Fluorescent carbon nanodots are a promising nanomaterial for different applications in biophotonics, sensing and optical nanothermometry fields due to their strong fluorescence properties. However, their multi-modal applications are considerably limited, requiring the use of several nanoagents that could solve different tasks simultaneously. In this paper, we report the first experimental results on a facile “green” laser-based synthesis of multi-modal carbon–metallic nanocomposites with tuned optical performance. This simple approach leads to the appearance of finely controlled plasmonic properties in carbon-based nanocomposites whose spectral position is adapted by using an appropriate material. Thus, longer laser ablation provokes 29-fold increase in the absorption intensity of carbon–gold nanocomposites due to the increase in the metal content from 13% (30 s) to 53% (600 s). Despite strong plasmonic properties, the metal presence results in the quenching of the carbon nanostructures’ fluorescence (2.4-fold for C-Au NCs and 3.6-fold for C-Ag NCs for 600 s ablation time). Plasmonic nanocomposites with variable metal content reveal a ~3-fold increase in the laser-to-heat conversion efficiency of carbon nanodots matching the temperature range for mild hyperthermia applications. The findings presented demonstrate a facile approach to expanding the properties of chemically prepared semiconductor nanostructures due to the formation of novel semiconductor–metallic nanocomposites using a “green” approach. Together with the ease in control of their performance, it can considerably increase the impact of semiconductor nanomaterials

The design of semiconductor-metallic nanostructures using pulsed laser ablation in liquids (PLAL) is a very demanding task for biomedical applications being at an early stage of its development. Only few recent papers show the possibility of such a synthesis of composite nanoparticles as well as their perspectives for biosensing applications. However, mechanisms of the laser-stimulated formation of semiconductor-metallic nanoparticles involving several processes are not clarified yet being considerably depended on experimental conditions. In this work, we demonstrated an impact of the laser irradiation of colloidal solutions of silicon nanoparticles at different exposure time in the presence/absence of a gold target. In particular, longer ablation of the metal led to a stronger plasmonic maximum in silicon nanoparticles at around 520 nm. It also decreased the hydrodynamic size from 165 nm to 85 nm as well as the ξ-potential from –46 mV to –30 mV by increasing the ablation time from 0 s to 600 s. At the same time, the lowest electrical conductivity value (~1.5 μS/cm) of the plasmonic nanocomposites was detected at 120 s irradiation time. The highest concentration of synthesized composite nanoparticles (~3·1011 NPs/mL) was achieved at 180 s ablation time. Another purpose of the paper was to reveal an influence of the used laser irradiation on properties of the colloidal solutions of silicon nanoparticles themselves. It was found a considerable decrease of their absorbance with the increase of the laser exposure time that can be associated with the change of their properties (e.g. concentration, size, oxidation state etc.). Thus, the laser irradiation strongly affects properties of colloidal solutions of silicon nanoparticles that must also be taken into account considering possible mechanisms of the formation of composite nanostructures. Presented in the paper fast optical diagnostic can help to determine properties of colloidal solutions of nanocomposites formed by PLAL prior their biomedical or catalytic applications.

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.

The design of luminescent multi-functional nanoplatforms that can be simultaneously employed for various applications is still an important research task nowadays. Nanosilicon is one of the most promising nanomaterial having unique structural and optoelectronic properties that can be used in biomedicine, optoelectronics, sensing and nanothermometry. However, its properties do not allow the creation of one luminescent multi-functional nanoplatform requiring merging of different nanomaterials. In this work, temperature-sensitive silicon-based nanocomposites with tuned multi-band emission are demonstrated. One can easily achieve the change of their single- and multi-band photoluminescence spectral position from ~1.6 eV to ~2.9 eV by varying the experimental parameters. Moreover, the “white” emission of silicon nitride is also observed that can be further applied for sensing or optoelectronic applications. Furthermore, the presence of silver nanoparticles leads to 80% increase of the temperature sensitivity of the photoluminescence maximum position (from ~540 μeV/◦ C to ~975 μeV/◦C). The plasmonic nanostructures also considerably modify the ratiometric temperature behavior of nanocomposite emission. The shown findings suggest perspectives of silicon-based nanostructures as multi-task luminescent nanoplatforms in the fields of nanothermometry, molecule sensing, optoelectronics and biomedicine.

Laser-assisted material processing using ultrafast laser sources is an important and promising research direction aiming surface or volumetric modifications of different materials. In particular, pulsed laser ablation in liquids (PLALs) method allows forming a wide set of nanostructures in the form of colloidal solutions. Recently, this approach has also been demonstrated as an effective facile route of the successful formation of silicon-gold nanoparticles (Si-Au NPs) [1] that extended the application of silicon nanostructures in the field of plasmonics [2]. Nevertheless, the laser-assisted nanosynthesis of multi-element semiconductor-metallic nanoparticles is still challenging being at the initial stage of its development.

