Good Water Dispersibility Research Articles

Pyrene-based sulfonated organic porous materials for rapid adsorption of cationic dyes in water

ABSTRACT Porous organic polymers (POP) have gained attention because of their high specific surface area, porosity and their simplicity in synthesis, but for the most part, they are hydrophobic because of their organic backbone, making it difficult to expand their applications. Here, we have obtained poly(pyrene) porous organic polymers (PyPOP) through the polymerization of pyrene monomers catalysed by aluminium trichloride, which is a simple and inexpensive synthesis method. The sulfonated poly(pyrene) porous organic polymers (PyPOP-SO3H) obtained showed rapid adsorption of cationic dyes, especially malachite green (MG adsorption 1607 mg/g) and methylene blue (MB adsorption 1220 mg/g) in pH = 7 aqueous solution, room temperature. The results show that the Freundlich model is more in line with the adsorption process than the Langmuir model, whether for methylene blue or malachite green. In addition, the PSO kinetic model fits better than PFO kinetic model, whether it is for the adsorption of methylene blue or malachite green. The excellent adsorption performance of PyPOP-SO3H for cationic dyes may be due to the introduction of sulfonic acid groups, which not only increases the specific surface area but also allows better dispersion in water, increasing contact points and adsorption efficiency. This research expands the scope of exploration and application of POP.

Reusable poly(2-acrylamido-2-methylpropanesulfonic acid)-grafted magnetic nanoparticles as anionic nano-adsorbents for antibody and antigen

Magnetite nanoparticles (MNPs) grafted with poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) and their use as anionic nano-adsorbents for positively charged antibody were herein presented. PAMPS grafted on MNP surface provided good water dispersibility and high negatively charged surface for electrostatic adsorption with positively charged entities, and MNPs provided a good magnetic responsiveness to facilitate the separation process. From transmission electron microscopy results, the size of the nanoclusters ranged between 50 and 200 nm in diameter with ca. 50–150 particles/cluster. Degree of the negative charge of PAMPS-grafted MNPs increased when increasing pH of the dispersion, indicating the pH-responsive properties of the MNPs. These MNPs were successfully used as nano-adsorbents for adsorption with anti-rabbit IgG through ionic interaction between negative charge of PAMPS-grafted MNP and positive charge of the antibody. In addition, the MNPs also provided the reusable ability by adsorption-desorption cycling process with higher than 80% adsorption ability after five consecutive reusing cycles. These hybrid materials should be alternative nano-adsorbents for other positively charged entities with high adsorption efficiency and reusable supports in magnetic separation applications.

Mini review on the synthetic methodology of citric acid functionalized magnetic graphene oxide characterization and its implementation in waste water treatment

Abstract: Water is an essential element for day-to-day activities like agriculture, industry and domestic uses, etc for human beings. Now-a-day, water pollution by heavy metal ion is one of the most crucial environmental issues. Various methods like ion exchange, chemical precipitation, coagulation, flocculation, membrane filtration, adsorption, and flotation have been adopted to get rid of heavy metal ions from the waste water. Among all these methods, the adsorption process has been widely used for the elimination of heavy metals due to its environment friendly, cost-effective nature and easier availability. The commercial adsorbents, bioadsorbents, and nanosorbents possess high removal capacity, thus used for the eradication of heavy metals from waste water. In recent years, nanosorbents are used in environmental remediation as it occupies large surface area and high substance specificity. The present review aims to assemble the role of citric acid functionalized magnetic graphene oxide in waste water treatment. The presence of functional groups like citric acid, Fe2O3 on graphene oxide holds ample of sites which lead increase its surface area and enhance its adsorptivity. The magnetic nature of graphene oxide provides good dispersity in water and makes it easily separable.

Grafting Hollow Covalent Organic Framework Nanoparticles with Thermal-Responsive Polymers for the Controlled Release of Preservatives.

