Search query: Photoluminescence properties of graphene versus other carbon nanomaterials

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abstract: Photoluminescent nanomaterials continue to garner research attention because of their many applications. For many years, researchers have focused on quantum dots (QDs) of semiconductor nanocrystals for their excellent performance and predictable fluorescence color variations that depend on the sizes of the nanocrystals. Even with these advantages, QDs can present some major limitations, such as the use of heavy metals in the high performance semiconductor QDs. Therefore, researchers continue to be interested in developing new QDs or related nanomaterials. Recently, various nanoscale configurations of carbon have emerged as potential new platforms in the development of brightly photoluminescent materials. As a perfect p conjugated single sheet, graphene lacks electronic bandgaps and is not photoluminescent. Therefore, researchers have created energy bandgaps within graphene as a strategy to impart fluorescence emissions. Researchers have explored many experimental techniques to introduce bandgaps, such as cutting graphene sheets into small pieces or manipulating the p electronic network to form quantum confined sp(2) "islands" in a graphene sheet, which apparently involve the formation or exploitation of structural defects. In fact, defects in graphene materials not only play a critical role in the creation of bandgaps for emissive electronic transitions, but also contribute directly to the bright photoluminescence emissions observed in these materials. Researchers have found similar defect derived photoluminescence in carbon nanotubes and small carbon nanoparticles, dubbed carbon "quantum" dots or "carbon dots" However, they have not systematically examined the emissions properties of these different yet related carbon nanomaterials toward understanding their mechanistic origins. In this Account, we examine the spectroscopic features of the observed photoluminescence emissions in graphene materials. We associate the structural characteristics in the underlying graphene materials with those emission properties as a way of classifying them into two primary categories: emissions that originate from created or induced energy bandgaps in a single graphene sheet and emissions that are associated with defects in single and/or multiple layer graphene. We highlight the similarities and differences between the observed photoluminescence properties of graphene materials and those found in other carbon nanomaterials including carbon dots and surface defect passivated carbon nanotubes, and we discuss their mechanistic implications.
author_names: Li Cao

Mohammed Meziani

Sushant P Sahu

Ya-Ping Sun
title: Photoluminescence properties of graphene versus other carbon nanomaterials.
venue: Accounts of chemical research
year: 2013

abstract: Graphene quantum dots (GQDs) as a new graphene material, possess advantageous chemical physical properties. Owing to their distinctive photoluminescence (PL) property and low biological toxicity, GQDs have been shown to be good candidates for applications in bioimaging and medical analysis. However, the prepared GQDs have their own slew of problems, including low luminescent efficiency, uncertain luminescent mechanism and lack of effective methods to tuning the luminescence property. Heteroatom doping is a good strategy, which could partially address these above problems. Because the doping atoms will be located in the internal structure of carbon nanomaterials thus change their local electronic configuration, polarizability, defect degree and band structure, etc. the physical and chemical properties of GQDs could be well tuned. At present, GQDs doped with Cl, F, N, S, B, P, etc. have been prepared. These obtained GQDs with heteroatom doping not only exhibited tunable optical properties, but also showed enormous potential applications in the field of photocatalysis. Herein, in order to further improve the PL performance of GQDs and extend their application, we prepared pure GQDs and single elemental doped GQDs with Cl, N, P and S by using the electrochemical method and hydrothermal method. Fourier transform infrared spectroscopy (FT IR) X ray photoelectron spectroscopy, (XPS) and Raman measurements were used to characterize their elemental composition, surface element state and structural defect. Based on the experimental results, the position and bonding state of heteroatoms in doped GQDs were analyzed. The doping amounts in these doped GQDs are different, i.e. 1.35% of Cl GQDs, 7.95% of N GQDs, 10.08% of P GQDs and 3.25% of S GQDs, respectively. The degree of defect state is decreased in the order as follows: P GQDs>S GQDs>GQDs>Cl GQDs>N GQDs. Meanwhile, the PL performance was tested, and the fluorescent quantum efficiencies were calculated to be 8.2% for Cl GQDs, 5.3% for N GQDs, 4.0% for GQDs, 2.8% for S GQDs, and 0.037% for P GQDs, respectively. It can be concluded that the diverse doping atoms play different roles for the improvement of PL performance. The doping of Cl and N can form the luminescent center, which improves the fluorescent intensity of GQDs. Especially for the Cl doping, the fluorescent intensity of Cl GQDs is increased twice compared to the pure GQDs, due to larger atomic radius and more outer shell electron of Cl than that of the others doped elementals. In the S GQDs, the doped S could become small quenching centers, which decreased the fluorescent intensity slightly compared to that of pure GQDs. However, different from the above doped GQDs, P GQDs showed the negligible fluorescence. Because the P atoms mainly are present in the surface functional groups of P GQDs, these P atoms induced defects may become the large fluorescent quenching center and greatly decrease their PL intensity. Besides the measurement and analysis of luminescence intensity, the emission peak positions and corresponding excitation wavelengths of these doped GQDs were also well studied. The excitation wavelength of pure GQDs is located at 340 nm, while the doped GQDs are all located at 360 nm. The strongest emission peaks of Cl GQDs and N GQDs are around 450 nm, while the strongest emission peaks of S GQDs and pure GQDs are around 430 nm. These results indicate that the doping of heteroatoms could change the band gap of GQDs to some extent.
author_names: Ying-Min Wang

