Search query: Optimum quantum dot size for highly efficient fluorescence bioimaging

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abstract: Semiconductor quantum dots of few nanometers have demonstrated a great potential for bioimaging. The size determines the emitted color, but it is also expected to play an important role in the image brightness. In this work, the size dependence of the fluorescence quantum yield of the highly thermal sensitive CdTe quantum dots has been systematically investigated by thermal lens spectroscopy. It has been found that an optimum quantum yield is reached for 3.8 nm quantum dots. The presence of this optimum size has been corroborated in both one photon excited fluorescence experiments and two photon fluorescence microscopy of dot incubated cancer cells. Combination of quantum yield and fluorescence decay time measurements supports that the existence of this optimum size emerges from the interplay between the frequency dependent radiative emission rate and the size dependent coupling strength between bulk excitons and surface trapping states.
author_names: Laura Martinez Maestro

Carlos Jacinto

Ueslen Rocha

M Carmen Iglesias-de la Cruz

Francisco Sanz-Rodriguez

Angeles Juarranz

Jose Garcia Sole

Daniel Jaque
title: Optimum quantum dot size for highly efficient fluorescence bioimaging
year: 2012

abstract: Carbon dots (CDs) are a new class of photoluminescent (PL) biocompatible, environment friendly, and low cost carbon nanomaterials. Synthesis of highly efficient red emitting carbon dots (R CDs) on a gram scale is a great challenge at present, which heavily restricts the wide applications of CDs in the bioimaging field. Herein, R CDs with a high quantum yield (QY) of 53% are produced on a gram scale by heating a formamide solution of citric acid and ethylenediamine. The as prepared R CDs have an average size of 4.1 nm and a nitrogen content of about 30% with an excitation independent emission at 627 nm. After detailed characterizations, such strong red fluorescence is ascribed to the contribution from the nitrogen and oxygen related surface states and the nitrogen derived structures in the R CD cores. Our R CDs show good photostability and low cytotoxicity, and thus they are excellent red fluorescence probes for bioimaging both in vitro and in vivo.
author_names: Hui Ding

Ji-Shi Wei

Ning Zhong

Q Y Gao

Huan-Ming Xiong
title: Highly Efficient Red Emitting Carbon Dots with Gram Scale Yield for Bioimaging.
venue: Langmuir the ACS journal of surfaces and colloids
year: 2017

abstract: Abstract Herein, highly blue graphitic carbon nitride quantum dots (g CNQDs) were synthesized by one step microwave assisted evaporation condensation strategy using bulk g C 3 N 4 as the precursor within 5 min. In contrast with conventional chemical routes, the as synthesized g CNQDs exhibited a high crystalline quality, excellent fluorescence characteristics, and a narrow size distribution with an average diameter of 3.5 0.5 nm. More importantly, by using a household microwave oven, this method has the advantages of wide accessibility, environmental friendliness, a high yield of ~40% and can be facilely synthesized in a large scale (scaled up to a gram scale) Notably, owing to the absence of any organic reagents, the blueas prepared g CNQDs show the excitation wavelength independent photoluminescence (PL) behavior. Moreover, benefiting from the stable PL emission, good water solubility, and extraordinary biocompatibility with a high quantum yield of ~17% the fluorescent g CNQDs can serve as a potential sensitive and selective probe for Fe 3+ detection with a super low detection limit of 2 nM and an effective labeling agent for live cell imaging. This work provides a unique opportunity to obtain g CNQDs in large scale via a facile route, which may pave the way for the further design of g CNQDs with other applications.
author_names: Ying Yin

Yumin Zhang

Tangling Gao

Tai Yao

Jiecai Han

Zhengbin Han

Zhihua Zhang

Qiong Wu

Bo Song
title: One pot evaporation condensation strategy for green synthesis of carbon nitride quantum dots: An efficient fluorescent probe for ion detection and bioimaging
year: 2017

abstract: In this work, uniform molybdenum disulfide (MoS2)/tungsten disulfide (WS2) quantum dots are synthesized by the combination of sonication and solvothermal treatment of bulk MoS2/WS2 at a mild temperature. The resulting products possess monolayer thickness with an average size about 3 nm. The highly exfoliated and defect rich structure renders these quantum dots plentiful active sites for the catalysis of hydrogen evolution reaction (HER) The MoS2 quantum dots exhibit a small HER overpotential of 120 mV and long term durability. Moreover, the strong fluorescence, good cell permeability, and low cytotoxicity make them promising and biocompatible probes for in vitro imaging. In addition, this work may provide an alternative facile approach to synthesize the quantum dots of transition metal dichalcogenides or other layered materials on a large scale.
author_names: Shengjie Xu

