Carbon Quantum Dots Loading Research Articles

Efficiency enhancement of photovoltaic cells under infrared light irradiation by synergistic upconversion luminescence of NaYF4:Yb3+/Er3+/Tm3+@TiO2-CQDs

Rare-earth doped upconversion luminescence (UCL) is of great significance in improving the utilization of infrared (IR) light from solar radiation, especially in the efficiency enhancement of photovoltaic (PV) cells. However, the low level of luminescence efficiency remains a great challenge. Here, we designed NaYF4:Yb3+/Er3+/Tm3+@TiO2-CQDs upconversion luminescent materials. The construction of the core–shell structure and the loading of carbon quantum dots (CQDs) resulted in a 9-fold enhancement of upconversion luminescence and a 3.02% enhancement of the efficiency of the photovoltaic cell. These data indicate that the construction of the core–shell structure can effectively inhibit the surface quenching of the luminescent particles, and that the energy transfer between the carbon quantum dots and the rare earth ions has a synergistic effect on the efficiency enhancement of the photovoltaic cell. Meanwhile, the TiO2 shell layer also enables the prepared materials to have better properties of self-cleaning and degradation of organic pollutants, which will further improve the visible light utilization of PV cells. NaYF4:Yb3+/Er3+/Tm3+@TiO2-CQDs provides new ideas for the practical application of PV cell efficiency enhancement and the design of new materials.

Ultralow loading of carbon quantum dots leading to significantly improved breakdown strength and energy density of P(VDF-TrFE-CTFE)

The scheme of the CQD structure and its interaction with the polymer matrix; the comparison between the 0.1 wt% CQD nanocomposite and pristine polymer.

Carbon Quantum Dots Bridged TiO2/CdIn2S4 toward Photocatalytic Upgrading of Polycyclic Aromatic Hydrocarbons to Benzaldehyde.

Conversion of hazardous compounds to value-added chemicals using clean energy possesses massive industrial interest. This applies especially to the hazardous compounds that are frequently released in daily life. In this work, a S-scheme photocatalyst is optimized by rational loading of carbon quantum dots (CQDs) during the synthetic process. As a bridge, the presence of CQDs between TiO2 and CdIn2S4 improves the electron extraction from TiO2 and supports the charge transport in S-scheme. Thanks to this, the TiO2/CQDs/CdIn2S4 presents outstanding photoactivity in converting the polycyclic aromatic hydrocarbons (PAHs) released by cigarette to value-added benzaldehyde. The optimized photocatalyst performs 87.79% conversion rate and 72.76% selectivity in 1 h reaction under a simulated solar source, as confirmed by FT-IR and GC-MS. A combination of experiments and theoretical calculations are conducted to demonstrate the role of CQDs in TiO2/CQDs/CdIn2S4 toward photocatalysis.

Extremely low loading of carbon quantum dots for high energy density in polyetherimide nanocomposites

• Functionalized CQDs were synthesized, which showed monodispersity in solvent. • Coulomb-blockade effect of CQDs was utilized to increase the E b of PEI matrix. • The composite with 0.5 wt% CQDs exhibited a high U e of 10.66 J/cm 3 at 600 kV/mm. There is an urgent need for dielectric capacitors with high energy density and efficiency with the rapid progress of power electronic devices. Inorganic/organic composites were once considered as a potential candidate for dielectrics. However, the inevitable defects induced by the inorganic fillers always lead to the decreased breakdown strength and limited energy density and efficiency. In this work, carbon quantum dots (CQDs) with abundant functional groups were synthetized and introduced into linear dielectric polyethyleneimine (PEI) matrix. Due to the unique Coulomb-blockade effect of quantum dots, the movement of carriers can be hindered under the applied electric field, leading to the improvement of breakdown strength. Compared with most of the reported nanocomposites with high loading of fillers, the nanocomposites in this work with extremely low loading of CQDs exhibit obviously enhanced performance. The nanocomposite with 0.5 wt% CQDs exhibits a high discharge energy density of 10.66 J/cm 3 and efficiency of 88.3% at 600 kV/mm, corresponding to a 62.3% improvement over that of PEI (6.57 J/cm 3 at 490 kV/mm). This work provides an effective strategy to break down the long-standing contradiction between the enhancement of dielectric constant and the reduced in breakdown strength. The film dielectrics with extremely low loading of fillers contributing to enhanced energy density and high energy efficiency is very important for practical applications.