Yuyu Jing

Lifeng Wang

Wen-hui Kong

Sen Wang

Zhao Wang

Yan Li

Qipeng Lu
title: Photoluminescence of graphene quantum dots doped with different elements
year: 2019

abstract: Expeditious evolution of antimicrobial resistance in recent years has been identified as a growing concern by various health organizations around the world. Herein, we report a facile and environmentally benign production of highly antibacterial carbonaceous nanomaterials from Colocasia esculenta and Nelumbo nucifera leaves for the first time. After carbonization and oxidative treatment, smaller graphene domains are formed in Colocasia esculenta derivatives whereas larger sheet like structures are spotted in the case of Nelumbo nucifera Smaller particle size makes quantum confinement effects more prominent as evident in fine tuning of photoluminescence emission after each stage of treatment. We also demonstrate the influence of precursor materials in dictating the antibacterial properties of nano systems. When microbicidal activity was tested against model bacteria Pseudomonas aeruginosa nanocomposite derived from Colocasia esculenta leaves displayed higher activity than the antibiotic drug Clarithromycin (control) with a measured zone of inhibition of 40 0.5 mm. This is one of the highest values reported in comparison with other plant based carbon silver nano systems. From quantitative analysis, it is discerned that nanocomposite obtained from Colocasia esculenta leaves has antimicrobial efficacy equivalent to commercial antibiotic drugs and is able to eradicate bacteria at much lower concentrations when compared to those from Nelumbo nucifera leaves.
author_names: Anu N Mohan

Manoj B
title: Extraction of graphene nanostructures from Colocasia esculenta and Nelumbo nucifera leaves and surface functionalization with tin oxide: Evaluation of their antibacterial properties.
venue: Chemistry
year: 2020

abstract: Light weight composite materials of superior thermal transport properties are important to thermal management and other applications. Carbon nanomaterials with their high thermal conductivities have been widely pursued for such a purpose. Specifically, carbon nanotubes have been shown both theoretically and experimentally to possess extraordinarily high thermal conductivities at the individual nanotube level, and thus are logically considered as ideal fillers for highly thermally conductive polymeric nanocomposites. However, the predicted dramatically enhanced thermal transport in polymers upon the incorporation of carbon nanotubes has not yet materialized. Recently, graphene research has brought new opportunities to the development of polymer/carbon nanocomposites of high thermal conductivities, with already some successful uses of exfoliated graphite sheets as nanoscale fillers. In this work poly(vinyl alcohol) (PVA) was selected as the polymer matrix for the dispersion of single walled carbon nanotubes (seamlessly with PVA functionalization and solubilization) vs. few layer graphene sheets as nanoscale carbon fillers for a more direct comparison on the thermal transport performance in the resulting nanocomposites. The effect of aligning the nanotubes embedded in the nanocomposite films via mechanical stretching was also evaluated. Implications of the comparison between the nanotubes and nanosheets with respect to their potentials in thermally conductive polymeric nanocomposites are discussed.
author_names: Wei-Li Song

