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Recently, carbon dots (CDs) have been among the most promising emerging fluorescent labels for cellular imaging. In this work, a new facile synthesis method was developed for fabricating CDs from polystyrene foam waste and common organic solvents. The CDs obtained have tunable emission from blue to orange and are expected to be of use for labeling different cellular structures simultaneously. Transmission electron microscopy, x-ray diffraction, Raman spectra, Fourier transform infrared spectrometry, UV-vis, and fluorescence spectrophotometry (PL) were employed to investigate the structures and luminescence properties of CDs. The highest quantum yield (QY) achieved was 36%. The mechanisms for the formation and luminescence of the CDs are analyzed. The ability of the solvent to disperse the CDs plays a very important role in the origin of PL. The type of organic solvent has an important influence on the position of emission peaks and the QY. Different emissive traps play the dominant role in the luminescence of carbon materials. Furthermore, a hemolysis assay was performed to evaluate the biocompatibility of these CDs in vitro. The biocompatibility of the CDs, even at very high doses, ensures their potential in biomedical applications. [ABSTRACT FROM AUTHOR]

A unique assembly approach was developed to fabricate conjugated polymer and photosensitizer-doped mesoporous silica nanoparticles with effective Forster resonance energy transfer (FRET) from poly[(9,9-di(3,30-N,N0-trimethylammonium)-propylfluorenyl-2,7-diyl)- alt-co-(1,4-phenylene)] (PFP) to porphyrin-based photosensitizers (PSs). PFP and silica nanoparticles form a complex through electrostatic interactions, and efficient energy transfer from PFP to porphyrin-based PSs occurs upon irradiation. This approach is stable, effective, and diversified. PS-doped mesoporous silica nanoparticles showed three- to four-fold enhanced emission with the excitation of the maximum absorption wavelength of PS in the presence of PFP in comparison to the case without PFP. Doping fluorescence dyes into the nonporous core and adjusting the content of PS conjugated with the shell can endow the silica nanoparticles with a combinational optical signal of dyes and PS. These silica nanoparticles exhibit further improved performance on the basis of enhanced energy transfer offered by light-harvesting conjugated polymers. [ABSTRACT FROM AUTHOR]

Preparation of a p–n heterojunction with hierarchical structure is of great significance for photocatalysis due to its large specific surface area, abundant active sites and increased charge separation rate. Herein, we designed the novel p–n heterojunction photocatalyst TiO2/SnO microflower (TiO2/F-SnO) with hierarchical architecture by decorating TiO2 nanoparticles on the surface of the SnO microflower via a simple hydrothermal route. Compared to pure TiO2 and TiO2/SnO with a microplate structure (TiO2/P-SnO), TiO2/F-SnO heterojunctions exhibited significantly enhanced photocatalytic performances for organics removal such as toluidine blue O (TBO) and methylene blue (MB) under daylight fluorescent lamp irradiation (350–800 nm). The improved performance was not only ascribed to the promoted charge transfer and separation efficiency induced by the formation of p–n junction, but also attributed to the larger specific surface area, sufficient active sites and stronger redox ability provided by the hierarchical microflowers. Moreover, after three photocatalytic cycles (24 h), the TiO2/SnO heterojunction still exhibited a stable photocatalytic activity. Finally, the photocatalytic enhancement mechanism for the TiO2/SnO heterojunction was proposed based on band alignments calculation and the active species trapping experiments. [ABSTRACT FROM AUTHOR]

Tunable transport properties and Fano resonances are predicted in a circular bilayer phosphorene nanoring. The conductance exhibits Fano resonances with varying incident energy and applied perpendicular magnetic field. These Fano resonance peaks can be accurately fitted with the well known Fano curves. When a magnetic field is applied to the nanoring, the conductance oscillates periodically with magnetic field which is reminiscent of the Aharonov–Bohm effect. Fano resonances are tightly related to the discrete states in the central nanoring, some of which are tunable by the magnetic field. [ABSTRACT FROM AUTHOR]

Resistive switching nanostructures are a promising candidate for next-generation non-volatile memories. In this report, we investigate the switching behaviors of single-crystalline ZnO nanowires suspended in air. They exhibit significantly higher current density, lower switching voltage, and more pronounced multiple conductance states compared to nanowires in direct contact with substrate. We attribute the effect to enhanced Joule heating efficiency, reduced surface scattering, and more significantly, the positive feedback established between the current density and local temperature in the suspended nanowires. The proposed mechanism has been quantitatively examined by finite element simulations. We have also demonstrated an innovative approach to initiating the current–temperature mutual enhancement through illumination by ultraviolet light, which further confirmed our hypothesis and enabled even greater enhancement. Our work provides further insight into the resistive switching mechanism of single-crystalline one-dimensional nanostructures, and suggests an effective means of performance enhancement and device optimization. [ABSTRACT FROM AUTHOR]

