Nanoparticles alloying in liquids: Laser-ablation-generated Ag or Pd nanoparticles and laser irradiation-induced AgPd nanoparticle alloying

International audienceLaser irradiation of a mixture of single element micro/nanomaterials may lead to their alloying and fabrication of multielement structures. In addition to the laser induced alloying of particulates in the form of micro/nanopowders in ambient atmosphere which forms the basis of the field of additive manufacturing technology another interesting problem is the laser induced alloying of a mixture of single element nanoparticles in liquids since this process may lead to the direct fabrication of alloyed nanoparticles colloidal solutions. In this work Ag and Pd bare, surface ligand-free nanoparticles in solution were prepared by laser ablation of the corresponding bulk target materials separately in water, the two solutions were mixed and the mixed solution was laser irradiated for different time durations in order to investigate the laser induced nanoparticles alloying in liquid. Nanoparticles alloying and formation of AgPd alloyed nanoparticles takes place with the decrease of the intensity of the surface plasmon resonance peak of the Ag nanoparticles (at ~405 nm) with the irradiation time while the low wavelength interband absorption peaks of either Ag or Pd nanoparticles remain unaffected by the irradiation for times even as long as 30 mins. The alloyed nanoparticles have lattice constants with values between those of the pure metals which indicates that they consist of Ag and Pd in approximately 1:1 ratio similar to the atomic composition of the starting mixed nanoparticles solution. Formation of nanoparticle networks consisting of bimetallic alloyed nanoparticles and nanoparticles which remain as single elements even after the end of the irradiation, joining together, are also formed. The binding energies of the 3d core electrons of both Ag and Pd nanoparticles shift to lower energies with the irradiation time also a typical characteristic of AgPd alloyed nanoparticles

Theoretical analysis of damping effects of guided elastic waves at solid/fluid interfaces

International audienceA theoretical description of ideal and viscous fluid media is proposed to address the problem of modeling damping effects of surface acoustic waves and more generally of any guided elastic waves at the interface between viscous fluids and solids. It is based on the Fahmy-Adler eigenvalue representation of the elastic propagation problem, adapted to provide Green's function of the considered media. It takes advantage of previous efforts developed to numerically stabilize Green's-function computation process. This function is used to compute a harmonic admittance according to the Blötekjaër approach. The influence of acoustic radiation and viscosity effects on different kinds of waves excited on various substrates is reported and discussed

Integrated Love Wave Device Dedicated to Biomolecular Interactions Measurements in Aqueous Media

Mass-sensitive electro-acoustic devices such as surface acoustic wave (SAW)micro-balances, capable to operate with aqueous media are particularly favorable for thedevelopment of biosensors. Their dimensions and physical properties offer a large potentialin biological fluid investigations, especially for measuring physical phenomenon (massdeposition, adsorption, pressure...). In this work, we propose a specific gratingconfiguration to lower the influence of viscosity of fluids which reduces the signal dynamicsof the surface wave transducers. A dedicated liquid cell also has been developed to isolatethe electro-active part of the device. The fabrication of the cell is achieved using theSU-8TMphoto-resist, allowing for manufacturing thick structures preventing any contact between thetested liquids and the transducers. Furthermore, the sensing area has been optimized tooptimize the sensor gravimetric sensitivity. The operation of the sensor is illustrated bydetecting bovine serum albumin (BSA) adsorption in the sensing area

Analysis of Palladium and Yttrium-Palladium alloy layers used for Hydrogen detection with SAW device

