An AIEE-active Triphenylethylene Derivative with Photoresponsive Character for Latent Fingerprints Detection via a Simple Soaking Method.

Latent fingerprints (LFPs) is one of the most important physical evidence in the criminal scene, playing an important role in forensic investigations. Therefore, developing highly sensitive and convenient materials for the visualization of LFPs is of great significance. We designed and synthesized an organic fluorescent molecule TP-PH with aggregation-induced enhanced emission (AIEE) activity. By simply soaking, blue fluorescent images with high contrast and resolution are readily developed on various surfaces including tinfoil, steel, glass and plastic. Remarkably, LFPs can be visualized within 5 min including the first-, second- and tertiary-level details. In addition, TP-PH exhibits interesting photoactivated fluorescence enhancement properties. Under irradiation of 365 nm UV light with a power density of 382 mW/cm2, the fluorescence quantum yield displays approximately 21.5-fold enhancement. Mechanism studies reveals that the photoactivated fluorescence is attributed to the irreversible cyclodehydrogenation reactions under UV irradiation. This work provides a guideline for the design of multifunctional AIEE fluorescent materials.

Multi-wavelength excited triplet-triplet upconversion microcrystals based on hot-band excitation for optical information encryption.

Multi-wavelength hot-band excitation, forbidden in the conventional Stokes fluorescence mechanism, is found to be available with cascading triplet-triplet annihilation upconversion (TTA-UC). Selective excitation of Pt(II)octaethylporphyrin (PtOEP) by diode lasers with wavelengths of 532 nm, 589 nm, 635 nm, 655 nm, and 671 nm respectively can all induce 9,10-diphenylanthracene (DPA) to emit blue upconversion, with the maximum anti-Stokes shift of 0.95 eV in the microcrystals exposed to air. Whether the zero-vibrational energy level excitation or the hot-vibrational energy level excitation in the ground state, the PtOEP/DPA pair showed triplet-triplet energy transfer (TTET) efficiencies approaching ∼95%. The doped microcrystal samples without encapsulation can emit blue upconversion from green/yellow/red excitation with stability for ∼20 days under atmospheric conditions, demonstrating their potential applications in multiple information encryption.

The effect of triethylamine on dye-sensitized upconversion luminescence and its application in nanoprobes and photostability.

Triethylamine (TEA) is an effective medium for inhibiting dye aggregation and improving the luminescence of dye-sensitized lanthanide-doped upconversion nanoparticles (UCNPs). However, excessive TEA will cause quenching of upconversion luminescence. In this paper, the possible mechanism of TEA affecting upconversion luminescence is discussed. It is found that TEA can enhance the nucleophilicity of the solvent, leading to dye shedding from the nanoparticles. Reducing the dielectric constant of the solvent can make TEA play a more positive role in upconversion luminescence and photostability of dye-sensitized UCNPs. When heptanol is selected as the solvent for CyBSO-sensitized ß-NaYF4:20%Yb3+,2%Er3+ (UNs), TEA can increase the upconversion luminescence by 6.0 times relative to that in methanol. More importantly, the optimal content of TEA in heptanol is 3700 times more than that in methanol. Under the action of large amounts of TEA in heptanol, a novel upconversion nanoprobe for detecting ascorbic acid is developed with a limit of detection of 0.103 µM and high selectivity over potential interfering species. Meanwhile, the high concentration of TEA in heptanol can improve the photostability of CyBSO-sensitized UNs by 10.4 times, which is of paramount importance for the practical application of dye-sensitized UCNPs.

Highly-efficient red-to-yellow/green upconversion sensitized by phthalocyanine palladium with high triplet energy-level.

Soluble 3,7,11,15-tetra(tert-butyl)phthalocyanine palladium (TBPcPd) and 3,7,11,15-tetra(pentyloxy)phthalocyanine palladium (POPcPd) were synthesized and employed as sensitizers in expectation of achieving red-to-yellow/green upconversion (UC), doped with rubrene (Rub) and 9,10-bis(phenylethynyl)anthracene (BPEA), respectively. Under excitation of a 655 nm diode laser (∼1.5 W cm-2), a maximum red-to-green UC efficiency of 0.07% and a maximum red-to-yellow UC efficiency of 8.03% were obtained and the latter can drive a Si-photodiode to generate obvious photocurrent. The results showed that although a large triplet energy-level difference (ΔE = 3 E sen. - 3 E anni.) of the sensitizer (3 E sen.)/annihilator (3 E anni.) pair helps to improve the upconversion, the sensitizer/annihilator pair with a ΔE value less than zero still works. However, when the ΔE ≤ -0.05 eV, this bicomponent pair is not valid anymore. Thus, a comparison of the ΔE value can predict whether the sensitizer/annihilator pair is useful, which presents a quantitatively evaluated approach for exploring new-type upconversion systems for the first time.

Correction: Photon upconversion: from two-photon absorption (TPA) to triplet-triplet annihilation (TTA).

Correction for 'Photon upconversion: from two-photon absorption (TPA) to triplet-triplet annihilation (TTA)' by Changqing Ye et al., Phys. Chem. Chem. Phys., 2016, DOI: .

Photon upconversion: from two-photon absorption (TPA) to triplet-triplet annihilation (TTA).

Organic upconversion is a unique process in which low-energy light (usually NIR light) is converted to high-energy light through either the two-photon absorption (TPA) mechanism or the triplet-triplet annihilation (TTA) mechanism. Both TPA upconversion (TPA-UC) and TTA upconversion (TTA-UC) have been actively investigated in recent years due to their intriguing applications in optics, biophotonics, and solar energy utilization. Although they show some similarity (i.e., belonging to the nonlinear two-quantum process and needing focused excitation light), TPA-UC and TTA-UC are very different, such as in mechanism, characteristics involved, molecular design and potential applications. Here, we collectively reviewed these two kinds of upconversion processes and compared their respective characteristics and merits. We also present recent advances made in the areas of TPA- and TTA-UC, the remaining challenges and opportunities, with particular emphasis on molecular engineering of these two active upconversion materials.

