Environmentally Friendly Improvement of Plasmonic Nanostructure Functionality towards Magnetic Resonance Applications

Plasmonic nanostructures have attracted a broad research interest due to their application perspectives in various fields such as biosensing, catalysis, photovoltaics, and biomedicine. Their synthesis by pulsed laser ablation in pure water enables eliminating various side effects originating from chemical contamination. Another advantage of pulsed laser ablation in liquids (PLAL) is the possibility to controllably produce plasmonic nanoparticles (NPs) in combination with other plasmonic or magnetic materials, thus enhancing their functionality. However, the PLAL technique is still challenging in respect of merging metallic and semiconductor specific features in nanosized objects that could significantly broaden application areas of plasmonic nanostructures. In this work, we performed synthesis of hybrid AuSi NPs with novel modalities by ultrashort laser ablation of bulk gold in water containing silicon NPs. The Au/Si atomic ratio in the nanohybrids was finely varied from 0.5 to 3.5 when changing the initial Si NPs concentration in water from 70 µg/mL to 10 µg/mL, respectively, without requiring any complex chemical procedures. It has been found that the laser-fluence-insensitive silicon content depends on the mass of nanohybrids. A high concentration of paramagnetic defects (2.2·× 1018 spin/g) in polycrystalline plasmonic NPs has been achieved. Our findings can open further prospects for plasmonic nanostructures as contrast agents in optical and magnetic resonance imaging techniques, biosensing, and cancer theranostics

Modification of stainless steel by low-energy focused nitrogen ion beam

The results of experiments on the modification of SUS 321 stainless steel by a nitrogen ion beam extracted from a gas plasma of the non-self-sustained arc discharge with hot cathode PINK are presented. Extraction and focusing of the beam was carried out through a grid electrode of the definite curvature. When negative electric pulsed bias is applied to the grid electrode and a specimen located under the same potential, a ballistically focused nitrogen ion beam is formed. As a result of the processing, a nitride layer is formed on the surface of stainless steel with an increased hardness compared to the initial one

Low-energy plasma-immersion implantation of nitrogen ions in titanium by a beam with ballistic focusing

The results of experiments on low-energy implantation of nitrogen ions into VT1-0 titanium alloy are presented. Processing was performed by a nitrogen ion pulsed beam obtained using a ballistic ion focusing system. An ion source was a nitrogen plasma of the non-self-sustained gas arc discharge with a thermionic cathode. It has been shown that when the specimens are processed in such a system, hardness of the surface increases from 1.5 to 2.5 times. In addition, the surface of the specimens undergoes ion etching which causes the formation of an etching cavity whose profile depends on the ion effect parameters

Modification of stainless steel by low-energy focused nitrogen ion beam

The results of experiments on the modification of SUS 321 stainless steel by a nitrogen ion beam extracted from a gas plasma of the non-self-sustained arc discharge with hot cathode PINK are presented. Extraction and focusing of the beam was carried out through a grid electrode of the definite curvature. When negative electric pulsed bias is applied to the grid electrode and a specimen located under the same potential, a ballistically focused nitrogen ion beam is formed. As a result of the processing, a nitride layer is formed on the surface of stainless steel with an increased hardness compared to the initial one

Carbon dot dressing as a treatment of alkali-induced skin burns

Background. Chemical burns, comprising 5–10 % of total burns but causing 30 % of burn-related deaths, are now a notable concern in Ukraine. Current clinical protocols lack specific approaches for chemical burns, and research on this type of burn is limited. Carbon-based nanoparticles show promise for wound healing because of anti-inflammatory, antioxidant, and antibacterial activities. So, the ability of carbon dots obtained from citric acid and urea (further called CD) to improve the healing of alkali-induced skin burn was aimed to be discovered. Materials and Methods. The study was conducted on male Wistar rats. Burn was modeled by application of gauze disc soaked with 3 M NaOH solution on shaved skin of anesthetized rats for 10 min. A CD dressing, consisting of a CD solution (1 mg/mL) mixed with cellulose-based hydrogel that served as a vehicle, was applied to burned skin daily during a 7-day period. There were following groups: control (healthy rats), a burn-only group (rats that received no dressing), a burn + vehicle group (rats that received vehicle dressing), and a burn + CD group (rats that received CD dressing). The study involved monitoring of burn areas, conducting skin histopathology, and perfor­ming blood biochemical analyses. Results. The daily CD dressing significantly decreased alkali-induced burn area (by 76 % compared to 40 % in burn-only group) after seven daily dressings. The level of inflammation in the burn site was also less expressed in CD-treated animals, compared to respective controls (non-treated animals and animals treated with Vehicle). There was no substantial systemic toxicity of the burn (of such area) and its healing, manifested by absence of body weight loss, and absence of dramatical changes in serum biochemical parameters (indicators of liver and kidney function). However, animals of all the groups that experienced burns had a significantly lower body weight gain and mesenteric lymph nodes weight compared to healthy rats. Conclusions. So, the application of carbon dots mixed with hydrogel speeded up alkali-induced burn healing without negative impact on the organism

Multi-Modal Laser-Fabricated Nanocomposites with Non-Invasive Tracking Modality and Tuned Plasmonic Properties

