Fluorescent Carbon Dots for Super-Resolution Microscopy.

Conventional fluorescence microscopy is limited by the optical diffraction of light, which results in a spatial resolution of about half of the light's wavelength, approximately to 250-300 nm. The spatial resolution restricts the utilization of microscopes for studying subcellular structures. In order to improve the resolution and to shatter the diffraction limit, two general approaches were developed: a spatially patterned excitation method and a single-molecule localization strategy. The success of super-resolution imaging relies on bright and easily accessible fluorescent probes with special properties. Carbon dots, due to their unique properties, have been used for super-resolution imaging. Considering the importance and fast development of this field, this work focuses on the recent progress and applications of fluorescent carbon dots as probes for super-resolution imaging. The properties of carbon dots for super-resolution microscopy (SRM) are analyzed and discussed. The conclusions and outlook on this topic are also presented.

Titanium lanthanum three oxides decorated magnetic graphene oxide for adsorption of lead ions from aqueous media.

The current study presents a viable and straightforward method for synthesizing titanium lanthanum three oxide nanoparticles (TiLa) and their decoration onto the ferrous graphene oxide sheets to produce FeGO-TiLa as efficient magnetic adsorbent. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and vibration sample magnetometer (VSM) were used to evaluate the physical and chemical properties of the produced nanocomposites. The FeGO-TiLa was used to enhance the removal of lead ions from aqueous solution. The FeGO-TiLa nanocomposite exhibited a much higher removal efficiency (93%) for lead ions than pure TiLa nanoparticles (81%) and magnetic graphene oxide (74%). The influence of FeGO-TiLa dosage, contact time, solution pH, solution temperature, and starting quantity on the lead ions was evaluated and adjusted. The investigations demonstrated that a pH 6 with 40 mg adsorbent resulted in >91% removal of lead ions at ambient temperature after 120 min. Isotherm models were used to analyze experimental results, and Langmuir model fitted the data well as compared Freundlich model with a maximum adsorption capacity of 109.89 mg g-1. Kinetic and studies are performed the lead adsorption over FeGO-TiLa follow pseudo-second-order rate. Langmuir and Free energy suggested the lead ions uptake with FeGO-TiLa was monolayer and physical adsorption mechnaism, respectively. Finally, the FeGO-TiLa nanocompoiste can be used as an alternative adsorbent for water remediation.

Magnetic sporopollenin supported polyaniline developed for removal of lead ions from wastewater: Kinetic, isotherm and thermodynamic studies.

This study evaluated the synthesis of novel binary functionaladsorbent based on sporopollenin, magnetic nanoparticles, and polyaniline to produce MSP-PANI. The MSP-PANI was applied to enhance uptake of lead ions (Pb2+) from wastewater samples. The functionalities, surface morphology, magnetic properties, and elemental composition of the newly synthesized nanocomposite were investigated using Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), vibration sample magnetometer (VSM), and energy-dispersive X-ray spectroscopy (EDX), respectively. The experimental condition for the adsorption process was MSP/PANI ratio 1:1, pH ∼6, adsorbent dosage 40 mg, and contact time 90 min at room temperature. Under the proposed condition, lead ions removal were obtained as 83%, 88% and 95% for MSPE, PANI, and MSP/PANI, respectively. Based on the experimental and predicted data, the adsorption was corresponded to the psudo-second-order (R2 = 0.999) kinetics model, and the adsorption equilibrium corresponded to the Langmuir model (R2 = 0.996). Langmuir isotherm showed the maximum adsorption capacity of MSP-PANI for lead ions was 163 mg/g and followed the monolayer pattern. Hence, thermodynamic model under Van't Hoff equation suggested that the adsorption mechanism was physio-sorption with endothermic nature. Therefore, this research can help the researchers to use magnetic nanoparticles for lead removal in highly polluted areas.

Charge separation effect in the nanocomposites of Co3O4-QDs: visible light photocatalytic dye degradation in aqueous solutions.

Photo-treatment of water is a promising environmentally friendly process that provides clean water and makes wastewater reusable in industry. Thus, efforts toward finding highly efficient photocatalysts have gained a huge attention to remove the organic contaminants in water. Quantum dots (QDs) are extensively utilized for photocatalytic remediation regarding their prominent optical, electrical, and chemical properties. Herein, we report the highly efficient and environmentally friendly synthesis of Co3O4-QDs-based graphene quantum dots (GQDs) and infinite coordination polymer comprising Zn nodes (Zn-ICP) nanocomposites as active and robust photocatalysts for photo-assisted water treatment. The pristine Co3O4-QDs, GQDs, and Zn-ICP showed lower activity under visible light. However, after functionalization of GQDs and Zn-ICP with Co3O4-QDs, the activity increased, and more photocatalytic efficiency was achieved. For instance, Zn-ICP, GQDs, Co3O4-QDs, Co3O4-QDs/Zn-ICP, and Co3O4-QDs/GQD degraded 21, 19, 52, 73, and 83% of rhodamine B (RhB) and 34, 46, 50, 73, and 76% of methylene blue (MB) after 60 min. The high photocatalytic efficiency was ascribed to the conjugation of Co3O4-QDs with GQDs and Zn-ICP which causes efficient absorption of visible light. The existence of Co3O4-QDs was found to be essential not only for effective charge separation but also widening the region of light absorption followed by increase in photocatalytic performances. Charge separation in photocatalytic reactions, energy levels of nanocomposites, and mechanism of the photocatalytic process were investigated by photoluminescence spectra (PL), Mott-Schottky, electrochemical impedance (EIS), and diffuse reflectance UV-Vis spectroscopy (DRS).

