SERS and RI sensing properties of heterogeneous dimers of Au and Si nanospheres

Heterogeneous dimers of Au and Si nanoparticles are expected to exhibit different plasmon properties from that of homogeneous noble metal nanoparticle dimers. It is crucial to unveil the potential applications in surface-enhanced Raman scattering (SERS) and refractive-index (RI) sensing of the prototype dimer of Au and Si nanospheres. The near-field coupling between the two components within the dimer is revealed to not affect the resonance energy of Si mode in the extinction spectra, but decrease that of Au mode. It also accounts for the plasmon ruler behavior of the fractional shifts of both its dipolar peak wavelength of localized surface plasmon resonance (LSPR) and corresponding RI sensitivity factor [Formula: see text], which provide another kind of substitute to estimate the gap distance in between components within the dimer as that of noble metal nanoparticle dimers. Additionally, by tracking the inflection point shift of the corresponding extinction spectra, its [Formula: see text] is revealed to improve 36% than that of traditional one. The maximum [Formula: see text] and SERS enhancement factor [Formula: see text] at 2 nm gap distance are demonstrated to reach 336 nm RIU[Formula: see text] and [Formula: see text], respectively. This work paves a new way for developing efficient SERS and RI sensing substrates by combining noble metal and dielectric nanoparticles.

A computational analysis of nanoparticle-mediated optical breakdown

A theoretical model of the optical breakdown phenomena during picosecond and femtosecond laser pulse exposure with gold nanoparticles in water was developed. The model provides new and valuable insight into the dependence of the optical breakdown on the wavelength, morphology and environment in the vicinity of the nanoparticles. The developed model was successfully validated against experimental data, which also revealed some insights to the criterion for optical breakdown. Three studies were performed using the model. In the first study, the effects of the dielectric environment on the optical extinction spectra of individual bare and silica-coated gold nanorods were examined. The experimental extinction spectra of an individual gold nanorod was compared to a calculation from a numerical model that included environmental features present in the measurements and the morphology of the corresponding nanorod measured by transmission electron microscopy. The combination of these experimental and theoretical tools permitted a detailed interpretation of the optical properties of an individual gold nanorod. In the second study, a strongly coupled finite element model of nanoparticle-mediated optical breakdown phenomena was developed. This model was used to theoretically study a 6 ps laser pulse interaction with uncoupled and plasmon coupled gold nanoparticles. The study showed how the one-dimensional assembly of nanoparticles affects the optical breakdown threshold of its surroundings. The optical breakdown threshold had a stronger dependence on the optical near-field enhancement than on the volume of the nanostructure or its absorption cross-section. Finally, a model was developed to study the wavelength dependence of the threshold of gold nanorod-mediated optical breakdown during picosecond and femtosecond near infrared optical pulses. This study showed that the wavelength dependence in the picosecond regime is governed solely by the changes of the nanorod’s optical properties. On the other hand, the optical breakdown during femtosecond pulse exposures was found to depend on the multiphoton ionization and its wavelength dependence when, Eratio, the ratio of the maximum electric field from the outside to the inside of the nanorod was greater than 7. The developed model and conducted research deepens the understanding of the nanoparticlemediated optical breakdown in water and updates the theoretical formulation of the process with the latest findings, which leads to advancing this technology further.

A computational analysis of nanoparticle-mediated optical breakdown

A theoretical model of the optical breakdown phenomena during picosecond and femtosecond laser pulse exposure with gold nanoparticles in water was developed. The model provides new and valuable insight into the dependence of the optical breakdown on the wavelength, morphology and environment in the vicinity of the nanoparticles. The developed model was successfully validated against experimental data, which also revealed some insights to the criterion for optical breakdown. Three studies were performed using the model. In the first study, the effects of the dielectric environment on the optical extinction spectra of individual bare and silica-coated gold nanorods were examined. The experimental extinction spectra of an individual gold nanorod was compared to a calculation from a numerical model that included environmental features present in the measurements and the morphology of the corresponding nanorod measured by transmission electron microscopy. The combination of these experimental and theoretical tools permitted a detailed interpretation of the optical properties of an individual gold nanorod. In the second study, a strongly coupled finite element model of nanoparticle-mediated optical breakdown phenomena was developed. This model was used to theoretically study a 6 ps laser pulse interaction with uncoupled and plasmon coupled gold nanoparticles. The study showed how the one-dimensional assembly of nanoparticles affects the optical breakdown threshold of its surroundings. The optical breakdown threshold had a stronger dependence on the optical near-field enhancement than on the volume of the nanostructure or its absorption cross-section. Finally, a model was developed to study the wavelength dependence of the threshold of gold nanorod-mediated optical breakdown during picosecond and femtosecond near infrared optical pulses. This study showed that the wavelength dependence in the picosecond regime is governed solely by the changes of the nanorod’s optical properties. On the other hand, the optical breakdown during femtosecond pulse exposures was found to depend on the multiphoton ionization and its wavelength dependence when, Eratio, the ratio of the maximum electric field from the outside to the inside of the nanorod was greater than 7. The developed model and conducted research deepens the understanding of the nanoparticlemediated optical breakdown in water and updates the theoretical formulation of the process with the latest findings, which leads to advancing this technology further.

