Metal-Doped Carbon Nitrides: Synthesis, Structure and Applications

The photocatalytic splitting of water into molecular hydrogen and molecular oxygen with sunlight is the dream reaction for solar energy conversion. Since decades, transition-metal-oxide semiconductors and supramolecular organometallic structures have been extensively explored as photocatalysts for solar water splitting. More recently, polymeric carbon nitride materials consisting of triazine or heptazine building blocks have attracted considerable attention as hydrogen-evolution photocatalysts. The mechanism of hydrogen evolution with polymeric carbon nitrides is discussed throughout the current literature in terms of the familiar concepts developed for photoelectrochemical water splitting with semiconductors since the 1970s. We discuss in this perspective an alternative mechanistic paradigm for photoinduced water splitting with carbon nitrides, which focusses on the specific features of the photochemistry of aromatic N-heterocycles in aqueous environments. It is shown that a water molecule which is hydrogen-bonded to an N-heterocycle can be decomposed into hydrogen and hydroxyl radicals by two simple sequential photochemical reactions. This concept is illustrated by first-principles calculations of excited-state reaction paths and their energy profiles for hydrogen-bonded complexes of pyridine, triazine and heptazine with a water molecule. It is shown that the excited-state hydrogen-transfer and hydrogen-detachment reactions are essentially barrierless, in sharp contrast to water oxidation in the electronic ground state, where high barriers prevail. We also discuss in some detail the products of possible reactions of the highly reactive hydroxyl radicals with the chromophores. We hypothesize that the challenge of efficient solar hydrogen generation with carbon-nitride materials is less the decomposition of water as such, but rather the controlled recombination of the photogenerated radicals to the closed-shell products H2 and H2O2.

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Solar Energy Harvesting with Carbon Nitrides: Do We Understand the Mechanism?

10.26434/chemrxiv.6843812.v1 ◽

2018 ◽

Author(s):

Wolfgang Domcke ◽

Johannes Ehrmaier ◽

Andrzej L. Sobolewski

Keyword(s):

Excited State ◽

Solar Energy ◽

Water Molecule ◽

Hydrogen Evolution ◽

Water Splitting ◽

Hydroxyl Radicals ◽

Carbon Nitride ◽

Carbon Nitrides ◽

Polymeric Carbon ◽

Carbon Nitride Materials

The photocatalytic splitting of water into molecular hydrogen and molecular oxygen with sunlight is the dream reaction for solar energy conversion. Since decades, transition-metal-oxide semiconductors and supramolecular organometallic structures have been extensively explored as photocatalysts for solar water splitting. More recently, polymeric carbon nitride materials consisting of triazine or heptazine building blocks have attracted considerable attention as hydrogen-evolution photocatalysts. The mechanism of hydrogen evolution with polymeric carbon nitrides is discussed throughout the current literature in terms of the familiar concepts developed for photoelectrochemical water splitting with semiconductors since the 1970s. We discuss in this perspective an alternative mechanistic paradigm for photoinduced water splitting with carbon nitrides, which focusses on the specific features of the photochemistry of aromatic N-heterocycles in aqueous environments. It is shown that a water molecule which is hydrogen-bonded to an N-heterocycle can be decomposed into hydrogen and hydroxyl radicals by two simple sequential photochemical reactions. This concept is illustrated by first-principles calculations of excited-state reaction paths and their energy profiles for hydrogen-bonded complexes of pyridine, triazine and heptazine with a water molecule. It is shown that the excited-state hydrogen-transfer and hydrogen-detachment reactions are essentially barrierless, in sharp contrast to water oxidation in the electronic ground state, where high barriers prevail. We also discuss in some detail the products of possible reactions of the highly reactive hydroxyl radicals with the chromophores. We hypothesize that the challenge of efficient solar hydrogen generation with carbon-nitride materials is less the decomposition of water as such, but rather the controlled recombination of the photogenerated radicals to the closed-shell products H2 and H2O2.

