Carbon dots (CDs) with an emission in the near infrared spectral region are attractive due to their promising applications in bio-related areas, while their fabrication still remains a challenging task. Herein, we developed a template-assisted method using porous silica microspheres for the formation of CDs with optical transitions in the near infrared. Two organic dyes, Rhodamine 6G and IR1061 with emission in the yellow and near infrared spectral regions, respectively, were used as precursors for CDs. Correlation of morphology and chemical composition with optical properties of obtained CDs revealed the origin of their emission, which is related to the CDs’ core optical transitions and dye-derivatives within CDs. By varying annealing temperature, different kinds of optical centers as derivatives of organic dyes are formed in the microsphere’s pores. The template-assisted method allows us to synthesize CDs with an emission peaked at 1085 nm and photoluminescence quantum yield of 0.2%, which is the highest value reported so far for CDs emitting at wavelengths longer than 1050 nm.

An approach has been developed that allows the synthesis of submicron spherical silica particles with a controlled micro-mesoporous structure possessing a large specific surface area (up to 1300 m ² g ⁻¹ ). Particle synthesis is carried out by the hydrolysis of a mixture of various organosilanes mostly associated either with CTAB or with each other. A change in the concentration of CTAB in the reaction mixture apparently leads to a change in the formation mechanism of nuclei for the silica particle growth, which allows for varying the diameter of the synthesized particles in the range from 40–450 nm. The effect of the composition of the silica precursor ([3-(methacryloyloxy)propyl]trimethoxysilane, (3-aminopropyl)triethoxysilane and tetraethoxysilane) on the formation process and porosity of the resulting particles is studied. It was shown that by simply varying the ratio of organosilanes in the composition of the precursor, one can control the pore diameter of the particles in a wide range from 0.6–15 nm. The large-pore (up to 15 nm) silica particles are used as a matrix for the spatial distribution of luminescent carbon dots. The incorporation of carbon dots into SiO ₂ particles prevents their aggregation leading to emission quenching after drying, thus allowing us to obtain highly luminescent composite particles. LEDs based on the obtained composite material show bright visible luminescence with spectral characteristics similar to that of a commercial cold white LED.

Luminescent composites based on entirely non-toxic, environmentally friendly compounds are in high demand for a variety of applications in photonics and optoelectronics. Carbon dots are a recently developed kind of luminescent nanomaterial that is eco-friendly, biocompatible, easy-to-obtain, and inexpensive, with a stable and widely tunable emission. Herein, we introduce luminescent composites based on carbon dots of different chemical compositions and with different functional groups at the surface which were embedded in a nanoporous silicate glass. The structure and optical properties of these composites were comprehensively examined using electron microscopy, Fourier transform infrared transmission, UV-Vis absorption, and steady-state and time-resolved photoluminescence. It is shown that the silicate matrix efficiently preserved, and even enhanced the emission of different kinds of carbon dots tested. The photoluminescence quantum yield of the fabricated nanocomposite materials reached 35–40%, which is comparable to or even exceeds the values for carbon dots in solution.

Single-stage synthesis has been used to obtain submicrometer monodisperse spherical mesoporous silica particles exhibiting bright wide-band luminescence in the visible spectral range. The particles have a specific surface area of 550 m/g, pore volume of 0.36 cm/g, and average pore diameter of 0.3 nm. The synthesis technology provides formation of an active inner surface (surface of mesopores), which will enable binding and retention of medicinal preparations upon their introduction into the particles. The particles are promising for application in theranostics of cancerous growths as nanocontainers simultaneously serving as biomarkers.