Fluorescent Nanosheets Research Articles

AIEE based fluorescent detection of Enrofloxacin using methyl isobutyl ketone as a backbone for the resilient 2D MIBK-Sn nanosheets

For the first time, we proposed a novel approach to create enduring and robust fluorescent nanosheets by using MIBK as the backbone to form the 2D MIBK-Sn nanosheets (2D MIBK-Sn NS) for detecting ENR. These nanosheets were synthesized in situ using probe ultrasonication to facilitate the formation of MIBK-based 2D tin nanosheets. The LOD and LOQ for ENR in aqueous solutions was 4.90 and 16.1 nM, respectively. Linear calibration curves were obtained with correlation coefficient (R2) = 0.9920 in a linear range of 0–2 µM. Recovery results from real samples ranged from 90 to 106 % of the nominal values. Milk and urine samples were analyzed at concentrations ranging from 0.3 to 1.7 µM.

Synthesis of two-dimensional bismuth molybdenum oxide (2D-BMO) nanosheets and their application as fluorescent probes for the detection of explosive nitroaromatic compounds

2D-BMO fluorescent nanosheets were synthesized using a solvothermal method followed by probe sonication.

Surfactant assisted exfoliation of near infrared fluorescent silicate nanosheets.

Fluorophores that emit light in the near infrared (NIR) are advantageous in photonics and imaging due to minimal light scattering, absorption, phototoxicity and autofluorescence in this spectral region. The layered silicate Egyptian blue (CaCuSi4O10) emits as a bulk material bright and stable fluorescence in the NIR and is a promising NIR fluorescent material for (bio)photonics. Here, we demonstrate a surfactant-based (mild) exfoliation procedure to produce nanosheets (EB-NS) of high monodispersity, heights down to 1 nm and diameters <20 nm in large quantities. The approach combines planetary ball milling, surfactant assisted bath sonication and centrifugation steps. It avoids the impurities that are typical for the harsh conditions of tip-sonication. Several solvents and surfactants were tested and we found the highest yield for sodium dodecyl benzyl sulfate (SDBS) and water. The NIR fluorescence emission (λem ≈ 930-940 nm) is not affected by this procedure, is extremely stable and is not affected by quenchers. This enables the use of EB-NS for macroscopic patterning/barcoding of materials in the NIR. In summary, we present a simple and mild route to NIR fluorescent nanosheets that promise high potential as NIR fluorophores for optical applications.

Covalently Functionalized Egyptian Blue Nanosheets for Near-Infrared Bioimaging.

Fluorophores emitting in the near-infrared (NIR) wavelength region present optimal characteristics for photonics and especially bioimaging. Unfortunately, only few NIR fluorescent materials are known, and even fewer are biocompatible. For this reason, the scientific interest in designing NIR fluorophores is very high. Egyptian Blue (CaCuSi4O10, EB) is an NIR fluorescent layered silicate that can be exfoliated into fluorescent nanosheets (EB-NS). So far, its surface chemistry has not been tailored, but this is crucial for colloidal stability and biological targeting. Here, we demonstrate covalent surface functionalization of EB nanosheets (EBfunc) via Si-H activation using hydrosilanes with variable functionalities. In the first part of this work, EB-NS are grafted with the visible fluorescent pyrene (Pyr) moieties to demonstrate conjugation by colocalization of the Vis/NIR fluorescence on the (single) EB-NS level. Next, the same grafting procedure was repeated and validated with carboxyl group (COOH)-containing hydrosilanes. These groups serve as a generic handle for further (bio)functionalization of the EB-NS surface. In this way, folic acid (FA) could be conjugated to EB-NS, allowing the targeting of folic acid receptor-expressing cancer cells. These results highlight the potential of this surface chemistry approach to modify EB-NS, enabling targeted NIR imaging for biomedical applications.

Ultrathin Cd-3,5-PDC nanosheets enhanced NAP fluorescence probe for visualized detection of peroxynitrite

