spectroscopie infrarosie – Baza de Date

Tuner lasere pentru îmbunătățirea spectroscopiei în infraroșu (Tunable lasers to improve infrared spectroscopy )

a creat un nou laser revoluționar, cu bandă largă, reglabil, care are implicații majore pentru detectarea drogurilor și a explozivilor.
Robustul, tot laserul solid, poate fi reglat rapid pentru a emite în intervalul lungimii de undă care cuprinde regiunea critică a „amprentelor digitale” în care cele mai multe caracteristici moleculare sunt absorbite și identificate prin detectarea în infraroșu. În experimente, laserul și-a demonstrat capacitatea de a capta amprenta spectrală unică a gazelor.

Posted: Jun 09, 2016
Tunable lasers to improve infrared spectroscopy (Nanowerk News) A new development from Northwestern Engineering’s Manijeh Razeghi could be another tool for protecting our borders.
Supported by the Department of Homeland Security, Razeghi’s lab has created a new, revolutionary, broad-band tunable infrared laser that has major implications for the detection of drugs and explosives.
The robust, all solid-state laser can be rapidly tuned to emit in the wavelength range that encompasses the critical “fingerprint” region where most molecular features are absorbed and identified through infrared sensing. In experiments, the laser has demonstrated its ability to capture the unique spectral fingerprint of gases.
“The only moving part in the entire system is the fan used to keep the laser cool,” said Manijeh Razeghi, Walter P. Murphy Professor of Electrical Engineering and Computer Science. “This is a major advantage over existing systems that require mechanical parts to achieve tuning, and we expect to demonstrate remarkable stability.”
The initial, patent-pending results have been published in the June 8 issue of Nature Scientific Reports („Monolithically, widely tunable quantum cascade lasers based on a heterogeneous active region design”). The research and development of the laser system is the culmination of more than 18 years of quantum cascade laser development work at Northwestern’s Center for Quantum Devices.
The laser has been integrated into a system that contains all of the laser driver electronics and tuning software necessary for integration into a spectroscopy system. It produces a stable, single-aperture spot less than 3 millimeters in diameter that is suitable for standoff detection and is capable of linear or random access scanning with stabilization times of less than 1 millisecond per wavelength.

Source: Northwestern University

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Scrutând(cercetand) vârful sondelor moleculare

Autorii au folosit date din spectroscopie infraroșie și termogravimetrie pentru a identifica rezistența interacțiunii dintre sondă și suprafața de oxid, care le-a ajutat, de asemenea, să determine tipul de legare la suprafață.
Ei au stabilit doi parametri cheie: în primul rând, densitatea speciilor de suprafață adsorbite utilizate pentru a caracteriza interacțiunea moleculei de sondă cu suprafața. Acest parametru depinde de natura nanoparticulelor de oxid și de existența nanoporilor. Al doilea parametru exprimă raportul dintre moleculele conținute în stratul de suprafață având un comportament dinamic din sticlă față de numărul total al moleculelor adsorbite.
Studiul arată că valoarea densității de suprafață poate fi utilizată pentru a diviza compozitele în mai multe grupuri. Acest lucru ajută la determinarea faptului că moleculele de sondă aplicate pe suprafața unui grup dat pot prezenta interacțiuni similare, așa cum se observă în suprafețele aceleiași familii.

Posted: Feb 29, 2016
Scrutinizing the tip of molecular probes (Nanowerk News) Studies of molecules confined to nano- or micropores are of considerable interest to physicists. That’s because they can manipulate or stabilise molecules in unstable states or obtain new materials with special properties.
In a new study published in EPJ Plus („Rod-like cyanophenyl probe molecules nanoconfined to oxide particles: Density of adsorbed surface species”), Stefan Frunza from the National Institute of Materials Physics in Romania and colleagues have discovered the properties of the surface layer in probe molecules on the surface of oxide particles. These properties depend on the interaction at the interface.
In this particular study, probes are formed by adsorption of rod-like cyanophenyl derivates on the surface of oxide particles. The authors found that their surface layers behave like glass-forming liquids.

The solid lines indicate the temperature range used to estimate the amount of molecules loaded onto the probe.
What physicists already knew is that confinement of molecules may induce disorder. Confinement and disorder have a considerable influence both on the structure of the trapped molecule but also on its mobility. As a result, they also affect aspects such as molecular dynamics upon relaxation of the material. Such structurally well-defined monolayers on solid surfaces will allow researchers to model a large variety of interfacial phenomena.
The authors used data from infrared spectroscopy and thermogravimetry to identify the strength of the interaction between the probe and the oxide surface, which also helped them determine the type of bonding to the surface.
They established two key parameters: firstly, the density of the adsorbed surface species used to characterise the interaction of the probe molecule with the surface. This parameter depends on the nature of the oxide nanoparticles and on the existence of nanopores. The second parameter expresses the ratio of the molecules contained in the surface layer having a glassy dynamic behaviour to the total number of the adsorbed molecules.
The study shows that the value of the surface density can be used to divide the composites into several groups. This helps to determine that the probe molecules applied to the surface of a given group can display similar interactions, as observed in surfaces of the same family.

Source: SciencePOD

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