Pillararene-based AIEgens: research progress and appealing applications.

As a photophysical phenomenon, aggregation-induced emission (AIE) was proposed by Tang in 2001. Due to their excellent fluorescence emission performance, AIEgens and AIE-based fluorescence materials have shown great application potential in a wide range of science fields. Hence, exploring new AIEgens and construction of novel AIE materials are especially vital. In addition, as a new class of macrocyclic hosts, pillararenes have shown excellent performance in supramolecular chemistry. Interestingly, pillararenes also exhibited fairly bright application prospects in the AIE area: firstly, some research studies suggested that pillararenes could serve as a novel AIEgen with considerable fluorescence emission in the aggregated state; moreover, they could also participate in the construction of AIE materials and have potential application in various areas. In this review, we summarised the recent development of pillararene-based AIE materials from the following aspects: pillararenes as novel AIEgens, the TPE functionalized pillararene-based AIE materials, the pillararene-based AIE materials constructed by supramolecular assembly, and the functionalized pseudo-pillararene-based AIE materials. It is hoped that this feature article will attract increasing attention and pave a new way for the development and application of pillar[n]arene-based AIE materials in more fields.

Transparency and AIE tunable supramolecular polymer hydrogel acts as TEA-HCl vapor controlled smart optical material.

Stimuli-responsive optical materials attract lots of attention due to their broad applications. Herein, a novel smart stimuli-responsive supramolecular polymer was successfully constructed using a simple tripodal quaternary ammonium-based gelator (TH). The TH self-assembles into a supramolecular polymer hydrogel (TH-G) and shows aggregation-induced emission (AIE) properties. Interestingly, the transparency and fluorescence of the TH-G xerogel film (TH-GF) could be reversibly regulated by use of triethylamine (TEA) and hydrochloric acid (HCl) vapor. When alternately fumed with TEA and HCl vapor, the optical transmittance of the TH-GF was changed from 8.9% to 92.7%. Meanwhile, the fluorescence of the TH-G shows an "ON/OFF" switch. The reversible switching of the transparency and the fluorescence of the TH-GF is attributed to the assembly and disassembly of the supramolecular polymer TH-G. Based on these stimuli-response properties, the TH-GF could act as an optical material and shows potential applications as smart windows or fluorescent display material controlled by TEA and HCl vapor.

A novel AIE-based supramolecular polymer gel serves as an ultrasensitive detection and efficient separation material for multiple heavy metal ions.

Recently, ultrasensitive stimuli-responsive materials have received extensive attention due to their high sensitivity and wide applications. Herein, we report a novel approach to design ultrasensitive responsive materials by rationally introducing the aggregation-induced emission (AIE) effect into supramolecular polymer gels. According to this approach, by rationally introducing self-assembly moieties and a fluorophore, the obtained gelator DNS can act as an AIEgen; it showed strong AIE after aggregating into the supramolecular polymer gel GDNS. More interestingly, because the aggregation of DNS led to amplification of the detective signal, the AIE-based supramolecular polymer gel GDNS could ultrasensitively detect the heavy metal ions Hg2+, Cu2+, and Fe3+ by a signal amplification mechanism; the lowest detection limits reached 10-11 M. In addition, the xerogel of GDNS could adsorb and separate Hg2+, Cu2+, and Fe3+ from aqueous solution with favourable adsorption properties, and the adsorption rates ranged from 94.70% to 99.37%. Furthermore, the gel GDNS could act as a convenient test kit for Hg2+, Cu2+, and Fe3+ as well as a smart fluorescent display material.

A novel bis-component AIE smart gel with high selectivity and sensitivity to detect CN-, Fe3+ and H2PO4.

A novel bis-component AIE-gel TG was facilely constructed from two "easy-to-synthesize" tripodal gelators by a simple host-guest self-assembly process. Interestingly, the TG shows strong aggregation-induced emission (AIE) and could be used for highly efficient and sensitive detection and separation of ions (CN-, Fe3+ and H2PO4-). The LODs (limits of lowest detection) of TG for CN-, Fe3+ and H2PO4- are in the range of 4.93 × 10-9-7.80 × 10-8 M. Meanwhile, the xerogel of TG could adsorb and separate Fe3+ from aqueous solutions, and the adsorption rate is 96%. In addition, a thin film based on the TG could act as a convenient test kit for the detection of CN- and Fe3+. What is more, the TG-Fe film could not only be used as an erasable secure fluorescent display material, but also as a convenient reversible H2PO4- test kit.

Rationally introduce AIE into chemosensor: A novel and efficient way to achieving ultrasensitive multi-guest sensing.

Recently, ultrasensitive detection and multi-guest sensing have received extensive attention due to their high sensitivity and efficiency. Herein, we report a novel approach to achieve ultrasensitive detection of multi-analyte. This approach is concluded as "rationally introduce Aggregation-Induced Emission (AIE) into chemosensor". According to this approach, by rationally introducing self-assembly moiety, the obtained chemosensor DNS could serve as a novel AIEgen and show strong AIE in DMSO/H2O (water fraction 80%) binary solution. Interestingly, a simple fluorescent sensor array based on the DNS has been developed. This sensor array could selectively sense Fe3+, Al3+, H2PO4- and L-Arg in water solution. More importantly, this sensor array shows ultrasensitive detection for Fe3+, Al3+ and L-Arg. The LODs of the sensor array for Fe3+, Al3+ and L-Arg are in the range of 3.54×10-9M to 9.42×10-9M. Moreover, H2PO4- could realize the reversible detection of Fe3+ in the DMSO/H2O (water fraction 80%) solution. Meanwhile, DNS-based test papers and thin films were prepared, which could serve as test kits for convenient detection Fe3+, Al3+, and L-Arg in water. In addition, they could also act as efficient erasable fluorescent display materials.

Anion induced supramolecular polymerization: a novel approach for the ultrasensitive detection and separation of F.

A novel approach for the ultrasensitive detection and separation of F- has been successfully developed. F- could induce a tripodal naphthalene imide sensor (TNA) to result in supramolecular polymerization, leading to strong AIEE. The TNA could act as an excellent recyclable material for F- detection and separation.