Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

Aggregation-Induced Emission: Together We Shine, United We Soar!

Microbial fuel cell (MFC) research is a rapidly evolving field that lacks established terminology and methods for the analysis of system performance. This makes it difficult for researchers to compare devices on an equivalent basis. The construction and analysis of MFCs requires knowledge of different scientific and engineering fields, ranging from microbiology and electrochemistry to materials and environmental engineering. Describing MFC systems therefore involves an understanding of these different scientific and engineering principles. In this paper, we provide a review of the different materials and methods used to construct MFCs, techniques used to analyze system performance, and recommendations on what information to include in MFC studies and the most useful ways to present results.

Microbial Fuel Cells: Methodology and Technology†

Luminogenic materials with aggregation-induced emission (AIE) attributes have attracted much interest since the debut of the AIE concept in 2001. In this critical review, recent progress in the area of AIE research is summarized. Typical examples of AIE systems are discussed, from which their structure–property relationships are derived. Through mechanistic decipherment of the photophysical processes, structural design strategies for generating new AIE luminogens are developed. Technological, especially optoelectronic and biological, applications of the AIE systems are exemplified to illustrate how the novel AIE effect can be utilized for high-tech innovations (183 references).

Aggregation-induced emission

Aggregation-induced emission: phenomenon, mechanism and applications.

"United we stand, divided we fall."--Aesop. Aggregation-induced emission (AIE) refers to a photophysical phenomenon shown by a group of luminogenic materials that are non-emissive when they are dissolved in good solvents as molecules but become highly luminescent when they are clustered in poor solvents or solid state as aggregates. In this Review we summarize the recent progresses made in the area of AIE research. We conduct mechanistic analyses of the AIE processes, unify the restriction of intramolecular motions (RIM) as the main cause for the AIE effects, and derive RIM-based molecular engineering strategies for the design of new AIE luminogens (AIEgens). Typical examples of the newly developed AIEgens and their high-tech applications as optoelectronic materials, chemical sensors and biomedical probes are presented and discussed.

Aggregation-Induced Emission: The Whole Is More Brilliant than the Parts

The development of sensors and receptors for biologically important anions is currently of great interest because of their indispensable roles in vital (or physiological) processes. Among the anions, fluoride ions are one of the most attractive targets because of their considerable significance for health and environmental issues. As an essential element of the body, the U.S. Public Health Service affirmed the optimal level to be 1 mg of consumed fluoride per day. On the other hand, unnecessary and inappropriate fluoride ingestion can result in fluorosis, urolithiasis, or even cancer. The EPA (United States Environmental Protection Agency) gives an enforceable drinking water standard for fluoride of 4 mg L 1 to prevent osteofluorosis and a secondary fluoride standard of 2 mgL 1 to protect against dental fluorosis. Hence, the accurate determination of the levels of fluoride in drinking water is necessary. To date, the ion-selective electrode, ion chromatography, and standard Willard and Winter methods are generally used for quantitative fluoride analysis. However, all these methods involve disadvantages, such as complicated procedures, high costs, or low mobility. Therefore, it is important to develop highly selective, sensitive, convenient, and rapid fluoride detection methods. Fluorescent chemosensors with high specificity and sensitivity, ease, and safety of handling have received considerable attention, and a number of fluorescence sensors have been reported that are capable of detecting fluoride ions. The recognition proceeded mostly through hydrogen bonding or Lewis acid coordination, and the sensors could only be operated in organic solvents to detect tetrabutylammonium (TBA) fluoride rather than inorganic fluoride salts. This incompatibility with aqueous environments is one of the main drawbacks that restrict the application of these sensors. Unavoidable interference from H2PO4 , AcO , or CN ions is the other disadvantage. To improve the performance of fluoride sensors, another strategy based on the chemical affinity between fluoride and silicon was developed. tertButyldimethylsilyl (TBDMS) and tert-butyldiphenylsilyl (TBDPS) were chosen as additional substituents for the dye molecule, and rendered the dye unreactive to potentially interfering compounds and thus sensitive only to fluoride ions. This approach was pioneered by Kim and Swager, who developed a fluorescent fluoride receptor in organic solvents. Subsequently, several research groups reported different chemodosimeters that can probe NaF in mixtures of organic solvents and water or even pure water. However, several tens of minutes or even hours are needed to complete the detection process because low concentrations of these chemodosimeters severely reduce the reaction rate between the fluoride ions and the silyl moieties. However, the low concentration is necessary for general organic dyes to avoid fluorescence quenching induced by concentration effects, such as self-absorption and self-quenching. To date, most fluorescent sensors were based on the specific fluoride ion dependence of the emission intensity and could be significantly influenced by the excitation power and the detector sensitivity. More importantly, fluorescence intensity changes are not suitable for direct observation with the naked eye. To develop a more convenient fluorescence sensor, it is essential to make use of other fluoridedependent measurable signals other than intensity. The fluorescence color change, which can be measured directly with a colorimeter or even distinguished easily by eye, is thus a good choice. Herein we describe a rapid and portable sensor for fluoride ions in aqueous solution. The sensor, which has a high sensitivity, operates through the special affinity between fluoride ions and silicon, and provides two independent modes of signal transduction based on fluoride-dependent changes of fluorescence color (color metric mode) or intensity (power metric mode), respectively. For the design of the sensor, we chose N-(3-(benzo[d]thiazol-2-yl)-4-(hydroxyphenyl) benzamide (3-BTHPB) as an excited-state intramolecular proton transfer (ESIPT) compound. Just like other ESIPT compounds, 3-BTHPB shows two emission bands, which originate from the enol and keto forms at 418 and 560 nm, respectively. The ratio of the two bands is determined by the number of molecules that could undergo ESIPT reactions. We coupled the tert-butyldiphenylchlorosilane with the sodium salt of 3-BTHPB to afford a derivative N-(3(benzo[d]thiazol-2-yl)-4-(tert-butyldiphenyl silyloxy)phenyl)benzamide (BTTPB). As expected, BTTPB shows only blueviolet fluorescence, which was almost identical to the emission of the enol form of 3-BTHPB (see the Supporting [*] R. Hu, J. Feng, D. H. Hu, Dr. S. Q. Wang, Dr. S. Y. Li, Prof. Dr. G. Q. Yang Beijing National Laboratory for Molecular Sciences Key Laboratory of Photochemistry, Institute of Chemistry Chinese Academy of Sciences Beijing 100190 (China) Fax: (+ 86)10-8261-7315 E-mail: shayuli@iccas.ac.cn gqyang@iccas.ac.cn

