Search

Carbon "quantum" dots or carbon dots (CDots) exploit and enhance the intrinsic photoexcited state properties and processes of small carbon nanoparticles via effective nanoparticle surface passivation by chemical functionalization with organic species. The optical properties and photoinduced redox characteristics of CDots are competitive to those of established conventional semiconductor quantum dots and also fullerenes and other carbon nanomaterials. Highlighted here are major advances in the exploration of CDots for their serving as high-performance yet nontoxic fluorescence probes for one- and multi-photon bioimaging in vitro and in vivo , and for their uniquely potent antimicrobial function to inactivate effectively and efficiently some of the toughest bacterial pathogens and viruses under visible/natural or ambient light conditions. Opportunities and challenges in the further development of the CDots platform and related technologies are discussed.

Ischemic stroke is a typical cerebrovascular illness with high morbidity and mortality worldwide. Nevertheless, strategies for the prevention and treatment of cerebral ischemia/reperfusion injury (CIRI) are limited. Gallic acid (GA) is a plant polyphenol that has been used against CIRI. However, the pharmacokinetic (PK) properties of GA, such as its low absorption, poor bioavailability, and quick elimination, have negative effects on its application. To strengthen its effectiveness, a delivery system of GA-loaded o-carboxymethyl chitosan nanoparticles (GA-NPs) was synthesized in our study. In PKs study, GA-NPs apparently increases the area under the curve of plasma concentration-time and prolonged half-life of GA. Then, we measured the in vitro and in vivo effects of the GA-NPs in the oxygen glucose deprivation model and the middle cerebral artery occlusion model. The results from our pharmacodynamic studies, including assessment of neurological deficit, cerebral infarction, levels of inflammation, and oxidative stress, showed that GA-NPs possess better neuroprotection compared with GA. In conclusion, GA-NPs may be used as an efficacious delivery vehicle for GA in the treatment of CIRI.

This study was designed to investigate the antimicrobial effects of CDots in combination with other antimicrobial reagents, including H2O2, Na2CO3, and AcOH (acetic acid). CDots were synthesized and passivated with 2,2'-(ethylenedioxy)bis(ethylamine) (EDA). The minimal inhibitory concentration (MIC) of CDots was 64 μg/mL on both Gram negative bacteria E.coli cells and Gram positive bacteria Bacillus subtilis cells. When CDots were combined with H2O2, antibacterial synergistic effects were observed based on the fractional inhibitory concentration (FIC) index, and further confirmed by an isobologram analysis and viable cell number counting methods. With the combination treatment of 10 μg/mL CDots with 8.82 mM H2O2, the viable E.coli cell numbers decreased 2.46 log, which was significant lower than the log reduction from 8.82 mM H2O2 (1.57 log) or 10 μg/mL CDots (0.14 log) treatment alone. However, the combination of CDots with Na2CO3 or AcOH did not show synergistic effects, instead, exhibiting indifference effects according to the FIC index. This study indicated that the combination of CDots with their synergistic antimicrobial reagents, such as H2O2, could reach the goal of inhibiting bacteria growth by using lower concentration of each individual chemical in the combination than using one chemical treatment alone, reduce the risks imposed on environmental health and the possibilities of the development of microbial resistances.

This study reported the first assessment of carbon dots' (CDots) antiviral activity to human norovirus virus-like-particles (VLPs), GI.1 and GII.4 VLPs. CDots with different surface passivation molecules, 2,2'-(ethylenedioxy)bis(ethylamine) (EDA)-CDots and 3-ethoxypropylamine (EPA)-CDots, were synthesized and evaluated. The results indicated both EDA- and EPA- CDots were highly effective to inhibit both strains of VLPs' bindings to histo-blood group antigens (HBGA) receptors on human cells at CDots concentration of 5 µg/mL, with EDA-CDots achieving 100% inhibition and EPA CDots achieving 85-99% inhibition. At low CDots concentration (2 µg/mL), positively charged EDA-CDots exhibited higher inhibitory effect (~82%) than non-charged EPA-CDots (~60%), suggesting the surface charge status of CDots played a role in the interactions between CDots and the negatively charged VLPs. Both types of CDots also exhibited inhibitory effect on VLP's binding to their respective antibodies, but much less effective than those to HBGA binding. After CDots treatments, VLPs remained intact, and no degradation was observed on VLPs' capsid proteins. Taken together, the observed antiviral effects of CDots on noroviruses were mainly through the effective inhibition of VLPs' binding to HBGA receptors and moderate inhibition of VLPs' binding to their antibodies, without affecting the integrity of viral capsid protein and the viral particle.

