Changgui Lu

Postsynthetic Doping of MnCl2 Molecules into Preformed CsPbBr3 Perovskite Nanocrystals via a Halide Exchange-Driven Cation Exchange

Unlike widely used postsynthetic halide exchange for CsPbX3 (X is halide) perovskite nanocrystals (NCs), cation exchange of Pb is of a great challenge due to the rigid nature of the Pb cationic sublattice. Actually, cation exchange has more potential for rendering NCs with peculiar properties. Herein, a novel halide exchange-driven cation exchange (HEDCE) strategy is developed to prepare dually emitting Mn-doped CsPb(Cl/Br)3 NCs via postsynthetic replacement of partial Pb in preformed perovskite NCs. The basic idea for HEDCE is that the partial cation exchange of Pb by Mn has a large probability to occur as a concomitant result for opening the rigid halide octahedron structure around Pb during halide exchange. Compared to traditional ionic exchange, HEDCE is featured by proceeding of halide exchange and cation exchange at the same time and lattice site. The time and space requirements make only MnCl2 molecules (rather than mixture of Mn and Cl ions) capable of doping into perovskite NCs. This special molecular doping nature results in a series of unusual phenomenon, including long reaction time, core-shell structured mid states with triple emission bands, and dopant molecules composition-dependent doping process. As-prepared dual-emitting Mn-doped CsPb(Cl/Br)3 NCs are available for ratiometric temperature sensing.

Multiwavelength generation in a Raman fiber laser with sampled Bragg grating

Simultaneous continuous-wave multiwavelength operation of a Raman fiber laser is demonstrated with sampled Bragg grating (SBG) at room temperature. The characteristics of multiwavelength fiber ring laser can be easily controlled by adjusting the parameters of the SBG, including the sampling period and the sampling length. In the proposed fiber laser, stable four oscillating wavelengths with 100- and 50-GHz spacing has been achieved, respectively, as well as five oscillating ones with a wavelength spacing of only 25 GHz by varying the sampling period of the SBG.

Near-infrared BODIPY-based two-photon ClO− probe based on thiosemicarbazide desulfurization reaction: naked-eye detection and mitochondrial imaging

Hypochlorite serves as a significant antimicrobial agent in the human immune system, and its detection is of great importance. Herein, a novel near-infrared BODIPY-based ClO- fluorescent probe (NCS-BOD-OCH3) was designed and synthesized. The emission bands of NCS-BOD-OCH3 concentrated at 595 nm and 665 nm. Since the electron withdrawing group 1,3,4-oxadiazole was formed after the desulfurization reaction, the fluorescence intensity of NCS-BOD-OCH3 decreased significantly in THF/H2O (v/v, 1 : 1, buffered with 10 mM PBS pH = 7.4), which is visible to the naked eye with an obvious color change. NCS-BOD-OCH3 can realize the two-photon up-converted fluorescence emission. The low detection limit was calculated from the titration results, with the figure for NCS-BOD-OCH3/ClO- being 1.15 × 10-6 M. The result of living cell imaging experiment demonstrated that NCS-BOD-OCH3 can successfully detect ClO- in living cells and can serve as a NIR mitochondrial imaging agent. It is an excellent platform for developing NIR ClO- fluorescent probes.

A smart two-photon fluorescent platform based on desulfurization–cyclization: a phthalimide–rhodamine chemodosimeter for Hg2+ NIR emission at 746 nm and through-bond energy transfer

A smart two-photon fluorescent platform based on desulfurization–cyclization was developed by attaching rhodamine to a cyanine skeleton through the Knoevenagel reaction. Based on the platform, a CyRSN probe was rationally designed and synthesized, in which morpholinyl naphthalimide and modified rhodamine thiohydrazide were linked to form a structure of monothio-bishydrazide. The probe exhibits excellent two-photon properties toward Hg2+ under Ti:sapphire pulsed laser 800 nm irradiation, allowing the naked-eye signal and fluorescence “turn-on” signal at 746 nm to be obviously distinguished. The addition of Hg2+ to the probe ensured that the naphthalimide donor and modified rhodamine acceptor were connected with electronically conjugated bonds (1,2,4-oxadiazole). Hence, a typical TBET process took place, resulting in an increase of the modified rhodamine NIR emission at 746 nm by about 34-fold as well as a decrease of the naphthalimide emission at 540 nm and producing a colorimetric change from pale yellow to green. The chemodosimeter exhibits a stable response for Hg2+ over other metal ions with a detection limit of 1.91 × 10−7 M, high sensitivity, a rapid response time, and pH independence under neutral conditions (pH 6.0–10.0). In addition, the CyRSN probe was successfully applied in the detection and quantification of Hg2+ in water samples with satisfactory recovery results.

