Coffee Grounds-Derived CNPs for Efficient Cr(VI) Water Remediation

Abstract

Carbon nanomaterials are a group of materials characterized by sp2/sp3 carbon backbone which, combined with surface atoms and/or chemical groups, ensures peculiar physical chemical features for a wide range of applications. Among these materials, carbon dots and carbon nanoparticles belong to carbon nanomaterials with a few nanometer dimensions. In this work, carbon nanoparticles were produced from spent coffee grounds as sustainable carbon source through a simple, cheap and eco-friendly procedure according to an oxidation process (at controlled temperature) driven by hydrogen peroxide. Atomic Force Microscope (AFM) and fluorescence, UV-Vis absorption, FT-IR and Raman spectroscopy were used to assess the formation of carbon nanomaterials of about 10 nm with the typical emission and absorption properties of carbon dots and peculiar surface features. In fact, the presence of heteroatoms, i.e., phosphorus, and the carbonyl/carboxyl surface groups on carbon nanoparticles, was proposed to confer peculiar properties allowing the fast Mn(VII) reduction to Mn(II) at neutral pH and the Cr(VI) reduction to Cr(III) in weak acid aqueous media.

Photoinduced and Electrochemical Applications of Carbon-Based Nanoparticles from Spent Coffee Grounds

“…The fluorescence emission of the synthesized CNPs was investigated by changing the excitation wavelength from 300 to 500 nm with a step of 20 nm (Figure A). The typical CD emission dependent on excitation wavelength has been observed, , with the maximum recorded at 525 nm upon 360 nm excitation, clearly resulting in green-emitting CNPs. The green emission feature could be mainly ascribable to the presence of heteroatoms, ,− despite the low oxidation and conjugation degree of the CNP surface .…”

“…SCGs were considered since coffee production and consumption in the world is huge and produces an enormous quantity of waste rich in carbonaceous compounds (for example, caffeine and tannins) and inorganic materials (such as compounds of K, Mg, and P). , In this frame, SCG valorization fits pretty well with circular economy principles, avoiding also the accumulation of toxic and nonbiodegradable compounds . SCGs, indeed, represent a multifaced carbon source, − allowing the incorporation of interesting heteroatoms within the produced CNPs.…”

Synthesis and Characterization of Gold Chiral Nanoparticles Functionalized by a Chiral Drug

“…Raman spectroscopy was performed using a microRaman Xplora Horiba. Fourier Transform Infrared characterization (FTIR) with ATR tool [46] was used for monitoring the presence of CTAB and penicillamine: the AuNPs were deposited directly on ATR crystal via drop-casting and 64 scans in the range 3400-800 cm −1 were acquired for each sample using a Perkin-Elmer Spectrum One spectrophotometer.…”