Highly selective and sensitive monitoring of peroxynitrite (ONOO-) in living systems is of significance since it is closely related with the occurrence of multiple diseases. Herein, we successfully constructed ultrathin NAP@Cd-3,5-PDC (NAP@Cd-3,5-PDC-NS, NAP: 2-(6-(4-methylpiperazin-1-yl)− 1,3-dioxo-1 H-benzo[de]isoquinolin-2(3 H)-yl) acetic acid, 3,5-PDC = 3,5-pyridine dicarboxylic acid) fluorescent nanosheets through a simple solution route and subsequent ultrasonication at room temperature. Experiments revealed that the presence of Cd-3,5-PDC-NS significantly enhanced the fluorescence emission of NAP. Under excitation of 398 nm light, the as-obtained NAP@Cd-3,5-PDC-NS could emit about 7-fold stronger photoluminescence than NAP with an equivalent concentration. Also, the as-obtained composite nanosheets could be stably dispersed in phosphate buffer solution (PBS) for 42 days without obvious structure and fluorescence changes. Intriguingly, the strong fluorescence of NAP@Cd-3,5-PDC-NS could be severely quenched by ONOO- without interferences from some other active species, anions/cations, and amino acids. The detection limit of NAP@Cd-3,5-PDC-NS for ONOO- was as low as 61.5 nM, which was 15 times lower than that of the NAP probe alone. Moreover, the as-obtained fluorescent probe could be applied to HepG2 cell imaging, showing its potential application in disease diagnosis.

Exfoliated Silicate Nanosheets As Novel Near-Infrared Fluorophores for (Bio)Photonics

The near-infrared (NIR) region of the electromagnetic spectrum presents optimal characteristics for imaging of complex (biological) samples: this is mainly due to reduced light scattering, absorption, phototoxicity and autofluorescence. However, despite their clear potential over commonly employed visible fluorophores, only few NIR fluorescent materials are known so far, and even less are suitable for biomedical applications. For this reason, it is of great interest to search for novel materials that can enrich the so far poor library of NIR fluorophores.We exfoliated a class of layered silicates: Egyptian Blue (CaCuSi4O10, EB), Han Blue (BaCuSi4O10, HB) and Han Purple (BaCuSi2O6, HP). These pigments fluoresce in the NIR (λ emi ≈ 920-950 nm) with a long excited state lifetime (τ ≈ 10-100 µs). By milling, tip sonication and several centrifugation steps, small and monodisperse 2D nanosheets (NS) could be exfoliated. Most interestingly, the intense NIR fluorescence emission of the bulk counterparts is retained. In comparison to state-of-the-art fluorophores, EB-NS show no bleaching while displaying outstanding fluorescence intensity. Such qualities of EB-NS enabled us to inject them into systems of biological relevance such as developing Drosophila embryos, and perform in vivo single-particle tracking and microrheology measurements. Furthermore, it is possible to successfully detect EB-NS in plants. [1] In general, all the above mentioned three silicate NS prove bright enough to be imaged through several cm of tissue phantoms, which demonstrates the potential for (bio)photonics. Finally, we used the microsecond fluorescence lifetimes of EB-NS, HB-NS and HP-NS for micro- and macroscopic fluorescence lifetime imaging (FLIM). The results show that lifetime engineering of these silicate nanostructures is possible and can be used for lifetime-encoded imaging. [2]In summary, we present a new exfoliation route that yields NIR fluorescent nanosheets of high promise as novel NIR fluorophores for bioimaging and photonics.Literature:[1] G. Selvaggio et al., Nat. Commun. 2020, 11, 1495.[2] G. Selvaggio et al., in preparation.

Highly water-stable Cd-MOF/Tb3+ ultrathin fluorescence nanosheets for ultrasensitive and selective detection of Cefixime

Two-dimensional Cd-MOF/Tb3+ (Cd-MOF = [Cd (μ-2,3-pdc) (H2O)3]n (2,3-pdc = 2,3-pyridine dicarboxylic acid)) fluorescent nanosheets with the thickness of 1.4 nm were successfully synthesized by a simple solution route with subsequent ultrasonic exfoliation at room temperature. It was found that as-obtained Cd-MOF/Tb3+ ultrathin nanosheets could be homogeneously dispersed in aqueous system to form a sol with excellent stability. Also, the fluorescence intensity of nanosheets remarkably increased to almost 12 times higher than that of Cd-MOF/Tb3+ microsheets before exfoliation. Further investigations uncovered that the above strong fluorescence of Cd-MOF/Tb3+ nanosheets could be highly sensitively quenched by Cefixime antibiotic in aqueous solution without interference from other antibiotics, amino acids and pesticides. Hence, the as-obtained ultrathin Cd-MOF/Tb3+ nanosheets could be prepared as a highly selective and sensitive fluorescence probe for the detection of Cefixime in aqueous system. Compared with the bulk Cd-MOF/Tb3+ sensor, the Cd-MOF/Tb3+ ultrathin nanosheets sensor exhibited a far lower detection limit down to 26.7 nM for CFX. Also, the as-obtained nanosheets sensor presented satisfactory recovery ranging from 98.07% to 103.01% and acceptable repeatability (RSD < 6.29%, n = 6) for the detection of CFX in domestic water. Furthermore, the sensing mechanism studies revealed that the high selection of the present fluorescent probe for detection of CFX should be attributed to the cooperation of the photoinduced electron transfer and the inner filter effect.