Covalent organic frameworks (COFs) hold great potential in various applications because of their well-defined pore structures and morphologies. However, most COF materials demonstrate poor dispersibility in solvents that significantly limits their processing and applications. Herein, we report the synthesis of COF-based hollow nanoparticles (h-NPs) with good water dispersibility, high capacity, and thermal responsiveness to load essential oil molecules for longer-term preservation of fruits. Imine-based COF h-NPs possessing a pore width of 1.3 nm, inner/outer diameters of ∼150/239 nm, and high crystallinity were synthesized and grafted with water-soluble polymers such as polyethylene glycol or poly(N-isopropylacrylamide) (PNIPAM) with molecular weights of 1-3 kDa. The h-NP products with grafting densities of 0.6-2.1 nm-2 can be well dispersed in water at room temperature. PNIPAM-grafted ones are temperature-responsive in that they can precipitate out from the dispersion at 40 °C and redisperse at 25 °C for at least 15 cycles. The h-NPs are used as nanocarriers to load essential oils such as hexanal and trans-2-hexenal with a high capacity of 1.1 g/g for fruit fresh-keeping, and the encapsulated preservatives can be released controllably at 25-40 °C as regulated by the grafted polymers. As a result, the storage time of cherry tomatoes can be prolonged by 4 days compared to the control run. Moreover, these h-NPs can be recycled and reused. Our work highlights the potential of COF nanomaterials grafting with stimuli-responsive polymers for controlled release application in various food preservation.

Tumor-Selective Biodegradation-Regulated Photothermal H2 S Donor for Redox Dyshomeostasis- and Glycolysis Disorder-Enhanced Theranostics.

H2 S-mediated tumor therapy has received great attention due to its unique physiological activity and synergistical enhancement, but suffers from limited H2 S donors with promised biosafety to regulate the H2 S delivery and subsequently the elusive pathway to augment the combined therapy. Herein, a PEGylated porous molybdenum disulfide nanoflower (MSP) with abundant defects is facilely synthesized for tumor-targeted theranostics. MSP possesses good water-dispersity and high photothermal ability, which is used for photoacoustic imaging and photothermal therapy. Interestingly, MSP is selectively degraded upon exposure to superfluous glutathione (GSH) within tumor cells, the mechanism of which is investigated, as a reduction-coordination reaction. This special degradation induces redox dyshomeostasis via GSH depletion for reactive oxygen species-accumulated chemodynamic therapy. Meanwhile, the selective biodegradation of MSP regulates a sustained H2 S release within tumor and achieves a targeted H2 S gas therapy via enhancing the glycolysis to acidify the tumor cells (glycolysis disorder). Synergistically, these performances are further enhanced via near-infrared photothermal heating, where excellent therapeutic outcomes with good biosafety are accomplished in vitro and in vivo. These characteristics, together with the unique biodegradation and no obvious side-effects of the nanoparticles, suggest a potential therapeutic strategy for precise tumor treatments.

Preparation of L-cysteine modified MnFe2O4 nanoparticles based on high-gravity technology and application for the removal of lead

MnFe2O4 nanoparticles, usually applied as a magnetic adsorbent for removing heavy metals in wastewater, have attracted widespread attention for the characteristics of excellent magnetic properties and chemical stability. This study firstly used high-gravity technology coupled with surface modification by L-cysteine to prepare novel L-cysteine modified MnFe2O4 nanocomposite (MnFe2O4-Cys) with small size (< 10 nm), narrow size distribution range and good dispersion in water, and serves as the efficient adsorbent for Pb(II) removal from water. The different preparation conditions were optimized and the obtained products were charactered through a series of characterization methods. As compared to a traditional stirred reactor, the MnFe2O4-Cys prepared via high-gravity technology using impinging stream-rotating packed bed (IS-RPB) reactor (MnFe2O4-Cys-R) has higher crystallinity and saturation magnetization (57.16 emu·g-1). As seen from TEM images and DLS results, the MnFe2O4-Cys-R exhibits a small average size of 7.25 nm and good dispersion in water. Besides, the BET specific surface area of MnFe2O4-Cys-R (169.63 m2·g-1) is 31.2% higher than that of unmodified MnFe2O4 (129.26 m2·g-1) prepared by IS-RPB reactor (MnFe2O4-R). The adsorption behavior of Pb(II) on MnFe2O4-Cys-R is best described by pseudo-second-order kinetic and Temkin isotherm models, respectively, whereas Elovich kinetic and Freundlich isotherm models are best for describing the adsorption of Pb(II) on MnFe2O4-R. The realized experimental maximum adsorption capacity of MnFe2O4-Cys-R is 137.45 mg·g-1, which is 1.98 times that of MnFe2O4-R (69.50 mg·g-1). This study provides a new route for production of small uniform MnFe2O4 nanoparticles with excellent magnetic and adsorption performance for wastewater treatment.