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Mechanism of photocatalytic water splitting with triazine-based carbon nitrides: insights from ab initio calculations for the triazine–water complex

Physical Chemistry Chemical Physics ◽

10.1039/c8cp01998c ◽

2018 ◽

Vol 20 (21) ◽

pp. 14420-14430 ◽

Cited By ~ 17

Author(s):

Johannes Ehrmaier ◽

Mikołaj J. Janicki ◽

Andrzej L. Sobolewski ◽

Wolfgang Domcke

Keyword(s):

Ab Initio Calculations ◽

Ab Initio ◽

Water Splitting ◽

Carbon Nitride ◽

Model System ◽

Photocatalytic Water Splitting ◽

Water Complex ◽

Carbon Nitrides ◽

Carbon Nitride Materials

Valuable theoretical insights into the mechanism of photocatalytic water-splitting using triazine as a model system for carbon-nitride materials.

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Exploring siRNA Umpired Nanogels: A Tale of Barrier Combating Carrier

Current Pharmaceutical Design ◽

10.2174/1381612826666200417143800 ◽

2020 ◽

Vol 26 (27) ◽

pp. 3234-3250

Author(s):

Sushil K. Kashaw ◽

Prashant Sahu ◽

Vaibhav Rajoriya ◽

Pradeep Jana ◽

Varsha Kashaw ◽

...

Keyword(s):

Drug Delivery ◽

Biomedical Engineering ◽

Viral Infections ◽

Slow Release ◽

Molecular Level ◽

Release Kinetics ◽

Biologically Active ◽

Release Process ◽

Rapid Release ◽

Wide Range

Potential short interfering RNAs (siRNA) modulating gene expression have emerged as a novel therapeutic arsenal against a wide range of maladies and disorders containing cancer, viral infections, bacterial ailments and metabolic snags at the molecular level. Nanogel, in the current medicinal era, displayed a comprehensive range of significant drug delivery prospects. Biodegradation, swelling and de-swelling tendency, pHsensitive drug release and thermo-sensitivity are some of the renowned associated benefits of nanogel drug delivery system. Global researches have also showed that nanogel system significantly targets and delivers the biomolecules including DNAs, siRNA, protein, peptides and other biologically active molecules. Biomolecules delivery via nanogel system explored a wide range of pharmaceutical, biomedical engineering and agro-medicinal application. The siRNAs and DNAs delivery plays a vivacious role by addressing the hitches allied with chronic and contemporary therapeutic like generic possession and low constancy. They also incite release kinetics approach from slow-release while mingling to rapid release at the targets will be beneficial as interference RNAs delivery carriers. Therefore, in this research, we focused on the latest improvements in the delivery of siRNA loaded nanogels by enhancing the absorption, stability, sensitivity and combating the hindrances in cellular trafficking and release process.

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Metal Doped-C3N4/Fe2O4: Efficient and Versatile Heterogenous Catalysts for Organic Transformations

Current Organic Chemistry ◽

10.2174/1385272823666190709113758 ◽

2019 ◽

Vol 23 (12) ◽

pp. 1284-1306

Author(s):

Vijai K. Rai ◽

Fooleswar Verma ◽

Suhasini Mahata ◽

Smita R. Bhardiya ◽

Manorama Singh ◽

...

Keyword(s):

Ring Opening ◽

Carbon Nitride ◽

Addition Reaction ◽

High Surface ◽

Graphitic Carbon ◽

Graphitic Carbon Nitride ◽

Organic Transformations ◽

Reduction Reactions ◽

Activation Reaction ◽

Metal Doped

The polymeric graphitic carbon nitride (g-C3N4) has been one of the interesting earth abundant elements. Though g-C3N4 finds application as a photocatalyst, its photocatalytic behaviour is limited because of low efficiency, mainly due to rapid charge recombination. To overcome this problem, several strategies have been developed including doping of metal/non-metal in the cavity of g-C3N4. Moreover, the CoFe2O4 NPs have been used in many organic transformations because of its high surface area and easy separation due to its magnetic nature. This review describes the role of cobalt ferrite as magnetic nanoparticles and metal-doped carbon nitride as efficient heterogeneous catalysts for new carbon-carbon and carbon-hetero atom bond formation followed by heterocyclization. Reactions which involved new catalysts for selective activation of readily available substrates has been reported herein. Since nanoparticles enhance the reactivity of catalyst due to higher catalytic area, they have been employed in various reactions such as addition reaction, C-H activation reaction, coupling reaction, cyclo-addition reaction, multi-component reaction, ring-opening reaction, oxidation reaction and reduction reactions etc. The driving force for choosing this topic is based-on huge number of good publications including different types of spinels/metal doped-/graphitic carbon nitride reported in the literature and due to interest of synthetic community in recent years. This review certainly will represent the present status in organic transformation and for exploring further their catalytic efficiency to new organic transformations involving C-H activation reaction through coupling, cyclo-addition, multi-component, ring-opening, oxidation and reduction reactions.

