Dual Emission Behavior Research Articles

Dynamic Structural Evolution and Dual Emission Behavior in Hybrid Organic Lead Bromide Perovskites.

The optoelectronic properties of organic lead halide perovskites (OLHPs) strongly depend on their underlying crystal symmetry and dynamics. Here, we exploit temperature-dependent synchrotron powder X-ray diffraction and temperature-dependent photoluminescence to investigate how the subtle structural changes happening in the pure and mixed A-site cation MA1-xFAxPbBr3 (x = 0, 0.5, and 1) systems influences their optoelectronic properties. Diffraction investigations reveal a cubic structure at high temperatures and tetragonal and orthorhombic structures with octahedral distortion at low temperatures. Steady state photoluminescence and time correlated single photon counting study reveals that the dual emission behavior of these OLHPs is due to the direct-indirect band formation. In the orthorhombic phase of MAPbBr3, the indirect band is dominated by self-trapped exciton (STE) emission due to the higher-order lattice distortions of PbBr6 octahedra. Our findings provide a comprehensive explanation of the dual emission behavior of OLHPs while also providing a rationale for previous experimental observations.

Dual emissive Ln(iii)–Ag(i) heterometallic chains based on tris(2-pyridyl)phosphine oxide

Tris(2-pyridyl)phosphine oxide has been successfully used to assemble novel 1D Ln(iii)–Ag(i) heterometallic coordination polymers demonstrating dual emission behavior and excitation wavelength dependent photoluminescence.

Exploring the structural and optical properties of Eu3+, Sb3+ co-doping effect on Cs2NaInCl6 double perovskites for LEDs applications

In the present study Eu3+, Sb3+ co-doped Cs2NaInCl6 double perovskite has been synthesized by using the hot injected method. The crystal structure of the prepared samples has been investigated by XRD data with the help of Rietveld refinement analyzes. The obtained structural property result revealed that all the samples [Cs2NaInCl6, Sb3+ doped Cs2NaInCl6 and (Sb3+, Eu3+) co-doped Cs2NaInCl6] are crystallized in a cubic crystal structure with a space group Fm-3m (225). Further, the electronic properties have been performed by using UV absorbance spectroscopy. It shows that the electronic band gap of the Cs2NaInCl6 and Sb3+ doped compounds exhibits 4.8 eV and 3.9 eV respectively, which is good agreement with other results. The energy band gap value of Eu3+, Sb3+ co-doped Cs2NaInCl6 compounds exhibited ∼4.0 eV, which is very close to Sb3+ doped Cs2NaInCl6 double perovskite. The Photoluminescence study revealed that Sb3+, Eu3+ co-doped Cs2NaInCl6 compounds exhibited dual emission from the self trapped excitation to Eu3+ ion. The blue emission (440 nm) is due to the transition of 3P1→1S0 from Sb3+ ion and orange-red emissions (570–706 nm) are due to the transition of 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3 and 5D0 → 7F4 from Eu3+ ions. The dual emission behavior of the Sb3+, Eu3+ co-doped Cs2NaInCl6 double perovskites suitable for optoelectronic devices and light emitting diodes (LED's) applications.

Spectroscopic and DFT Analysis of (Z)-3-(Anthracen-9-yl)-2-(naphthalen-1-yl)acrylonitrile Fluorophore

Fluorophore molecule (Z)-3-(anthracen-9-yl)-2-(naphthalen-1-yl)acrylonitrile (ANCN) containing anthracene as donor (D), acrylonitrile as acceptor (A) and naphthalene as donor (D) has been synthesized and characterized. ANCN is crystallized in monoclinic crystal system with P21/c space group. The absorption spectra of the compounds are dominated by intramolecular charge transitions that arise from the anthracene core to the acceptor groups. The compounds display distinct dual and single emission behaviour in different solvent environments. The CIE colour chromaticity diagram shows that the emission of ANCN in dichloromethane solution is in blue region, while neat film in greenish blue and 1% ANCN doped with PMMA in bluish-green region. Frontier molecular orbitals of the compound show that the localization of HOMO can be visualized on the anthracene unit and the LUMO is localized on the acrylonitrile unit. Thus, there is an intramolecular charge transfer (ICT) from HOMO to LUMO.

