ABSTRACT
The rise in interest in two-dimensional (2D) nanomaterials has been notable in recent years. In particular, hexagonal boron nitride (h-BN), recognized as an optimal substrate for enhancing graphene properties, holds promise for electronic applications. However, the widely employed spontaneous Raman microscopy, a gold standard for graphene study, faces strong limitations in h-BN due to its large bandgap and low cross section. In this Letter, high-resolution femto/picosecond coherent anti-Stokes Raman scattering (fs/ps-CARS) spectroscopy is used for hyperspectral imaging of nanometric h-BN layers. Our study establishes that CARS signal effectively enhances Raman signature related to in-plane ring vibrations, thus providing valuable quantitative insights into sample thickness and crystalline quality, also corroborated by additional AFM measurements.
ABSTRACT
We present a multi-focus fs/ps-CARS scheme to perform spectroscopy on multiple points simultaneously for gas phase measurements and microscopy, using a single birefringence crystal or a combination of birefringent stacks. CARS performances are first reported for 1 kHz single-shot N2 spectroscopy on two points set few millimeters apart, allowing thermometry measurements to be carried out in the vicinity of a flame. Then, simultaneous acquisition of toluene spectra is demonstrated on two points set 14 µm apart in a microscope setup. Finally, two-point and four-point hyperspectral imaging of PMMA microbeads in water is performed, demonstrating a proportional increase in acquisition speed.
ABSTRACT
Electropulsation has become a powerful technological platform for electromanipulation of cells and tissues for various medical and biotechnological applications, but the molecular changes that underlay the very first initiation step of this process have not been experimentally observed. Here, we endowed a wide-field Coherent anti-Stokes Raman Scattering platform with an ad-hoc electromagnetic exposure device and we demonstrated, using artificial lipid vesicles (i.e. liposomes), that electropulsation is initiated by the increase of interstitial water content in liposome membranes. A pulse-dependent accumulation of the interstitial water molecules is observed in the membranes and a plausible mechanism supported by a computational electrochemical model is presented and discussed.
Subject(s)
Liposomes , Spectrum Analysis, Raman , Electricity , Spectrum Analysis, Raman/methods , WaterABSTRACT
Single shot hybrid fs/ps-CARS spectroscopy of N2 is demonstrated at repetition rate up to 5 kHz using an amplified probe delivering a constant energy per pulse between 1 and 5 kHz. We performed 5 kHz CARS thermometry in a laminar CH4/air flame and in ambient air, with a precision under 0.5% at typical flame temperature, which is 2 times more precise and 5 times faster than previous state of the art with this technique. Temperature was measured during long acquisition times up to 100 s, making the system suitable to record signals in the 0.01-2500â Hz spectral window; in our case 10â Hz temperature oscillations were probed.
ABSTRACT
Laser-induced fluorescence imaging of aluminum atoms (Al-PLIF) is used to analyze the spatio-temporal behavior of aluminized solid propellant combustion. Using alternating LIF and chemiluminescence emission images of the particles in the gaseous and liquid phase evolving close to and far above the dynamically varying propellant surface, sequences of images were recorded and analyzed. The good sensitivity achieved enabled us to track the dynamics of the flame in the vicinity of particles detected all along the flame extension and up to 1.5 MPa. Analysis of wide-field images enabled droplet velocity measurements due to the high LIF sampling rate (5 kHz). The observed typical plume structures were in good agreement with alumina-formation prediction and previous shadowgraphy visualization. High-resolution sequences of images showed gaseous distribution behavior around the molten particles. The Al vapor phase was thus found to extend between 3 and 6.5 radii around the particles. Particle detachment dynamics were captured just above the propellant surface.