Carbon nanoparticles are in all of the carbon nanomaterials that are presently widely pursued for potential bioapplications, but their in vivo biodistribution-related properties are largely unknown. In this work, highly (13)C-enriched carbon nanoparticles were prepared to allow their quantification in biological samples by using isotope-ratio mass spectroscopy. The in vivo biodistribution results are presented and discussed, and also compared with those of the aqueous suspended carbon nanotubes reported previously. The distribution profile and time dependencies are largely similar between the nanoparticles and nanotubes, with results on both suggesting meaningful accumulation in some major organs over an extended period of time. Therefore, the surface modification of carbon nanoparticles, preferably the chemical functionalization of the nanoparticles with biocompatible molecules or species, is desirable or necessary in the pursuit of these nanomaterials for various bioapplications.

Carbon Dots (CDs) are a new promising type of small (5 nm), biocompatible and multicolor luminescent nanoparticle. Here, we demonstrate super-resolution imaging of CDs at the nanoscale through STimulated Emission Depletion (STED) microscopy. In addition, we report the application of STED for detection of CD localization in both fixed and living cells, achieving a spatial resolution down to 30 nm, far below the diffraction limit, showing great promise for high resolution visualization of cellular dynamics.

Carbon nanomaterials have generated a tremendous amount of attention in the scientific community. While most of the research and development efforts have been on fullerenes, carbon nanotubes, and graphene sheets, carbon nanoparticles (which are often considered as impurities or unwanted complications in the other carbon nanomaterials) have recently emerged as a unique class of highly fluorescent nano-dots. However, little or no attention has been paid to potential uses of carbon nanoparticles as chromophores in photochemical reactions or for photon harvesting and photoconversion in general. In the study reported herein we demonstrate the chromophore-equivalent functions of aqueous-suspended small carbon nanoparticles in harvesting visible photons for the reductive coating of the nanoparticles with silver and gold and, as a result, the preparation of unique carbon-noble-metal core-shell nanostructures., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Increasing atmospheric CO(2) levels have generated much concern, driving the ongoing carbon sequestration effort. A compelling CO(2) sequestration option is its photocatalytic conversion to hydrocarbons, for which the use of solar irradiation represents an ultimate solution. Here we report a new strategy of using surface-functionalized small carbon nanoparticles to harvest visible photons for subsequent charge separation on the particle surface in order to drive the efficient photocatalytic process. The aqueous solubility of the catalysts enables photoreduction under more desirable homogeneous reaction conditions. Beyond CO(2) conversion, the nanoscale carbon-based photocatalysts are also useful for the photogeneration of H(2) from water under similar conditions., (© 2011 American Chemical Society)

The authors synthesized a kind of upconversion nanocrystals NaYF4:Yb3+, Er3+ via the hydrothermal assisted homogeneous precipitation method, and then the nanocrystal was coated with silica. The SEM image demonstrated that the as-prepared samples were uniform in size distribution with ca. 25 nm before and ca. 250 nm after silica coating, respectively. The upconversion spectra and photoluminescence lifetime measurement showed that the silica shell had hardly effect on the properties of fluorescence of the NaYF4:Yb3+, Er3+ nanocrystals. At the same time, the naked eye-visible green upconversion fluorescence pattern was acquired from the as-prepared upconversion nanoparticles in the PBS buffer (2 wt%) excited by 980 nm laser at room temperature. These water-soluble nanoparticles were linked to the antibodies using the coupling reagents glutaraldehyde. The circular dichroism (CD) spectra of antibody and upconversion nanoparticles-antibody conjugates were very similar to each other, indicating that the secondary structure of antibody remained largely intact after the conjugation. Finally, antigen-antibody recognition reaction was performed on the surface of a silicon slide. The immunofluorescence in vitro indicated that the upconversion nanoparticles-antibody bioconjugates had excellent species-specific detection ability with hardly non-specific binding. Based on the present results, it is anticipated that the silica-coated upconversion nanoparticles are suitable for use as biolabeling materials.

