Graphene quantum dots (GQD) are nanoparticles consisting of a single or several layers of graphene sheets whose thickness does not exceed 100 nanometers. For their ease of preparation, biocompatibility and tunable absorption and emission properties, they have become extremely popular in optoelectronics, as nanocarriers for cancer therapy drugs and in bioimaging techniques.[1]
In this work,...
Silicates are ubiquitously found as small dust grains in the interstellar medium, where they are processed due to high-energy processes, such as UV radiation absorption. These abundant nanosilicates are likely to play an important role in astrochemistry. In this work, we form small magnesium silicate clusters via laser vaporization of a binary Mg2Si target in the presence of diluted molecular...
Hydrogen-bonded networks sustain a broad range of structural and charge transfer processes in supramolecular materials. The modelling of the proton dynamics in these systems is challenging and demands insights into prototypical benchmark complexes. Intramolecular H-bonding in 3-hydroxyglutaric acid (M) provides an intriguing case study of entangled proton dynamics. We combine infrared action...
We use a multiconfiguration Dirac-Fock code [1,2] to calculate electronic excitation cross sections and radiative decay transition probabilities for a large number of atomic levels in Pm-like bismuth. By numerically solving a set of equilibrium equations we were able to obtain the level populations of the $4f^{14}5s$, $4f^{13} 5s5f$, $4f^{13} 5s5d$, $4f^{13} 5s5p$, and $4f^{13} 5s^2$...
Microfluidics devices with internal gas flows are nowadays subject of a rapid development. These devices often operate in rarefied gas flow regimes, since the ratio of the molecular mean free path over the channel dimensions becomes non-negligible. In those rarefied flows, effects like temperature-jumps near the wall are expected to occur. However, there is a lack of experimental techniques...
Neutrons play a dominant role in the stellar nucleosynthesis of heavy elements. We review a scheme for the experimental determinations of neutron-induced reaction cross sections using a high-intensity neutron source based on the 18O(p,n)18F reaction with an 18O-water target at SARAFโs upcoming Phase II. The quasi-Maxwellian neutron spectrum with effective thermal energy kT โ 5 keV,...
Practical density functional theory (DFT) owes its success to the groundbreaking work of Kohn and Sham that introduced the exact calculation of the non-interacting kinetic energy of the electrons using an auxiliary mean-field system. However, the full power of DFT will not be unleashed until the exact relationship between the electron density and the non-interacting kinetic energy is found....
Gas Proportional Scintillation Counters (GPSC) are gas-filled detectors in which the charge signal produced by radiation interaction is amplified by secondary scintillation promoted by electron impact (electroluminescence) taking place in the gas. Primary electrons produced by the interacting radiation are driven towards a scintillation region, where the applied electric field is high enough...
The interest in CuInS2 (CIS) quantum dots (QDs) has increased significantly in the past few years due to broad range of their potential applications, such as photodynamic therapy or solar cells [1]. This owes to extraordinary optoelectronic properties of this material, such as broad photoluminescence with a large Stokes shift and long charge carrier lifetimes. To elucidate the...
For a long time, space was thought to be a hostile environment characterized by extreme conditions, in which the formation of any molecular system was highly unlikely, if not impossible. However, advances in three fundamental areas of molecular astrophysics (theoretical modeling, experimental laboratories, and observational missions), as well as, their joint effort are reponsible for more than...
Protonation and deprotonation processes in derivatives of aromatic systems play an important role in various areas of chemistry. The 'competition' between different centers to accept or donate a proton depends on a number of parameters, including electron density effects. This competition can result in the formation of different tautomers, each one having a different photophysical behavior....
In the present work, static and dynamic quantities of carbon dioxide (CO2) are studied by means of Raman spectroscopy in gas flows.
CO2 is a molecule of great importance in several current challenges, like characterization of exoplanets atmospheres, development of accurate climate models or synthesis of fuels through plasmas. Most of these problems involve non-local thermodynamic...
Many state-of-the-art optical readout micro-patterned gaseous detectors (MPGDs) are equipped with of standard Gas Electron Multipliers (GEMs), which are 50 ฮผm thick. The COBRA_125, a 125 ฮผm thick, triple-electrode MPGD has the potential to further increase the optical gain of these detectors: whereas in a GEM, the Electroluminescence light is only produced in the holes, the two independent...
Graphene quantum dots (GQD) are nanoparticles consisting of a single or several layers of graphene sheets whose thickness does not exceed 100 nanometers. GQD have become extremely popular in optoelectronics as nanocarriers for cancer therapy drugs and in bioimaging techniques, mostly due to their ease of preparation, biocompatibility and tunable absorption and emission properties...
Benzimidazole: One molecule - two photoreactions
Igor Reva
CIEPQPF, Department of Chemical Engineering, University of Coimbra,
Coimbra 3030-790, Portugal
Email: reva@eq.uc.pt
Monomers of benzimidazole trapped in an argon matrix at 15 K were characterized by vibrational spectroscopy and identified as 1H-tautomers exclusively. The photochemistry of matrix-isolated 1H-benzimidazole was...
The joint journey of rotational spectroscopy and radioastronomy is firmly pushing the frontiers of interstellar chemistry based on the detection of new molecules with ever-higher degrees of molecular complexity. However, for several families of compounds (e.g., carboxylic acids) the census of identified interstellar species has remained untouched for almost a quarter century. Herein, we...