Multicomponent nanostructures consisting of several elements have attracted a broad research interest being served for various aspects in the field of biosensing, catalysis, photovoltaics and biomedicine. Their synthesis by a pulsed laser ablation in a water enables eliminating various side effects originated from chemical contamination. Variable experimental conditions lead to tuning plasmonic and magnetic features influenced by physicochemical reactions during synthesis, thus enhancing their functionality. In this work, we performed synthesis of hybrid AuSi nanoparticles (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. 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 ꞏ1018 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.

Multicomponent nanostructures consisting of several elements have attracted a broad research interest being served for various aspects in the field of biosensing, catalysis, photovoltaics and biomedicine. Their synthesis by a pulsed laser ablation in a water enables eliminating various side effects originated from chemical contamination. Variable experimental conditions lead to tuning plasmonic and magnetic features influenced by physicochemical reactions during synthesis, thus enhancing their functionality. In this work, we performed synthesis of hybrid AuSi nanoparticles (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. 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 ꞏ1018 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.

An environment-friendly method of pulsed laser ablation in liquids is successfully employed for structural modification of silicon nanoparticles leading to a considerable narrowing of their size distribution accompanied with a reduction of the mean size. Contamination-free conditions of synthesis ensure the chemical purity of formed nanostructures that may reduce toxicity issues. Such a laser-induced modification leads to the appearance of plasmonic properties in semiconductor-based nanomaterials. Their spectral position can easily be varied in the whole visible range. Combined in one nanoparticle properties of semiconductors and noble metals can strongly promote applications of composite laser-synthesized nanoparticles for biosensing (using their plasmonic-based surface-enhanced ability) and bioimaging (using their both optical and magnetic abilities) purposes.

Multicomponent nanostructures consisting of several elements reveal a large research interest being served for various aspects in the field of biomedicine [1, 2]. Combining different elements in a nanoparticle one can easily vary their physicochemical properties in a wide range adjusting their functionality. However, using chemical-based methods for synthesis can considerably obstruct their applications in biomedical fields due to their contamination by chemical residuals. To overcome the aforementioned issues a versatile method of pulsed laser ablation in liquids is widely employed for the synthesis of pure one-and bi-metallic nanostructures widening their functional properties. As a result, they show wide prospects for applications in various fields of biomedicine, eg as contrast agents for magnetic resonance imaging [3, 4]. However, manufacturing of composite metallic-based nanoparticles doped with semiconductor elements by means of pulsed laser ablation method is still challenging being at the early stage of its development. Nevertheless, laser-synthesized metallic-semiconductor nanocomposites have already shown promising perspectives for molecule detection using surface-enhanced Raman scattering (SERS) or infrared absorption techniques (SEIRA) having tracking features as Raman modality or paramagnetic defect labels at the same time [5, 6]. In this work, gold-silicon nanocomposites with dual modalities were fabricated by direct femtosecond laser ablation in deionized water and characterized by structural and optical techniques. A method of chemical content variation is developed allowing fine-tuning of ratio between gold and …

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.

Silicon nanostructures can be prepared by different methods that considerably change their optical properties depending on experimental conditions. They are also very sensitive to molecular environment and external influences that can be used for multiple applications in different areas. Silicon nanostructures prepared by laser ablation show large perspectives for molecular sensing and biomedical applications. In this paper, an overview of optical properties of silicon nanostructures with focus on nanoparticles prepared by ultrafast laser ablation in liquids is provided. It is shown that they reveal wide prospects for applications in nanobiomedicine and their unique characteristics can be significantly enhanced due to laser-induced metal incorporation. Metal inclusions lead to appearance of plasmonic properties in semiconductor nanomaterials that can be applied for molecule detection using surface enhancing of optical response.

Silicon-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.

Presenting a safe alternative to conventional compound quantum dots and other functional nanostructures, nanosilicon can offer a series of breakthrough hyperthermia-based therapies under near-infrared, radiofrequency, ultrasound, etc., excitation, but the size range to sensitize these therapies is typically too large (>10 nm) to enable efficient imaging functionality based on photoluminescence properties of quantum-confined excitonic states. Here, it is shown that large Si nanoparticles (NPs) are capable of providing two-photon excited luminescence (TPEL) and second harmonic generation (SHG) responses, much exceeding that of smaller Si NPs, which promises their use as probes for bi-modal nonlinear optical bioimaging. It is finally demonstrated that the combination of TPEL and SHG channels makes possible efficient tracing of both separated Si NPs and their aggregations in different cell compartments, while the resolution of such an approach is enough to obtain 3D images. The obtained bi-modal contrast provides lacking imaging functionality for large Si NPs and promises the development of novel cancer theranostic modalities on their basis.