International audienceBecause of its physicochemical properties, hydrogen appears as an efficient source of energy for powering devices. Its abundance on earth and the simplicicty of the process needed for its extraction from water make this compound a promising solution for an increasing number of applications (energy production and storage, car industry, space, etc.). However, due to its unstable properties, a particular care must be dedicated to control gaseous leaks close to facilities using this resource. Surface Acoustic Wave (SAW) sensors consisting in Rayleigh-wave delay lines equipped with a sensitive overlay can be efficiently used to detect hydrogen. In this paper, we propose a SAW device exhibiting either pure palladium or palladium-yttrium alloy sensing area for the detection of hydrogen in standard environmental conditions. An X-ray diffraction analysis of these sensitive materials is also presented and correlated with the simultaneously acquired signal of our sensor. Mesurements of hydrogen in the 0.5-2 % concentration range diluted in nitrogen are presented. The effect of combining yttrium and palladium as sensing layer on the sensor response is reported and its interest for improving our sensor's sensitivity is finally discussed

Real Time Cascade Impactor Based On Surface Acoustic Wave Delay Lines for PM10 and PM2.5 Mass Concentration Measurement

In this research, Surface Acoustic Wave (SAW) sensors are combined with a cascade impactor to perform real time PM10 and PM2.5 mass concentration measurements. The SAW sensors consist of 125 MHz delay lines based on Love waves propagating on an AT-cut quartz substrate. The Love waves are guided on the substrate’s surface using a silica layer. SAW sensors themselves are not capable to discriminate particles by their size, therefore, particle separation based on aerodynamic diameter is achieved using a 3 Lpm dedicated cascade impactor. The latter was designed to integrate the SAW sensors which are monitored using a phase shift measurement. The collected particles impact on the acoustic sensor’s surface inducing a gravimetric effect that modifies the acoustic wave propagation conditions. The resulted phase shift allows the measurement of the mass deposited on the sensitive zone. The novel cascade impactor with SAW sensors as particle collecting stages is exposed to different aerosols in the 0–150 μg/m3 concentration range and proved to be able to detect and differentiate particles based on their size in real time. The system’s response was compared to a commercial optical counter based on light scattering technology and was found to be in good agreement with it

Development of Love Wave devices based on delay line configuration for the high detection and monitoring of carbon monoxide

International audienceCarbon Monoxide is produced by incomplete combustion. Its high toxicity and the lack of detection capability of human olfaction render CO a dangerous compound which is known as the silent killer. Therefore, there is the necessity to develop a device to detect the presence of low CO concentrations in indoor air. We here report on results obtained for CO detection by using SAW devices functionalized with new materials such as cobalt corroles. During the tests, CO sensors have been exposed to changes of several experimental parameters (temperature, flow, pressure, presence of analyte gas). In order to exclusively extract the information concerning CO adsorption, we used a specific differential setup comprising two SAW devices A minimum of 450ppb of CO concentration have been monitored and the experimentations have shown a great repeatability and stability of measurements. The test bench permits the regeneration of the trapping sites of CO allowing the reusability of the devices. These good results pave the way to the detection of other gas and even particles

Detection and Monitoring of Hydrogen using Palladium Film on SAW

International audienceWith predicted shortage of fossil energy resources and the increasing concern towards environmental pollution, hydrogen is seen as one of the most promising ways to store energy in automotive applications and consumer electronics. However, this odorless and colorless gas is highly explosive over 4% in air. Thus, the fast and accurate detection of hydrogen prior to the explosive concentration at room temperature is still a great problem. There are many methods of hydrogen detection and a comprehensive review can be found in the literature [1]. In this paper, thin palladium film is using as sensor material because of its well-known absorption properties relative to hydrogen. Phase variations of SAW devices using Rayleigh waves have been monitored versus various H2 flow. Moreover, a specific testing setup has been developed to follow hydrogen at atmospheric pressure and to allow regeneration of the sensor

Nanoparticles alloying in liquids: Laser-ablation-generated Ag or Pd nanoparticles and laser irradiation-induced AgPd nanoparticle alloying