Boron‐Containing Molecules with Fluorescence‐Phosphorescence Dual‐Emission for Mechanochromism and Single Molecular White Light‐Emitting Diodes

AbstractOrganic molecules with fluorescence‐phosphorescence dual‐emission have attracted significant attention for their potential applications in white organic light‐emitting diodes (WOLEDs). Herein, donor–accepter molecules, Mes*BA‐Cz and FXylBA‐Cz, are designed and synthesized, and the photoluminescence of these two compounds in solid state exhibits fluorescence‐phosphorescence dual‐emission. Through the single crystal study, the phosphorescent emission is mainly caused by the molecular stacking in the crystalline state, which is beneficial for aggregation‐induced intersystem crossing. Dual emission behavior further caused the mechanochromism of the two compounds, with emission color changed between amorphous and crystalline state. White light photoluminescence with CIE coordinates of (0.33, 0.34) is achieved by doping FXylBA‐Cz in the poly (methyl methacrylate) film. Furthermore, a WOLED based on FXylBA‐Cz is manufactured with CIE coordinates of (0.31, 0.33), and the external quantum efficiency (EQE) reached 0.49%.

Iridium Complex with Specific Intercalation in the G-Quadruplex: A Phosphorescence and Electrochemiluminescence Dual-Mode Homogeneous Biosensor for Enzyme-Free and Label-Free Detection of MicroRNA

Design and exploitation of high-property and multifunctional emitters for achieving immobilization-free, label-free, enzyme-free, and dual-mode determination of microRNA (miRNA) with high sensitivity and selectivity are particularly urgent but remain a huge challenge. Herein, for the first time, we reported an Ir3+-based N-heterocyclic complex, namely, IrPyPt, ascertained its phosphorescence and electrochemiluminescence (ECL) dual-emission behavior in homogeneous solution, and discovered its turn-up phosphorescence and signal-off ECL response to G-quadruplex DNA over other DNAs. Inspired by this, IrPyPt was pioneered as an emitter to combine nucleic acid probes (ON1 and ON2) for developing a phosphorescence and ECL dual-mode homogeneous biosensor, which was applied to label-free, enzyme-free, highly sensitive, and credible analysis of miRNA-21 used as a target analyte. miRNA-21 triggered the hybridization chain reaction of ON1 and ON2 to generate abundant G-quadruplexes, which caught IrPyPt to yield IrPyPt@G-quadruplex, in which the intramolecular rotary motion of IrPyPt was inhibited and IrPyPt was unable to diffuse to the electrode, contributing to a highly boosted phosphorescence emission and a sharply declined ECL emission. With this design, dual-mode analysis of miRNA-21 was achieved with limits of detection down to 1.40 and 0.18 pM, respectively. Furthermore, the dual-mode biosensor was triumphantly applied to determine the concentration of miRNA-21 in cancer cell lysates and thus provided a great potential alternative for miRNA-related diseases' early and accurate diagnosis.

Boosting CO2 photoreduction by π–π-induced preassembly between a Cu(I) sensitizer and a pyrene-appended Co(II) catalyst

The design of a highly efficient system for CO2 photoreduction fully based on earth-abundant elements presents a challenge, which may be overcome by installing suitable interactions between photosensitizer and catalyst to expedite the intermolecular electron transfer. Herein, we have designed a pyrene-decorated Cu(I) complex with a rare dual emission behavior, aiming at additional π-interaction with a pyrene-appended Co(II) catalyst for visible light-driven CO2-to-CO conversion. The results of 1H NMR titration, time-resolved fluorescence/absorption spectroscopies, quantum chemical simulations, and photocatalytic experiments clearly demonstrate that the dynamic π-π interaction between sensitizer and catalyst is highly advantageous in photocatalysis by accelerating the intermolecular electron transfer rate up to 6.9 × 105 s-1, thus achieving a notable apparent quantum yield of 19% at 425 nm with near-unity selectivity. While comparable to most earth-abundant molecular systems, this value is over three times of the pyrene-free system (6.0%) and far surpassing the benchmarking Ru(II) tris(bipyridine) (0.3%) and Ir(III) tris(2-phenylpyridine) (1.4%) photosensitizers under parallel conditions.