A Rapid Aqueous Fluoride Ion Sensor with Dual Output Modes

Feeling blue: the luminescence of a triarylboron compound has a high quantum yield (at least 0.64) over a wide temperature range (-50 to +100 °C) and changes from green to blue as the temperature is increased. The luminescence color was determined by the population of the two distinct excited-state conformations-a local excited state (high temperature) and a twisted intramolecular charge-transfer state (low temperature).

A triarylboron-based fluorescent thermometer: sensitive over a wide temperature range.

A novel class of 2-(2‘-hydroxyphenyl)benzothiazole-based (HBT-based) excited-state intramolecular proton-transfer (ESIPT) compounds, N,N‘-di[3-Hydroxy-4-(2‘-benzothiazole)phenyl]isophthalic amide (DHIA) and N,N‘-di[3-Hydroxy-4-(2‘-benzothiazole)phenyl]5-tert-butyl-isophthalic amide (DHBIA) has been feasibly synthesized and the properties of their nanoparticles in THF/H2O mixed solvent were investigated. Both compounds were found to exhibit aggregation-induced emission enhancement (AIEE) due to restricted intramolecular motion and easier intramolecular proton transfer in solid state. On identical experimental conditions, the emission of DHBIA aggregates increased more remarkably than that of DHIA. Different aggregation forms of these two organic compounds, due to the steric hindrance of a single tert-butyl group, could be responsible for the notably different degrees of the fluorescence enhancement. Their aggregation modes were investigated on the basis of time-dependent absorption, scanning electron micro...

Aggregation-induced emission enhancement of 2-(2'-hydroxyphenyl)benzothiazole-based excited-state intramolecular proton-transfer compounds.

Nanoparticles of intramolecular proton transfer molecule N,N‘-bis(salicylidene)-p-phenylenediamine have been prepared with the reprecipitation method in water. The evolving processes have been monitored by means of UV−vis absorption, fluorescence emission, transient emission spectroscopy, and scanning electron microscopy. The fluorescent intensity is increased beyond 60 times in the nanoparticles compared to that in solution. With the increase of aging time, nanoparticles convert spontaneously from spherical to rodlike and finally to beltlike aggregates. A mechanism for the enhanced emission is proposed on the basis of flattened molecules, and a possible model for change of the nanoparticles' shape is also proposed on the basis of theoretical calculations.

Enhanced Fluorescent Emission of Organic Nanoparticles of an Intramolecular Proton Transfer Compound and Spontaneous Formation of One-Dimensional Nanostructures

Guoqiang Yang

Papers

A Rapid Aqueous Fluoride Ion Sensor with Dual Output Modes

A triarylboron-based fluorescent thermometer: sensitive over a wide temperature range.

Aggregation-induced emission enhancement of 2-(2'-hydroxyphenyl)benzothiazole-based excited-state intramolecular proton-transfer compounds.

Enhanced Fluorescent Emission of Organic Nanoparticles of an Intramolecular Proton Transfer Compound and Spontaneous Formation of One-Dimensional Nanostructures

Nanofibers of 1,3‐Diphenyl‐2‐pyrazoline Induced by Cetyltrimethylammonium Bromide Micelles