Dian Yi Li

Peiyi Wu
title: One Pot, Facile, and Versatile Synthesis of Monolayer MoS 2 /WS 2 Quantum Dots as Bioimaging Probes and Efficient Electrocatalysts for Hydrogen Evolution Reaction
year: 2015

abstract: This paper presents the synthesis of aqueous cadmium sulfide (CdS) quantum dots (QDs) and silica encapsulated CdS QDs by reverse microemulsion method and utilized as targeted bio optical probes. We report the role of CdS as an efficient cell tag with fluorescence on par with previously documented cadmium telluride and cadmium selenide QDs, which have been considered to impart high levels of toxicity. In this study, the toxicity of bare QDs was efficiently quenched by encapsulating them in a biocompatible coat of silica. The toxicity profile and uptake of bare CdS QDs and silica coated QDs, along with the CD31 labeled, silica coated CdS QDs on human umbilical vein endothelial cells and glioma cells, were investigated. The effect of size, along with the time dependent cellular uptake of the nanomaterials, has also been emphasized. Enhanced, high specificity imaging toward endothelial cell lines in comparison with glioma cells was achieved with CD31 antibody conjugated nanoparticles. The silica coated nanomaterials exhibited excellent biocompatibility and greater photostability inside live cells, in addition to possessing an extended shelf life. In vivo biocompatibility and localization study of silica coated CdS QDs in medaka fish embryos, following direct nanoparticle exposure for 24 hours, authenticated the nanomaterials' high potential for in vivo imaging, augmented with superior biocompatibility. As expected, CdS QD treated embryos showed 100% mortality, whereas the silica coated QD treated embryos stayed viable and healthy throughout and after the experiments, devoid of any deformities. We provide highly cogent and convincing evidence for such silica coated QDs as a model nanoparticle in practice, to achieve in vitro and in vivo precision targeted imaging.
author_names: Srivani Veeranarayanan

Aby Cheruvathoor Poulose

Mohamed Sheikh Mohamed

Yutaka Nagaoka

Seiki Iwai

Yuya Nakagame

Shosaku Kashiwada

Yasuhiko Yoshida

Toru Maekawa

D Sakthi Kumar
title: Synthesis and application of luminescent single CdS quantum dot encapsulated silica nanoparticles directed for precision optical bioimaging
venue: International journal of nanomedicine
year: 2012

abstract: Recently, carbon dots (CDs) have been playing an increasingly important role in industrial production and biomedical field because of their excellent properties. As such, finding an efficient method to quickly synthesize a large scale of relatively high purity CDs is of great interest. Herein, a facile and novel microwave method has been applied to prepare nitrogen doped CDs (N doped CDs) within 8 min using L glutamic acid as the sole reaction precursor in the solid phase condition. The as prepared N doped CDs with an average size of 1.64 nm are well dispersed in aqueous solution. The photoluminescence of N doped CDs is pH sensitive and excitation dependent. The N doped CDs show a strong blue fluorescence with relatively high fluorescent quantum yield of 41.2% which remains stable even under high ionic strength. Since the surface is rich in oxygen containing functional groups, N doped CDs can be applied to selectively detect Fe(3+ with the limit of detection of 10( 5) M. In addition, they are also used for cellular bioimaging because of their high fluorescent intensity and nearly zero cytotoxicity. The solid phase microwave method seems to be an effective strategy to rapidly obtain high quality N doped CDs and expands their applications in ion detection and cellular bioimaging.
author_names: Guili He

Minghan Xu

Mengjun Shu

Xiaolin Li

Zhi Yang

Lilin Zhang

Yanjie Su

Nantao Hu

Yafei Zhang
title: Rapid solid phase microwave synthesis of highly photoluminescent nitrogen doped carbon dots for Fe(3+ detection and cellular bioimaging.
venue: Nanotechnology
year: 2016

abstract: Near infrared emissive organic dots with a high fluorescence quantum efficiency (AEE dots) are prepared by using an amphiphilic polymer poly(styrene co maleic anhydride) (PSMA) as the co encapsulation matrix and a novel small molecule fluorogen (DPPBPA) with high near infrared emission as the core. The PSMA dots show small particle size of about 20 nm, a large Stokes shift of 304 nm and really high fluorescence quantum efficiency of 20% The streptavidin dots are obtained by conjugating streptavidin to carboxyl groups on the surface of PSMA dots. These streptavidin dots can effectively and specifically label the target cell without any nonspecific binding, such as MCF 7 cells. Together with the negligible cytotoxicity, the near infrared emissive AEE dots are promising red fluorescent probes for future bioimaging applications.
author_names: Yan Zhang