Strategy to synthesize dual-emission carbon dots and their application for pH variation and hydrogen sulfide sensing and bioimaging

In this work, dual emission nitrogen and sulfur co-doped fluorescent carbon dots (DE-CDs) were designed for pH variation and hydrogen sulfide (H2S) sensing and bioimaging through fluorescence enhancement. The DE-CDs with green-orange emission were facilely prepared by one-pot hydrothermal strategy using neutral red and sodium 1,4-dinitrobenzene sulfonate as precursors, manifesting intriguing dual-emission behavior at 502 and 562 nm. As the pH increases from 2.0 to 10.2, the fluorescence of DE-CDs gradually increases. The linear ranges are 2.0–3.0 and 5.4–9.6, respectively, which are attributed to the abundant amino groups on the surface of the DE-CDs. Meanwhile, H2S can be employed as an enhancer to increase the fluorescence of DE-CDs. The linear range is 25–500 μM, and the LOD is calculated to be 9.7 μM. Besides, the DE-CDs can be used as imaging agents for pH variation and H2S sensing in living cells and zebrafish due to their low toxicity and good biocompatibility. All of the results demonstrated that the DE-CDs can monitor pH fluctuations and H2S in aqueous and biological environments, and have promising applications in the fields of fluorescence sensing, disease detection, and bioimaging.

Dual emissive cyclometallated iridium complexes: Synthesis, structure and photophysical properties

Herein, we present a new set of dual emissive heteroleptic cationic cyclometallated iridium complexeDepartment of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal By-pass Road, Bhauri, Bhopal, 462 066, Madhya Pradesh, Indias [(L)2Ir(N^N)]+ ([1]+ - [3]+) using extended π-conjugated 1-isopentyl-2-phenyl-1H-naphtho [2,3-d] imidazole (L) as C^N chelating ligand. The complexes were characterized using various analytical techniques including single crystal X-ray crystallography. The complexes exhibit dual emission behavior (560 nm, 610 and 670 nm) at ambient condition (298 K). The photophysical properties along with DFT results indicate that the origin of emission bands is not only from the lowest energy T1 state but also there is involvement of other higher energy excited triplet states. The DFT study further reveals that the lowest excited triplet state (T1) has 3MLLCT character, whereas the closely lying other higher excited triplet states are predominately of 3LLCT/3ILCT character which could be responsible for such dual emission.

Dual-Color Emission from Spatially Distributed Quantum Dots in Poly(l-lactide) Films with Diverse Morphologies.

Polymer-based multicolor emissive materials have growing demand due to their potential applications in various fields such as full-color displays, bioimaging, and light sources because of their processability and high stability. Herein, we report dual-color emissive hybrid materials based on biocompatible poly(l-lactide) and polyethylene glycol-modified two-dimensional layered double hydroxide quantum dots (PEG-LDHQDs). The morphology of polymer films tunes the spatial distribution of QDs within the polymer matrix, modulating the energy transfer between the QDs and affording the dual emission behavior in the aggregated states. The amorphous hybrid films show single emission (blue) from the finely dispersed QDs (mostly isolated) within the polymer matrix. In contrast, dual emission (blue and red) was observed when the polymer was crystallized due to the possible accumulation of QDs at the interface of crystalline and amorphous phases in the lamellar structure. Furthermore, the dual emission could be enhanced by the aggregation of QDs on the pores of the breath figure pattern constructed on the surface of the hybrid film.

Sterically Hindered Diarylethenes with a Benzobis(thiadiazole) Bridge: Enantiospecific Transformation and Reversible Photosuperstructures.

