Photosensitizer-Conjugated Ultrasmall Carbon Nanodots as Multifunctional Fluorescent Probes for Bioimaging

Highly luminescent ultrasmall carbon nanodots (CDs) have been prepared by one-step microwave-assisted pyrolysis and functionalized with fluorescein photosensitizer by a diazo-bond. The absorption edge of such prepared fluorescein–NN–CDs was red-shifted in comparison with the bare one. Nevertheless, the emission signal induced by the nanoparticle quantum-sized graphite structure was quenched due to photoisomerization of the diazo group at the photoexcited state. In order to restrict the photoisomerization, i.e., rotation around the nitrogen–nitrogen bond, the diazo group was fixed by a metal cation to form a complex compound or chelate. The obtained metal complex of fluorescein–NN–CDs shows an absorbance maximum the same as bare CDs but a recovered emission signal from the nanoparticle moiety, which was bathochromically shifted. They exhibit lower quantum yield in comparison with the bare CDs but better photostability toward emission quenching in nutrition cell culture. The formed photosensitizer-conjugated nanoprobes were proposed as multifunctional fluorophores for intracellular <i>in vivo</i> imaging due to their attractive photophysical attributes and tunable and excitation-dependent emission. The bioapplication of photosensitizer-conjugated CDs was demonstrated as fluorescent tracers for endocytosis pathways in cultured Tobacco cells. Their successful staining and lower toxicity to the plant cells were compared with conventional quantum dots (CdSe/ZnS core–shell type, which caused an acute toxicological <i>in vivo</i> effect)

Photosensitizer-Conjugated Ultrasmall Carbon Nanodots as Multifunctional Fluorescent Probes for Bioimaging

Highly luminescent ultrasmall carbon nanodots (CDs) have been prepared by one-step microwave-assisted pyrolysis and functionalized with fluorescein photosensitizer by a diazo-bond. The absorption edge of such prepared fluorescein–NN–CDs was red-shifted in comparison with the bare one. Nevertheless, the emission signal induced by the nanoparticle quantum-sized graphite structure was quenched due to photoisomerization of the diazo group at the photoexcited state. In order to restrict the photoisomerization, i.e., rotation around the nitrogen–nitrogen bond, the diazo group was fixed by a metal cation to form a complex compound or chelate. The obtained metal complex of fluorescein–NN–CDs shows an absorbance maximum the same as bare CDs but a recovered emission signal from the nanoparticle moiety, which was bathochromically shifted. They exhibit lower quantum yield in comparison with the bare CDs but better photostability toward emission quenching in nutrition cell culture. The formed photosensitizer-conjugated nanoprobes were proposed as multifunctional fluorophores for intracellular <i>in vivo</i> imaging due to their attractive photophysical attributes and tunable and excitation-dependent emission. The bioapplication of photosensitizer-conjugated CDs was demonstrated as fluorescent tracers for endocytosis pathways in cultured Tobacco cells. Their successful staining and lower toxicity to the plant cells were compared with conventional quantum dots (CdSe/ZnS core–shell type, which caused an acute toxicological <i>in vivo</i> effect)

Defective TiO₂ Nanotube Arrays for Efficient Photoelectrochemical Degradation of Organic Pollutants

Oxygen vacancies (OVs) are one of the most critical factors that enhance the electrical and catalytic characteristics of metal oxide-based photoelectrodes. In this work, a simple procedure was applied to prepare reduced TiO2 nanotube arrays (NTAs) (TiO2–x) via a one-step reduction method using NaBH4. A series of characterization techniques were used to study the structural, optical, and electronic properties of TiO2–x NTAs. X-ray photoelectron spectroscopy confirmed the presence of defects in TiO2–x NTAs. Photoacoustic measurements were used to estimate the electron-trap density in the NTAs. Photoelectrochemical studies show that the photocurrent density of TiO2–x NTAs was nearly 3 times higher than that of pristine TiO2. It was found that increasing OVs in TiO2 affects the surface recombination centers, enhances electrical conductivity, and improves charge transport. For the first time, a TiO2–x photoanode was used in the photoelectrochemical (PEC) degradation of a textile dye (basic blue 41, B41) and ibuprofen (IBF) pharmaceutical using in situ generated reactive chlorine species (RCS). Liquid chromatography coupled with mass spectrometry was used to study the mechanisms for the degradation of B41 and IBF. Phytotoxicity tests of B41 and IBF solutions were performed using Lepidium sativum L. to evaluate the potential acute toxicity before and after the PEC treatment. The present work provides efficient PEC degradation of the B41 dye and IBF in the presence of RCS without generating harmful products