Kaiwen Chang

Bin Xu

Jinlong Chen

Lulin Yan

Suqian Ma

Changfeng Wu

Wenjing Tian
title: Highly efficient near infrared organic dots based on novel AEE fluorogen for specific cancer cell imaging
year: 2015

abstract: Abstract Halophenols (HPs) inflict adverse impacts on human and environment due to their toxic, carcinogenic as well as teratogenic properties. Additionally, it is of great importance and urgency for the development of simple, efficient and inexpensive approaches to minimize the harm of HPs. Here we report an innovatively making poison profitable method to prepare carbon dots (C dots) using 3 bromophenol residual as a precursor. The effects of solvent and carbonization temperature on the preparation of insecticide based C dots were investigated. The results indicate that higher organic solvent content in solution and higher carbonization temperature are in favor of the formation of C dots with smaller size and higher quantum yields. Meanwhile, all C dots displayed excellent water solubility and high photostability against ionic strengths and light illumination. The possible mechanisms of polymerization and carbonization of C dots were rationally proposed, and the incompact framework structure of C dots was reasonably inferred by room temperature phosphorescence measurement. Also, a kind of low toxicity, good biocompatibility and photostability C dots, which were synthesized via a lab leveled mimetic insecticide residuals approach, were utilized as colorless inks for printing patterns and as fluorescence probe for bioimaging. This proposed approach opened up a potential prospect to efficiently utilize pesticide residuals and other hazardous chemicals for biolabeling and bioimaging.
author_names: Wen-sheng Zou

Yazhou Ji

Xiufang Wang

Qingyue Zhao

Junxiang Zhang

Qun Shao

Jin Liu

Feng Wang

Ya-qin Wang
title: Insecticide as a precursor to prepare highly bright carbon dots for patterns printing and bioimaging: A new pathway for making poison profitable
year: 2016

abstract: In this study, a new imaging mesoporous nanoparticle is reported with exceptionally efficient and stable fluorescence emission, which was constructed by embedding and stabilizing quantum dots (QDs) of different sizes into porous nanobeads, following a lipid PEG2000 COOH coating which was further encoded with cRGD targeting peptide through biotin streptavidin bridges. The mesopores had ~10 nm diameter, were chemically modified, and facilitated internalization and stabilization of the QDs within the nanobeads upon the preparation protocol. Their outstanding optical contrasts render the highly fluorescent QDs as ideal fluorophores for wavelength and intensity multiplex color coding. The QDs tagged nanobeads showed optically strong and chemically stable imaging capability, both in vitro and in vivo, indicating powerful contrast modality among other alternatives. The cRGD encoded lipid coated QDs tagged nanobeads (cRGD encoded LQNBs) exhibited significantly increased avb3 expressing cell targeting toward MCF 7 breast cancer cells over the avb3 low expressing in HeLa cervix cancer cells, as confirmed by confocal laser scanning microscopy and flow cytometry. In MCF 7 xenograft nude mice, the cRGD encoded LQNBs revealed prolonged accumulation time at the tumor site. In addition, the QNBs also demonstrated relatively high cell viability as compared to 3 mercaptopropionic acid (MPA) functionalized QDs, indicating a successful design of highly cytocompatible nanoparticulate platform capable of providing cell specific targeting and nano imaging modalities for biomedical applications.
author_names: Po-Jung Chen

Shang-Hsiu Hu

Wen-Ting Hung

San-Yuan Chen

Dean-Mo Liu
title: Geometrical confinement of quantum dots in porous nanobeads with ultraefficient fluorescence for cell specific targeting and bioimaging
year: 2012

abstract: Carbon dots with long wavelength emissions, high quantum yield (QY) and good biocompatibility are highly desirable for biomedical applications. Herein, a green, facile hydrothermal synthesis of highly efficient red emissive nitrogen doped carbonized polymer dots (CPDs) with optimal emission at around 630 nm are reported. The red emissive CPDs possess a variety of superior properties including excellent water dispersibility, good biocompatibility, narrow bandwidth emission, an excitation independent emission, and high QY (10.83% (in water) and 31.54% (in ethanol) Further studies prove that such strong red fluorescence is ascribed to the efficient conjugated aromatic p systems and hydrogen bonds of CPDs. And the fluorescence properties of CPDs can be regulated by adjusting the dosage of HNO3 before the reaction. Additionally, the as prepared CPDs are successfully used as a fluorescent probe for bioimaging, both in vitro and in vivo. More importantly, biodistribution results demonstrate that most CPDs and their metabolites are not only excreted in urine but also excreted by hepatobiliary system in a rapid manner. Besides, the CPDs could easily cross the blood brain barrier, which may provide a valuable strategy for the theranostics of some brain diseases through real time tracking.
author_names: Junjun Liu

Daowei Li

Kai Zhang

Mingxi Yang

Hongchen Sun

Bai Yang
title: One Step Hydrothermal Synthesis of Nitrogen Doped Conjugated Carbonized Polymer Dots with 31% Efficient Red Emission for In Vivo Imaging.
venue: Small
year: 2018