Investigating the Effect of Reaction Time on Carbon Dot Formation, Structure, and Optical Properties

Carbon dots, a young member of the carbon nanomaterial family, are quasi-spherical nanoparticles, which have fluorescent properties as their key characteristic. A wide range of starting materials and synthetic routes have been reported in the literature, divided into two main categories: a top-down and bottom-up approach. Moreover, a series of different parameters that affect the properties of carbon dots have been investigated, including temperature, starting pH, as well as precursor concentration. However, the effect of reaction time has not been extensively monitored. In our study, a biomass derivative was treated hydrothermally with varying reaction times to draw a solid formation mechanism. In addition, we monitored the effect of reaction time on optical and structural characteristics, as well as the chemical composition of our materials. Our key findings include a four-stage formation mechanism, a higher level of crystallinity, and an increasing brightness over reaction time

A one-pot hydrothermal synthesis of sulfur and nitrogen doped carbon aerogels with enhanced electrocatalytic activity in the oxygen reduction reaction

A one-pot, hydrothermal synthesis of nitrogen and sulfur dual doped carbon aerogels is presented, derived from our previously published hydrothermal carbonization approach. Two co-monomers, S-(2-thienyl)-L-cysteine (TC) and 2-thienyl carboxaldehyde (TCA), were used for sulfur incorporation, giving rise to distinct morphologies and varying doping levels of sulfur. Nitrogen-doping levels of 5 wt% and sulfur-doping levels of 1 wt% (using TCA) to 4 wt% (using TC) were obtained. A secondary pyrolysis step was used to further tune the carbon aerogel conductivity and heteroatom binding states. By comparing solely nitrogen-doped with nitrogen- and sulfur-doped carbon aerogels, it was observed that the presence of sulfur improves the overall electrocatalytic activity of the carbon material in both basic and acidic media. This study of the synergistic effect of combined sulfur- and nitrogen-doping in the catalysis of the “oxygen reduction reaction” (ORR) is expected to be significant to future research concerning the improvement of heterogeneous, metal-free, carbon-based catalysts

Biocompatible microcapsules functionalized with inorganic nanoparticles for enhanced external triggering via light and ultrasound

Designing and fabricating functional composite capsules are of considerable interest to both academic and industrial fields. Inorganic nanoparticles (NPs) have great potential to modify properties of Layer-by-layer (LbL) polyelectrolyte (PE) capsules, but using prefabricated NPs to functionalize capsules still has considerable challenges such as poor distribution in the capsule walls. The present work proposed and validated a novel approach of fabricating functional capsules with in situ formation and incorporation of inorganic carbon dots (CDs), TiO2 and SiO2 NPs in PAH/PSS multilayers.[1,2] CDs were synthesized within capsule shells through autoclaving the PE capsules in dextran solution, while SiO2 and TiO2 NPs functionalized capsules were fabricated by hydrolysis of Titanium butoxide (TIBO), Tetraethyl orthosilicate (TEOS) respectively. The morphology, composition, shell thickness, permeability and stimuli sensitivity, etc. of the formed capsules with different composition were investigated, and characterized by SEM, TEM, EDX, FTIR, and CLSM. The three types of capsules demonstrated prominent properties compared with the traditional capsule without hybrid with inorganic NPs: i) the PE/CDs capsules displayed a rigid bowl-like morphology (Figure 1A), increased shell thickness (178.4nm, Figure 1B) and an excellent fluorescent property originated from the CDs (Figure 1D, E), and it can efficiently prevent the penetration of a small molecule Rhodamine B (Figure 1F); ii) the PE/SiO2 capsules showed a free-standing sphere morphology and a reduced permeability; iii) the capsules in situ composited with TiO2 NPs were found as a sphere shape and susceptible to UV irradiation (320-400nm, ~110 mW cm-2). Ultrasound irradiation tests demonstrated that all these three types of capsules possessed effective ultrasound sensitivity. It was validated by the fragmentation of PE/SiO2 and PE/TiO2 capsules in a few seconds of 50W ultrasound irradiation and the completely break of PE/CDs capsules in a few minutes of the treatment (Figure 1C). Besides, the cell viability data demonstrated that all the three types of composite capsules possessed good biocompatibility. In summary, those innovative composite capsules were demonstrated with great capability of small molecule encapsulation, high mechanical strength, good biocompatibility and high sensitivity to ultrasound and UV, which could be promising for various applications such as cosmetics, environment and biomedicine areas. Please click Additional Files below to see the full abstract