Understanding the behaviour of endogenous therapeutic peptides (ETPs), short cationic peptides that have the ability to target and disrupt the pathological membranes, which typically contain a high concentration of anionic lipids, is crucial for the development of effective therapeutic strategies [1,2]. This study investigates multiple ETPs and their interaction with model lipid...
The application of THCOBRA based detectors for X-ray imaging has been studied. The optimization of detector performance is intrinsically related with the study of the gas mixture capable of providing the better image quality. When operating in gas flow mode with a gas mixture of Ne/CH$_4$ (95/5), a charge gain of $10^4$ was achieved, together with an energy resolution of about 22% (@ 8 keV),...
One-particle reduced density matrix (1RDM) functional theory is an alternative formalism to both density functional and wavefunction based methods. A pragmatic approach results in approximate functionals of the 1RDM in its diagonal form, that is, the use of natural orbitals and its occupation numbers as the fundamental variables, which define a natural orbital functional (NOF).
In this...
The current accuracy of atomic calculations is impressive, allowing us to explain and probe novel and extremely rich physical phenomena. In turn, novel experiments constantly allow us to validate and adjust our theories and calculations. The atomic data we can calculate encompasses many physical interactions, providing a wide range of fields with the necessary data for their own studies.
The...
Triatomic ultra-long Rydberg molecules are formed by the interaction of a Rydberg atom, an excited atom with an electron with high principal quantum number, and a polar molecule. The study of Rydberg molecules is motivated by its interesting properties [1-3], and possible applications in ultracold chemical reactions [4] or quantum simulations [5]. In this work, we investigate the electronic...
The search for dark matter is one of the highest priorities in contemporary modern particle physics roadmaps. Direct detection experiments employing noble liquid detectors are currently limited by the radioactivity from the detector materials, mostly from the specially radio-clean photomultiplier tubes (PMTs), contributing to the background at ~ 80% level. Large area avalanche photodiodes and...
\title{Non--Covalent Interactions in Carbon Dioxide Clusters: Comparison Between the Thiophenol--CO$_2$ and Benzylmercaptan--CO$_2$ Dimers Using Microwave Spectroscopy}
Carbon dioxide (CO$_2$), as a greenhouse gas causing global warming, has received great attention concerning its pollution effects and reactivity.\footnote{S. C. Peter, {\it ACS Energy Lett.\/}, {\bf 3}, 1557--1561...
The detection of particle dark matter (DM) remains an unresolved challenge in contemporary physics. The XENONnT experiment, located at the Laboratori Nazionali del Gran Sasso, in Italy, utilizes a multi-tonne liquid xenon time projection chamber to probe DM interactions. With an active target of 5.9 tonnes, low background, and keV-level threshold, XENONnT completes its science program with...
We present a new potential energy surface (PES) for the interaction between the Hydrogen molecule ion and the Helium atom in its electronic ground state. The PES of (H2+)He cluster is represented by two contributions: a polarization energy term due to the electric field generated by the molecular cation in the position of the polarizable He atom and dispersion-repulsion forces characterized by...
The sigmatropic isomerization reaction of previtamin D3 to vitamin D3, when encapsulated within a dimer of ฮฒ-cyclodextrin, exhibits a 40-fold enhanced rate compared to its counterpart in an isotropic organic solution [1]. Despite several hypotheses, the exact mechanism by which ฮฒ-cyclodextrin dimer catalyzes the reaction remained elusive.
We have conducted a rigorous investigation of...
The structures and energetics of Li+2-doped He clusters have been determined by means of evolutionary programming optimizations and classical molecular dynamics simulations [1]. The underlying interactions in the HeN Li+2 complexes are described by sum-of-potentials ab initio-based models [2]. The classical picture of the He atoms surrounding the cationic dimer shows a selective growth of the...
SHโบ is a widespread molecular ion in diffuse interstellar clouds, and has also been detected in emission toward the Orion Bar photodissociation region (PDR). In warm and dense PDRs, SHโบ is thought to form by exothermic reactions of Sโบ with vibrationally excited H2 (v>1). The viability of this hypothesis have been confirmed by theoretical simulations reaction which demonstrate that for...
The computational simulation of biological processes is a complex task which requires the combination of different quantum and classical mechanical techniques. Moreover, these hybrid calculations are often performed within a dynamic framework to account for conformational sampling. In the case where the process under investigation takes place in a long-time scale, the application of enhanced...
Curcumin, a natural yellow pigment derived from the rhizome of turmeric (Curcuma longa L.), possesses significant biological properties. Nonetheless, its therapeutic potential is hindered by its limited bioavailability.[1] To address this challenge, and thus enhance the bioavailability and pharmacological efficacy of curcumin, one proposed strategy is the co-administration of curcumin with...
Understanding the formation of PoliAromatic Hydrocarbons (PAHs) can shed light on the origin of the prebiotic Earth and even on the origin of life.[1] Unfortunately, to date, the formation of organic compounds in space is a scarcely understood area.
In this arena, automated protocols for the identification of reaction mechanisms show great potential to aid in the learning of how PAHs are...
Given the recent detection of multiple neutron-star merger events, in particular the AT2017gfo observation, in which the ejection of hot and radioactive matter, termed kilonovae, was detected as an electromagnetic signal. It is critical to combine a more comprehensive description of nuclear and atomic properties with advanced astrophysical simulations in order to produce accurate predictions...
Host defense peptides (HDPs) are short cationic peptides that have a critical role in the innate immune response across all living organisms [1]. Their primary mode of action does not depend on protein receptors, but instead on their ability to target and disrupt the membranes of various pathogenic and pathological cells, such as those found in cancer, bacteria, or even our own senescent...