It was found and recently reported that small carbon nanoparticles can be surface-passivated by organic or biomolecules to become strongly fluorescent. These fluorescent carbon nanoparticles, dubbed "carbon dots", can be successfully used for in vitro cell imaging with both one- and two-photon excitations, as already demonstrated in the literature. Here we report the first study using carbon dots for optical imaging in live mice. The results suggest that the carbon dots remain strongly fluorescent in vivo, which, coupled with their biocompatibility and nontoxic characteristics, might offer great potential for imaging and related biomedical applications.

The photoluminescence in carbon dots (surface-passivated small carbon nanoparticles) could be quenched efficiently by electron acceptor or donor molecules in solution, namely that photoexcited carbon dots are both excellent electron donors and excellent electron acceptors, thus offering new opportunities for their potential uses in light energy conversion and related applications.

Semiconductor quantum dots and nanoparticles composed of metals, lipids or polymers have emerged with promising applications for early detection and therapy of cancer. Quantum dots with unique optical properties are commonly composed of cadmium contained semiconductors. Cadmium is potentially hazardous, and toxicity of such quantum dots to living cells, and humans, is not yet systematically investigated. Therefore, search for less toxic materials with similar targeting and optical properties is of further interest. Whereas, the investigation of luminescence nanoparticles as light sources for cancer therapy is very interesting. Despite advances in neurosurgery and radiotherapy the prognosis for patients with malignant gliomas has changed little for the last decades. Cancer treatment requires high accuracy in delivering ionizing radiation to reduce toxicity to surrounding tissues. Recently some research has been focused in developing photosensitizing quantum dots for production of radicals upon absorption of visible light. In spite of the fact that visible light is safe, this approach is suitable to treat only superficial tumours. Ionizing radiation (X-rays and gamma rays) penetrate much deeper thus offering a big advantage in treating patients with tumours in internal organs. Such concept of using quantum dots and nanoparticles to yield electrons and radicals in photodynamic and radiation therapies as well their combination is reviewed in this article.

The rapid expansion of a supercritical solution into a liquid solvent (RESOLV) technique with benign supercritical carbon dioxide was applied to obtain aqueous suspended nanoparticles of the highly potent anticancer drug paclitaxel. The paclitaxel nanoparticles were protected from agglomeration by using a known nontoxic stabilization agent. The aqueous suspended paclitaxel nanoparticles of different average particle sizes were evaluated in vitro against human breast cancer cells. The results suggest that the nanosized paclitaxel particles are effective, with an antineoplastic activity comparable to that of the commercial paclitaxel formulation. The technique should be generally applicable to the processing of nanoparticles from other important drugs with aqueous solubility problems.

Carbon dots (CDots) are small carbon nanoparticles with effective surface passivation by organic functionalization. In the reported work, the surface functionalization of preexisting small carbon nanoparticles with N-ethylcarbazole (NEC) was achieved by the NEC radical addition. Due to the major difference in microwave absorption between the carbon nanoparticles and organic species such as NEC, the nanoparticles could be selectively heated via microwave irradiation to enable the hydrogen abstraction in NEC to generate NEC radicals, followed by in situ additions of the radicals to the nanoparticles. The resulting NEC-CDots were characterized by microscopy and spectroscopy techniques including quantitative proton and 13C NMR methods. The optical spectroscopic properties of the dot sample were found to be largely the same as those of CDots from other organic functionalization schemes. The high structural stability of NEC-CDots benefiting from the radical addition functionalization is highlighted and discussed. [ABSTRACT FROM AUTHOR]

Nanocomposites of high-density polyethylene (HDPE) modified with 0.2 phr graphene-zinc oxide (GN-ZnO) exhibited optimal mechanical properties and thermal stability. Two other nano-materials—GN and nano-ZnO—were also used to compare them with GN-ZnO. Increasing the content of GN-ZnO gradually enhanced the antibacterial and barrier properties, but the addition of 0.3 phr GN-ZnO led to agglomeration that caused defects in the nanocomposites. Herein, we investigated the antibacterial and barrier properties of HDPE nanocomposites infused with different nanoparticles (GN, ZnO, GN-ZnO) of varying concentrations. HDPE and the nanoparticles were melt-blended together in a Haake-Buchler Rheomixer to produce a new environment-friendly nano-material with improved physical and chemical properties. The following characterizations were conducted: tensile test, thermogravimetric analysis, morphology, differential scanning calorimetry, X-ray diffraction, antibacterial test, and oxygen and water vapor permeation test. The results showed that the crystallinity of HDPE was affected with the addition of GN-ZnO, and the nanocomposites had effective antibacterial capacity, strong mechanical properties, high thermal stability, and excellent barrier performance. This type of HDPE nanocomposites reinforced with GN-ZnO would be attractive for packaging industries. [ABSTRACT FROM AUTHOR]