Application of a cationic amylose derivative loaded with single-walled carbon nanotubes for gene delivery therapy and photothermal therapy of colorectal cancer.

Single‐walled carbon nanotubes (SWNTs) are cylindrical graphitic helix molecules that exhibit superb mechanical and physical properties. Many polymers, such as polyethylene glycol and glycated chitosan, have been used to modify SWNTs to enhance the stability and biocompatibility of delivery systems; thus, a novel modification for SWNTs with amylose derivatives containing poly(L‐lysine) dendrons (ADP@SWNT) is developed. Infrared spectra analysis, 1H NMR analysis, circular dichroism spectra analysis and thermogravimetric analysis are used to characterize and confirm complex formation. The aqueous dispersion stability, cytotoxicity, gene transfection efficiency and photothermal effect of the complex are studied in vitro and in vivo. Results suggest that the ADP@SWNT complex is successfully synthesized with good water dispersion stability and pDNA transfection capacity. ADP@SWNT/TNFα inhibits tumor growth and metastasis both in vivo and in vitro, and the anti‐tumor effect is enhanced by NIR irradiation, suggesting its high potential for application in tumor therapy.

Lignin Nanoparticles and Alginate Gel Beads: Preparation, Characterization and Removal of Methylene Blue.

A novel and effective green system consisting of deep eutectic solvent (DES) was proposed to prepare lignin nanoparticles (LNPs) without any lignin modification. The LNPs are obtained through the dialysis of the kraft lignin-DES solution. The particle size distribution, Zeta potential and morphology of the LNPs are characterized by using dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The average diameter of LNPs is in the range 123.6 to 140.7 nm, and the LNPs show good stability and dispersibility in water. The composite beads composed of LNPs and sodium alginate (SA) are highly efficient (97.1%) at removing methylene blue (MB) from the aqueous solution compared to 82.9% and 77.4% by the SA/bulk kraft lignin composite and pure SA, respectively. Overall, the LNPs-SA bio-nanocomposite with high adsorption capacity (258.5 mg/g) could be useful in improving water quality and other related applications.

Self-assembled porphyrin polymer nanoparticles with NIR-II emission and highly efficient photothermal performance in cancer therapy.

The development of new organic nanoagents with extremely high photothermal conversion efficiency and good biocompatibility has gained considerable attention in the area of photothermal cancer therapy. In this work, we designed and synthesized a new porphyrin polymer (P-PPor) with donor-acceptor (D-A) structure. P-PPor displayed intense absorbance in the near-infrared (NIR) region with the maximum peak around at 850 ​nm. Under excitation of 808 ​nm, P-PPor demonstrated the significant fluorescence in the NIR-II region (λmax ​= ​1015 ​nm), with the fluorescence quantum yield of 2.19%. Due to the presence of hydrophilic PEG chains and hydrophobic alkyl chains in the conjugated skeleton, the amphiphilic P-PPor could self-assemble into the nanoparticles (P-PPor NPs) with good dispersibility in water and enhanced absorption in the NIR region. Moreover, P-PPor NPs exhibited quenched fluorescence because of the aggregation-caused quenching (ACQ) effect, resulting in the distinct photothermal effect. The photothermal conversion efficiency (PCE) of P-PPor NPs was measured as 66% under 808 ​nm laser irradiation, higher than most of PTT agents. The remarkable photothermal effect of P-PPor NPs was further demonstrated in vitro and in vivo using 4T1 tumor mode. Meanwhile, the NIR-II fluorescence imaging in vivo indicated the high distribution of P-PPor NPs in tumor site. These results suggested that P-PPor NPs could effectively damage the cancer cells in mice under 808 ​nm laser irradiation, and did not cause any obvious side effects after phototherapy. Thus, P-PPor NPs could be used as a potential agent in photothermal cancer therapy with high effectiveness and safety.