Exfoliated near infrared fluorescent silicate nanosheets for (bio)photonics

Imaging of complex (biological) samples in the near-infrared (NIR) is beneficial due to reduced light scattering, absorption, phototoxicity, and autofluorescence. However, there are few NIR fluorescent materials known and suitable for biomedical applications. Here we exfoliate the layered pigment CaCuSi4O10 (Egyptian Blue, EB) via ball milling and facile tip sonication into NIR fluorescent nanosheets (EB-NS). The size of EB-NS can be tailored to diameters <20 nm and heights down to 1 nm. EB-NS fluoresce at 910 nm and the fluorescence intensity correlates with the number of Cu2+ ions. Furthermore, EB-NS display no bleaching and high brightness compared with other NIR fluorophores. The versatility of EB-NS is demonstrated by in-vivo single-particle tracking and microrheology measurements in Drosophila melanogaster embryos. EB-NS can be uptaken by plants and remotely detected in a low-cost stand-off detection setup. In summary, EB-NS have the potential for a wide range of bioimaging applications.

Spontaneously Self-Assembled Naphthalimide Nanosheets: Aggregation-Induced Emission and Unveiling a-PET for Sensitive Detection of Organic Volatile Contaminants in Water.

A simple design strategy of long alkyl chain substitution was formulated to block the detrimental π-π interaction that potentially transforms the aggregation-caused quenching (ACQ) chromophores into aggregation-induced emission (AIE) active smart nanomaterials. The long octadecyl pendant chain substituted naphthalimide (NI) derivatives self-assembled into fluorescent nanosheets (NS)-like structures that spontaneously have surfaces coated with NI cores in water. The fluorescent NS were subsequently used to recognize the organic volatile contaminants (OVCs) at ppb levels via an acceptor-excited photoinduced electron transfer (a-PET) mechanism, unveiled as the first representative example. A new design strategy is thereby provided to detect toxic xylene derivatives in water using smart nanomaterials.

Spontaneously Self‐Assembled Naphthalimide Nanosheets: Aggregation‐Induced Emission and Unveiling a‐PET for Sensitive Detection of Organic Volatile Contaminants in Water

AbstractA simple design strategy of long alkyl chain substitution was formulated to block the detrimental π–π interaction that potentially transforms the aggregation‐caused quenching (ACQ) chromophores into aggregation‐induced emission (AIE) active smart nanomaterials. The long octadecyl pendant chain substituted naphthalimide (NI) derivatives self‐assembled into fluorescent nanosheets (NS)‐like structures that spontaneously have surfaces coated with NI cores in water. The fluorescent NS were subsequently used to recognize the organic volatile contaminants (OVCs) at ppb levels via an acceptor‐excited photoinduced electron transfer (a‐PET) mechanism, unveiled as the first representative example. A new design strategy is thereby provided to detect toxic xylene derivatives in water using smart nanomaterials.

Electrophoretically Deposited Y2O3:Bi3+,Eu3+ Nanosheet Films with High Transparency for Near-Ultraviolet to Red Light Conversion.

Fluorescent films were fabricated by depositing Y2O3:Bi3+,Eu3+ nanosheets, which emit red light under near-UV irradiation. The Y2O3:Bi3+,Eu3+ nanosheets were obtained by calcining hydroxide precursor nanosheets synthesized through a hydrothermal method. An aqueous dispersion of positively charged Y2O3:Bi3+,Eu3+ nanosheets with polyethyleneimine adsorbed to the surface was prepared for their deposition. Fluorescent nanosheets were electrophoretically deposited on a transparent conductive substrate under a constant voltage. The obtained nanosheet films were dense and uniform and showed excellent photostability against the excitation light. Growth of the nanosheet film caused a decrease in transmittance and an increase in the photoluminescence intensity. The former effect was attributed to light scattering from inner voids and the rough surface of the film. A polyvinylpyrrolidone (PVP) coating on the film improved the transmittance to be greater than 70% over the visible region. These effects were attributed to antireflection effects at the film surface owing to the low refractive index of PVP. Furthermore, suppression of light scattering by coating the rough surface with a smooth PVP film and filling of voids in the nanosheet film with PVP also improved the transmittance.