Optical properties of Gobi dust and its pure compounds: experimental extinction spectra and complex refractive indices determination.

<p>Spectrometers are powerful instruments to detect atmospheric aerosols, especially on satellites since they allow measurements at a global scale and over different spectral ranges with high spectral resolution. However, to fully exploit their capabilities and to link optical properties, chemical composition and mass concentration, it is essential to have reference optical properties of various particles and mainly the complex refractive indices (CRI). The CRI of a natural aerosol source can be determined from a real sample of it or applying the effective medium approximation using the CRI of the pure compounds present in the natural sample. But in that case, it is necessary to know the mass fraction of each individual compound and above all their CRI. Nevertheless, the literature and CRI databases provide only reflectance measurements on bulk materials or pressed pellets and over a limited wavelength range (Querry <em>et al.</em>, 1987).</p><p>In the present work, dust from the Gobi desert is studied as it is the second most active dust source, after the Sahara desert, in terms of mass emissions (Querol <em>et al.</em>, 2019). For that extinction spectra have been recorded for natural Gobi dust sample and for its major compounds (Illite, Calcite and Quartz). Particles as a powder in a vessel are generated thanks to a magnetic stirring and a flow of nitrogen (Hubert <em>et al.</em>, 2017). The continuous flow of aerosols is directed into a 10-meters multipass cell fitted to a Fourier transform infrared spectrometer and a 1-meter singlepass cell within a UV-Visible spectrometer which cover a continuous spectral range from 650 cm<sup>-1</sup> to 40000 cm<sup>-1</sup>. Moreover, at the exit of the spectrometers the size distribution is recorded by an aerodynamic particle sizer and a scanning mobility particle sizer which allow to measure size particles from 14 nm to 20 µm. An inversion algorithm is carried out using experimental extinction spectra and the size distribution as input data (Herbin <em>et al.</em>, 2017). Applying the Mie theory and the single subtractive Kramers-Kröning integral, the real and the imaginary part of the CRI are retrieved at each wavelength with an optimal estimation method.</p><p>For the first time, CRI of Illite has been retrieved with a high spectral resolution (1 cm<sup>-1</sup>) and over a wide spectral range for suspended particles. For calcite and quartz particles, the crystalline phase has to be considered by introducing the ordinary and extraordinary indices. These pure compound sets of CRI will be used for testing effective medium approximation on Gobi dust for which effective CRI have been also retrieved.</p>

Лазерная доставка и спектральное исследование хлоринсодержащего препарата для лечения онихомикоза при последовательном лазерном (λ=2819 nm) и фотодинамическом (λ=656± 10 nm) воздействии

For the first time, the possibility of a dual-stage active laser delivery of a modern chlorin-containing photodynamic preparation under the nail plate for photodynamic therapy of onychomycosis was investigated and demonstrated. The extinction spectra of the photodynamic preparation Revixan (Areal Ltd., Russia) were investigated at different temperatures, as well as before and after exposure to Er:YLF-laser radiation with a wavelength of 2810 nm and photodynamic LED radiation with a wavelength of 656 ± 10 nm. It is shown that after heating and laser exposure, the amount of monomers in the chlorin-containing photodynamic preparation increases, and after photodynamic exposure decreases, which can affect the effectiveness of photodynamic therapy of onychomycosis.

Оптическое поглощение гибридных молекулярных кластеров С-=SUB=-32-=/SUB=-Н-=SUB=-24-=/SUB=-, С-=SUB=-32-=/SUB=-Н-=SUB=-36-=/SUB=- на основе фрагментов даймондена и графена

Using the density functional theory (DFT), the geometry optimised for molecular clusters C32H24 and C32H36, constructed with a hybrid of fragments of diamondene and graphene with the dangling bonds passivated with hydrogen. The time-dependent DFT allowed calculating molar extinction spectra of the clusters. The comparison of the calculated spectra with the results of astrophysical observations evidence on a possible contribution of the clusters to the extinction spectrum of light by the carbon-based constituent of the interstellar medium.