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Photochemistry of carbon nitrides and heptazine derivatives

Chemical Communications ◽

10.1039/d1cc02745j ◽

2021 ◽

Author(s):

Doyk Hwang ◽

Cody W. Schlenker

Keyword(s):

Carbon Nitride ◽

Monomer Unit ◽

Carbon Nitrides

This article highlights the photochemistry of heptazine derivatives, a structural monomer unit of carbon nitride photocatalysts.

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Understanding spontaneous dissolution of crystalline layered carbon nitride for tuneable photoluminescent solutions and glasses

Journal of Materials Chemistry A ◽

10.1039/d0ta11070a ◽

2021 ◽

Author(s):

Adam J. Clancy ◽

Theo M. Suter ◽

Alaric Taylor ◽

Sayantan Bhattacharya ◽

Thomas S. Miller ◽

...

Keyword(s):

Carbon Nitride ◽

2D Materials ◽

Carbon Nitrides

The spontaneous dissolution of 2D carbon nitrides with polytriazine imide (PTI) diverges dramatically from the inherent insolubility of other 2D materials such as graphene. The dissolution may be controlled to give tuneable photoluminescence.

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Low-Temperature Synthesis of Solution Processable Carbon Nitride Polymers

Molecules ◽

10.3390/molecules26061646 ◽

2021 ◽

Vol 26 (6) ◽

pp. 1646

Author(s):

Junyi Li ◽

Neeta Karjule ◽

Jiani Qin ◽

Ying Wang ◽

Jesús Barrio ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Carbon Nitride ◽

Spatial Organization ◽

Surface Display ◽

Liquid Media ◽

Low Temperature Synthesis ◽

Temperature Synthesis ◽

X Ray ◽

N2 Atmosphere ◽

Carbon Nitride Materials

Carbon nitride materials require high temperatures (>500 °C) for their preparation, which entails substantial energy consumption. Furthermore, the high reaction temperature limits the materials’ processability and the control over their elemental composition. Therefore, alternative synthetic pathways that operate under milder conditions are still very much sought after. In this work, we prepared semiconductive carbon nitride (CN) polymers at low temperatures (300 °C) by carrying out the thermal condensation of triaminopyrimidine and acetoguanamine under a N2 atmosphere. These molecules are isomers: they display the same chemical formula but a different spatial distribution of their elements. X-ray photoelectron spectroscopy (XPS) experiments and electrochemical and photophysical characterization confirm that the initial spatial organization strongly determines the chemical composition and electronic structure of the materials, which, thanks to the preservation of functional groups in their surface, display excellent processability in liquid media.

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Subinhibitory Antimicrobial Concentrations: A Review of In Vitro and In Vivo Data

Canadian Journal of Infectious Diseases ◽

10.1155/1992/793607 ◽

1992 ◽

Vol 3 (4) ◽

pp. 193-201 ◽

Cited By ~ 14

Author(s):

George G Zhanel ◽

Daryl J Hoban ◽

Godfrey KM Harding

Keyword(s):

Antimicrobial Activity ◽

Animal Studies ◽

Molecular Level ◽

Bacterial Virulence ◽

Antibacterial Effects ◽

Wide Range ◽

Immune Defences

Antimicrobial activity is not an ‘all or none’ effect. An increase in the rate and extent of antimicrobial action is usually observed over a wide range of antimicrobial concentrations. Subinhibitory antimicrobial concentrations are well known to produce significant antibacterial effects, and various antimicrobials at subinhibitory concentrations have been reported to inhibit the rate of bacterial growth. Bacterial virulence may be increased or decreased by subinhibitory antimicrobial concentrations by changes in the ability of bacteria to adhere to epithelial cells or by alterations in bacterial susceptibility to host immune defences. Animal studies performed in rats, hamsters and rabbits demonstrate decreased bacterial adherence, reduced infectivity and increased survival of animals treated with subinhibitory antimicrobial concentrations compared to untreated controls. The major future role of investigation of subinhibitory antimicrobial concentrations will be to define more fully, at a molecular level, how antimicrobials exert their antibacterial effects.

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