Sustainable metal-free carbogels as oxygen reduction electrocatalysts

crosscheck: This document is CrossCheck deposited related_data: Supplementary Information copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 5 March 2017; Accepted 2 May 2017; Accepted Manuscript published 2 May 2017Kathrin Preuss would like to thank the Materials Research Institute of Queen Mary, University of London for a PhD studentship. Liviu C. Tănase and Cristian M. Teodorescu acknowledge funding from the UEFISCDI Agency through the Project PN-II-RU-TE-2014-4-0456 and by the NIMP Core Project PN16-48012, both projects being granted by the Romanian Ministry of Research and Innovation

Strain induced electrochemical behaviors of ionic liquid electrolytes in an electrochemical double layer capacitor: Insights from molecular dynamics simulations.

Electrochemical Double Layer Capacitors (EDLCs) with ionic liquid electrolytes outperform conventional ones using aqueous and organic electrolytes in energy density and safety. However, understanding the electrochemical behaviors of ionic liquid electrolytes under compressive/tensile strain is essential for the design of flexible EDLCs as well as normal EDLCs, which are subject to external forces during assembly. Despite many experimental studies, the compression/stretching effects on the performance of ionic liquid EDLCs remain inconclusive and controversial. In addition, there is hardly any evidence of prior theoretical work done in this area, which makes the literature on this topic scarce. Herein, for the first time, we developed an atomistic model to study the processes underlying the electrochemical behaviors of ionic liquids in an EDLC under strain. Constant potential non-equilibrium molecular dynamics simulations are conducted for EMIM BF4 placed between two graphene walls as electrodes. Compared to zero strain, low compression of the EDLC resulted in compromised performance as the electrode charge density dropped by 29%, and the performance reduction deteriorated significantly with a further increase in compression. In contrast, stretching is found to enhance the performance by increasing the charge storage in the electrodes by 7%. The performance changes with compression and stretching are due to changes in the double-layer structure. In addition, an increase in the value of the applied potential during the application of strain leads to capacity retention with compression revealed by the newly performed simulations. [Abstract copyright: © 2023 Author(s). Published under an exclusive license by AIP Publishing.

Efficient harvesting and storage of solar energy of an all-vanadium solar redox flow battery with a MoS2@TiO2 photoelectrode

Solar redox flow batteries constitute an emerging technology that provides a smart alternative for the capture and storage of discontinuous solar energy through the photo-generation of the discharged redox species employed in traditional redox flow batteries. Here, we show that a MoS2-decorated TiO2 (MoS2@TiO2) photoelectrode can successfully harvest light to be stored in a solar redox flow battery using vanadium ions as redox active species in both the catholyte and anolyte, and without the use of any bias. The MoS2@TiO2 photoelectrode achieved an average photocurrent density of ∼0.4 mA cm−2versus 0.08 mA cm−2 for bare TiO2, when tested for the oxidation of V4+ to V5+, attributed to a more efficient light harvesting and charge separation for the MoS2@TiO2 relative to TiO2. The designed solar redox flow cell exhibited an optimal overall solar-to-output energy conversion efficiency (SOEE) of ∼4.78%, which outperforms previously reported solar redox flow batteries. This work demonstrates the potential of the MoS2@TiO2 photoelectrode to efficiently convert solar energy into chemical energy in a solar redox flow battery, and it also validates the great potential of this technology to increase reliability in renewable energies