CdS quantum dots encapsulated within the mesopores of MCM-41 and interlayers of montmorillonite as photocatalysts for rhodamine-B degradation in aqueous solution.

Capping agent-free CdS quantum dots (CdS-QDs) were synthesized within the mesopores of MCM-41 and interlayers of montmorillonite (MMT), using a safe manner by a facile ion exchange-precipitation protocol. The mesopores of MCM-41 and interlayers of MMT controlled the growth of CdS-QDs. The obtained CdS-QDs@MCM-41 and CdS-QDs/MMT were characterized by X-ray diffraction (XRD) analysis, energy-dispersive X-ray (EDX), diffuse reflectance UV-Vis, and photoluminescence spectroscopies. Photodegradation of rhodamine-B (RhB) over these embedded CdS-QDs was investigated under UV-Vis light irradiation. The influences of some parameters on the photodegradation of RhB such as pH, temperature, and UV-Vis irradiation time were investigated. The results showed that the CdS-QDs/MMT and CdS-QDs@MCM-41 have high efficiencies for RhB photodegradation under UV-Vis illumination.

Boric acid modified S and N co-doped graphene quantum dots as simple and inexpensive turn-on fluorescent nanosensor for quantification of glucose.

A new fluorescent nanosensor based on S and N co-doped graphene quantum dots (S,N-GQDs) modified by boric acid was designed for glucose detection. First, the S,N-GQDs was prepared via one pot hydrothermal process utilizing citric acid and thiourea as precursors. Then, S,N-GQDs was modified by boric acid to fabricate (B)/S,N-GQDs. The excitation dependent photoluminescence spectra of (B)/S,N-GQDs confirmed the heteroatom (S,N) dopant effect on GQDs emission. FT-IR and energy dispersive X-ray (EDX) spectroscopies confirmed the modification of S,N-GQDs with boric acid. The optical and electrochemical band gaps of the obtained (B)/S,N-GQDs were found to be 2.7 and 2.5 eV, respectively. The boric acid functionalized S,N-GQDs exhibited fluorescent enhancement at 455 nm upon addition of glucose. Such fluorescence response was used for glucose quantification with a detection limit of 5.5 µM which is comparable with previous boronic acid based fluorescent sensing systems. However, compared with earlier reported expensive boronic acid based glucose sensors, this modified system is simpler, more economical, and efficient. A mechanism was proposed for fluorescence enhancement based on the reaction of cis-diol units of glucose with the boric acid groups of (B)/S,N-GQDs which creates rigid (B)/S,N-GQDs-glucose structures, restricting the non-radiative intramolecular motions and results in the fluorescent enhancement.

Designing a New Efficient Photocatalyst Based on Functionalization of Zn-Infinite Coordination Polymer with Ru(acac)3 Complex for Dye Degradation in Aqueous Solutions: Charge Separation Effect.

A new Zn-containing infinite coordination polymer, Zn-ICP, functionalized with Ru(acac)3 complex was designed and utilized as an efficient visible light photocatalyst for dye degradation in aqueous solutions. Incorporation of Ru(acac)3 not only extended the light absorption of the Zn-ICP to the visible region but also led to electron-hole separation. Upon visible light illumination, photoinduced electron transfer from excited state of Zn-ICP to Ru(acac)3 occurred, resulting in electron-hole separation as indicated by photoluminescence and electrochemical impedance spectroscopy. The obtained Ru-Zn-ICP revealed enhanced visible light photocatalytic activity in degradation of organic pollutants compared to pristine Zn-ICP owing to photoinduced electron transfer in the Ru-Zn-ICP system and efficient separation of photogenerated electron-hole pairs. The prepared Ru-Zn-ICP photocatalyst was readily recycled without major loss of activity in the successive cycles.

Molecularly imprinted polymer containing fluorescent graphene quantum dots as a new fluorescent nanosensor for detection of methamphetamine.

A novel fluorescent nanosensor based on graphene quantum dots embedded within molecularly imprinted polymer (GQDs@MIP) was developed for detection and determination of methamphetamine (METH). The resulting GQDs@MIP nanocomposite exhibited higher methamphetamine selectivity in comparison with corresponding non-imprinted polymer (GQDs@NIP). Characterization of the GQDs@MIP nanocomposite was done by nitrogen adsorption and desorption analysis (BET method), transmission electron microscopy (TEM), photoluminescence (PL), ultraviolet-visible (UV-Vis), and Fourier transform infrared (FT-IR) spectroscopies. The fluorescence intensity of GQDs@MIP was efficiently quenched in the presence of methamphetamine template molecules while no quenching was observed in the presence of other analytes such as amphetamine, ibuprofen, codeine, and morphine. Using this method, the detection limit of 1.7 µg/L was obtained for methamphetamine determination.