion to human beings, exploring efficient probes for sensitive and selective detection of it is very important. In this study, we explore a simple one‐pot reaction to synthesize polyethyleneimine (PEI) solubilized Au(I)‐MUA (11‐mercaptoundecanoic acid) complexes under mild condition. The as prepared Au(I)‐MUA complexes exhibit strong red photoluminescence (PL) and can act as sensitive and selective CN^? optical sensor in aqueous media based on the chemical reaction between CN^? and gold atom that quench the fluorescence, and the limit of detection is 10 nM, which is ～270 times lower than the maximum contamination level (2.7 μM) in drinking water permitted by WHO. Additionally, real water sample from a local lake is tested with these optical sensors, and the PL variation caused by 0.1 μ CN^? can be observed.     

Luminescent PMMA Films and PMMA@SiO2 Nanoparticles with Embedded Ln3+ Complexes for Highly Sensitive Optical Thermometers in the Physiological Temperature Range**

In recent years, luminescent materials doped with Ln³⁺ ions have attracted much attention for their application as optical thermometers based on both downshifting and upconversion processes. This study presents research done on the development of highly sensitive optical thermometers in the physiological temperature range based on poly(methyl methacrylate) (PMMA) films doped with two series of visible Ln³⁺ complexes (Ln³⁺=Tb³⁺, Eu³⁺, and Sm³⁺) and SiO₂ nanoparticles (NPs) coated with these PMMA films. The best performing PMMA film doped with Tb³⁺ and Eu³⁺ complexes was the PMMA[TbEuL₁tppo]1 film (L₁=4,4,4-trifluoro-1-phenyl-1,3-butadionate; tppo=triphenylphosphine oxide), which showed good temperature sensing of S_r=4.21 % K⁻¹ at 313 K, whereas for the PMMA films doped with Tb³⁺ and Sm³⁺ complexes the best performing was the PMMA[TbSmL₂tppo]3 film (L₂=4,4,4-trifluoro-1-(4-chlorophenyl)-1,3-butadionate), with S_r=3.64 % K⁻¹ at 313 K. Additionally, SiO₂ NPs coated with the best performing films from each of the series of PMMA films (Tb–Eu and Tb–Sm) and their temperature-sensing properties were studied in water, showing excellent performance in the physiological temperature range (PMMA[TbEuL₁tppo]1@SiO₂: S_r=3.84 % °C at 20 °C; PMMA[TbSmL₂tppo]3@SiO₂: S_r=3.27 % °C at 20 °C) and the toxicity of these nanoparticles on human cells was studied, showing that they were nontoxic.