We report a one-step process for decorating poly(trimethylene terephthalate) (PTT) nanofibers with CdSe/ZnS core/shell quantum dots (QDs). Using the QD-decorated PTT nanofibers with diameters of 400-800 nm as active subwavelength waveguides, their high photostability for 630 nm red light and low absorption coefficient down to 2.6 cm [?] 1 were characterized by both evanescent waveguiding excitation and irradiation excitation. Compared with the irradiation excitation, a 200 times enhancement was obtained from the active subwavelength waveguides under the evanescent waveguiding excitation. [ABSTRACT FROM AUTHOR]

Highly branched Pd 2D nanowire networks are prepared by a template- and surfactant-free method in an ethylene glycol (EG)-dimethyl sulfoxide (DMSO) mixture under mild conditions. Pd nanowire networks with lengths ranging from hundreds of nanometers to several micrometers and branches with uniform diameters of [?]8 nm are grown. The most likely formation mechanism is also proposed. The as-produced Pd nanowire networks exhibit high surface-enhanced Raman scattering activity for 4-mercaptopyridine probe molecules with 5.0 × 10[?]8 M concentration. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) SnO hierarchical architectures were synthesized via a one-step dissolution–precipitation route under room temperature using SnCl2 · 2H2O and Na2CO3 as the initial reagents. The morphology and size of the prepared SnO structures could be easily tailored by alternating the solvent from deionized water with absolute ethanol. The SEM observation showed that the prepared 3D SnO hierarchical architectures consisted of nanosheets. The size of the SnO hierarchical architectures could be effectively reduced from 4–10 μm to 1–2 μm when the solvent was changed from water to ethanol while the thickness of the assembling nanosheets was reduced from 200–500 nm to 20–30 nm at the same time. The possible formation mechanism of the 3D SnO hierarchical architectures is proposed in this paper. The photodegradation of methylene blue revealed that the SnO hierarchical structures prepared using ethanol as the solvent exhibit much better photocatalytic activity due to its smaller particle size, larger specific surface area, and appropriate band structure as well. [ABSTRACT FROM AUTHOR]

Well-aligned tin-doped indium (ITO) nanowires have been prepared using the electrospinning process. The Sn doping mechanism and microstructure have been characterized by x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). Devices for I-V measurement and field-effect transistors (FETs) were assembled using ITO nanowires with top contact configurations. The effect of Sn doping on the electrical conductivity was significant in that it enhanced the conductance by over 107 times, up to [?]1 S cm[?]1 for ITO nanowires with an Sn content of 17.5 at.%. The nanowire FETs were operated in the depletion mode with an electron mobility of up to 0.45 cm2 V[?]1 s[?]1 and an on/off ratio of 103. [ABSTRACT FROM AUTHOR]

Modified g-C3N4 samples (g-X, where X corresponds to the number of hours of acid treatment of the melamine) with outstanding photocatalytic performance were prepared by using hydrochloric acid-treated melamine as a precursor and calcining at 550 °C for 2 h. An x-ray diffractometer, field-emission scanning electron microscope, infrared spectrometer, N2 adsorption–desorption test, x-ray photoelectron spectroscopy, and ultraviolet–visible diffuse–reflectance spectroscopy analysis were carried out to characterize the phase composition, microstructure, chemical structure, specific surface area (SSA), chemical states, elemental composition and optical properties of the samples, respectively. The photocatalytic performance of the samples was evaluated by degrading the Rhodamine B (RhB) aqueous solution. The results showed that the crystal structure and vibration bands of melamine changed due to the reaction with hydrochloric acid. The crystallinity and grain size of g-C3N4 in g-X (X = 1, 2, 4, 6, 8, 10) reduced, and the SSA values of g-X increased compared to that of the g-0 sample, which was synthesized from pristine melamine. The g-X samples exhibited excellent photocatalytic activity towards degradation of RhB compared to g-0. The photocatalytic activity of the g-X samples increased gradually as the acid treatment time of the melamine increased from 1 h to 2 h, and then decreased gradually with the extension of the acid treatment time. The rate constant (k) values of g-X are higher than that of g-0. g-2 presented the highest rate constant (k = 0.052 min−1), which was 5.5 times higher than that of g-0. The improved photocatalytic activity of the g-X samples was attributed to the higher SSA value, the appearance of surface defects, the outstanding photo-carrier separation efficiency and stronger light harvesting ability of g-X, with the last two factors being more significant. Acid treatment of melamine is helpful in the preparation of high performance g-C3N4 photocatalyst, and the microstructure and photocatalytic performance of g-C3N4 were affected significantly by the acid treatment time. [ABSTRACT FROM AUTHOR]

