Highly efficient and stable tandem luminescent solar concentrators based on carbon dots and CuInSe2-xSx/ZnS quantum dots

Semi-transparent large-area luminescent solar concentrators (LSCs) have been considered an essential part of zero-energy or low-energy consuming buildings in the future. Inorganic colloidal quantum dots (QDs) are promising candidates for LSCs due to the advantages of a tunable bandgap, engineered large Stokes shift, and relatively high photoluminescence (PL) quantum yield. However, LSCs that are fabricated using colloidal quantum dots exhibited an inferior stability under long-term illumination, demanding great efforts to explore the highly stable LSCs. Herein, we fabricated large-area (∼100 cm2) tandem LSCs based on highly stable carbon dots (CDs) and highly luminescent near-infrared emitting CuInSe2-xSx/ZnS (CuInSeS/ZnS) QDs. Coupled with a Si diode as a reference, the power conversion efficiency of the corresponding tandem (dimensions: 10 × 10 × 0.5 cm3) and single LSCs (dimensions: 10 × 10 × 0.3 cm3) based on CuInSeS/ZnS QDs under one sun illumination are 0.46% and 0.5%, respectively. For single CuInSeS/ZnS QD based LSCs at a low concentration (0.039 wt%), external and internal quantum efficiencies reach up to 2.87% and 36.37%, respectively. After UV illumination for 8 h, bottom LSCs based on CuInSeS/ZnS QDs retain 93.22% of the initial PL emission, which is higher than that of LSCs (∼80%) without the CD protection. The highly efficient and stable tandem LSCs employing green CDs and NIR CuInSeS/ZnS QDs as PL emitters pave the way for the realization of large area building-integrated photovoltaic (BIPV) devices.

Synergistic redox enhancement: silver phosphate augmentation for optimizing magnesium copper phosphate in efficient energy storage devices and oxygen evolution reaction

The implementation of battery-like electrode materials with complicated hollow structures, large surface areas, and excellent redox properties is an attractive strategy to improve the performance of hybrid supercapacitors. The efficiency of a supercapattery is determined by its energy density, rate capabilities, and electrode reliability. In this study, a magnesium copper phosphate nanocomposite (MgCuPO4) was synthesized using a hydrothermal technique, and silver phosphate (Ag3PO4) was decorated on its surface using a sonochemical technique. Morphological analyses demonstrated that Ag3PO4 was closely bound to the surface of amorphous MgCuPO4. The MgCuPO4 nanocomposite electrode showed a 1138 C g-1 capacity at 2 A g-1 with considerably improved capacity retention of 59% at 3.2 A g-1. The increased capacity retention was due to the fast movement of electrons and the presence of an excess of active sites for the diffusion of ions from the porous Ag3PO4 surface. The MgCuPO4-Ag3PO4//AC supercapattery showed 49.4 W h kg-1 energy density at 550 W kg-1 power density and outstanding capacity retention (92% after 5000 cycles). The experimental findings for the oxygen evolution reaction reveal that the initial increase in potential required for MgCuPO4-Ag3PO4 is 142 mV, indicating a clear Tafel slope of 49 mV dec-1.

Acetone-derived luminescent polymer dots: a facile and low-cost synthesis leads to remarkable photophysical properties

Carbon-based dots have been attracting much attention as potentially superior alternatives to more conventional semiconductor nanoparticles, due to their fascinating optical properties, chemical and photochemical stability, unique environmental-friendliness, and the versatility of fabrication routes. Many commercial materials and organic compounds have been considered so far as carbon precursors but in many cases the fabrication required high-temperature conditions or led to inhomogeneous final products. Here we report on a simple low-cost synthesis of non-conjugated carbon-rich polymer dots (PDs) that uses acetone as carbon precursor. Both hydrophilic and hydrophobic fractions of PDs were obtained, with the respective average diameters of 2–4 nm and ca. 6 nm. The as-obtained PDs reveal greenish-blue photoluminescence (PL) and high quantum yields (∼5–7%) and complex kinetics of the decays with the average lifetime of ∼3.5 ns. Such luminescent acetone-derived PDs may find application in several fields, including sensing and bioimaging.