Photothermal/photodynamic synergetic therapy of functionalgraphdiyne with porphyrin

<p indent="0mm">In this study, we designed and synthesized two novel porphyrin-modified graphdiyne derivatives (GDYO–TPP and GDY–TPP), which have good dispersity in organic solvents and water and exhibit favourable biocompatibility. It was found that the GDYO–TPP and GDY–TPP not only have excellent photothermal conversion performances, but also have outstanding singlet oxygen generation ability, and can be used for photothermal/photodynamic combination therapy of tumors, showing tremendous inhibition of tumor growth in animals, without side effects. Further studies showed that the efficient electron transfer between porphyrin and graphdiyne made the photothermal/photodynamic combination therapy effect of conjugated GDY–TPP much better than that of non-conjugated GDYO–TPP, which realized the regulation of the photothermal/photodynamic combination therapy by controlling the bonding mode of functional groups. The results provide new ways for designing novel functional graphdiyne and photothermal/photodynamic combination therapy of tumors.

Microencapsulation of Sichuan pepper essential oil in soybean protein isolate-Sichuan pepper seed soluble dietary fiber complex coacervates

Sichuan pepper essential oil (SPEO) possesses pleasant aroma, unique flavor, and various bioactivities; however, it has high volatility, poor stability, and low water solubility. In order to overcome the disadvantages and increase its application in foods, microcapsules of SPEO were developed through complex coacervation followed by spray drying. Sichuan pepper seed soluble dietary fiber (SDF) and soybean protein isolate (SPI) were used to develop SPI-SDF complex coacervates and used as the shell materials of SPEO. The optimal conditions for the complex coacervation between SPI and SDF were established to be pH 4.1 and SPI-to-SDF mass ratio of 6:1. SPEO microcapsules showed a spherical shape with an average particle size of 6.79 μm, and had a good dispersion in water. The SPI-SDF complex coacervates showed excellent encapsulation ability as indicated by high encapsulation efficiency (91.33%) and payload (45.19%). Encapsulated SPEO showed good thermal and storage stability, and possessed a slow-release property in model foods. Encapsulation enhanced the antibacterial activity of SPEO while preserving its antioxidant activity. Aforementioned results indicated that this study successfully improved the stability, solubility, and bioactivity of SPEO. This study provided valuable information for utilizing novel carriers to deliver essential oils and improve their defects through complex coacervation and offered a new pathway for the utilization of plant waste.

Hydrophobic and Hydrophilic Conjugated Polymer Dots as Binary Photocatalysts for Enhanced Visible-Light-Driven Hydrogen Evolution through Förster Resonance Energy Transfer.

