Huipeng Zhou

Low-dimensional nanostructures fabricated from bis(dioxaborine)carbazole derivatives as fluorescent chemosensors for detecting organic amine vapors

New triphenylamine functionalized bis(dioxaborine)carbazole derivatives (BDOBCn, n = 4, 8, 16) have been synthesized, and low-dimensional nanostructures with different morphologies have been fabricated from BDOBCn with carbon chains of different lengths. For example, 1D single-crystalline nanowires are generated from BDOBC4via a reprecipitation approach, 1D nanofibers based on BDOBC16 are prepared through an organogelation process, and amorphous nanoparticles are obtained from BDOBC8. It is interesting that the films formed from the obtained nanostructures can give strong fluorescence emission under irradiation and can act as fluorescent chemosensors for probing aniline vapors, with different response rates and different sensitivity controlled by their morphologies. The mesh-like film obtained from the BDOBC16-based gel exhibits faster fluorescent response in milliseconds and higher sensitivity than the nanoparticle- and nanowire-based films, because the supramolecular objects primarily formed in the gelling process percolate and fill the entire volume at a low-over all-volume fraction, and the entangled piling of the fibers leads to increased porosity. Thus, it not only provides a large surface for enhanced adsorption and accumulation of gaseous molecules but also enables expedient cross-film diffusion of gaseous species. Notably, the organogel fibers of BDOBC16 allow high selectivity for probing aniline vapor, and the detection limit reaches 8.6 ppm.

New dendritic gelator bearing carbazole in each branching unit: selected response to fluoride ion in gel phase

A new dendritic gelator with carbazole as the building block (HBCD) was synthesized. It was found that H-bonding between the amide groups and π-π interaction between the aromatic rings played predominant roles in the gel formation. Meanwhile, significant aggregation-induced emission enhancement was observed in the gel state due to the formation of J-aggregates and the restricted molecular motion. Notably, the gel state of HBCD can be destroyed upon addition of F(-), accompanied by fluorescence enhancement on account of the formation of N-HF(-), which could further lead to the increased coplanarity of HBCD. The sensory capability of HBCD exhibited a high selectivity towards F(-) instead of the Cl(-), Br(-), I(-) and AcO(-) anions, which could be explained by the fact that the steric hindrance of the dendrimer would go against the interactions between the larger anions and HBCD.

Luminescent Organic 1D Nanomaterials Based on Bis(β‐diketone)carbazole Derivatives

A series of new triphenylamine-functionalized bis(β-diketone)s bridged by a carbazole (CnBDKC, n=1, 4, 8, 16) with twisted intramolecular charge-transfer emission in polar solvents has been synthesized. The length of the carbon chains has a significant effect on the self-assembling properties of the compounds. Well-defined 1D nanowires were easily generated from C1BDKC with a methyl group by a reprecipitation approach directed by π-stacking interaction, and the molecules packed into J-aggregates in the nanowires. In addition, 1D nanofibers based on C16BDKC bearing a long hexadecyl chain were prepared through the organogelation process, and H-aggregates were formed driven by the synergistic effect of π-stacking interaction and van der Waals force in the gel phase. C4BDKC and C8BDKC containing butyl and octyl side chains, respectively, cannot arrange into dispersed nanostructures, probably because π-π interaction between conjugated moieties might be disturbed by the interaction between the side chains, which is, however, not strong enough to dominate the self-assembling process. Notably, the nanowires based on C1BDKC and the gel nanofibers from C16BDKC can emit strong green light under irradiation, which suggests that these 1D nanomaterials may have potential applications in emitting materials as well as photonic devices.

Aggregation-induced blue shift of fluorescence emission due to suppression of TICT in a phenothiazine-based organogel.

A new D-pi-A type gelator based on a phenothiazine derivative, which can gel cyclohexane, hexane, and ethanol/water under ultrasound treatment, has been synthesized. Because such gelators can act as twisted intermolecular charge transfer (TICT) probes, their emission in solution can be tuned by varying the polarity of the solvents. It is notable that an unusual aggregation-induced blue shift of the emission has been detected on account of the suppression of TICT in the gel phase.

Phenothiazine-based oligomers as novel fluorescence probes for detecting vapor-phase nitro compounds

To meet the need for rapid and low-cost chemical sensing of explosive, new fluorescence chemosensors based on oligophenothiazines for probing vapor-phase nitro compounds have been developed. The phenothiazine-based trimer P3 and pentamer P5 have been synthesized via Heck and Wittig reactions by convergent approach. It was found that they can detect the vapors of nitro compounds, including p-nitrotoluene (p-NT), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT) with good sensitivity and reversibility. And the sensor of P3 film gave a linear fluorescence quenching response to 7-800 ppb TNT with the detection limit of 4 ppb. For DNT vapor, a linear working range of the sensor was 2-24 ppm with the detection limit of 40 ppb. Meanwhile, the interferents, including common organic solvents, p-nitrophenol and 2,4-dinitrophenylhydrazine cannot lead to obvious fluorescence quenching, meaning that the film based on oligophenothiazines exhibited good specificity of fluorescence response to explosive. Based on the fluorescence lifetime and UV-vis absorption measurements, we suggested that the fluorescence quenching of oligophenothiazine-based films exposed to the vapors of nitro compounds was due to the formation of non-fluorescent charge-transfer complex between oligophenothiazine and nitro compounds.

Synthesis of star-shaped monodisperse oligo(9,9-di-n-octylfluorene-2,7-vinylene)s functionalized truxenes with two-photon absorption properties

A series of new star-shaped monodisperse conjugated truxene derivatives bearing oligo(fluorene-vinylene) arms (Tr-OFVn, n = 1, 2, 3, 4) have been synthesized. It is found that the conjugation of the oligomers can be extended with prolonging the arms. Notably, the branched oligomers Tr-OFVn without strong donor and acceptor units exhibit two-photon absorption properties, and the two-photon absorption cross sections (δ(max)) increase with increasing the number of fluorene-vinylene units in the arms. The maximum value of δ(max) reaches 8073 GM for compound Tr-OFV4, which made it one of the most competitive compounds with enhanced TPA cross section. It provides a new platform for exploiting strong TPA compounds, in which the extended π-conjugated systems are involved in the absence of strong donor and acceptor units.