Synthesis of Y2O3:Bi3+,Yb3+ nanosheets from layered yttrium hydroxide precursor and their photoluminescence properties

Morphologies, photoluminescence properties, and photostability were characterized for Y2O3:Bi3+,Yb3+ fluorescent nanosheets prepared through calcining solvothermally synthesized layered yttrium hydroxide precursors.

Synthesis of Y2O3:Bi3+,Eu3+ nanosheets from layered yttrium hydroxide precursor and their photoluminescence properties

Morphologies, photoluminescence properties, and photostability were characterized for Y2O3:Bi3+,Eu3+ fluorescent nanosheets prepared through calcining solvothermally synthesized layered yttrium hydroxide precursors.

Bioinspired Fluorescent Nanosheets for Rapid and Sensitive Detection of Organic Pollutants in Water

Detection of organic pollutants in aqueous media is crucial for guaranteeing water safety. Conventional methods for organic pollutant detection suffer from time-consuming operation procedures (on the order of hours) and expensive devices. Inspired by dog noses, herein, we constructed self-assembled fluorescent nanosheets for rapid and sensitive detection of organic pollutants based on the grasp-report strategy. Tetraphenylethene decorated cyclodextrins (TPE-CDs) self-assembled into nanosheets with hydrophobic TPE layers sandwiched between two hydrophilic cyclodextrin layers. The hydrophobic cavity of the outer cyclodextrin layers grasped and collected organic pollutants, and subsequently transported them to the TPE layers and quenched the fluorescence emission of TPE layers. Such nanosheets allowed rapid detection of xylene (on the order of seconds) at a concentration of 5 μg/L. With the merits of the ease of synthesis, simple operation, and high sensitivity, the fluorescent nanomaterials provide a promising candidate for rapid and sensitive detection of organic pollutants.

Label-Free Fluorescence Sensing of Lead(II) Ions and Sulfide Ions Based on Luminescent Molybdenum Disulfide Nanosheets

Fluorescent molybdenum disulfide (MoS2) nanosheets were synthesized hydrothermally by employing sodium molybdate and thiourea as the starting materials. Lead(II) ion was introduced as a chemical dopant into the fluorescent nanosheets for the first time, and it was found that the fluorescence of the doped MoS2 nanosheets showed a considerable enhancement compared with that of initial MoS2 nanosheets, implying that lead(II)-doping into the MoS2 nanosheets could result in an increase in the fluorescence quantum yield. In parallel, we exploited the lead(II)-induced fluorescence enhancement of MoS2 nanosheets to design a green and facile fluorescent “turn on” nanosensor for lead(II) detection. Moreover, we found that the fluorescent intensity of the doped MoS2 nanosheets was drastically quenched by the successive addition of sulfide ions. Hence, the “turn off” process was used to fabricate a green fluorescence quenching sensor for detection of sulfide ions. Finally, we elucidated the origin of the lead(II)-ind...

Crystallization-Induced Hybrid Nano-Sheets of Fluorescent Polymers with Aggregation-Induced Emission Characteristics for Sensitive Explosive Detection.

Fluorescent organic hybrid nanosheets were generated by crystallization of polymers capped with luminogenic molecules exhibiting aggregation-induced emission characteristics (AIE). During crystallization of polymers, AIE molecules were expelled out of lamellar crystals of polymers, and finally resided on the surface. The fluorescent nanosheets with dangling AIE molecules showed sensitive and specific response to explosives. Such polymer crystallization-induced fluorescent nanomaterials offers a unique avenue to fabricate functional nanomaterials with AIE molecule-enriched domains for potential applications in nanodevices, biological engineering, and so on.

Chemically tailoring graphene oxides into fluorescent nanosheets for Fe3+ ion detection

A method is presented to tailor the lateral size of graphene oxide (GO) in the range of 10–100nm and simultaneously tailor its edge structure by oxidation with periodic acid in a one-pot process. The obtained GO nanosheets are photoluminescent and exhibit lateral size-dependent behavior. The emission wavelength could be tuned from 550 to 470nm by decreasing the lateral size. The fluorescence of GO nanosheets shows a sensitive and selective quenching effect to Fe3+ ions, allowing it to be used as a fluorescent probe to detect Fe3+ ions with a detection limit of 1ppm.

Mesoscopic organic nanosheets peeled from stacked 2D covalent frameworks

Novel mesoscopic organic nanosheets were developed by functionalizing bulk 2D organic covalent framework polymers with small molecules. The water-soluble fluorescent nanosheets are promising as nanocarriers for biological applications.