ConspectusPhotochromic diarylethenes featuring reversible regulation by external light irradiation have attracted increasing attention in versatile applications such as logic gates, supramolecular systems, liquid crystals, and super-resolution imaging because of their outstanding bistability and fatigue resistance. However, for typical diarylethene systems, there always exist three typical unsolved issues. The first is how to modulate the bistability between the open and closed forms from the viewpoint of ethene bridge aromaticity. The second is how to decrease and avoid the photoinactive parallel conformer in order to achieve a high quantum yield, since the open form possesses the photoactive antiparallel (ap) conformation and the photoinactive parallel (p) conformation. Because of the typical rapid rotation of the flexible side aryl groups, the two conformers cannot be separated efficiently, thereby resulting in a relatively low photocyclization quantum yield. The third is how to fulfill the enantiospecific transformation with reversibility to photomodulate the chirality. Stereochemically, the ap conformer with C2 symmetry can be further subdivided into a pair of enantiomers with P and M helicity originating from the central hexatriene moiety. Similarly, the rapid rotation can also lead to the loss of intrinsic chirality, restricting the development and application of light-driven chiroptical switches. Accordingly, it is desirable to construct a specific diarylethene system to break through these bottlenecks for real versatile applications.Our group has recently developed a unique sterically hindered diarylethene system based on benzobis(thiadiazole) as the ethene bridge for completely solving these issues. We introduce a low-aromaticity benzobis(thiadiazole) unit into the diarylethene as a central ethene bridge with incomparably high bistability. To block or freeze the rotation of flexible side aryls, we further incorporate a large bulky benzothiophene unit to induce a large steric hindrance, or rotation barrier, between the ethene bridge and side aryls, thereby successfully separating multiple conformers of the diarylethenes with high photocyclization quantum yields and enantiospecific photoreaction. Consequently, given such a fantastic building block, we enhance its performance by means of supramolecular self-assembly, thereby realizing unique conformer-dependent self-assembly as well as unprecedented concerted isomerization and enantiospecific photoreaction of photoresponsive metallacycles. In addition, decoration of the intrinsically chiral diarylethenes with mesogenic units can enable us to manipulate the helical superstructure of liquid crystals, thus achieving a multiple anticounterfeiting technique and a quadridimensional manipulable laser. We also unravel the dual aggregation-induced emission (AIE) behavior of the sterically hindered diarylethene, especially as applied in super-resolution imaging.

A Series of D–A–D Structured Disilane-Bridged Triads: Structure and Stimuli-Responsive Luminescence Studies

A series of σ-π extended octamethyltetrasilanes, which have phenothiazine, 9,9-dimethyl-9,10-dihydroacridine, or phenoxazine (1, 2, and 3) groups as donor moieties and thienopyrazine or benzothiadiazole (a and b) groups as acceptor fragments, has been prepared, and their optical properties have been studied as an extension of our work. All six compounds exhibited fluorescence in the solid state with maximum wavelengths centered in the range of 400 and 650 nm upon excitation by a UV lamp. Compound 2b showed apparent dual emission behavior in solution, which depends on solvent polarity, and a reversible photoluminescent change under mechanical and thermal stimuli in the solid state. Quantum chemical calculations suggest the contribution of a quasi-axial conformer of the 9,9-dimethyl-9,10-dihydroacridine moiety in 2b to the dual emission in solution and the mechanofluoroluminescence in the solid state, similarly to 1a. These studies provide new insight into the preparation of disilane-bridged triads capable of responding to multiple stimuli.

Co-facial π-π Interaction Expedites Sensitizer-to-Catalyst Electron Transfer for High-Performance CO2 Photoreduction.

The sunlight-driven reduction of CO2 into carbonaceous fuels can lower the atmospheric CO2 concentration and provide renewable energy simultaneously, attracting scientists to design photocatalytic systems for facilitating this process. Significant progress has been made in designing high-performance photosensitizers and catalysts in this regard, and further improvement can be realized by installing additional interactions between the abovementioned two components, however, the design strategies and mechanistic investigations on such interactions remain challenging. Here, we present the construction of molecular models for intermolecular π–π interactions between the photosensitizer and the catalyst, via the introduction of pyrene groups into both molecular components. The presence, types, and strengths of diverse π–π interactions, as well as their roles in the photocatalytic mechanism, have been examined by 1H NMR titration, fluorescence quenching measurements, transient absorption spectroscopy, and quantum chemical simulations. We have also explored the rare dual emission behavior of the pyrene-appended iridium photosensitizer, of which the excited state can deliver the photo-excited electron to the pyrene-decorated cobalt catalyst at a fast rate of 2.60 × 106 s–1 via co-facial π–π interaction, enabling a remarkable apparent quantum efficiency of 14.3 ± 0.8% at 425 nm and a high selectivity of 98% for the photocatalytic CO2-to-CO conversion. This research demonstrates non-covalent interaction construction as an effective strategy to achieve rapid CO2 photoreduction besides a conventional photosensitizer/catalyst design.