Acetone-derived polymer dots (PDs) have been fabricated, according to a base-mediated synthesis route at room temperature. As-obtained hydrophobic and hydrophilic PDs revealed a strong greenish-blue emission due to the crosslink-enhanced effect.

Facile Synthesis of "Boron-Doped" Carbon Dots and Their Application in Visible-Light-Driven Photocatalytic Degradation of Organic Dyes

Carbon dots (C-dots) were facilely fabricated via a hydrothermal method and fully characterized. Our study shows that the as-synthesized C-dots are nontoxic, negatively charged spherical particles (average diameter 4.7 nm) with excellent water dispersion ability. Furthermore, the C-dots have a rich presence of surface functionalities such as hydroxyls and carboxyls as well as amines. The significance of the C-dots as highly efficient photocatalysts for rhodamine B (RhB) and methylene blue (MB) degradation was explored. The C-dots demonstrate excellent photocatalytic activity, achieving 100% of RhB and MB degradation within 170 min. The degradation rate constants for RhB and MB were 1.8 × 10⁻² and 2.4 × 10⁻² min⁻¹, respectively. The photocatalytic degradation performances of the C-dots are comparable to those metal-based photocatalysts and generally better than previously reported C-dots photocatalysts. Collectively considering the excellent photocatalytic activity toward organic dye degradation, as well as the fact that they are facilely synthesized with no need of further doping, compositing, and tedious purification and separation, the C-dots fabricated in this work are demonstrated to be a promising alternative for pollutant degradation and environment protection.

Size-Dependent Photocatalytic Activity of Carbon Dots with Surface-State Determined Photoluminescence

Carbon dots (CDs) were synthesized by a microwave-mediated method and separated by size exclusion chromatography into three different size fractions. There was no correlation of the size with photoluminescence (PL) emission wavelength, which shows that the PL mechanism is not quantum-size dependent. UV/vis absorption and diffuse reflectance spectroscopies showed that the light absorption properties as well as the band gap of the CDs changed with the size of the particle. The combination of FTIR and XPS measurements revealed the composition on the surface of each fraction. The three CDs fractions were separately used in the photocatalytic degradation of organic dyes under simulated sunlight irradiation. The catalytic activity of the as-prepared CDs was found to increase as the size of the particles decreased. Complete degradation of both rhodamine B (RhB) and methylene blue (MB) was achieved in 150 min by the 2-nm CDs. The scavenger studies showed that the holes and superoxide radicals are the main species involved in the photocatalytic degradation of the dye by the 2-nm CDs. These CDs displayed high stability in the degradation of organic dyes for multiple cycles. The 2-nm CDs displayed promising photocatalytic degradation of p-nitrophenol (PNP) . These results demonstrate for the first time the application of bare carbon dots in the degradation of environmental contaminants.

Electrochemical Energy Storage Properties of Ni-Mn-Oxide Electrodes for Advance Asymmetric Supercapacitor Application

In this work, we report a facile one-spot synthesis process and the influence of compositional variation on the electrochemical performance of Ni-Mn-oxides (Ni:Mn = 1:1, 1:2, 1:3, and 1:4) for high-performance advanced energy storage applications. The crystalline structure and the morphology of these synthesized nanocomposites have been demonstrated using X-ray diffraction, field emission scanning electron microscopy, and transmission electron Microscopy. Among these materials, Ni-Mn-oxide with Ni:Mn = 1:3 possesses a large Brunauer?Emmett?Teller specific surface area (127 m² g^?1) with pore size 8.2 nm and exhibits the highest specific capacitance of 1215.5 F g^?1 at a scan rate 2 mV s^?1 with an excellent long-term cycling stability (?87.2% capacitance retention at 10 A g^?1 over 5000 cycles). This work also gives a comparison and explains the influence of different compositional ratios on the electrochemical properties of Ni-Mn-oxides. To demonstrate the possibility of commercial application, an asymmetric supercapacitor device has been constructed by using Ni-Mn-oxide (Ni:Mn = 1:3) as a positive electrode and activated carbon (AC) as a negative electrode. This battery-like device achieves a maximum energy density of 132.3 W h kg^?1 at a power density of 1651 W kg^?1 and excellent coulombic efficiency of 97% over 3000 cycles at 10 A g^?1.