Weitie Wang

Lucia Monica Veca

Chang Yi Kong

Maosheng Cao

Ping Wang

Mohammed Meziani

Haijun Qian

Gregory E LeCroy

Li Cao

Ya-Ping Sun
title: Polymer/carbon nanocomposites for enhanced thermal transport properties carbon nanotubes versus graphene sheets as nanoscale fillers
year: 2012

abstract: Graphene quantum dots (GQDs) as a new kind of carbon nanomaterial, have been widely prepared with graphene oxide (GO) as precursor via various methods. However, little work has been done to detail the structural relationship between GQDs and pristine GO. Herein, we synthesized GQDs through acidic oxidation of GO and separated blue photoluminescent GQDs (b GQDs) and green photoluminescent GQDs (g GQDs) by a simple dialysis technique. Although the transmission electron microscopy (TEM) and atomic force microscopy (AFM) images reveal their similar morphology, the results of X ray photoelectron spectroscopy (XPS) Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and zeta potential measurements reveal their distinct structures with different origins from the GO. The b GQDs may originate from the intact sp2 cluster of GO, while the g GQDs are derived from the relaxed carbon backbone with numerous oxygen containing functional groups. Besides photoluminescence (PL) properties, the peroxidase like catalytic activity of the two GQDs was also compared. Interestingly, the g GQDs exhibit higher peroxidase like catalytic activity and can be used to detect H2O2 with a detection limit of 87 nM, which is lower than most other reported methods. We believe this work provides important insights into the structure, PL properties and potential applications of GO derived GQDs.
author_names: Duosi Tang

Jingjing Liu

Xiaomei Yan

Longtian Kang
title: Graphene oxide derived graphene quantum dots with different photoluminescence properties and peroxidase like catalytic activity
year: 2016

abstract: 'Nanocarbon science' ignited interest owing to its substantial scope in biomedicine, energy and environment beneficial applications. Carbon dots (C dots) a multi faceted nanocarbon material, emerged as a homologue to graphene and henceforth geared extensive investigation both on its properties and applications. Eximious properties like excitation wavelength tunable fluorescence emission, up converted photoluminescence, photon induced electron transfer, low cytotoxicity, chiroptical behavior, high chemical and photostability set the ground for astounding applications of carbon dots. Abundant availability of raw 'green' precursors complementary to other molecular/graphitic precursors make them environmentally benign, inexpensive and ultimately 'nanomaterials of the current decade' This review focuses on the synthesis of carbon dots not only from natural sources but also from other carbonaceous precursors and contemplates the inherent but controversial properties. We also aim to garner the attention of readers to the recent progress achieved by C dots in one of its prestantious area of applications as nanosensors.
author_names: Nagaraju Kottam

Smrithi S P
title: 'Luminescent carbon nanodots: Current prospects on synthesis, properties and sensing applications'
venue: Methods and applications in fluorescence
year: 2020

abstract: Abstract Fluorescent carbon dots (C dots) are new class of nanomaterials with widespread applications in optoelectronics, bio imaging, catalysis, and sensing. The origin of photoluminescence of carbon dots is a debatable issue which is pretend to depend on the chemical structures such as graphitic conjugated core, molecular fluorophores and the surface defect states found to be dependent on the method of preparation. In this review, we have illustrated the important issues and challenges of the luminescent carbon dots and their potential applications. Graphitic conjugated core containing carbon dots is being synthesized usually from bulk materials like graphite, graphene and graphene oxide which exhibit size dependent photoluminescence behaviour due to quantum confinement. On the other hand, carbon dots synthesized from small molecules exhibit excitation dependent emission due to the presence of surface energy trap states which can be tuned by surface modification. Again, presence of both conjugated core and surface defect generates dual emission property. It is evident that various molecular fluorophores are produced inside carbon dots during low temperature synthesis. Hetero atom doping is another strategy to tune the photoluminescence properties of carbon dots. Red emitting carbon dots are found to be suitable for bio imaging applications after surface modification. Again, high quantum yield and solar light absorbing carbon dots are required for light harvesting and optoelectronic applications. Surface modified carbon dots are found to be appropriate for sensing applications. Analysis reveals that carbon dots based hybrid systems provide good applicability towards construction of solar cell devices because of their efficient charge separation.
author_names: Monoj Kumar Barman