Wood-cellulose photoluminescence material based on carbon quantum dot for light conversion

To expand the application of transparent wood (TW) in the field of photoluminescence, lignin-based carbon quantum dots (CDs) were impregnated into wood cellulose template (CT) as a fluorescent functional material, the photoluminescent transparent wood (PTW) with light conversion was prepared. The results showed that FTW with different wavelength emissions could be obtained by controlling the CDs' conjugated size and surface functional groups. The loading of CDs does not affect the excellent transmittance (86.1%) and optical haze (73%) of TW. Compared to the original wood, the tensile properties of PTW have been enhanced from 368 MPa to 422 MPa. By controlling the content of different CDs, a PTW for white light conversion was prepared with the CIE color coordinates of (0.29, 0.34). This study is a new attempt to apply CDs to TW, providing a broad prospect for uniform light conversion and color display.

Synthesis and Characterization of Dried Leaves Derived Carbon Quantum Dots and g-C3N4 Composite

In this work, carbon quantum dots (CDs) was successfully synthesized by hydrothermal treatment using dried leaves as green precursor. Graphitic carbon nitride (g-C3N4) was combined with CDs to prepare CDs/g-C3N4 composites with three different weight percentage at 0.6, 0.8 and 1.0 wt%, respectively. The morphological structure, optical properties and chemical compositions of CDs and composites were characterized using various spectroscopic techniques. CDs solution portrayed a significant fluorescence property that bright blue-green fluorescence can be observed by naked eye under ultraviolet (UV) light irradiation. The highest fluorescence emission was recorded at 320 nm with the optimal excitation wavelength of 423 nm. Ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS) results displayed red-shifted adsorption spectra of CDs/g-C3N4 composites from 500 nm to 800 nm. No upconversion photoluminescence (UCPL) was detected in CDs based on the photoluminescence (PL) study. The loading of CDs on g-C3N4 reduced the band gap from 2.7 eV to 2.59 eV.

Visible-light-driven pollutants degradation with carbon quantum dots/N-TiO2 under mild condition: Facile preparation, dramatic performance and deep mechanism insight

Because pure TiO2 has high photogenerated charge carriers recombination rate and inferior visible light capture capability, the optical activity is very weak. N doping can generate a lower energy gap energy and carbon quantum dots (CDs) have excellent properties that can transfer electrons smoothly and reserve electrons quickly, so we think that doping of N into TiO2 and loading of CDs can modify TiO2. We synthesized a brand new carbon quantum dots/N-TiO2(CDs/N-TiO2) by mechanically mixing carbon quantum dots with N-TiO2 instead of the conventional calcination or solvothermal step. The degradation ratio of RhB(10 mg/L) was increased from 6.66 % and 19.97 %–99.8 % in 5 min under visible light when compared with TiO2 and N-TiO2. The kinetic constants of RhB degradation by 30CDs/N-TiO2 are 85.52 and 25.40 times higher than those of TiO2 and N-TiO2, respectively. Besides, Cr(Ⅵ) (20 mg/L) photoreduction can be completely achieved in 4 min under solar light irradiation. Besides, We analyzed the behavior of photogenerated charge carriers by the surface photovoltage spectra (SPV) and transient photovoltage spectra (TPV) measurement analyses, showing the deep mechanism of photodegradation process of dye. Doping of nitrogen into TiO2 can extend the photo absorption range of TiO2 and let n-type TiO2 show p-type conducting character that makes it easier to transfer electrons to the CDs. Loading of CDs can enhance the electron-hole pairs separation efficiency.

