Publications by authors named "Carlos Cairos"
Light emissions from cavitating liquids serve as a diagnostic tool for chemical activity, bubble collapse conditions, or excited species. Here we demonstrate the influence of mechanical stirring on sonoluminescence (SL) and sonochemiluminescence (SCL) emissions emerging in the presence of dissolved sodium salts and luminol in different sonicated liquids. In the systems investigated, driven in the 20-40 kHz range, stirring can change the spatial distribution of blue/white broadband SL emissions and of the orange sodium D-line emission, as well as their relative intensities.
View Article and Find Full Text PDFArticle Synopsis
- We developed a compact instrument that captures wavefront phase in real time, simplifying the setup and reducing capture time compared to traditional methods using defocused images.
- Our study focused on optimizing an electrically tunable lens within the camera, addressing its limitations and enhancing performance.
- We tested our camera on various targets, like deformable mirrors and lenses with aberrations, achieving high resolution and increased sensitivity to detailed signals.
The fabrication of three-dimensional (3D) nanostructures within optical materials is currently a highly sought-after capability. Achieving nanoscale structuring of media within its inner volume in 3D and with free design flexibility, high accuracy and precision is a development yet to be demonstrated. In this work, a 3D laser nanolithography technique is developed which allows producing mm-long hollow nanopores inside solid-state laser crystals and with a high degree of control of pore cross-sectional aspect ratio and size.
View Article and Find Full Text PDFArticle Synopsis
- Ultrasound, initially explored in sonochemistry nearly 90 years ago, continues to generate interest in Analytical Chemistry due to its numerous benefits aligned with Green Analytical Chemistry principles.
- * Recent applications of ultrasound focus on areas like synthesizing new materials (especially nanomaterials), developing sonoelectroanalytical sensors, and innovative spectroscopic techniques.
- * The review article aims to provide an overview of ultrasound's applications in Analytical Chemistry, along with insights into its fundamentals and emerging trends for future research.
Article Synopsis
- The study assessed microplastics on six beaches in Tenerife, Canary Islands, during late 2018, focusing on the presence and types of microplastics sampled above the high tide line.
- Most beaches had low microplastic levels, generally below 3.5 g/m and 0.069 g/L, except Playa Grande, which had significantly higher microplastic content at 99 g/m and 2.0 g/L.
- The primary types of microplastics identified were polyethylene (69%), polypropylene (18%), and polystyrene (4%), with additional tar pollution observed at Playa Grande.
Article Synopsis
- The research focuses on how ultrasonic cavitation bubbles behave in the microholes of PMMA plates, highlighting the lack of understanding in this area despite growing interest in ultrasonic cleaning methods.
- Using high-speed imaging, the study investigates various sizes of blind and through holes, demonstrating that trapped gas in these holes can be effectively removed through ultrasound agitation.
- The findings indicate that factors like hole diameter and liquid type influence bubble dynamics, and show that ultrasound can enhance liquid movement and mixing within small structures.
Article Synopsis
- - Multibubble sonoluminescence (MBSL) involves the release of light from collapsing bubbles in a dense bubble group, and new high-speed recording techniques have enhanced the ability to observe this process in detail.
- - This research focuses on the extremely bright MBSL observed in xenon-saturated phosphoric acid, allowing for the examination of how bubble motion and interactions affect light emission.
- - Findings show that only the largest bubbles emit light brightly and continuously, where bubble collisions can either enhance or terminate emissions, and some collapsing bubbles can reach extreme temperatures of around 38,000 K.
Sonoluminescence and dynamics of cavitation bubble populations in sulfuric acid.
Ultrason Sonochem
January 2017
The detailed link of liquid phase sonochemical reactions and bubble dynamics is still not sufficiently known. To further clarify this issue, we image sonoluminescence and bubble oscillations, translations, and shapes in an acoustic cavitation setup at 23kHz in sulfuric acid with dissolved sodium sulfate and xenon gas saturation. The colour of sonoluminescence varies in a way that emissions from excited non-volatile sodium atoms are prominently observed far from the acoustic horn emitter ("red region"), while such emissions are nearly absent close to the horn tip ("blue region").
View Article and Find Full Text PDFArticle Synopsis
- There is a gap in understanding how cavitation bubbles are distributed on solid surfaces during high frequency ultrasound reactions, which affects control over surface reactions.
- This study explores the distribution of cavitation bubbles on a solid sample using imaging techniques at different ultrasound frequencies (580, 860, and 1142 kHz).
- Findings indicate that the sample's position, orientation, and material properties significantly impact bubble distribution due to changes in the acoustic field, with optimal cavitation coverage achieved when the sample is nearly vertical to the ultrasound wave.
Cavitation bubbles collapsing in the vicinity to a solid substrate induce intense micro-convection at the solid. Here we study the transient near-wall flows generated by single collapsing bubbles by chronoamperometric measurements synchronously coupled with high-speed imaging. The individual bubbles are created at confined positions by a focused laser pulse.
View Article and Find Full Text PDFMicropatterning for the control of surface cavitation: visualization through high-speed imaging.
ACS Appl Mater Interfaces
February 2015
For the first time, we apply a high-speed imaging technique to record the activity of acoustically driven cavitation bubbles (86 kHz) on micropatterned surfaces with hydrophobic and hydrophilic stripes. The width of the hydrophobic stripes lies between 3.5 and 115 μm.
View Article and Find Full Text PDFArticle Synopsis
- - The study investigates the relationship between bubble dynamics and chemical reactions in cavitation, focusing on the sonochemical conversion of maleic acid to fumaric acid in a controlled bubble environment.
- - Experimental results indicate that chemical activity is primarily associated with small bubble clusters, while single bubbles exhibit passive behavior without significant reaction products.
- - The researchers conclude that strong bubble collapse and non-spherical dynamics enhance the mixing of liquid and gas phases, which is crucial for the chemical reaction to occur, aligning with previous findings in the field.
The sonoluminescence spectra from acoustic cavitation in aqueous NaCl solutions are systematically studied in a large range of ultrasonic frequencies under variation of electrical power and argon sparging. At the same time, bubble dynamics are analysed by high-speed imaging. Sodium line and continuum emission are evaluated for acoustic driving at 34.
View Article and Find Full Text PDFArticle Synopsis
- Recent advancements in Hyperspectral Imaging technology allow for rapid analysis of tablet surfaces in pharmaceutical applications, particularly for identifying component distribution and defects.
- A new methodology utilizing correlation coefficients is introduced to analyze hyperspectral images without prior knowledge about the sample, enabling detection of defects and contaminants effectively.
- This method, which incorporates Principal Component Analysis (PCA) and enhanced contrast functions, has been successfully applied to ibuprofen tablets, suggesting its potential as a quality control tool across various hyperspectral imaging systems.
The diffuse reflectance near-infrared (NIR) spectrum of a powdered sample includes the contribution of specular and diffuse reflectance, which is a function of absorbance and scattering. The fraction of light scattered depends in a complex manner on the physical properties of the sample such as particle size, refraction index, etc. Several theories to study the dependence of NIR spectra on the particle size have been proposed.
View Article and Find Full Text PDF