PCCP Blog

Jos Oomens, Renato Zenobi and co-workers have investigated the structures and energetic properties of four common oxazine dyes using both experimental and theoretical approaches. The structural information obtained in the gas phase provides an important step towards an in-depth understanding of the fluorescent properties of the dyes.

The group studied Nile red, Nile blue A, cresyl violet and brilliant cresyl blue using both infrared multiple photon dissociation spectroscopy and quantum chemical calculations. Nile red is a commonly used probe for the investigation of many chemically important systems and, despite its well-characterised fluorescence in solution and widespread use, its gas-phase fluorescence has not been observed before. The group determined the true structure of the protonated fluorophore and, out of the many possible sites, they found that that the site of protonation of Nile red is at the carbonyl oxygen.

Significant differences can exist between the fluorescence properties of an isolated ion in the gas phase and its solvated counterpart. As these differences can be unpredictable, a definitive structural description of a gaseous flourophore is essential for the prediction of the associated fluorescent properties.

Read more in this PCCP article:

Infrared multiple photon dissociation (IRMPD) spectroscopy of oxazine dyes
Robert J. Nieckarz, Jos Oomens, Giel Berden, Pavel Sagulenko and Renato Zenobi
DOI: 10.1039/C3CP00158J

Diau, Yeh et al. studied the effects of the 4-tert-butylpyridine (TBP) additive in the electrolyte on the performance of two different porphyrin sensitizers from both photoelectric and photophysical points of views.

The scientists from Taiwan carried out time-resolved investigations of thin-film samples using femtosecond fluorescence up-conversion spectroscopy, charge extraction and transient photoelectric measurements of the corresponding devices. The two push-pull porphyrin sensitizers, which had different anchoring groups, showed similar device performance without TBP. Upon addition of TBP, the power conversion efficiency of the device containing one dye increased, and the device containing the other decreased.

Read more in this HOT PCCP article today:

The influence of electron injection and charge recombination kinetics on the performance of porphyrin-sensitized solar cells: effects of the 4-tert-butylpyridine additive
Yu-Cheng Chang, Hui-Ping Wu, Nagannagari Masi Reddy, Hsuan-Wei Lee, Hsueh-Pei Lu, Chen-Yu Yeh and Eric Wei-Guang Diau
DOI: 10.1039/C3CP44555K

Scientists from Wuhan University of Technology have found that the visible-light absorption and photocatalytic activities of B-, C- and B/C-doped anatase TiO₂ are not only influenced by the energy gaps and the distributions of energy states, but also by the locations of Fermi levels and the energies of the band gap edges. They also found that the stability of the doped TiO2 was dependant on its growth conditions.

Jiaguo Yu, Peng Zhou and Qin Li used density functional theory calculations to investigate the structures, formation energies and electronic properties of B-, C- and B/C-doped anatase TiO2. Their study provides insights into the design and synthesis of multi-doped TiO2 with desirable electronic properties, important in areas such as heterogeneous catalysis.

Read this HOT article:

New insight into the enhanced visible-light photocatalytic activities of B-, C- and B/C-doped anatase TiO2 by first-principles
Jiaguo Yu, Peng Zhou and Qin Li
DOI: 10.1039/C3CP44651D

Remi Chauvin and Christine Lepetit give the topological resonance energy (TRE) acyclic reference of any π-cyclic molecule, for 36 years merely defined by an abstract matching polynomial, a real chemical structure: the Mobius-twisted head-to-tail metathesis cyclo-dimer of the parent ring.

The aromaticity of a cyclically conjugated molecular system can be qualitatively defined as its tendency to resist the loss of its cyclic character under constraint or relief of external perturbations, or fundamentally quantified as the difference between the energy of the cyclic system and the energy of some acyclic reference. This acyclic reference is rigorously defined as the abstract reference of the TRE, but might not exist as a chemical species. In their recent PCCP paper, Chauvin and Lepitit report the long-sought chemical nature of TRE, and of topological aromaticity.

Read the details in this HOT article today:

The fundamental chemical equation of aromaticity
Remi Chauvin and Christine Lepetit
DOI: 10.1039/C2CP44075J

Hernandez and Schmidt investigate the role of anisotropic water-carbon interactions on water in low-diameter carbon nanotubes (CNTs) in their recent PCCP paper, and demonstrate the importance of the anisotropy. Extensive simulations provide a comprehensive picture of the effects of the interaction anisotropy on the structure and dynamics of water confined in narrow, single-walled CNTs.

Carbon based materials are generally accepted as being hydrophobic, but the calculated water-graphene interaction is found to be non-negligible and, moreover, orientation-dependant. The authors firstly calibrated new parameters for a Lennard-Jones potential, emphasising the anisotropy in the carbon-water interaction. They then performed molecular dynamics studies, using these parameters, of water inside various CNTs to examine properties such as structure, Lindemann index, mean square displacements and H-bonding patterns.

In contrast to previous simulations employing spherical interaction models, they found that the water molecules tend to form denser clusters displaying liquid-like behaviour, allowing for self-diffusion along the CNT axis.

Structures and hydrogen-bonding networks of water molecules inside CNTs can be radically different to those found in bulk water, due to the fact that the water molecules are confined in tubes with diameters not much larger than their own size. A central issue in many applications of CNTs is the possibility of conveying or storing fluids, hence the importance of understanding these systems.

Read about these fascinating results in this article:

Anisotropy of the Water-Carbon Interaction: Molecular Simulations of Water in Low-Diameter Carbon Nano-Tubes
Burkhard Schmidt
DOI: 10.1039/C3CP44278K

A recent theoretical study by Zhijan Wu, Aimin Ren and co-workers predicts novel BODIPY derivatives with interesting and potentially very useful nonlinear optical properties.

The group studied a series of aza-BODIPY fluorophores with structures expected to have large two-photon cross-sections at telecommunication wavelengths. They found that it is possible to finely tune the linear and non-linear optical properties by chemical modification of the aza-BODIPY core and peripheral moieties, resulting in excellent, original candidates for nonlinear transmission and fluorescent labelling materials.

Read the full paper:

New insights into two-photon absorption properties of functionalized aza-BODIPY dyes at telecommunication wavelengths: a theoretical study
Xiaoting Liu, Jilong Zhang, Kai Li, Xiaobo Sun, Zhijian Wu, Aimin Ren and Jikang Feng
DOI: 10.1039/C3CP44435J