Organic semiconducting polymers exhibited promising photocatalytic behavior for hydrogen (H2) evolution, especially when prepared in the form of polymer dots (Pdots). However, the Pdot structures were formed using common nonconjugated amphiphilic polymers, which have a negative effect on charge transfer between photocatalysts and reactants and are unable to participate in the photocatalytic reaction. This study presents a new strategy for constructing binary Pdot photocatalysts by replacing the nonconjugated amphiphilic polymer typically employed in the preparation of polymer nanoparticles (Pdots) with a low-molecular-weight conjugated polyelectrolyte. The as-prepared polyelectrolyte/hydrophobic polymer-based binary Pdots truly enhance the electron transfer between the Pt cocatalyst and the polymer photocatalyst with good water dispersibility. Moreover, unlike the nonconjugated amphiphilic polymer, the photophysics and mechanism of this photocatalytic system through time-correlated single-photon counting (TCSPC) and transient absorption (TA) measurements confirmed the Förster resonance energy transfer (FRET) between the polyelectrolyte as a donor and the hydrophobic polymer as an acceptor. As a result, the designated binary Pdot photocatalysts significantly enhanced the hydrogen evolution rate (HER) of 43 900 μmol g-1 h-1 (63.5 μmol h-1, at 420 nm) for PTTPA/PFTBTA Pdots under visible-light irradiation.

Preparation and application of multi-wavelength-regulated multi-state photoswitchable fluorescent polymer nanoparticles

The photoswitchable system with color and multi-state fluorescence changes is the key to the realization of advanced multi-level information storage, and its application potential has far exceeded the monochromatic fluorescent system. Herein, we introduced a novel multi-state photoswitchable fluorescent polymeric nanoparticles, which contains two energy-matched photoswitchable fluorescent molecules, i.e. diarylethene derivative (BH, donor) and spiropyran derivative (SPMA, acceptor), to construct a tunable fluorescence resonance energy transfer (FRET) system. By optimizing the feeding ratio of the two photochromic molecules to control the efficiency of energy transfer, the fluorescence of the nanoparticles can be reversibly switched among none, red, orange, and green by adjusting the wavelength of light stimuli. In addition, the nanoparticles display good water dispersibility, high brightness, fast responsiveness, excellent photoreversibility, and long-term fluorescence stability. We also verified that the system has great potential in optical data storage, multi-layer information encryption, and anti-counterfeiting.

Self-transformation synthesis of hierarchically porous benzene-bridged organosilica nanoparticles for efficient drug delivery

Herein, a feasible outside-in hydrothermal self-transformation strategy is presented to fabricate hierarchically porous benzene-bridged organosilica nanoparticles (HPBONs), and detailed mechanistic investigations were performed to study the formation of hierarchically porous nanostructures. The obtained HPBONs consisted of a mesoporous core (2.3 nm) and a large mesoporous flocculent shell (12.6 nm), which corresponded to an overall diameter of ∼ 200 nm and good water dispersibility, respectively. Owing to the unique hierarchically porous structure and high surface area (877 m2/g), HPBONs showed a high coloading capacity for the hydrophilic drug doxorubicin (DOX) and the hydrophobic photosensitizer chlorin e6 (Ce6) (355 µg/mg, 38 µg/mg, respectively) and acid-responsive DOX drug release (42.62%), leading to precise chemo-photodynamic therapy in vitro, as the cytotoxicity assay revealed 70% killing of breast cancer (MCF-7) cells. This research provides a new method to construct hierarchically porous organosilica-based nanodelivery systems.

Starch Capped Atomically Thin CuS Nanocrystals for Efficient Photothermal Therapy.

Photothermal therapy requires efficient plasmonic nanomaterials with small size, good water dispersibility, and biocompatibility. This work reports a one-pot, 2-min synthesis strategy for ultrathin CuS nanocrystals (NCs) with precisely tunable size and localized surface plasmon resonance (LSPR), where a single-starch-layer coating leads to a high LSPR absorption at the near-IR wavelength 980nm. The CuS NC diameter increases from 4.7 (1nm height along [101]) to 28.6nm (4.9nm height along [001]) accompanied by LSPR redshift from 978 to 1200nm, as the precursor ratio decreases from 1 to 0.125. Photothermal temperature increases by 38.6°C in 50mg L-1 CuS NC solution under laser illumination (980nm, 1.44 W cm-2 ). Notably, 98.4% of human prostate cancer PC-3/Luc+ cells are killed by as little as 5mg L-1 starch-coated CuS NCs with 3-min laser treatment, whereas CuS NCs without starch cause insignificant cell death. LSPR modeling discloses that the starch layer enhances the photothermal effect by significantly increasing the free carrier density and blue-shifting the LSPR toward 980nm. This study not only presents a new type of photothermally highly efficient ultrathin CuS NCs, but also offers in-depth LSPR modeling investigations useful for other photothermal nanomaterial designs.