An ultrafine tin dioxide/N, P-doped porous carbon (SnO 2 /NPPC) nanocomposite is prepared through in-situ growth of tin dioxide (SnO 2) nanoparticles in N, P-doped porous carbon (NPPC). Owing to the in-situ growth method, the size of SnO 2 nanoparticles in SnO 2 /NPPC is quite small and uniform (generally less than 5.0 nm). NPPC provides a support and a conductive carbon skeleton for the SnO 2 nanoparticles. The small SnO 2 nanoparticles are less likely to aggregate during the discharge–charge process due to the presence of Sn–O–C bonding and nanoconfinement effect of SnO 2 nanoparticles in carbon matrix. The N and P doping can provide abundant defects to facilitate the penetration of Li+ or Na+ into the interior of the electrode. In addition, the presence of Sn–N bonding can further improve the electrochemical properties of the electrodes. Thus, as an anode material for lithium-ion batteries, SnO 2 /NPPC possesses an enhanced rate performance, an excellent cycling stability, and a high initial Coulombic efficiency. The structure of the ultrafine SnO 2 nanoparticles is well maintained in cycled SnO 2 /NPPC. Meanwhile, SnO 2 /NPPC also possesses good electrochemical performance as an anode for sodium-ion batteries. The good electrochemical properties for SnO 2 /NPPC materials can be ascribed to the synergetic effect between small SnO 2 nanoparticles and NPPC. [ABSTRACT FROM AUTHOR]

Carbon-based hybrid nanostructures, especially carbon hybrid dots with metal oxides, are important to both fundamental studies and technological applications. In this work, carbon–TiO2 hybrid dots in two different structural configurations were prepared and investigated comparatively for their optical properties and photoinduced redox characteristics, and the results suggested major differences. In the configuration of small carbon nanoparticles each coated/doped with only a small amount of TiO2, the TiO2 played the role of enhancing the surface passivation effect in conjunction with organic surface functionalization agents for the hybrid dots to exhibit a much improved performance over that of their corresponding neat carbon dots. In the other configuration, however, the hybrid dots of TiO2 nanocrystals each composited with nanoscale carbon domains were apparently similar to dye-sensitized TiO2 nanoparticle systems, with the carbon domains providing the dye function for the harvesting of visible photons. While combining nanoscale carbon and TiO2 for various applications has been a popular topic in the recent literature, the results reported here provide new insights into the different structural configurations or arrangements between the carbon and TiO2 and their associated effects on the optical and photoinduced redox properties of the hybrid nanostructures. Significant implications of the results on an understanding of the mechanistic relationships between the hybrid nano-structures/configurations and optical/redox properties are highlighted, and opportunities in the further exploration of carbon–metal oxide hybrid dots and their applications are discussed. [ABSTRACT FROM AUTHOR]

Magnetic CoFe 2 O 4 nanoparticles immobilized on biochar derived from rape straw were synthesized and applied in degrading sulfamethoxazole by peroxymonosulfate activation. [Display omitted] • Magnetic CoFe 2 O 4 /BC composite was successfully fabricated by a facile solvothermal method. • The synergy endowed the CoFe 2 O 4 /BC composite excellent PMS activation performance. • Both radical and non-radical pathway were involved in the SMX degradation. Utilizing biomass waste to create highly efficient biochar-based catalysts has drawn intensively interest since it adheres to the idea of waste recycling in environmental conservation. Herein, CoFe 2 O 4 nanoparticles immobilized on biochar (BC) derived from rape straw were synthesized and applied in degrading sulfamethoxazole (SMX) by activating peroxymonosulfate (PMS). Experimental results indicated that the 30 wt% CoFe 2 O 4 /BC composite catalyst had the best catalytic activity with the SMX degradation efficiency of 93% within 20 min, which was probably the fact that BC as a carrier not only effectively inhibited the agglomeration of CoFe 2 O 4 nanoparticles and increased the active sites, but also could simultaneously participate in the catalytic degradation reaction as an activator of PMS. In addition, cycle experiments illustrated that the as-prepared catalyst possessed the excellent stability, and the magnetic property measurements implied that they were convenient for separation and recovery. According to quenching experiments, electron paramagnetic resonance (EPR) and electrochemical studies, both radical and non-radical process participated into degrading SMX, where the generated SO 4 · - , · OH and O 2 · - as the major radical active species while 1 O 2 and direct electron transfer were responsible for the non-radical route. Besides, using high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis, a potential SMX degradation pathway was suggested. The present CoFe 2 O 4 /BC composite would be a promising PMS activation catalyst for environmental remediation. [ABSTRACT FROM AUTHOR]