Foodborne pathogens are perpetual threats to human and animal health. Detection of pathogens requires accurate, sensitive, rapid and point-of-care diagnostic assays. In this study, we described a simple and sensitive electrochemiluminescent (ECL) assay to detect the deadly bacteria Escherichia coli O157:H7 by -coated ZnO nanorods arrays (NAs). The -coated ZnO NAs were fabricated by immobilizing on ZnO NAs with a large specific surface area and good conductivity. An -2-(dibutylamino)-ethanol (DBAE) system coated on ZnO NAs exhibits high ECL intensity, rapid response and good stability. This system was further developed as an ECL immunosensor used in the detection of E. coli O157:H7. The proposed ECL immunosensor exhibits a broad detection range within the scope of 200–100 000 CFU ml−1 and quite a low detection limit of 143 CFU ml−1. The high specificity, remarkable reproducibility and good stability offer a sensitive, selective, and convenient pathway for detecting E. coli O157:H7 in the field of food safety and clinical diagnosis. [ABSTRACT FROM AUTHOR]

With the high demand for developing novel composites with integrated performance, graphene-based nanostructures have been drawing great attention in environmental and biomedical applications because of their extraordinary physicochemical properties and biocompatibility. Although graphene oxide (GO) nanosheets exhibit some antibacterial activities, novel GO based nanostructures with enhanced antibacterial activities are highly desired. To realize this aim, polyethyleneimine (PEI) modified GO as a tetracycline hydrochloride (TCH) carrier and release platform was constructed (pGO-TCH). The nanostructures were fully characterized by TEM, AFM, FTIR and Raman spectra, which demonstrated that TCH were uniformly and compactly deposited on PEI modified GO nanosheets. The antibacterial performances of the prepared nanostructures were investigated by disk diffusion method and bacterial growth kinetics method towards Gram-positive S. aureus and Gram-negative E. coli. Results show that pGO-TCH nanostructures exhibit good antibacterial behavior. The mechanism of antibacterial activity was studied. Moreover, the nanostructures showed good cytocompatibility. This study not only highlights a promising pGO-TCH nanostructure as a candidate of graphene-based antibacterial agent, but also provides us antibacterial mechanism between bacteria and graphene-based nanomaterials. [ABSTRACT FROM AUTHOR]

Chemical sensors based on semiconducting metal oxide nanocrystals are of academic and practical significance in industrial processing and environment-related applications. Novel alcohol response sensors using two-dimensional WO3 nanoplates as active elements have been investigated in this paper. Single-crystalline WO3 nanoplates were synthesized through a topochemical approach on the basis of intercalation chemistry (Chen et al 2008 Small 4 1813). The as-obtained WO3 nanoplate pastes were coated on the surface of an Al2O3 ceramic microtube with four Pt electrodes to measure their alcohol-sensing properties. The results show that the WO3 nanoplate sensors are highly sensitive to alcohols (e.g., methanol, ethanol, isopropanol and butanol) at moderate operating temperatures (260-360 degC). For butanol, the WO3 nanoplate sensors have a sensitivity of 31 at 2 ppm and 161 at 100 ppm, operating at 300 degC. For other alcohols, WO3 nanoplate sensors also show high sensitivities: 33 for methanol at 300 ppm, 70 for ethanol at 200 ppm, and 75 for isopropanol at 200 ppm. The response and recovery times of the WO3 nanoplate sensors are less than 15 s for all the test alcohols. A good linear relationship between the sensitivity and alcohol concentrations has been observed in the range of 2-300 ppm, whereas the WO3 nanoparticle sensors have not shown such a linear relationship. The sensitivities of the WO3 nanoplate sensors decrease and their response times become short when the operating temperatures increase. The enhanced alcohol-sensing performance could be attributed to the ultrathin platelike morphology, the high crystallinity and the loosely assembling structure of the WO3 nanoplates, due to the advantages of the effective adsorption and rapid diffusion of the alcohol molecules. [ABSTRACT FROM AUTHOR]

There has been increased interest in the use of polymeric nanoparticles as carriers for near-infrared fluorescence (NIRF) dyes for cancer diagnosis. However, efficient delivery of nanoparticles to the tumors after systemic administration is limited by various biobarriers. In this study, we investigated the pharmacokinetics, biodistribution, and tumor uptake of sub-nanometer sized polymeric nanoparticles (<100 nm in diameter) coated with polyethylene glycol in tumor-bearing mice. To facilitate our studies, these particles were labeled with gamma emitter indium-111. We found that two NIRF nanoparticles having the same size ([?]20 nm) and chemical composition but different structures (i.e., hydrogel versus core-shell nanolatex), or the same core-shell nanolatex particles with different sizes (20, 30, and 60 nm), had different blood circulation times, biodistribution, and tumor uptake. Interestingly, the tumor uptake of the nanolatex particles correlated well with their blood residence times (R2 = 0.95), but similar correlations were not found between nanogel and nanolatex particles (R2 = 0.05). These results suggest that both the blood circulation time and the extent of hydration of the nanoparticles play an important role in the tumor uptake of nanoparticles. Prolonged blood circulation of these NIRF nanoparticles allowed clear visualization of tumors with g-scintigraphy and optical imaging after intravenous administration. A better understanding with regard to how the characteristics of nanoparticles influence their in vivo behavior is an important step towards designing NIRF nanoparticles suitable for molecular imaging applications and for efficient tumor delivery. [ABSTRACT FROM AUTHOR]