Excitation wavelength dependent (Ex-De) emission materials have potential applications in anti-counterfeiting labels and bioimaging.N evertheless,f ew purely organic chromophores are used in these areas.I nt his study,m ultiple excited states were incorporated into am olecule that was excited state intramolecular proton transfer (ESIPT) active, with the goal of manipulating the relaxation pathwayso ft he excited states.T he triazole derivative exhibits Ex-De photoluminescence (PL), and the maximum PL wavelength is located at 526 nm and 593 nm under as eries of excitation wavelengths.S pectral identification indicates that the excimer and ESIPT processes are responsible for the green (526 nm) and orange (593 nm) fluorescence,r espectively.I mportantly, the quickr esponse code and test strip prepared with this triazole derivative can be used for anti-counterfeiting and food spoilage detection applications,r espectively.T his research opens the door for developing novel Ex-De materials for anti-counterfeiting purposes.The luminescence behavior of most fluorescent molecules follows Kashasr ule,t hat is,t he photoluminescence (PL) wavelength is independent of the excitation wavelength. Exceptions to Kashasrule arise when large energy gaps exist between excited states because of the suppression of the internal conversion (IC) process. [1] Excitation wavelength dependent (Ex-De) emission materials are highly desirable for use in biological labels,a nti-counterfeiting applications [5] and various optoelectronic devices. [2] At ypical Ex-De mol-ecule is azulene,w hich has been widely studied since the 1960s. [1c, 3] However,itisessentially useless because of the low PL efficiencya nd poor color difference.R ecent focus of Ex-De materials has been on nanoparticles (nanocrystals and carbon/silica dots) and metal complexes. [4] Forthe former, the emission wavelength can be shifted by using size control (or size distribution), element doping, and surface states.Surface functional groups,s uch as CÀN/CÀOa nd/or CÀN, can efficiently introduce new energy levels for electron transitions and lead to the Ex-De phenomenon. [4a-c] Fort he latter, incorporating metal ions into an organic ligand, which generally facilitates intersystem crossing from the singlet to triplet states,r esulted in phosphorescence and prompt fluorescence. [4e, 5] Purely organic materials that have the advantages of excellent processability,w ide variety,g ood biocompatibility,a nd appreciable stability are attractive alternatives.U nfortunately,m ost of the purely organic materials exhibit af ast IC process from S 2 to S 1 ,e specially in the aggregated state,a nd as ar esult, the Ex-De fluorescence behavior is rarely observed. Moreover,t heir potential application, especially in anti-counterfeiting applications,has not been well demonstrated.Thetriazole compound BH-BA(Scheme 1), which has the trade name "deferasirox", is aknown commercial drug for the treatment of transfusional chronic iron overload. [6] Interestingly,w ef ind that this purely organic m...
Many piezochromic luminescent (PCL) dyes are known for their fluorescent switching capacity in the powdered phase, but they are usually difficult to utilize practically owing to poor mechanical properties. Herein, a nanofiber film fabricated through an electrospinning process is doped with PCL dye. The electrospun film not only reveals the mechanics of macromolecular materials, but also achieves precise, gradient pressure recognition (ratiometric PCL behavior). The PCL sensitivity and color difference of the dye in a crystalline state are calculated to be 15.7 nm GPa−1 and 149 nm, respectively. The sensitivity of an electrospun film containing 0.1 % (w/w) dye decreased to 3.6 nm GPa−1. Moreover, the individual effects of molecular conformation and intermolecular interaction on the PCL properties have been clearly distinguished through in situ high‐pressure experiments. Intermolecular interactions play a more significant role in PCL color difference and sensitivity. The film fabricated through an electrospinning process contributes to understanding of the working mechanism and real applications of piezochromic materials.
Organic materials with excitation wavelength‐dependent (Ex‐de) emission are highly attractive for anticounterfeiting, optoelectronics and bioassay applications; however, the realization of Ex‐de fluorescence, independent of aggregation states, remains a challenge. We herein report a photoinduced electron transfer (PeT) strategy to design Ex‐de fluorescence materials by manipulating the relaxation pathways of multiple excited states. As expected, the o‐carborane dyad presents a clear Ex‐de fluorescence colour in the aggregated states, resulting from the tunable relative intensity of the dual‐fluorescence spectra. Taking TP[1]B as an example, the amorphous powders emitted bright blue‐violet, white and yellow colours under 390 nm, 365 nm and 254 nm UV illumination, respectively. Importantly, multicolour, flexible and transparent films as well as an anticounterfeiting application using this o‐carborane dyad are demonstrated.
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