A high-efficient nano pesticide-fertilizer combination fabricated by amino acid-modified cellulose based carriers.

As the global population grows, large quantities of agrochemicals are used to secure food demand and there is an urgent need to develop efficient and environmentally friendly pesticides and fertilizers. Compared with traditional pesticides, nanopesticide formulations can achieve better foliar wettability, chemical stability, and water dispersibility without or with the minimal use of organic solvents, in line with the development of sustainable agriculture. In this research, glycidyl methacrylate (GMA) was used as an intermediate and glycine methyl ester (GLY) was used as an organic nitrogen source to modify carboxymethyl cellulose (CMC) to synthesize a pesticide nanocarrier CMC-PGMA-GLY. A nanopesticide EB@CMC-PGMA-GLY (EB@CPG) was formed by the hydrophobic and electrostatic interactions of emamectin benzoate (EB), which had good water dispersion. The good affinity of the composite towards leaves led to the effective moistening of the leaf surface by the pesticide and through the pH control pesticide release. Biological experiments show that nanopesticides can maintain high insecticidal activity and have no toxicity to seed germination. The results of pot experiment showed that the nanocarriers could be used as an organic nitrogen fertilizer to increase the fresh weight of plants by 39.77%. This environmentally friendly pesticide carrier can be used as a fertilizer to provide sufficient nutrients for crops, opening a new method for the development of sustainable agriculture. © 2021 Society of Chemical Industry.

Silver Nanoparticles AgNPs Preparation by Chemical Method to Obtain Optimal Characteristics of The Pharmaceutical Form and Study Their Effect on The Leishmania Parasite in Laboratory

This study aimed first to prepare silver nanoparticles AgNPs in a chemical reduction, The silver nanoparticles AgNPs properties were characterized using spectroscopy of Vision and UV- Visible (UV- Vis), and atomic force microscopy (AFM) and a ZetaSizer device. This study also aimed to study the results effect of preparing Silver nanoparticles on the Leishmania parasite using an artificial environment. The results of the spectrophotometer of the secondary silver solution with yellow color, showed maximum absorption at a wavelength of 400 mm, while the image of atomic force microscope (AFM) showed the hierarchical morphology shape of the prepared Silver nanoparticles with an average size of (10- 30 nm). Silver secondary particles were estimated with a diameter ranging from (12- 60 nm) and with good dispersion in water by ZetaSizer device. The results illustrated that the number of Promastigotes of the Leishmania parasite decreased after adding the Silver nanoparticles AgNPs in varying proportions, as the concentration of 500 μg/ml had the highest effect after 72 hours from incubation, and the percentage of remaining parasites was 5.2% comparing with the control percentage of 14.99%, while the value of IC50 was 253.075 μg/ml, The value of R2 = 0.8809, slope = 0.0478 after 24 hours from incubation.

Hyaluronic Acid-Glycine-Cholesterol Conjugate-Based Nanoemulsion as a Potent Vaccine Adjuvant for T Cell-Mediated Immunity.