Carbon dots hybrid for dual fluorescent detection of microRNA-21 integrated bioimaging of MCF-7 using a microfluidic platform

BackgroundMicroRNAs have short sequences of 20 ~ 25-nucleotides which are similar among family members and play crucial regulatory roles in numerous biological processes, such as in cell development, metabolism, proliferation, differentiation, and apoptosis.ResultsWe reported a strategy for the construction of a dual-emission fluorescent sensor using carbon dots (CDs) and confirmed their applications for ratiometric microRNA-21 sensing and bioimaging of cancer cells in a microfluidic device. The composition of blue CDs (B-CDs) and yellow CDs (Y-CDs) depicts dual-emission behavior which is centered at 409 and 543 nm under an excitation wavelength of 360 nm. With increasing microRNA-21 concentration, the robust and specific binding of DNA probe functionalized B-CDs to complementary microRNA-21 target induced perturbations of probe structure and led to changing fluorescence intensity in both wavelengths. Consequently, the ratio of turn-on signal to turn-off signal is greatly altered. With monitoring of the inherent ratiometric fluorescence variation (ΔF540nm/ΔF410nm), as-prepared BY-CDs were established as an efficient platform for ratiometric fluorescent microRNA-21 sensing, with a wide linear range of 0.15 fM to 2.46 pM and a detection limit of 50 aM.ConclusionsFurthermore, the proposed assay was applied for detecting microRNA-21 in dilute human serum samples with satisfactory recovery and also in MCF-7 cell lines in the range 3000 to 45,000 (cell mL−1) with a detection limit (3 cells in 10 μL), demonstrating the potential of the assay for clinic diagnosis of microRNA-associated disease. More importantly, the images revealed that MCF-7 cells well labeled with BY-CDs could exhibit the applicability of the proposed microfluidic system as an effective cell trapping device in bioimaging.Graphical

Control of the dual emission behaviour of μ-oxo-bridged Si(iv) corrole dimers by substituent bulkiness

μ-Oxo-bridged Si(iv) corrole dimers show dual emission behavior. Their conformational relaxation can be controlled by substituent bulkiness.

Investigation into dual emission of a cyclometalated iridium complex: The role of ion-pairing

Time-resolved emission of [Ir(ppy)2dcbpy]Cl (1a, ppy = 2-phenylpyridine, dcbpy = 2,2′-bipyridine-5,5′-dicarboxylic acid) dissolved in DMF revealed a biexponential decay of the excited state. Prior studies on cyclometalated iridium complexes indicated that such dual emission behavior can be attributed to an impurity, compounds that have two LUMO states that are close in energy, or the presence of ion-pairing. To probe each of these effects, a series of homoleptic, Ir(ppy)3 (2), and heteroleptic complexes, [Ir(ppy)2dcbpy]X [X = PF6−(1b), BPh4−(1c)] and [Ir(ppy)2bpy]X [bpy = 2,2′-bipyridine, X = Cl− (3a) PF6−(3b)], were synthesized and photophysically characterized. Among these complexes, only 1a exhibited dual emission with the emission lifetimes of 430 ± 5 ns (80%) and 125 ± 6 ns (20%) in DMF. These lifetimes were further confirmed with the nanosecond transient absorption kinetics, indicating that the dual emission likely did not originate from an impurity. When probing the emission and absorption kinetics of the salts 1b and 1c only one lifetime of 550 ± 10 ns was observed, indicating that the short lifetime of the Cl− salt (1a) comes from a putative ion-paired complex. Density-Functional Theory (DFT) calculations on 1 and 2 fragments in DMF helped uncover the reason behind the ion-pair formation, with carboxyl substituents in 1a causing a loss in electron density on the 3,3′-position of dcbpy. Additionally, the loss in electron density was experimentally validated with 1H NMR, which showed a noticeable downfield shift of the 3,3′-protons in relative to the shifts in 1b and 1c. The data supports that the dual emission observed in 1a is not from two separately emissive states, rather from the dissociated and ion-paired complexes.

Nitrogen/sulfur-doped dual-emission carbon dots with tunable fluorescence for ratiometric sensing of ferric ions and cell membrane imaging