Ultrapure composite nanostructures combining semiconductor and metallic elements as a result of ultrafast laser processing are important materials for applications in fields where high chemical purity is a crucial point. Such nanocrystals have already demonstrated prospects in plasmonic biosensing by detecting different analytes like dyes and bacteria. However, the structure of the nanocomposites, as well as the control of their properties, are still very challenging due to the significant lack of research in this area. In this paper, the synthesis of silicon–gold nanoparticles was performed using various approaches such as the direct ablation of (i) a gold target immersed in a colloidal solution of silicon nanoparticles and (ii) a silicon wafer immersed in a colloidal solution of plasmonic nanoparticles. The formed nanostructures combine both plasmonic (gold) and paramagnetic (silicon) modalities observed by absorbance and electron paramagnetic resonance spectroscopies, respectively. A significant narrowing of the size distributions of both types of two-element nanocrystals as compared to single-element ones is shown to be independent of the laser fluence. The impact of the laser ablation time on the chemical stability and the concentration of nanoparticles influencing their both optical properties and electrical conductivity was studied. The obtained results are important from a fundamental point of view for a better understanding of the laser-assisted synthesis of semiconductor–metallic nanocomposites and control of their properties for further applications

Expedient paramagnetic properties of surfactant-free plasmonic silicon-based nanoparticles

Surfactant-free multifunctional semiconductor-metallic nanostructures possessing several modalities are formed due to laser-induced structural modification of pure silicon nanoparticles in the presence of gold. It results to variable size-dependent chemical composition examined by energy-dispersive X-ray spectroscopy. Laser-synthesized silicon-based nanocomposites exhibit remarkable both plasmonic and paramagnetic properties. Their plasmonic maxima are found to be easily adjusted in the whole visible spectral range. Influence of resonant laser irradiation on spin behaviour of silicon-gold nanoparticles is established. Their spin–lattice and spin–spin relaxation processes are investigated as well. Such multifunctional nanoparticles can reveal a huge potential for different applications in field of nanomedicine, in particular, for biosensing and bioimaging

Enhanced Thermal Sensitivity of Silicon Nanoparticles Embedded in (Nano-Ag/)SiNx for Luminescent Thermometry

International audienceSteady-state photoluminescence of silicon nanoparticles embedded in solid-state (nano-Ag/)SiNx thin films at above room temperature is studied and compared to silicon nanoparticles dispersed in low-polar liquids. Roles of local surface plasmons as well as general mechanisms responsible for the temperature-dependent photoluminescence are pointed out. Thermal sensitivities of photoluminescence spectral shape, maximum position, and full width at halfmaximum are estimated and application of the (nano-Ag/)SiNx layers as photoluminescent thermal screens is proposed

Development of silicon nitride-based nanocomposites with multicolour photoluminescence

International audienceSilicon-rich nitride nanocomposites with stable multicolour photoluminescence (PL) are developed in this work. Firstly, a single PL band can be adjusted in the visible spectral range. Secondly, simultaneous emission of an additional PL band is achieved due to boron-doping of the nanocomposites. Impact of thermal annealing of the silicon nitride films in different atmospheres at various temperatures on their PL spectra is studied. Processes responsible for multicolour emission in the boron-doped nanocomposites are discussed. The developed nanocomposites can be further applied for nanothermometry or biosensing applications. They can be also used for synthesis of silicon nanoparticles with multicolour PL. Graphic abstract Intense violet-based multicolour photoluminescence of silicon nitride nanocomposite with tunableemission position is achieved

Merging of Bi-Modality of Ultrafast Laser Processing: Heating of Si/Au Nanocomposite Solutions with Controlled Chemical Content

Ultrafast laser processing possesses unique outlooks for the synthesis of novel nanoarchitectures and their further applications in the field of life science. It allows not only the formation of multi-element nanostructures with tuneable performance but also provides various non-invasive laser-stimulated modalities. In this work, we employed ultrafast laser processing for the manufacturing of silicon–gold nanocomposites (Si/Au NCs) with the Au mass fraction variable from 15% (0.5 min ablation time) to 79% (10 min) which increased their plasmonic efficiency by six times and narrowed the bandgap from 1.55 eV to 1.23 eV. These nanostructures demonstrated a considerable fs laser-stimulated hyperthermia with a Au-dependent heating efficiency (~10–20 °C). The prepared surfactant-free colloidal solutions showed good chemical stability with a decrease (i) of zeta (ξ) potential (from −46 mV to −30 mV) and (ii) of the hydrodynamic size of the nanoparticles (from 104 nm to 52 nm) due to the increase in the laser ablation time from 0.5 min to 10 min. The electrical conductivity of NCs revealed a minimum value (~1.53 µS/cm) at 2 min ablation time while their increasing concentration was saturated (~1012 NPs/mL) at 7 min ablation duration. The formed NCs demonstrated a polycrystalline Au nature regardless of the laser ablation time accompanied with the coexistence of oxidized Au and oxidized Si as well as gold silicide phases at a shorter laser ablation time (<1 min) and the formation of a pristine Au at a longer irradiation. Our findings demonstrate the merged employment of ultrafast laser processing for the design of multi-element NCs with tuneable properties reveal efficient composition-sensitive photo-thermal therapy modality