Clinical cases of allergic reaction that are due to excipients containing polyethylene glycol (PEG), a hydrophilic molecule commonly used in drug/vaccine formulations, has attracted much attention in recent years. In order to develop PEG-free adjuvants, we investigated the feasibility of natural ingredients in the human body such as hyaluronic acid in the form of hyaluronic acid-glycine cholesterol (HACH) conjugate as an excipient for vaccine formulation. Interestingly, HACH grafted with ~13 wt.% cholesterol has good water dispersity and can serve as an emulsifier to stabilize the squalene/water interfaces, yielding a milky white and isotropic emulsion (SQ@HACH) after being passed through a high-shear microfluidizer. Our results show that SQ@HACH particles possessed a unimodal average hydrodynamic diameter of approximately 190 nm measured by dynamic light scattering and exhibited good stability upon storage at 4 °C and 37 °C for over 20 weeks. The results of immunogenicity using a mouse model with ovalbumin (OVA) as the antigen revealed that SQ@HACH significantly enhanced antigen-specific immune responses, including the polarization of IgG antibodies, the cytokine secretions of T cells, and enhancement of cytotoxic T lymphocyte (CTL) activation. Moreover, SQ@HACH revealed lower local inflammation and rapidly absorbing properties compared with AlPO4 after intramuscular injection in vivo, indicating the potential functions of the HA-derived conjugate as an excipient in vaccine formulations for enhancement of T cell-mediated immunity.

Sandwich structured MnO2/carbon nanosheet/MnO2 composite for high-performance supercapacitors

In view of the uniform lamellar structure of potassium citrate-derived carbon nanosheets (PC-Cs) and a good dispersion in water, PC-Cs are prepared via high-temperature carbonization method and acted as sacrificial template for reacting with KMnO4 to generate MnO2 nanosheets arrays on both sides of carbon nanosheet. When the mass ratio of PC-Cs/KMnO4 is 1/15, sandwich structured MnO2/PC-Cs/MnO2 composite is obtained. Through the characterization in microstructure, X-ray diffraction spectrum, X-ray photoelectron spectroscopy and thermogravimetric curve, the sandwich composite has a thickness of 320 nm, containing 79.9% MnO2 and 20.1% residual carbon. When used in three-electrode supercapacitor, the optimized composite delivers a high capacitance of 397 F g−1 at 1 A g−1, with capacitance retention of 93.1% after cycling for 5000 cycles. An asymmetric supercapacitor is assembled by MnO2/PC-Cs/MnO2 positive electrode and PC-Cs negative electrode, which presents a capacitance of 81.5 F g−1 at 0.5 A g−1, with no capacitance decay for 5000 cycles, and the energy density is 21.9 W h kg−1 at 143.8 W kg−1. Compared to existing C/MnO2 composites, sandwich composite displays an obvious superiority, due to the high fraction of MnO2 and nanosheets arrays structure. Moreover, residual carbon layer sandwiched between two MnO2 layers reduces the internal resistance, enhances electronic conductivity, further improving the long-term cycling stability.

Versatile Fluorescent Carbon Dots from Citric Acid and Cysteine with Antimicrobial, Anti-biofilm, Antioxidant, and AChE Enzyme Inhibition Capabilities.

Nanostructured fluorescent particles derived from natural molecules were prepared by a green synthesis technique employing a microwave method. The precursors citric acid (CA) and cysteine (Cys) were used in the preparation of S- and N-doped Cys carbon dots (Cys CDs). Synthesis was completed in 3min. The graphitic structure revealed by XRD analysis of Cys CDs dots had good water dispersity, with diameters in the range of 2-20nm determined by TEM analysis. The isoelectric point of the S, N-doped CDs was pH value for 5.2. The prepared Cys CDs displayed excellent fluorescence intensity with a high quantum yield of 75.6 ± 2.1%. Strong antimicrobial capability of Cys CDs was observed with 12.5mg/mL minimum bactericidal concentration (MBC) against gram-positive and gram-negative bacteria with the highest antimicrobial activity obtained against Staphylococcus aureus. Furthermore, Cys CDs provided total biofilm eradication and inhibition abilities against Pseudomonas aeruginosa at 25mg/mL concentration. Cys CDs are promising antioxidant materials with 1.3 ± 0.1μmol Trolox equivalent/g antioxidant capacity. Finally, Cys CDs were also shown to inhibit the acetylcholinesterase (AChE) enzyme, which is used in the treatment of Alzheimer's disease, even at the low concentration of 100μg/mL.