Polyolefins like polyethylene (PE) and polypropylene (PP) without any conventional or nonconventional fluorescent chromophores have never been considered as raw materials for the preparation of fluorescent polymers. Here we report...

Through-bond conjugation (TBC) and/or through-space conjugation (TSC) determine the photophysical properties of organic luminescent compounds. No systematic studies have been carried out to understand the transition from aromatic TBC to non-aromatic TSC on the photoluminescence of organic luminescent compounds. In this work, a series of small aromatic and aliphatic aldimines were synthesized. For the aromatic imines, surprisingly, N,1-diphenylmethanimine with the highest TBC is non-emissive, while N-benzyl-1-phenylmethanimine and N-cyclohexyl-1-phenylmethanimine emit bright fluorescence in aggregate states. The aliphatic imines are all emissive, and their maximum emission wavelength decreases while the quantum yield increases with a decrease in steric hindrance. The imines show concentration-dependent and excitation-dependent emissions. Theoretical calculations show that the TBC extents in the aromatic imines are not strong enough to induce photoluminescence in a single molecule state, while the intermolecular TSC becomes dominant for the fluorescence emissions of both aromatic and aliphatic imines in aggregate states, and the configurations and spatial conformations of the molecules in aggregate states play a key role in the formation of effective TSC. This study provides an understanding of how chemical and spatial structures affect the formation of TBC and TSC and their functions on the photoluminescence of organic luminescent materials.

Herein, a dual emissive fluorescent probe for Fe2+ based on papain-stabilized Ag nanoclusters was developed.

We transplanted RADA16-PRG self-assembled nanopeptide scaffolds (SAPNSs), bone mesenchymal stem cells (BMSCs), and a brain-derived neurotrophic factor (BDNF)-expressing adeno-associated virus (AAV) into rats subjected to acute spinal cord injury (SCI) to investigate the effects of these transplantations on acute SCI repair and explore their mechanisms. Forty-eight SCI rats were randomly divided into four groups: BBR, BR, B, and NC groups. Seven and 28 days after SCI, evoked potentials (EPs) and BBB scores were assessed to evaluate the recovery of rats’ motor behavior and sensory function after injury. HE and toluidine blue staining were performed to investigate the histological structure of the spinal cord tissue of rats from each group, and immunofluorescence staining was used to observe the red fluorescent protein (RFP) intensity of BMSCs and glial fibrillary acidic protein (GFAP) and neurofilament (NF) in the damaged area in each group. RT–PCR was utilized to detect the expression levels of the BDNF, GFAP, and neuron-specific enolase (NSE) genes in the injured area in each group. The results showed that cotransplantation of RADA16-PRG-SAPNs, BMSCs, and BDNF-AVV promoted the spinal cord’s motor and sensory function of SCI rats; increased levels of BMSCs, inhabited glial cells proliferation, and promoted neurons proliferations in the injured area; and increased NF, BDNF, and NSE levels and decreased its GFAP in the injured area. Thus, cotransplantation of RADA16-PRG-SAPNS, BMSCs, and BDNF-AAV can prolong the survival time of BMSCs in rats, reduce the postoperative scarring caused by glial proliferation, and promote the migration and proliferation of neurons in the injured area, resulting in the promotion of functional repair after acute SCI.

Photoluminescence (PL) mechanisms of nontraditional luminogens (NTLs) have attracted great interests, and they are generally explained with intra/intermolecular through-space conjugation (TSC) of nonconventional chromophores (NCCs). Here we propose a new concept of nonaromatic through-bond conjugation (TBC) and proved that it plays an important role in the PL of NTLs. The PL behaviors of cyclohexanedione (CHD), dimethyl-1,3-cyclohexanedione (DMCHD) and their three respective isomers are studied and correlated with their chemical structures and aggregate structures. These compounds show different fluorescence emissions from blue to yellow region, and they also show different concentration-dependent emission (CDE) and excitation-dependent emission (EDE) characteristics. The position of ketone groups and the steric hindrance of methyl groups in the compounds determine the occurrence of keto-enol tautomerism or not. The compounds with conjugated keto-enol structure (i.e., nonaromatic TBC) show red-shifted emissions with comparison to the compounds with only isolated diketone structures. Theoretical calculations show that TBC effect reduces the HOMO-LUMO energy gaps of single molecules, and it facilitates the formation of stronger TSC in the aggregate state. The cooperative effect of nonaromatic TBC and TSC leads to more significantly red-shifted emissions. This work provides a novel and deeper understanding of the PL mechanisms of NTLs and is of great importance for directing the design and synthesis of NTLs with enhanced and red-shifted emissions.