Amitava Patra
title: Current status and prospects on chemical structure driven photoluminescence behaviour of carbon dots
year: 2018

abstract: A novel strategy to precisely detect or monitor various biomaterials in living cells poses paramount importance in understanding cellular processes. Graphene, a newly emerged two dimensional carbon material, has been widely utilized for biosensors owing to its multifarious characteristics including mechanical, electrical, and optical properties (e.g. stability, conductivity, fluorescence quenching and photoluminescence) In addition, graphene derivatives and their innate characteristics, such as biocompatibility low cytotoxicity and water solubility have facilitated the use of graphene based materials for live cell biosensing, wherein graphene is utilized as a core material by itself or in combination with other functional nanomaterials to load target specific probes, fluorescent dyes, and other signaling molecules. Such graphene based hybrid nanomaterials have been employed to detect various cellular entities in living cells, including ions, biomolecules, genetic molecules, proteins, enzymes, and even whole cells. The following review will discuss a number of previous studies in which graphene based hybrid constructs were used for live cell biosensing, and their potential applications in cancer research and stem cell therapy.
author_names: Tae-Hyung Kim

Donghyun Lee

Jeong-Woo Choi
title: Live cell biosensing platforms using graphene based hybrid nanomaterials.
venue: Biosensors bioelectronics
year: 2017

abstract: Metal free carbonaceous nanomaterials have witnessed a renaissance of interest due to the surge in the realm of nanotechnology. Among myriads of carbon based nanostructures with versatile dimensionality, one dimensional (1D) carbon nanotubes (CNTs) and zero dimensional (0D) carbon dots (CDs) have grown into a research frontier in the past few decades. With extraordinary mechanical, thermal, electrical and optical properties, CNTs are utilized in transparent displays, quantum wires, field emission transistors, aerospace materials, etc. Although CNTs possess diverse characteristics, their most attractive property is their unique photoluminescence. On the other hand, another growing family of carbonaceous nanomaterials, which is CDs, has drawn much research attention due to its cost effectiveness, low toxicity, environmental friendliness, fluorescence, luminescence and simplicity to be synthesized and functionalized with surface passivation. Benefiting from these unprecedented properties, CDs have been widely employed in biosensing, bioimaging, nanomedicine, and catalysis. Herein, we have systematically presented the fascinating properties, preparation methods and multitudinous applications of CNTs and CDs (including graphene quantum dots) We will discuss how CNTs and CDs have emerged as auspicious nanomaterials for potential applications, especially in electronics, sensors, bioimaging, wearable devices, batteries, supercapacitors, catalysis and light emitting diodes (LEDs) Last but not least, this review is concluded with a summary, outlook and invigorating perspectives for future research horizons in this emerging platform of carbonaceous nanomaterials.
author_names: Quan Xu

Weijun Li

Lan Ding

Wenjing Yang

Haihua Xiao

Wee-Jun Ong
title: Function driven engineering of 1D carbon nanotubes and 0D carbon dots: mechanism, properties and applications.
venue: Nanoscale
year: 2019

abstract: The results of X ray studies of the structure of components of composite materials based on milled microcrystalline cellulose are presented. The 3D model of the atomic arrangement in the short range order of amorphous carbon can be described by a mechanical mixture of two types of clusters in the ratio of 1 2. One type of clusters is formed by two planar graphene single layers shifted relative to each other and containing vacancies, and the other type is presented by six graphene grids. The cellulose matrix with silicon nanoparticles has a low photoluminescence signal degradation rate. The introduction of fullerenes into nanomaterial as a third nanofraction, as well as the action of ozone, leads to anomalous luminescence kinetics under UV (ultraviolet) photoexcitation, which can be associated with competing processes of hydrogen and oxygen adsorption on the surface of silicon nanoparticles. A change in the ionic conductivity of the porous cellulose matrix upon exposure to ozone can be used to develop effective ozone detectors. Such a filler as amorphous crystalline carbon causes not only ionic but also electronic conductivity in the sample; however, the processes of space charge redistribution remain dependent only on the ion current component. An increase in the total current passing through the pressed sample eliminates the need for a further increase in the signal in the design of ozone sensors.
author_names: Vitaly Pikulev

D V Loginov

Svetlana V Loginova
title: Effect of the carbon component on the electrical and optical properties of nanocellulose based composites
venue: Journal of Surface Investigation: X ray, Synchrotron and Neutron Techniques
year: 2017