Spherical carbon nanoparticles (carbon nanodots) with a silver shell were investigated as potential sensitizing agents. The cytotoxicity of the combination of ultraviolet radiation or x-rays with the nanodots was examined in cancer cells in vitro. The cell viability decreased following the exposure to the radiation. The carbon nanodots enhanced the radiation effects by significantly reducing the amount of surviving cells compared to that of the cells exposed only to the radiation. Carbon-core silver-shell nanodots can be proposed as a bimodal sensitization platform for biological and medicinal applications employing non-ionizing or ionizing radiation. [ABSTRACT FROM AUTHOR]

In this study, we describe a photocatalytic system based on spherical fluorescent carbon-core nanoparticles (nanodots) that can be activated with ultraviolet radiation. The carbon nanodots with a poly(propionylethylenimine-co-ethylenimine) coating were investigated in human prostate adenocarcinoma (Du145 and PC3) cell cultures in vitro. The cells become more sensitive to ultraviolet radiation when preincubated with the nanodots. The inverse slope of the cell survival curves is about 20-30% lower for the carbon nanodots and radiation compared to that for the radiation alone. Such photoactivatable carbon nanodots can be suggested for use in photocatalytic and photodynamic applications. [ABSTRACT FROM AUTHOR]

Photoluminescence properties of carbon nanoparticles from different treatments in various suspensions were evaluated, and the results were in general agreement with those available in the literature. An interesting observation was that the quenching of luminescence emissions in the aqueous suspended carbon nanoparticles by aliphatic amines deviated from the classical Stern-Volmer behavior in a somewhat unusual fashion, exhibiting reversed quenching (increasing luminescence intensities) at very low quencher concentrations. The implication of the observation to the mechanistic framework that may account for photoluminescence emissions in both functionalized and naked carbon nanoparticles is proposed and discussed. On a évalué les propriétés de photoluminescence de nanoparticules de carbone obtenues par divers traitements dans des suspensions variées et les résultats obtenus sont généralement en accord avec eux qu'on retrouve dans la littérature. On a toutefois fait l'observation intéressante que la décroissance des émissions de luminescence des nanoparticules de carbone en suspension aqueuse, sous l'influence d'amines aliphatiques, dévie du comportement classique de Stern-Volmer d'une façon assez inhabituelle alors qu'elle présente une décroissance inversée (augmentation des intensités de luminescence) à des concentrations très faibles de désactivateur. On propose et on discute des implications de ces observations aux concepts mécanistiques qui pourraient expliquer les émissions de photoluminescence des nanoparticules nues ou fonctionnalisées. [ABSTRACT FROM AUTHOR]

Silver nanoparticles of a relatively narrow size distribution were prepared in the structural cavities of the commercial ionomer membrane thin film Nafion. UV–vis absorption, X-ray powder diffraction, and transmission electron microscopy methods were used in the characterization of the nanoparticle–Nafion composite thin films. The population of silver nanoparticles in the membrane structure could be varied by changing the preparation conditions, but the sizes of the nanoparticles were found to remain generally similar. The results were explained in terms of the hosting of the silver nanoparticles in homogeneously distributed structural domains in the membrane structure, where each domain is probably a group of interconnected reverse micelle-like ion clusters according to the ion cluster model for ionomer membranes already in the literature. [Copyright &y& Elsevier]

A new macrocyclic oxamide coordination polymer [(CuL)3(ClO4)2Mn]n (1) (CuL, H2L=2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien) containing nanometric pores structure has been synthesized and structurally characterized. [Copyright &y& Elsevier]

