Snapshots into carbon dots formation through a combined spectroscopic approach

The design of novel carbon dots with ad hoc properties requires a comprehensive understanding of their formation mechanism, which is a complex task considering the number of variables involved, such as reaction time, structure of precursors or synthetic protocol employed. Herein, we systematically investigated the formation of carbon nanodots by tracking structural, chemical and photophysical features during the hydrothermal synthesis. We demonstrate that the formation of carbon nanodots consists of 4 consecutive steps: (i) aggregation of small organic molecules, (ii) formation of a dense core with an extended shell, (iii) collapse of the shell and (iv) aromatization of the core. In addition, we provide examples of routes towards tuning the core-shell design, synthesizing five novel carbon dots that all consist of an electron-dense core covered by an amine rich ligand shell

Water-Assisted Concerted Proton-Electron Transfer at Co(II)-Aquo Sites in Polyoxotungstates With Photogenerated RuIII(bpy)33+ Oxidant

The cobalt substituted polyoxotungstate [Co6(H2O)2(α-B-PW9O34)2(PW6O26)]17− (Co6) displays fast electron transfer (ET) kinetics to photogenerated RuIII(bpy)33+, 4 to 5 orders of magnitude faster than the corresponding ET observed for cobalt oxide nanoparticles. Mechanistic evidence has been acquired indicating that: (i) the one-electron oxidation of Co6 involves Co(II) aquo or Co(II) hydroxo groups (abbreviated as Co6(II)−OH2 and Co6(II)−OH, respectively, whose speciation in aqueous solution is associated to a pKa of 7.6), and generates a Co(III)−OH moiety (Co6(III)−OH), as proven by transient absorption spectroscopy; (ii) at pH>pKa, the Co6(II)−OH→RuIII(bpy)33+ ET occurs via bimolecular kinetics, with a rate constant k close to the diffusion limit and dependent on the ionic strength of the medium, consistent with reaction between charged species; (iii) at p

Naphthochromenones: Organic Bimodal Photocatalysts Engaging in Both Oxidative and Reductive Quenching Processes

Twelve naphthochromenone photocatalysts (PCs) were synthesized on gram scale.They absorb across theUV/Vis range and feature an extremely wide redox window (up to 3.22 eV) that is accessible using simple visible light irradiation sources (CFL or LED). Their excited-state redox potentials, PC*/PCC (up to 1.65 V) and PCC+/PC* (up to 1.77 V vs. SCE), are such that these novel PCs can engage in both oxidative and reductive quenching mechanisms with strong thermodynamic requirements. The potential of these bimodal PCs was benchmarked in synthetically relevant photocatalytic processes with extreme thermodynamic requirements. Their ability to efficiently catalyze mechanistically opposite oxidative/reductive photoreactions is a unique feature of these organic photocatalysts, thus representing a decisive advance towards generality, sustainability, and cost efficiency in photocatalysis

Naphthochromenones: Organic Bimodal Photocatalysts Engaging in Both Oxidative and Reductive Quenching Processes

Twelve naphthochromenone photocatalysts (PCs) were synthesized on gram scale.They absorb across theUV/Vis range and feature an extremely wide redox window (up to 3.22 eV) that is accessible using simple visible light irradiation sources (CFL or LED). Their excited-state redox potentials, PC*/PCC (up to 1.65 V) and PCC+/PC* (up to 1.77 V vs. SCE), are such that these novel PCs can engage in both oxidative and reductive quenching mechanisms with strong thermodynamic requirements. The potential of these bimodal PCs was benchmarked in synthetically relevant photocatalytic processes with extreme thermodynamic requirements. Their ability to efficiently catalyze mechanistically opposite oxidative/reductive photoreactions is a unique feature of these organic photocatalysts, thus representing a decisive advance towards generality, sustainability, and cost efficiency in photocatalysis

Selective interaction of a water soluble naphthalenediimide with single-walled carbon nanotubes

A water soluble naphthalenediimide (NDI) selectively interact with small diameter single-walled carbon nanotubes (SWCNTs), as demonstrated by Raman, along with absorption and emission spectroscopies

Customizing the Electrochemical Properties of Carbon Nanodots by Using Quinones in Bottom-Up Synthesis

We show how the redox potentials of carbon nanodots (CNDs) can be modulated by employing quinones as electroactive precursors during a microwave-assisted synthesis. We prepared and characterized a redox library of CNDs, demonstrating that this approach can promote the use of carbon nanodots for ad hoc applications, including photocatalysis

Fast and Efficient Microwave-Assisted Synthesis of Perylenebisimides

Perylene-3,4,9,10-tetracarboxylic acid bisimides have been widely studied as industrial pigments. Lately, these dyes have drawn considerable attention because of applications as photocatalysts and organic semi-conductors. Here, we report a novel method for fast and efficient synthesis of many different perylenebisimides, based on microwave-assisted reactions

Evaluating the use of industrial X-ray CT to the reverse engineering of bowed stringed instruments

For centuries, simple contact measuring instruments (e.g. callipers, profile and thickness gauges) have been used by violin makers for recording bi-dimensional information about their creations. Since its invention, film and digital photography have also been used to document shapes and colours. Traditionally, gypsum castings and RTM replicas are used to store information about the 3D shapes of back, bellies and scrolls. During the last 30 years the applications of non-contact systems such as X-ray computed tomography (CT), and laser and structured light scanners (LS) have opened new horizons to the bowed stringed instruments metrology. This work compares two state-of-the-art non-contact systems: an industrial X-ray computed tomography system and a Structured Light 3D scanner. Their results in terms of accuracy, repeatability and uncertainties are assessed and compared to reference tactile Coordinate Measuring Machine (CMM) measurements. Experimental results prove that, with the considered experimental set-up, CT provides better results than LS in terms of deviation from CMM reference measurements, and uncertainty