Lewis Acid-Relayed Singlet Oxygen Reaction with Enamines: Selective Dimerization of Enamines to Pyrrolin-4-ones.

Singlet oxygen (O)-mediated oxidation represents an attractive strategy for incorporation of oxygen atoms from air under mild and environmentally benign conditions. However, the O reaction with enamine suffers from fragmentation, leading to very unsuccessful transformation. Here, Lewis acid is introduced to intercept [2 + 2] or "ene" reaction intermediates of the O reaction and enables oxidative dimerization of enamines to produce pyrrolin-4-ones in good to excellent yields.

Surface-enhanced Raman scattering by the composite structure of Ag NP-multilayer Au films separated by AlO.

In the present study, a nanoparticle-multilayer metal film substrate was presented with silver nanoparticles (Ag NPs) assembled on a multilayer gold (Au) film by employing alumina (AlO) as a spacer. The SERS performance of the proposed structures was determined. It was suggested that the SERS effect was improved with the increase in the number of layers, which was saturated at four layers.

An Au Nanofilm-Graphene/D-Type Fiber Surface Plasmon Resonance Sensor for Highly Sensitive Specificity Bioanalysis.

A highly sensitive Au-graphene structure D-type fiber surface plasmon resonance biosensor is presented in this study to specifically detect biomolecules. The method of growing graphene is employed directly on the copper, and then a gold film of optimum thickness is sputtered, and the copper foil is etched to obtain the structure. This method makes the contact closer between the gold layer and the graphene layer to improve surface plasmon resonance performance.

Visible Light Irradiation of Acyl Oxime Esters and Styrenes Efficiently Constructs β-Carbonyl Imides by a Scission and Four-Component Reassembly Process.

Acyl radical triggered difunctionalizations of aryl olefins have been realized using oxime ester as the acyl precursor for the first time. Irradiation of -Ir(ppy) and oxime ester by visible light caused scission into three components, which recombined with olefins to yield significant β-carbonyl imides showing good functional group tolerance and high atom economy. Control experiments as well as spectroscopic and electrochemical studies revealed the efficient intermolecular reorganization of oxime ester into styrene with the aid of solvent exchange.

Direct Arylation of Unactivated Alkanes with Heteroarenes by Visible-Light Catalysis.

The functionalization of aliphatic C-H bonds is both a major challenge and a desirable goal in organic synthesis. Here, we describe the successful arylation of unactivated alkanes with heteroarenes by using iridium polypyridyl complexes as the photocatalyst and persulfate as the HAT catalyst precursor under visible-light irradiation. This reaction features good functional group tolerance and broad scope with regard to both alkane and heteroarene substrates (37 examples), which allows direct access to alkyl-substituted -heteroarenes, a key structural motif in natural products and bioactive molecules.

Photocatalytic C-C Bond Activation of Oxime Ester for Acyl Radical Generation and Application.

A unified strategy to generate acyl radical from oxime ester via selective C-C bond activation is reported. Under visible-light irradiation, single-electron transfer from fac-Ir(ppy) to related oxime takes place followed by a fast β-fragment of C-C bond to yield aryl and aliphatic acyl radicals, subsequently captured by diverse Michael acceptors. More interestingly, the single-electron transfer enables coupling with energy transfer of the excited fac-Ir(ppy) via enone intermediate formed in situ for cyclobutane formation.

1886-nm mode-locked and wavelength tunable Tm-doped CaF lasers.

A 3 at.% Tm-doped CaF crystal was grown successfully and used as a gain medium. A high-efficiency continuous-wave laser and wide tuning performance were demonstrated in this crystal, and passive mode-locking laser operation was realized for the first time, to the best of our knowledge.

Efficient continuous-wave and passive Q-switched mode-locked Er : CaF-SrF lasers in the mid-infrared region.

An Er-doped CaF-SrF mixed crystal was grown using the temperature gradient technique, and its laser characteristics were studied. In a compact linear cavity, a continuous-wave output power of 712 mW was obtained with the highest slope efficiency of 41.4%.

Mid-infrared self-Q-switched Er, Pr:CaF diode-pumped laser.

A diode-end-pumped self-Q-switched mid-infrared laser was demonstrated with Er, Pr co-doped CaF crystal for, to the best of our knowledge, the first time. Maximum average output power of 262 mW was achieved and the corresponding slope efficiency was 14.9%.

Highly efficient dual-wavelength mid-infrared CW Laser in diode end-pumped Er:SrF single crystals.

The spectral properties and laser performance of Er:SrF single crystals were investigated and compared with Er:CaF. Er:SrF crystals have larger absorption cross-sections at the pumping wavelength, larger mid-infrared stimulated emission cross-sections and much longer fluorescence lifetimes of the upper laser level (Er:I level) than those of Er:CaF crystals. Dual-wavelength continuous-wave (CW) lasers around 2.

Radical Addition of Hydrazones by α-Bromo Ketones To Prepare 1,3,5-Trisubstituted Pyrazoles via Visible Light Catalysis.

A novel efficient tandem reaction of hydrazones and α-bromo ketones is reported for the preparation of 1,3,5-trisubstituted pyrazoles by visible light catalysis. In this system, the monosubstituted hydrazones show wonderful reaction activity with alkyl radicals, generated from α-bromo ketones. A radical addition followed by intramolecular cyclization affords the important pyrazole skeleton in good to excellent yields.

A facile method to immobilize cucurbituril on surfaces through photocrosslinking with azido groups.

We develop a facile method to immobilize cucurbituril on silicon substrates through photochemical reaction with azido groups. Combining photolithography and the competitive molecular recognition between CB[7] and acridine orange base or 1-adamantanecarboxylic acid, a patterned surface with reversible fluorescence emission can be obtained.

Passively mode-locked Yb3+:Sc2SiO5 laser with reflection-type single-walled carbon nanotube absorber.

A reflection-type single-walled carbon nanotube saturable absorber fabricated by a vertical evaporation method was to our knowledge first used in a passively mode-locked Yb(3+):Sc(2)SiO(5)(Yb:SSO) laser. The laser operated at a repetition frequency of 94 MHz with a central wavelength of 1062.6 nm.

Continuous transform of transverse modes and transitional status analysis in solid-state laser.

With the agility of cavity control in solid-state-laser, we report abundant experimental phenomena of relatively complete Laguerre-Gaussian (LG) transverse multimodes transformation process including both stable and transitional status in a diode pumped Nd:YVO4 microcavity laser. Cavity structure, absorber, pump power, etc, synthetically have been found to contribute such abundant generation of patterns.