Here we present the first example of excitationindependent blue-emitting carbon dots (iC-dots) obtained by pyrolysis of citric acid (CA) without post-treatment chromatographic separation. To confine the growth and shape of carbon nanoparticles, silica gel with immobilized aminopropyl groups (SiO 2 −NH 2 ) was used as a nanoreactor. It was demonstrated that the carbonization of SiO 2 − NH 2 with embedded CA resulted in the formation of unbound wCdots and immobilized iC-dots. Because of their firm attachment to the surface, iC-dots can be easily separated from low-molecular impurities and wC-dots by simply rinsing the nanocomposite with water. From atomic force and transmission electron microscopies iC-dots can be represented as flattened spheroids with 2−4 nm of height and 5 nm in lateral size. The size distribution profile for wC-dots is very wide with about 95% the particles within the 2.5−5.5 nm size range. Increasing the template pore size from 4.9 up to 9.1 nm has no effect on the size of the iC-dots. From Fourier transform infrared analysis and X-ray photoelectron spectroscopy data it was assumed that iC-dots belong to N-doped C-nanoparticles with 9:1 carbon to nitrogen atomic ratio. As-prepared iC-dots demonstrate excitation-independent photoluminescence at 445 nm with quantum yields up to 16.8%, which makes them attractive for bioanalytical application.

A facile and robust synthesis of carbon dots (CDs) emitting blue-light in water without activation and stabilization has been developed by pyrolysis of citric acid (CA) adsorbed in silica gel (SiO 2 ) pores. Effect of the host pore size on luminescent properties of SiO 2 @CDs nanocomposite as well as water suspension of CDs has been studied. The synthesis conditions such as concentration of the precursor, duration of synthesis also have been investigated. It has been demonstrated that upon the thermal treatment of silica gels saturated with CA (60% of maximum loading) at 170°C for 5-600 min, luminescent CDs are shaped inside the nanoreactor pores. These SiO 2 @CDs emit photoluminescence centered at 450 nm. Silica-immobilized CDs can be separated from the source molecules and sideproducts by centrifugation, which allows avoiding the dialysis of the resulted mixture and so improve the scaling of the synthesis. The CDs can be easily released from SiO 2 @CDs by washing it with water. Water-eluted CDs demonstrate photoluminescence at 447 nm. The smaller pore size of the host and longer time of thermal treatment promote the formation of the CDs with better photoluminescent peak symmetry and higher quantum yield up to 10.1%.

Graphene oxide quantum dots incorporated into a mesoporous silica network have been used as a modifier of a carbon paste electrode for the determination of antibiotics and hormones.

Herein, we utilized carbon nanodots (R-CNDs) for the electrochemical detection of estrogens in tap and natural water samples and simulated effluents from Swedish waste water treatment plants (WWTPs). R-CNDs were prepared from 2-aminophenol by solvothermal synthesis and used as a modifier for chitosan-based selective membranes. The data obtained from atomic force microscopy and transmission electron microscopy suggest a spherical morphology of the R-CNDs with lateral size in the range of 3–8 nm and the height of 1–8 nm. In contrast to most other known carbon nanodots, R-CNDs are soluble in various organic solvents, including apolar, and less soluble in water. Small nanodots (3 nm) are more hydrophilic than large ones (6–8 nm) and can be separated from the bulk suspension of R-CNDs in heptane by their extraction into a water/ethanol mixture. Suspensions of large R-CNDs in apolar solvents exhibit green photoluminescence, while small R-CNDs in polar solvents have orange. This phenomenon was attributed to a solvatochromic rather than to a quantum effect. The R-CNDs were embedded on a chitosan-modified pencil electrode and the electrode was applied for voltammetric determination of four abandoned estrogens: estrone, estradiol, estriol, and ethynyl estradiol. The sensor demonstrates a group-selective response to the estrogens with a detection limit of 17.0 nmol L–1. It can be applied to determine the estrogens in the range of 0.05–4.6 μmol L–1 in the presence of typical interfering bioactive compounds, such as paracetamol, uric acid, progesterone, sulfamethoxazole, trimethoprim, ibuprofen, and caffeine. The developed sensors show repeatability and reproducibility values of 1.8–3.4% and 4.3%, respectively. The efficiency was proved by application for tap and lake water samples, where the recovery range was found to be 93–100%. The low cost, stability, and high sensitivity and selectivity of fabricated sensors make R-CNDs a perspective modifier for electrochemical sensors for the detection of estrogen microquantities in variable water samples.

This paper reveals the methodology for robust preparation of purified nitrogen-doped graphene oxide quantum dots with non-cytotoxic activity against monkey epithelial kidney cells (Vero ATCC® CCL-81™).

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Two samples of functionalized mesoporous silica containing anchored anthrylmethylamine groups (SiO₂-Ant) have been prepared by surface assembling (1) and one step silane immobilization (2). Both adsorbents can be attributed to bimodal balanced hydrophobic-hydrophilic adsorbents with loading of anthracene groups about 15-33%. The adsorbents have been used for SPE of anthracene from organic solvents (acetonitrile, acetone and heptane) and model solutions of lipids (myristic acid and vegetable oil). The obtained results were compared with commercial C18 SPE cartridge. While C18 cartridge recovers anthracene from water-containing media (acetonitrile/water, 1/1), SiO₂-Ant cartridges much more efficient in extraction of anthracene from non-polar solvent (heptane). Lipids macrocomponents such as myristic acid and vegetable oil do not decrease the dynamic adsorption capacity and recovery of the model PAH on SiO₂-Ant. It was demonstrated that π-π stacking interaction with the analyte determine the selectivity of SiO₂-Ant towards of anthracene. This makes SiO₂-Ant attractive for selective pre-concentration of PAHs from high lipid content objects, such as vegetable oils.

Two samples of functionalized mesoporous silica containing anchored anthrylmethylamine groups (SiO₂-Ant) have been prepared by surface assembling (1) and one step silane immobilization (2). Both adsorbents can be attributed to bimodal balanced hydrophobic-hydrophilic adsorbents with loading of anthracene groups about 15-33%. The adsorbents have been used for SPE of anthracene from organic solvents (acetonitrile, acetone and heptane) and model solutions of lipids (myristic acid and vegetable oil). The obtained results were compared with commercial C18 SPE cartridge. While C18 cartridge recovers anthracene from water-containing media (acetonitrile/water, 1/1), SiO₂-Ant cartridges much more efficient in extraction of anthracene from non-polar solvent (heptane). Lipids macrocomponents such as myristic acid and vegetable oil do not decrease the dynamic adsorption capacity and recovery of the model PAH on SiO₂-Ant. It was demonstrated that π-π stacking interaction with the analyte determine the selectivity of SiO₂-Ant towards of anthracene. This makes SiO₂-Ant attractive for selective pre-concentration of PAHs from high lipid content objects, such as vegetable oils.