Enhancing Built-in Electric Fields via Molecular Symmetry Modulation in Supramolecular Photocatalysts for Highly Efficient Photocatalytic Hydrogen Evolution.

Nature-inspired supramolecular self-assemblies are attractive photocatalysts, but their quantum yields are limited by poor charge separation and transportation. A promising strategy for efficient charge transfer is to enhance the built-in electric field by symmetry breaking. Herein, an unsymmetric protonation, N-heterocyclic π-conjugated anthrazoline-based supramolecular photocatalyst SA-DADK-H+ was developed. The unsymmetric protonation breaks the initial structural symmetry of DADK, resulting in ca. 50-fold increase in the molecular dipole, and facilitates efficient charge separation and transfer within SA-DADK-H+. The protonation process also creates numerous active sites for H2O adsorption, and serves as crucial proton relays, significantly improving the photocatalytic efficiency. Remarkably, SA-DADK-H+ exhibits an outstanding hydrogen evolution rate of 278.2 mmol g-1 h-1 and a remarkable apparent quantum efficiency of 25.1 % at 450 nm, placing it among the state-of-the-art performances in organic semiconductor photocatalysts. Furthermore, the versatility of the unsymmetric protonation approach has been successfully applied to four other photocatalysts, enhancing their photocatalytic performance by 39 to 533 times. These findings highlight the considerable potential of unsymmetric protonation induced symmetry breaking strategy in tailoring supramolecular photocatalysts for efficient solar-to-fuel production.

Water-soluble fluorescent sensor for Zn2+ with high selectivity and sensitivity imaging in living cells.

A new water-soluble 4-amino-1, 8-naphthalimide based fluorescent sensor, with iminoacetic acid and iminoethoxyacetic acid as receptor contained two different arms, was developed. Under physiological pH conditions, it demonstrates good water solubility, high selectivity and sensitivity for sensing Zn2+ with about 20-fold enhancement in aqueous solution, with a characteristic emission band of 4-amino-1, 8-naphthalimide with a green color centered at 550 nm. It was applied successfully to detect Zn2+ in living cells.

A highly selective and sensitive 1,8-naphthalimide-based fluorescent sensor for Zn2+ imaging in living cells.

A new 4-amino-1,8-naphthalimide-based fluorescent sensor, with iminoacetic acid and iminoethoxyacetic acid as receptor, was developed. It was applied successfully to detect Zn2+ in aqueous solution and living cells. Under physiological pH conditions, it demonstrates high selectivity and sensitivity for sensing Zn2+ with about 7-fold enhancement in aqueous solution, with a characteristic emission band of 4-amino-1,8-naphthalimide with a green color centered at 550 nm.

Fluorescent pH Sensors for Broad-Range pH Measurement Based on a Single Fluorophore.

We constructed a series of novel optical sensors for determination of broad-range pH based on a single fluorophore and multi-ionophores with different pK(a) values. These optical sensors use photoinduced electron transfer (PET) as the signal transduction and follow the design concept of "fluorophore-spacer-receptor (ionophore)" which employs 4-amino-1,8-naphthalimide as the single fluorophore, ethyl moiety as the spacer, and a series of phenols and anilines as the receptors. Key to the successful development of this sensor system is that coupling the receptors with six different pK(a) values with a single fluorophore produces the correct optical properties. This rational design affords a series of optical pH sensors with unique fluorescence property and accurately tunable pH measurement ranging from 1 to 14 pH units. Because of covalent immobilization of the indicators, these sensors demonstrate excellent stability, adequate reversibility, and satisfactory dynamic range up to full pH ranges (pH 1-14).

A fluorescent chemosensor for calcium with excellent storage stability in water.

This article describes the design, synthesis and characterization of an optical sensor suitable for practical measurement of ionized calcium in serum and whole blood samples. The key to the development of this sensor is the identification of a chemically very stable, nitrogen-containing, calcium selective ionophore, coupled with a fluorophore having the correct spectral and electron accepting properties. The slope of the sensor is about 34%/mM in the typical clinically significant range of 0.32-2.2mM. This sensor has been implemented into the disposable cartridge, used for commercially available OPTI CCA analyzer with precision better than +/-0.02 mM (1S.D.). The sensor displays excellent stability against hydrolysis and oxidation, leading to less than 0.02 mM measurement error after 9 months of wet storage at room temperature, up to 30 degrees C.

A fluorescent chemosensor for sodium based on photoinduced electron transfer.

A new optical sensor suitable for practical measurement of sodium in serum and whole blood samples is described. The optical sensor is based on a novel PET (photoinduced electron transfer) fluoroionophore immobilized in a hydrophilic polymer layer. The design concept of the fluoroionophore follows the receptor-spacer-fluorophore approach to sensor design using intramolecular PET-based signal transduction. Key to the development of this sensor is the identification of a nitrogen-containing, sodium-binding ionophore, coupled with a fluorophore having the correct spectral and electron-accepting properties. The slope of the sensor is approximately 0.5%/mM in the typical clinically significant range of 120-160 mM. This sensor has been implemented into a disposable cartridge, used for a commercially available critical care analyzer (Roche OPTI CCA) with precision better than +/- 1 mM (1 SD). The sensor displays excellent stability against hydrolysis and oxidation, leading to slope changes <5% after 9 months wet storage at 30 degrees C. On the basis of this design concept, fluoroionophores for other cations such as potassium, calcium and magnesium can be prepared by substitution of the ionophore.

A fluorescent sensor with high selectivity and sensitivity for potassium in water.

This communication describes a new optical sensor suitable for practical measurement of extracellular (serum or whole blood) potassium. The sensor responds rapidly and reversibly to changes in potassium concentrations typical of whole blood samples. No interferences from clinical concentrations of calcium or pH are observed, and the sodium interference is very minor. Excitation and emission occur in the visible light region. This new potassium sensor is currently used in the Roche OPTI CCA, a commercially available whole blood analyzer.