Multimodal contamination-free composite silicon/gold nanoparticles are synthesized by “green” laser ablation approach. Their concentration-dependent size distribution and chemical composition are studied by means of transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy. The influence of applied laser fluence on both size distribution and chemical composition is also investigated. The size-dependent chemical composition of formed nanocomposites is analyzed. Optoelectronic properties of silicon/gold nanoparticles as well as their ability to molecule detection using surface-enhanced Raman scattering are studied as well.

In food industry, detection of spoilage yeasts such as W. anomalus and B. bruxellensis and pathogens such as certain Listeria and E. coli species can be laborious and time-consuming. In the present study, a simple and repeatable technique was developed for rapid yeast detection using a combination of patterned gold coated polymer SERS substrates and gold nanoparticles [1−4]. For the first time, a state-of-the-art time-gated Raman detection approach was used as a complementary technique to show the possibility of using 532-nm pulsed laser excitation and avoid the destructive influence of induced fluorescence [3]. Conventional nanoparticles synthesized by colloidal chemistry are typically contaminated by non-biocompatible by-products (surfactants, anions), which can have negative impacts on many live objects under examination (cells, bacteria) and thus decrease the precision of bioidentification.

Recent progress in laser technologies provokes comprehensive studies on laser-matter interaction using various materials. One of the most interesting and most important employment of lasers is related to synthesis of new nanomaterials with unique properties for a wide set of applications. Interaction between ultrafast laser radiation and bulk/powder materials in different environments provokes efficient substance removal resulting to formation of nanoparticles with properties depending on experimental conditions [1]. Moreover, it has been shown lately that ultrafast laser irradiation significantly modifies semiconductor nanostructures in the presence of metal forming composite nanoparticles [2, 3]. Such a modification reveals unique modalities ensuring biomedical applications of nanocomposites, in particular, molecule detection by means of surface-enhanced Raman scattering [4]. Nevertheless, study of laser-synthesized composite nanostructures is at an early stage and information about their properties and applications as well is still missed in literature.

Contamination‐free silicon‐based nanoparticles (NPs) with several modalities are developed in this work. They are formed by non‐toxic laser‐assisted decomposition of silicon microgranules homogeneously dispersed in deionized water. Precise control of numerous experimental parameters allows repeatable fine tuning of nanoparticle size solving significant lacks of a direct laser ablation routine. Such a method provokes a huge amount of paramagnetic defect states of optically active silicon NPs that can serve as a contrast agent for magnetic resonance and nonlinear optical imaging. Perspectives of their bioapplication are driven by detected their fast size degradation in a NaCl‐based medium.

The ability of noble metal-based nanoparticles (NPs) (Au, Ag) to drastically enhance Raman scattering from molecules placed near metal surface, termed as surface-enhanced Raman scattering (SERS), is widely used for identification of trace amounts of biological materials in biomedical, food safety and security applications. However, conventional NPs synthesized by colloidal chemistry are typically contaminated by nonbiocompatible by-products (surfactants, anions), which can have negative impacts on many live objects under examination (cells, bacteria) and thus decrease the precision of bioidentification. In this article, we explore novel ultrapure laser-synthesized Au-based nanomaterials, including Au NPs and AuSi hybrid nanostructures, as mobile SERS probes in tasks of bacteria detection. We show that these Au-based nanomaterials can efficiently enhance Raman signals from model R6G molecules, while the enhancement factor depends on the content of Au in NP composition. Profiting from the observed enhancement and purity of laser-synthesized nanomaterials, we demonstrate successful identification of 2 types of bacteria (Listeria innocua and Escherichia coli). The obtained results promise less disturbing studies of biological systems based on good biocompatibility of contamination-free laser-synthesized nanomaterials.

Driven by surface cleanness and unique physical, optical and chemical properties, bare (ligand-free) laser-synthesized nanoparticles (NPs) are now in the focus of interest as promising materials for the development of advanced biomedical platforms related to biosensing, bioimaging and therapeutic drug delivery. We recently achieved significant progress in the synthesis of bare gold (Au) and silicon (Si) NPs and their testing in biomedical tasks, including cancer imaging and therapy, biofuel cells, etc. We also showed that these nanomaterials can be excellent candidates for tissue engineering applications. This review is aimed at the description of our recent progress in laser synthesis of bare Si and Au NPs and their testing as functional modules (additives) in innovative scaffold platforms intended for tissue engineering tasks.