Abstract Prussian Blue Analogues Mn 3 [Fe(CN) 6 ] 2 ·12H 2 O porous nanoparticles have been achieved by coprecipitation method and using polyvinyl pyrrolidone (PVP) as a protective matrix. The obtained nanoparticles were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TG), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM). The X-ray diffraction measurement results show that all the obtained nanoparticles are face centered cubic structure. The infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) measurement results indicate that Mn 3 [Fe(CN) 6 ] 2 ·12H 2 O nanoparticles are mixed-valence, and the ratios of MnIIFeIII to MnIIIFeII in obtained nanoparticles are different in water and water-methanol mixed solvent. The magnetic studies of nanocubes (about 480 nm, coming from water synthesis) and nanospheres (about 200 nm, from co-solvent synthesis) materials show that both samples have spin-glass behavior, but magnetic property measurement results indicated T c , T b and T g temperatures of Mn 3 [Fe(CN) 6 ] 2 ·12H 2 O decreases as the size of nanoparticle reduces. Graphical abstract Mn 3 [Fe(CN) 6 ] 2 ·12H 2 O nanoparticles with different sizes, charge distribution and morphologies by controlling the reaction solvent, which lead to the different magnetic behaviors. Although magnetic measurements show that Mn 3 [Fe(CN) 6 ] 2 ·12H 2 O nanocubes (about 480 nm) and nanospheres (about 200 nm) both have ferrimagnetic and spin-glass behaviors, their freezing temperature and Tc are obvious difference. fx1 [ABSTRACT FROM AUTHOR]

Carbon dots, generally small carbon nanoparticles with various forms of surface passivation, have achieved the performance level of semiconductor quantum dots in the green spectral region, but their absorption and fluorescence in red/near-IR are relatively weaker. Conceptually similar to endofullerenes, host-guest carbon dots were designed and prepared with red/near-IR dyes encapsulated as guest in the carbon nanoparticle core. Beyond the desired enhancement in optical properties, the host-guest configuration may significantly broaden the field of carbon dots. [ABSTRACT FROM AUTHOR]

Abstract Carbon dots (CDots), generally small carbon nanoparticles with surface passivation by a soft corona-like layer of mostly organic species, have been actively pursued for potential applications in optoelectronics, including various functions that have been served by some popular fullerene derivatives. For the preparation of CDots, chemical functionalization of pre-processed and selected small carbon nanoparticles by organic molecules, so far mostly molecules with primary and secondary amine groups, has been an effective method. In this study, carbon nanoparticles were functionalized by N -ethylcarbazole (NEC) under microwave-assisted reaction conditions for NEC-CDots, analogous but with advantages to the CDots of surface functionalization by poly(N -vinylcarbazole) (PVK, which holds a special place in optoelectronics). NEC molecules can apparently be activated under the reaction conditions for reactive functionalities such as radicals to bind to surface carbons of the nanoparticles, consistent with the observed high stability of NEC-CDots. These dots, likely with a unique surface passivation scheme, exhibited optical properties and photoinduced redox characteristics similar to those found in other high-performance CDots. The potentially broad applicability of the new functionalization approach is discussed, so are implications of the unique surface passivation of carbon nanoparticles by the carbazole moieties. Graphical abstract Image [ABSTRACT FROM AUTHOR]

A simple yet consequential modification was made to the popular carbonization processing of citric acid - polyethylenimine precursor mixtures to produce carbon dots (CDots). The modification was primarily on pushing the carbonization processing a little harder at a higher temperature, such as the hydrothermal processing condition of around 330 °C for 6 h. The CDots thus produced are comparable in spectroscopic and other properties to those obtained in other more controlled syntheses including the deliberate chemical functionalization of pre-processed and selected small carbon nanoparticles, demonstrating the consistency in CDots and reaffirming their general definition as carbon nanoparticles with surface passivation by organic or other species. Equally significant is the finding that the modified processing of citric acid - polyethylenimine precursor mixtures could yield CDots of record-setting fluorescence performance, approaching the upper limit of being quantitatively fluorescent. Thus, the reported work serves as a demonstration on not only the need in selecting the right processing conditions and its associated opportunities in one-pot syntheses of CDots, but also the feasibility in pursuing the preparation of quantitatively fluorescent CDots, which represents an important milestone in the development and understanding of these fluorescent carbon nanomaterials. [ABSTRACT FROM AUTHOR]