Fish-scale-derived carbon dots as efficient fluorescent nanoprobes for detection of ferric ions

Herein, highly fluorescent carbon dots (CDs) with the incorporation of N and O functionalities were prepared through a facile and cost-effective hydrothermal reaction using fish scales of the crucian carp as the precursor. The as-prepared CDs exhibit strong fluorescent emissions at 430 nm with a relative quantum yield of 6.9%, low cytotoxicity, and robust fluorescence stability against photobleaching and good ionic strength. More significantly, the fluorescence of these CDs can be effectively and selectively quenched by Fe3+ ions, which enables the application of CDs as fluorescent Fe3+ nanoprobes with a linear range of 1-78 μmol L-1 and a detection limit of 0.54 μmol L-1. The proposed fluorescent CD nanoprobes can also be used for the assay of spiked Fe3+ in real water samples and human serums with high recoveries and low standard deviations. Hence, CDs can be potentially applied as safe and reliable fluorescent nanoprobes for environmental and clinical Fe3+ analyses.

Hydrothermal green synthesis of magnetic Fe3O4-carbon dots by lemon and grape fruit extracts and as a photoluminescence sensor for detecting of E. coli bacteria

The aim of this work is preparing of a photoluminescence nanostructures for rapid detection of bacterial pathogens. Firstly, carbon dots (CDs) were synthesized by grape fruit, lemon, turmeric extracts and hydrothermal method. Then Fe₃O₄ (magnetite) nanoparticles was achieved using these bio-compatible capping agents. Finally, magnetite-carbon dots were synthesized as a novel magnetic and photoluminescence nanocomposite. X-ray diffraction (XRD) confirms the crystallinity and phase of the products, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigate the morphology, shape and size of the magnetite, carbon dot and nanocomposites. Fourier transform infrared (FT-IR) spectroscopy shows the purity of the nanostructures. Ultraviolet-visible (UV-Vis) absorption and photo-luminescence (PL) spectroscopy show suitable photo-luminescence under ultraviolet irradiation. Vibrating sample magnetometer (VSM) shows super paramagnetic property of the product. Interestingly carbon dots were used as a non-toxic photoluminescence sensor for detecting of Escherichia coli (E. coli) bacteria. Results show quenching of photoluminescence of the CDs nanocomposite by increasing amount of E. coli bacteria.

A multiscale hydrothermal carbon layer modified carbon fiber for composite fabrication

A novel multiscale hydrothermal carbon layer (MHTCL) for carbon fiber (CF) surface modification was developed. The MHTCL is a multiscale high-disorder amorphous carbon coating with a colored appearance, abundant functional groups, multiscale roughness, a large specific surface area, a high surface energy, and good wetting ability. The O/C atom ratios of the MHTCL-modified CF were in the range of 0.17–0.23, and the functional groups were mainly C–O and C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O groups. During the low-concentration glucose hydrothermal treatment with the carbon fibers (CFs), the glucose generates furan derivative intermediates, which adsorb on the surface of the CFs and carbonize continuously, finally forming the MHTCL on the CFs. The fracture and rupture of the MHTCL during the forming process produce new nucleation centers on the CF surface, which result in abundant multiscale irregular particles. The MHTCL is a facile method for the modification of CFs. The fabrication of the CF composites demonstrated that the MHTCL obviously increases the interlaminar shear strength of the CF/polyimide composite and the interfacial interaction of the CF and polyetheretherketone.

A novel multiscale hydrothermal carbon layer (MHTCL) for carbon fiber (CF) surface modification was developed.

Simultaneously obtaining fluorescent carbon dots and porous active carbon for supercapacitors from biomass

We present a facile and green approach to simultaneously synthesize fluorescent carbon dots and porous active carbon for supercapacitors via a two-step carbonization process from a widely available protein-rich biomass precursor – soybeans.