Analysis of luminescence, morphological and thermal behaviour of conjugated polymer/CdS electrospun nanofiber

Electro spun composite nanofibers of three series were prepared using different polymers (P1, P2, P3) and cadmium sulphide (CdS). Organic polymers of carbazole based quinoline (P1), quinoxaline (P2), and pyrazine (P3) hybrid with inorganic CdS nanofibers were characterized by XRD and FTIR technique. Collective arrangement of spiderweb-like morphology was observed for all nanofibers. Deviations of absorption and photoluminescence were monitored and a significant blue shift was found after doping CdS and PVA. It was found that the changes in the PL spectra of polymers originated from the chemical interactions between polymer and CdS. The diameter of nanofibers was observed as 127-347 nm from SEM analysis and 66-213 nm from TEM analysis. Optimum thermal stability of the composite nanofibers was achieved up to 200 °C. Compared with pure polymers and CdS, present nanofibers were good thermal stability, apparent blue shift with bluish emission which is suitable for optoelectronics application.

Active Manipulation of Fano Resonance at Visible and Near-Infrared Wavelengths in Metal Plasmonic Nanodevices Using Graphene

Active manipulation of Fano resonance at visible and near-IR wavelengths in metal nanodevices is one of the important challenges for applications such as chemical and biological sensing. Here, we theoretically research an active manipulation of Fano resonance at visible and near-IR wavelengths in gold plasmonic nanodevices with graphene. The surface plasmon resonance of the gold plasmonic nanodevice with graphene has three resonance peaks, and this can be explained by the distribution of the electric field in the nanodevice. The Fano resonance wavelength of the gold plasmonic nanodevice with graphene has a significant blue-shift compared with the gold nanodevices without graphene. Moreover, the Fano resonance dependens on the length and position of Au nanorods and the environment refractive index. The figure of merit of the gold nanodevice with graphene can be as high as 41.3, which makes the system suitable for high sensitivity applications. Finally, we actively manipulate the absorption spectrum and the reflected light phase through changing the Fermi energy of graphene. These results suggest an original method for the design of an actively manipulated Fano resonance nanodevice.

Spectral signatures of charge transfer in assemblies of molecularly-linked plasmonic nanoparticles

Self-assembly of functionalized nanoparticles (NPs) provides a unique class of nanomaterials for exploring and utilizing quantum-plasmonic effects that occur if the interparticle separation between NPs approaches a few nanometers and below. We review recent theoretical and experimental studies of plasmon coupling in self-assembled NP structures that contain molecular linkers between the NPs. Charge transfer through the interparticle gap of an NP dimer results in a significant blue-shift of the bonding dipolar plasmon (BDP) mode relative to classical electromagnetic predictions, and gives rise to new coupled plasmon modes, the so-called charge transfer plasmon (CTP) modes. The blue-shift of the plasmon spectrum is accompanied by a weakening of the electromagnetic field in the gap of the NPs. Due to an optical far-field signature that is sensitive to charge transfer across the gap, plasmonic molecules represent a sensor platform for detecting and characterizing gap conductivity in an optical fashion and for characterizing the role of molecules in facilitating the charge transfer across the gap.

Confinement Barrier Induced Enhancement in Thermal Stability of the Optical Response of InAs/InGaAs/GaAs Submonolayer Quantum Dot Heterostuctures

In this study the improvement in thermal stability of optical properties of InAs submonolayer quantum dot (SML QD) heterostructures is observed through incorporation of symmetric AlGaAs barrier layers. Low temperature photoluminescence (PL) spectra shows blue shift with less full width at half maxima, ascribe to the assimilation of AlGaAs barrier layers. The sample with confinement enhancing barrier shows the highest ground to ground transition energy with the lowest dot size distribution. Ex situ annealing of as grown samples, followed by PL analysis, confirms the improvement in thermal stability of optical behavior. For the samples with symmetric AlGaAs layer, annealing at higher temperatures under an inert condition can not change the downward transition energy effectively, whereas normal DWELL structures exhibits significant blue shift for the same.

Acid–base-controlled and dibenzylammonium-assisted aggregation induced emission enhancement of poly(tetraphenylethene) with an impressive blue shift

The non-covalent interaction between dibenzylammonium chloride and DB24C8 groups in poly(tetraphenylethene)-based conjugated polymers not only leads to an AIEE feature but also a significant blue shift from 515 to 483 nm.

Synthesis of the most anti-aromatic 16π porphyrin: an octaethylporphyrin zinc(II) complex with no meso-substituents

The most anti-aromatic 16π porphyrin, an octaethylporphyrin (OEP) zinc(II) complex with no substituents at the meso-positions was generated as a highly unstable species from the reaction of the corresponding 18π porphyrin using strong oxidants such as AgSbF 6/ I 2 or SbF 5. The porphyrin showed a significant blue-shift unique to 16π porphyrins in its UV-vis spectrum. 1 H NMR measurements revealed an evident high-field shift of the meso-protons of the porphyrin ring, thereby establishing that the novel 16π porphyrin has the strongest anti-aromaticity reported so far.

Properties and Analysis of Transparency Conducting AZO Films by Using DC Power and RF Power Simultaneous Magnetron Sputtering

DC power and RF power were introduced into the magnetic controlled sputtering system simultaneously to deposit AZO films in order to get an acceptable deposition rate with high quality transparency conducting thin film. The resistivity decreases with the RF power for the as-deposited samples. The resistivity of 6 × 10−4 Ω-cm and 3.5–4.5 × 10−4 Ω-cm is obtained for the as-deposited sample, and for all annealed samples, respectively. The transmittance of the AZO films with higher substrate temperature is generally above 80% for the incident light wavelength within 400–800 nm. The transmittance of the as-deposited samples reveals a clear blue shift phenomenon. The AZO films present (002) oriented preference as can be seen from the X-ray diffraction curves. All AZO films reveal compressive stress. The annealing process improves the electrical property of AZO films. A significant blue shift phenomenon has been found, which may have a great application for electrode in solar cell.

Theoretical Investigation on the Structure and Optical Properties of Alq3 and its Difluorinated Derivatives

The structures of tris(8-hydroxyquinoline) aluminum (Alq3) and its difluorinated derivatives were optimized for the ground state at the B3LYP/6-31G* level and for the excited-state at the CIS/6-31G* level. At the same time, the absorption and emission spectra based on the above structures were calculated by the time-dependent density functional theory (TD-DFT) using the PBE0 method with the 6-31G* set. A significant red shift was predicted for 3,5-difluoro-substituted Alq3 while a significant blue shift for 4,6-difluoro-substituted Alq3. In addition, the reorganization energies for electron carriers (λe) were predicted and it was found that the derivatives are potential materials for electron transport.

Aggregation of zinc tetraphenylporphyrin characterized by ensemble and single-molecule fluorescence spectroscopy

The aggregation of metalloporphyrins is believed to play a crucial role in the excited-state annihilation process known as triplet–triplet annihilation, which in turn has significant potential applications in photon upconversion schemes. In this work, the propensity of the water-soluble metalloporphyrin zinc (II) meso-tetra(4-sulfonatophenyl)porphine to undergo aggregation when adsorbed to glass cover slips was investigated by single-molecule fluorescence microscopy. In proof-of-principle experiments, it was demonstrated (1) that individual molecules of the metalloporphyrin can be directly visualized in spite of their very weak fluorescence emission, and (2) that at low concentrations (10−8 mol/L), the molecule has a strong tendency to form multimolecular aggregates. A subset of the multimolecular aggregates shows a significant blue-shift in fluorescence emission, though at present the precise nature of the molecular aggregates remains unclear.