A new medium for triplet-triplet annihilated upconversion and photocatalytic application.

Since the triplet-triplet annihilated upconversion (TTA-UC) materials work efficiently only in degassing organic solvents, it is of significance to find a new medium without toxicity and volatility and that promotes TTA-UC. Here, we firstly reported the effect of an OH-containing medium on low power upconversion and found that in alcohol solvent containing ß-cyclodextrin (ß-CD), the phosphorescence lifetime (τp) of the sensitizer (PdTPP) and the fluorescence quantum yield (Φf) of the acceptor (DPA) were enhanced with the increase in the number of OH-groups of the medium. A large triplet-triplet quenching constant (kq, 1.91 × 10(9) M(-1) s(-1)) and high upconversion efficiency (ΦUC, ∼ 36%) of PdTPP/DPA were obtained under the excitation of a diode laser (532 nm, 60 mW cm(-2)). Under our green-to-blue upconversion irradiation, in a demonstration experiment the photocurrent was recorded at 0.09 µA cm(-2), resulting from photocatalytic water splitting by a Cd0.7Zn0.3S photoanode and a Pt counter-electrode in a photoelectrochemical cell. The importance of this study suggests that upconversion-powered photoelectrochemistry possesses potential application for hydrogen generation from water under excitation of sun energy.

New anthracene derivatives as triplet acceptors for efficient green-to-blue low-power upconversion.

Three new anthracene derivatives [2-chloro-9,10-dip-tolylanthracene (DTACl), 9,10-dip-tolylanthracene-2-carbonitrile (DTACN), and 9,10-di(naphthalen-1-yl)anthracene-2-carbonitrile (DNACN)] were synthesized as triplet acceptors for low-power upconversion. Their linear absorption, single-photon-excited fluorescence, and upconversion fluorescence properties were studied. The acceptors exhibit high fluorescence yields in DMF. Selective excitation of the sensitizer Pd(II)octaethylporphyrin (PdOEP) in solution containing DTACl, DTACN, or DNA-CN at 532 nm with an ultralow excitation power density of 0.5 W cm(-2) results in anti-Stokes blue emission. The maximum upconversion quantum yield (Φ(UC) =17.4%) was obtained for the couple PdOEP/DTACl. In addition, the efficiency of the triplet-triplet energy transfer process was quantitatively studied by quenching experiments. Experimental results revealed that a highly effective acceptor for upconversion should combine high fluorescence quantum yields with efficient quenching of the sensitizer triplet.

Graphene sheet-starch platform based on the groove recognition for the sensitive and highly selective determination of iodide in seafood samples.

The functionalization of graphene nanosheets was realized using a simple starch mixture to achieve a highly selective recognition of iodide, thereby surmounting the complicated reactions possibly leading to low yield during functionalization. The groove recognition for starch to iodide, a novel recognition model, was established. The starch-to-graphene nanosheet mass ratio of 3:2 produced an optimal current signal. The recognition and measurement procedures were conducted in different cells, respectively. These procedures improved the selectivity and sensitivity, and overcame the possibility of interference from coexisting ions. Under optimal conditions, the graphene sheet-starch electrode was immersed in a recognition cell at pH 2.0 for 10min, afterward, in a measurement cell at pH 1.0 for quantitative analysis, resulting in the highest current signals obtained. The quantitative electrochemical measurements yielded a mean value of 214.6mg/kg in actual samples of commercially available seafood sample, whereas the spectrophotometric measurements produced a mean value of 226.7mg/kg. If the spectrophotometric value for the seafood sample is accurate, the percentage error for the electrochemical method is only 5.3%. Therefore, the electrochemical method is reliable for qualitative iodide measurements. The groove recognition was highlighted to elucidate the specific selectivity.

[(Dibenzo[b,d]thio-phen-4-yl)tellan-yl]methane-thiol.

In the title compound, C(13)H(10)S(2)Te, the dibenzothio-phene moiety is almost planar, the maximum atomic deviation being 0.055 (5) Å. The two Te-C bonds are nearly perpen-dicular to each other with a C-Te-C bond angle of 93.0 (2)°. An inter-molecular C-H⋯π inter-action is present between the methyl-ene group and thio-phene ring.

C-H⋠⋠⋠π interaction-modulated solid-state packing and carrier mobility in thienyl and thieno[3,2-b]thienyl end-capped distyrylarylene derivatives.

Research on structure-property relationships in distyrylarylene derivatives is far behind their wide applications in optoelectronic devices due to the absence of crystal structure information. Herein, the single crystals of 4,4'-bis(2-thienylvinyl)biphenyl (1) and 4,4'-bis(2-thieno[3,2-b]thienylvinyl)biphenyl (2) were successfully grown by the vapor transport method. Both molecules adopt the typical herringbone packing motif. However, the intermolecular C-H⋅⋅⋅π interaction in compound 2 is much stronger than that in compound 1. The correlations of interchain interaction with film morphology, optical and electronic properties were studied. Compound 2 formed higher crystalline films with (001) and (111) orientations. The organic field-effect transistor properties of both materials were investigated. Compound 2 showed better performance with a hole mobility higher than 0.01 cm(2) V(-1) s(-1) and an on/off current ratio over 10(6) . These results reveal that the intensity of C-H⋅⋅⋅π interactions can exert dramatic influences on the optical and electronic properties of distyrylarylene-based materials.