Semiconductor quantum dots (QDs) are known for their unique optical properties. In recent years, carbon nanomaterials of surface and/or structural defects have been found to exhibit similar properties after functionalization in various schemes. Among these carbon-based QDs are carbon dots, which are generally defined as small carbon nanoparticles with surface passivation. In fact, carbon dots now represent a rapidly advancing and expanding research field. As measured by the optical properties of carbon dots, the most effective passivation has been the surface functionalization of carbon nanoparticles with organic or polymeric molecules, corresponding to much brighter fluorescence emissions across the visible spectrum and extending into the near-IR. Therefore, carbon dots have been pursued extensively for potential bioimaging and other biomedical applications. The mechanistic framework for carbon dots includes photoinduced redox processes, similar to those found in conventional semiconductor QDs. As a result, carbon dots have also been pursued for their photocatalytic functions. In this article on surface-functionalized carbon nanoparticles or carbon dots, their representative syntheses and demonstrated properties and their potential uses as high-performance yet nontoxic fluorescence probes for bioimaging in vitro and in vivo are highlighted, so is their serving as potent photocatalysts in energy conversion applications. [ABSTRACT FROM AUTHOR]

In the CO 2 sequestration, a desirable yet challenging option is the photocatalytic conversion with solar irradiation. While nanoscale semiconductors have been at the center of attention in the development of suitable photocatalysts for the CO 2 conversion, carbon nanoparticles have recently emerged as a new class of photoactive materials for harvesting visible photons to drive photocatalytic processes. Results from this study demonstrate that aqueous suspended bare carbon nanoparticles could be excited with visible light to photocatalytically convert CO 2 into formic acid, with the performance competitive to that of widely used semiconductor nanoparticles. [ABSTRACT FROM AUTHOR]

The carbon dots in this study were small carbon nanoparticleswiththe particle surface functionalized by oligomeric poly(ethylene glycol)diamine molecules. Upon photoexcitation, the brightly fluorescentcarbon dots in aqueous solution served the function of excellent electrondonors to reduce platinum(IV) and gold(III) compounds into their correspondingmetals to be deposited on the dot surface. The deposited metals evenin very small amounts were found to have dramatic quenching effectson the fluorescence emission intensities, but essentially no effectson the observed fluorescence decays. The obviously exclusive near-neighborstatic quenching could be attributed to the disruption of electron–holeradiative recombinations (otherwise responsible for the fluorescenceemissions in carbon dots). The results provide important evidencefor the availability of photogenerated electrons that could be harvestedfor productive purposes, which in turn supports the current mechanisticframework on fluorescence emission and photoinduced redox propertiesof carbon dots. [ABSTRACT FROM AUTHOR]

Abstract: Silver and silver sulfide nanoparticles in stabilized suspensions, prepared via a supercritical fluid processing technique under various conditions, were evaluated systematically for optical limiting toward the second harmonic of a Q-switched Nd:YAG laser. These nanoparticle samples had very different average particle sizes and size distributions, and their suspensions were protected by different stabilization agents. However, the results show that all these variables have little effect on the optical limiting performance of the nanoparticles, suggesting that the observed limiting responses are likely dominated by a nonlinear absorption mechanism. The implication of the performance stability demonstrated by these optical limiting nanomaterials to their potential applications is discussed. [Copyright &y& Elsevier]

Abstract: Rapid expansion of a supercritical solution into a liquid solvent (RESOLV) was applied to the nanosizing of ibuprofen particles in aqueous suspension. When the rapid expansion was into neat water, the initially formed nanoscale ibuprofen particles agglomerated into large aggregates. Various water-soluble polymers of different molecular weights were added to the aqueous receiving medium in RESOLV as stabilization agent for the produced nanoparticle suspension, and their effects on the properties of the harvested ibuprofen nanoparticles were evaluated. A conclusion is that the selection of stabilization agent in RESOLV may also be used to alter the sizes and morphology of the nanosized drug particles. [Copyright &y& Elsevier]

Abstract: Silver nanoparticles were produced in the Rapid Expansion of a Supercritical Solution into a Liquid SOLVent (RESOLV). Perfluorinated surfactant-stabilized water-in-CO2 microemulsion was used to dissolve silver salt for the rapid expansion. It was found that well-behaved nanocrystalline silver particles could be obtained when the reductive solution at the receiving end of the rapid expansion was adjusted to be highly basic. The results suggest that the pre-expansion reverse micelles in the microemulsion might be playing a significant role in the formation of the nanoparticles and that such a role could be affected by the basicity of the receiving solution in RESOLV. The apparent correlation between the parameters of the pre-expansion microemulsion and the properties of the produced nanoparticles is discussed. [Copyright &y& Elsevier]