Vibrational resonance enhanced broadband multiphoton absorption in a triphenylamine derivative

Multiphoton absorption of 2,5-bis[4-(2-N,N-diphenylaminostyryl)phenyl]-1,3,4-oxadiazole was experimentally studied by using femtosecond laser pulses. This material demonstrates a very broad multiphoton absorption band of around 300nm width with two peaks of 1250 and 1475nm. The first peak results from the three-photon absorption process while the second is attributed to the vibrational resonance enhanced four-photon absorption process. Combination of these two processes provides a much broader multiphoton absorption band. In this letter, the analytical solution to nonlinear transmission of a three-photon absorption process is also given when the incident beam has a Gaussian transverse spatial profile.

INFLUENCES OF AGGREGATION ON THE TWO-PHOTON FLUORESCENCE PROCESS

Rhodamine B (RhB) is most often used as the reference in the two-photon induced fluorescence (TPIF) method to measure the two-photon absorption (TPA) cross-section. In this work, we investigate the influences of dimer formation, energy transfer and self-absorption on the two-photon fluorescence process. Those three effects will result in a large measurement error of the TPA cross-section. We thus provide a concentration gradient correction method by considering the above three processes to eliminate the measurement error.

A conjugated BODIPY–triphenylamine multi-aldoxime: Sonogashira coupling, ratiometric chemodosimeter and rapid detection of hypochlorite with two-photon excited fluorescence

A conjugated BODIPY–triphenylamine multi-aldoxime (BTN) was designed and synthesized by the Sonogashira coupling reaction. The chemodosimeter showed a red emission (670 nm), fast response (within seconds), high selectivity and good sensitivity towards hypochlorite based on the redox reaction of four aldoximes. BTN possessed two original absorption peaks at 366 nm and 588 nm, respectively, corresponding to fluorescence emissions at 440 nm and 660 nm, which exhibited a ratiometric change in the presence of hypochlorite. With the addition of hypochlorite, the redox reaction of aldoxime led to the termination of isomerization of the CN bond, the fluorescence intensity at 660 nm gradually changed from weak to strong, accompanied by a slight 10 nm red-shift; in contrast, the fluorescence intensity began to decrease at 440 nm. Moreover, as the two-photon excited fluorescent NaOCl probe, BTN afforded an enhanced signal response for hypochlorite at 686 nm under two-photon excitation (λTPEFex = 800 nm). Meanwhile, successful imaging of living cells was carried out for BTN towards hypochlorite in A-549 cells. The results demonstrated that BTN had potential application prospects and was promising for practical application in biological systems and environmental systems.

Study of low-threshold and high-intensity random lasing in dye doped liquid crystals

Random lasers in dye-doped nematic liquid crystal (DDNLC) cells with different structures are studied. By choosing the cell gap and the cells rubbing methods, the DDNLC random laser obtains lower energy threshold. The DDNLC random laser energy threshold can also be decreased with an Al mirror as the external feedback from 4.2 μJ/pulse to 1.5 μJ/pulse. It is worth mentioning that the random laser shifts red and intensity increases with the Al mirror. The study of the DDNLC random laser with cell structure is aimed to obtain a low power consumption laser at a lower cost.

Surface states controlled broadband enhancement of two-photon absorption

We demonstrate the controllable broadband enhancement of two-photon absorption in a wide spectral range from 710 nm to 960 nm by controlling the surface states of aqueous Co2+ doped CdTe quantum dots, which is consistent with the measurement results of surface potential and fluorescence decay. The enhancement can be tuned in the range between 1 and 1.7 by changing the dopant concentrations that determine the surface states.

The controllable intensity and polarization degree of random laser from sheared dye-doped polymer-dispersed liquid crystal

Abstract The random laser from sheared dye-doped polymer-dispersed liquid crystal (DDPDLC) is investigated. As the emission intensity weakens, the threshold of random laser from DDPDLC increases from 2.0 mJ/pulse to 4.0 mJ/pulse, and the degree of polarization (DOP) increases from 0.1 to 0.78, obviously when the shear distance increases from 0 mm to 4 mm. As the liquid crystal droplets are gradually oriented in the shear direction caused by alignment direction of polymer chain and anisotropy of droplet shape, the scattering intensity perpendicular to the shear direction gradually decreases and that parallel to the shear direction gradually increases. The anisotropic absorption of the laser dye also plays a certain role as the shear distance is 0 mm. The controllable intensity and polarization degree of random laser have a huge potential for sensing applications.