Revealing adsorption and the photodegradation mechanism of gas phase o-xylene on carbon quantum dots modified TiO2 nanoparticles

Here, we report the photocatalytic oxidation (PCO) of o-xylene on carbon quantum dots (CQDs) modified TiO2 nanoparticles. The results demonstrated that with 1 wt% CQDs loading, 87 % of o-xylene (50 ppm) can be photodegraded, which is 55.3 % higher than pure TiO2 (56 %) under UV/visible light. This improved photocatalytic activity is associated with the important role of CQDs on TiO2 surface, which increased the o-xylene adsorption and facilitated the photogenerated hole-electron separation process. Also, the 1 wt%CQDs/TiO2 nanocomposite showed photocatalytic activity in the visible region (λ > 400 nm) compared to pure TiO2 (inactive). The DFT study revealed that o-xylene strongly adsorb on TiO2 (001) surface than (101) through π electrons of the aromatic ring. The in situ DRIFTS study showed that free OH groups on the photocatalyst surface could act as effective Lewis sides for the o-xylene adsorption. The interaction of π electrons of the aromatic ring and isolated OH groups was also observed. The FTIR peaks for CO2 increased in the case of CQDs/TiO2 nanocomposite contrasted to pure TiO2, which suggested that the presence of CQDs improved the mineralization potency of TiO2. These findings should affect the quest for a better photocatalyst to photodegrade VOCs.

Enhanced Photoelectrochemical Performance of WO3 -Based Composite Photoanode Coupled with Carbon Quantum Dots and NiFe Layered Double Hydroxide.

An attractive photoanode material, WO3 , has suffered from its limited visible-light absorption and sluggish surface reaction kinetics, as well as poor stability in neutral electrolytes. Herein, a NiFe/CQD/WO3 composite photoanode was designed and fabricated, with loading of carbon quantum dots (CQDs) and electrodeposition of NiFe layered double hydroxide. The NiFe/CQD/WO3 photoanode obtained a photocurrent density of 1.43 mA cm-2 at 1.23 V vs. reversible hydrogen electrode, which is approximately three times higher than that of bare WO3 . During the test period of 3 h, the stability of WO3 was improved substantially after the loading of cocatalysts. Furthermore, mechanistic insights of the favored band structure and beneficial charge-transfer pathway elucidate the high photoelectrochemical performance of the NiFe/CQD/WO3 composite photoanode.

Mitochondria-based aircraft carrier enhances in vivo imaging of carbon quantum dots and delivery of anticancer drug.

The application of engineered bacteria-based drug delivery vehicles to treat cancer has been practiced for more than a century. Mitochondria, evolutionarily originated from bacteria, are ubiquitous, semi-autonomous cellular organelles. In this study, we present the first exploration of using mitochondria as a delivery system of carbon quantum dots (CQDs) for in vivo imaging and administration of the anticancer drug doxorubicin (DOX). The results show that mitochondria as carriers are compatible with CQD loading and preserve the optical properties of CQDs. Moreover, the mitochondria delivery system can improve the CQD bio-distribution in organs and prolong the retention time of CQDs after intravenous injection. Furthermore, mitochondria loaded with doxorubicin hydrochloride (Mito-DOX) show an enhanced therapeutic effect compared to free DOX. The mitochondria-based "aircraft" system may be a promising novel therapeutic platform with high potential for biological imaging and drug delivery to fight cancer and other diseases.

碳量子点负载TiO2纳米棒阵列的光电化学性能

The photoelectrochemical( PEC) performance and photocatalytic activity of Ti O2 nanorod arrays( NRs) loaded with carbon quantum dots( CQDs) were investigated. In comparison with Ti O2 NRs,the absorption ability of Ti O2 NRs loaded with CQDs was enhanced. The transient photocurrent and open-circuit potential under visible light illumination were increased of 300% and 2. 5%,respectively. After loaded with CQDs,the photocatalytic degradation efficiency of methylene blue( MB) under visible light illumination was increased from 25% to 33%. The electrochemical impedance spectra( EIS) and Mott-Schottky plots were measured to investigate the charge movement under the visible light illumination. The results suggest that the charge transfer resistance is reduced and the electron lifetime is increased for Ti O2 NRs loaded with CQDs. The loading of CQDs can induce the flat-band potential negative shift and the conduction band position raise,resulting in the enhancement of electron reduction properties.