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Size- and Surface-Dependent Photoresponses of Solution-Processed Aluminum Nanoparticles
摘要： Plasmonic aluminum nanoparticles have emerged as an exciting new materials platform due to the high natural abundance of aluminum, their ability to be synthesized in the solution phase, and the potential of these materials to be used for photocatalysis and sensing. However, the photothermal properties of solution-processed aluminum nanoparticles, in particular, how phonon energy transfer depends on the particle size and surface properties, are critical for practical applications and are currently unexplored. Here we use transient absorption spectroscopy, in combination with simulations of phonon and thermal energy dissipation, to investigate the photoresponses of aluminum nanoparticles of various diameters (54, 85, 121, and 144 nm) suspended in 2-propanol. Fast thermal-transfer rates to the solvent (170?280 ps) are observed for particles of all sizes and are facilitated by native oxide coverage, as veri?ed by a two-interface thermal energy-transfer model. Size-dependent phonon “breathing”/vibrational modes are also observed as oscillations in the total cross-section. We ?nd that both the oscillation frequency and the damping rate increase as the diameter of the particles decreases. On the basis of the results of ?nite element calculations, we attribute the damping strength and oscillation period observed to a combination of the noncrystalline nature of the native oxide shell and the presence of surface-bound ligands, both of which increase the vibrational mode damping rates relative to bare Al and Al particles with a bare crystalline oxide shell. These insights should guide future work on controlling energy transfer through the use of size and surface tuning in sustainable aluminum nanomaterial systems for applications in catalysis and sensing.
关键词： aluminum,phonons,surface effects,transient absorption,heat transfer,localized surface plasmon resonances
更新于2025-09-23 15:19:57
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Calibration of Scattering Models for Growing Corn and Soybean at C-Band Using Sentinel-1 and Radarsat-2 Observations
摘要： Soil moisture (SM) is an important land surface variable for understanding the water cycle, ecosystem productivity, and linkages between water-carbon cycles. For SM studies, observations at microwave frequencies < 10 GHz are more desirable due to larger penetration depths. The NASA Soil Moisture Active/Passive (SMAP) mission provides global observations of SM using passive sensor at L-band. Current active C-band systems such as Sentinel 1 have shown potentialities to estimate SM and improve spatial resolution of SM data from passive sensors. In addition to the SM sensitivity, radar backscatter is highly sensitive to roughness of soil surface and scattering within the vegetation. Despite much progress in the development of backscattering models, there is still a gap in validating such models under dynamic vegetation conditions such agricultural crops. The goal of this study is to calibrate coherent and incoherent backscattering models for corn and soybean using Sentinel 1 and Radarsat-2 observations.
关键词： Backscatter modeling,coherent model,vegetated terrain,periodic surface effects,SMAPVEX16-Microwex field campaign
更新于2025-09-10 09:29:36
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On the numerical investigation of size and surface effects on nonlinear dynamics of a nanoresonator under electrostatic actuation
摘要： This study aims to investigate the influences of nanostructure parameter and surface elasticity parameters on the nonlinear vibration of a nanoelectromechanical system under double-sided electrostatic actuation. For this, the effects of size dependency and surface energy are modeled through applying the consistent couple-stress theory together with the Gurtin–Murdoch elasticity theory. Taking into account the midplane stretching effect for doubly clamped boundary conditions, the nonlinear strain–displacement relationship is considered based on the Euler–Bernoulli beam assumption. Hamilton’s principle is utilized in order to establish the governing differential motion’s equation, and reduced-order model is obtained through implementing Galerkin’s procedure. Bifurcation diagrams are plotted to capture the steady-state response of the system with varying the nondimensional parameter, the ratio of AC to DC voltage amplitude. The influences of the length-scale parameter, surface elasticity modulus and density, and residual surface stress on the system dynamic response have been explored. The results reveal that the pull-in excitation frequency is highly influenced by these parameters, and also the interval length of the bifurcation parameter corresponding to the periodic and chaotic motions is extremely shifted by the amount of couple-stress and residual surface stress parameters.
关键词： Size-dependent NEMS,Chaos,Bifurcation,Surface effects
更新于2025-09-09 09:28:46
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Impact of heterogeneities and surface roughness on pXRF, pIR, XRD and Raman analyses: Challenges for on-line, real-time combined mineralogical and chemical analyses on drill cores and implication for “high speed” Ni-laterite exploration
摘要： On-line, real-time chemical and mineralogical analyses on drill cores are highly demanded by mining companies. However, they are a challenge because of drill core surface state and sample heterogeneities. We selected four rock samples: highly porous, siliceous breccia and serpentinized harzburgite coming from the base of a nickel laterite profile in New Caledonia which were sonic drilled, and fine grained, homogeneous sandstone and coarse grained granite which were diamond drilled and provided by Eijkelkamp Sonic Drill with unknown origin. The samples were analyzed at five surface states (diamond or sonic drilled, cut as squares, polished at 6 and 0.25 microns, powdered < 80 microns) by portable XRF spectroscopy (pXRF) in mining and soil modes and portable infrared spectroscopy (pIR, Visible and Near Infrared - Short Wave Infrared range (VNIR-SWIR)). A total of 52 pXRF and 200 pIR analyses were performed per sample at each surface state. This study shows that the surface state has minor influence on the results of the portable instruments. By comparing pIR and pXRF results with laboratory devices (Raman spectroscopy, XRD with Rietveld refinement, XRF spectroscopy and ICP-AES), we evidence the lower and less accurate information obtained from handheld instruments in terms of chemistry and mineralogy. The porosity and grain size effect on the measurement need to be taken into consideration for on-line drill core analyses. We show that the combination of complementary analytical techniques helps to overcome the drawbacks of the core texture and of the precision of portable instruments in order to define the regions of interest (ROI) for mining companies. We also demonstrate that a precise pXRF calibration is mandatory and that the concentration of light elements (Si, Mg), even if not accurate, shows sufficient contrast along the lateritic profile for ROI definition.
关键词： drill cores,nickel,portable instruments,surface effects,garnierite
更新于2025-09-04 15:30:14