International audienceLaser irradiation of a mixture of single-element micro/nanomaterials may lead to their alloying and fabrication of multi-element structures. In addition to the laser induced alloying of particulates in the form of micro/nanopowders in ambient atmosphere (which forms the basis of the field of additive manufacturing technology), another interesting problem is the laser-induced alloying of a mixture of single-element nanoparticles in liquids since this process may lead to the direct fabrication of alloyed-nanoparticle colloidal solutions. In this work, bare-surface ligand-free Ag and Pd nanoparticles in solution were prepared by laser ablation of the corresponding bulk target materials, separately in water. The two solutions were mixed and the mixed solution was laser irradiated for different time durations in order to investigate the laser-induced nanoparticles alloying in liquid. Nanoparticles alloying and the formation of AgPd alloyed nanoparticles takes place with a decrease of the intensity of the surface-plasmon resonance peak of the Ag nanoparticles (at ~405 nm) with the irradiation time while the low wavelength interband absorption peaks of either Ag or Pd nanoparticles remain unaffected by the irradiation for a time duration even as long as 30 min. The nanoalloys have lattice constants with values between those of the pure metals, which indicates that they consist of Ag and Pd in an approximately 1:1 ratio similar to the atomic composition of the starting mixed-nanoparticle solution. Formation of nanoparticle networks consisting of bimetallic alloyed nanoparticles and nanoparticles that remain as single elements (even after the end of the irradiation), joining together, are also formed. The binding energies of the 3d core electrons of both Ag and Pd nanoparticles shift to lower energies with the irradiation time, which is also a typical characteristic of AgPd alloyed nanoparticles. The mechanisms of nanoparticles alloying and network formation are also discussed

Sensitivity of Surface Acoustic Wave Sensors Based LiNbO3 128° Y-X and at-Quartz to PM10 and PM2.5

International audienceParticulate matter (PM) was estimated to cause around 7 million premature deaths worldwide per year according to<br&gtWorld Health organization [1]. These particles can cause diseases leading to premature death [2]. Over the last decade, the monitoring of PM became an important issue on a worldwide scale.The miniaturization of the existing bulky systems has also become necessary to reduce their cost. To address this need, a new miniaturized system for PM monitoring was previously developed in our team [3].It takes advantage of both a 3 Lpm cascade impactor and surface acoustic waves (SAW) sensors to respectively separate and measure particles. The present study aims to compare the sensitivity of two SAW devices. The first exploits Love waves on an ATcut Quartz substrate and the second is based on Rayleigh waves from a LiNbO3 Y-X 128° substrates. The latter presents a high electromechanical coupling factor that could be exploited for the self-cleaning of the device after the measurement. This could allow overcoming the fouling issue faced with impactors that wouldn’t be solved with quartz based sensors which suffer from an insufficient electromechanical coupling

Selective Detection of Hydrogen with Surface Acoustic Wave Devices Using Palladium Layer Properties

For an increasing number of applications, hydrogen represents a solution of the future as it is the most common element in the Earth. However, due to its unstable properties in gas phase, a particular care must be dedicated to control possible gaseous leaks close to tanks and facilities using this resource. In this paper, surface acoustic wave sensors are proposed for detecting gaseous hydrogen in standard environmental conditions (atmospheric pressure and room temperature). The proposed Surface Acoustic Wave sensors consists in two Rayleigh-wave delay lines built on Quartz, one equipped with a palladium overlay and the other exhibiting a free path between the two interdigited transducers. A specific gas test cell has been developed to test various sensor configurations submitted to hydrogen-composed atmospheres. A particular care was paid to avoid hydrogen leakage in the working environment and to perform the regeneration of the gas absorbing layer. The developed device allows for identifying different concentrations of hydrogen (in the 1-4 % range) diluted in nitrogen and is also able to detect hydrogen in current atmosphere. Surface Acoustic Wave devices exploiting hydrogen absorption capabilities of palladium thin films have been here used to make the detection and the identification of hydrogen concentrations in the 1-4 % range and the influence of outer parameters such as temperature and relative humidity variations on the sensor operation are also reported