Nitrogen/sulfur-doped dual-emission carbon dots (NS-CDs) with different sizes, long wavelength, tunable fluorescence, high nitrogen level and high photostability were solvothermally synthesized by treating different mass ratio of non-conjugated precursors of SA and GSH in formamide for ratiometric Fe 3+ sensing and targeted cell membrane imaging. • Nitrogen/sulfur-doped dual-emission CDs (NS-CDs) with tunable fluorescence were synthesized. • Nitrogen level and sp 2 -conjugated domains can be tuned by controlling the SA/GSH mass ratio in formamide. • NS-CDs showed high selectivity and sensitivity for ratiometric fluorescence detection of Fe 3+ . • Hydrophilic NS-CDs have intriguing targeted capability for cell membrane imaging. Intrinsic dual-emission carbon dots (CDs) with long wavelength and self-calibration attributes are critical in fluorescence sensing and imaging, but their synthesis remains a great challenge. Here, nitrogen/sulfur-doped dual-emission CDs (NS-CDs) of different sizes were controllably synthesized by solvothermally treatment of sodium alginate (SA) and glutathione (GSH) in formamide. Interestingly, these as-prepared NS-CDs exhibit enchanting dual-emission behavior at 480 and 650 nm, tunable fluorescence, superior photostability, and high nitrogen level up to 19.57%. The decreasing mass ratio of SA/GSH for the synthesis can lead to larger size and lower graphitic nitrogen for NS-CDs, ultimately giving the enhanced photoluminescence (PL) and tunable fluorescence changing from cyan to white-blue. The selected dual-emission NS-CDs showed superior selectivity and sensitivity for ratiometric Fe 3+ sensing with a detection limit as low as 0.56 μM because of the aggregation of NS-CDs induced by Fe 3+ , and achieved the Fe 3+ detection in environment water. Moreover, the fluorescence-tunable NS-CDs possessing plenteous hydrophilic groups exhibit excellent biocompatibility and unprecedented localized capability for specific cell membrane imaging. This study designs a facile and economical strategy to prepare dual-emission CDs with long wavlength, tunable fluorescence and high nitrogen level, which present bright prospects in environmental monitoring and cell imaging.

Rational manipulation of lattice strain to tailor the electronic and optical properties of nanostructures

Optoelectronic devices with different energy ranges requires materials with different band gaps, sometimes even within the same device. Structural distortions within the nanostructures produce lattice strains, which can change physical properties. However, the detailed knowledge of lattice strains in nanostructures remains confusing. Here, we rationally design and employ a simple and effective scheme to fabricate strained BiVO4/ZnS nanostructures. Lattice strain originates from lattice distortion caused by the intentional incorporation of metal ions into the inner layer of nanostructures. Experimental findings show that the maximum and minimum band gap energies of BiVO4/ZnS nanostructures are 2.87 and 2.79 eV under the tensile strain, which are increased by 4.4% and 1.4%, respectively, compared with that of the reference sample (2.75 eV). Impressively, BiVO4/ZnS nanostructures exhibit tunable dual emission behavior, and lattice strain significantly changes the electron band structure of the nanostructures. In addition, we identify the composite structure of BiVO4/ZnS nanomaterials and elucidate the mechanistic origin of regulation of the optical and electronic properties by lattice strain in combination with experimental and density functional theory calculations. These results provide a deep understanding of the relationship between lattice strain and optical properties and indicate that strain engineering can be potentially used in the design of nanostructures.

Achieving room temperature phosphorescence in aqueous phase through rigidifying the triplet state and information encryption

Room temperature phosphorescence materials show promising prospect in various fields, howbeit, it is difficult to overcome their unstable triplet state originated from dissolved oxygen, resulting in the challengeable synthesis of water-resistance room temperature phosphorescence materials. Here, we raised a facile strategy to originally prepare one kind of carbon dots (CDs) with blue fluorescence, and their phosphorescence with a high quantum yield of 23% is further activated in aqueous environment by forming the hydrogen bonds mediated complex between carbon dots and cyanuric acid (CA-CDs). Importantly, the bridge-like hydrogen bonds not only ensure the rigidify of the triplet state of CDs but also isolate oxygen, thus facilitating a small energy gap of 0.44 eV between the singlet and triplet states of CA-CDs, which provided the evidence for understanding the RTP appearing by another innovative way. Relying on their dual-emission behavior, the current RTP CA-CDs were successfully applied for the fingerprint recognition and advanced information encryption.

Solid-phase synthesis of red dual-emissive nitrogen-doped carbon dots for the detection of Cu2+ and glutathione

Red dual-emissive carbon dots (CDs) were prepared by a novel and facile solvent-free carbonization method using O-phenylenediamine (OPD) as precursor and Al(NO3)3·9H2O as assistant. The prepared CDs manifesting intriguing dual-emission behavior at 600 nm and 650 nm demonstrate good fluorescence quenching rate (99%) on Cu2+, in which the linear range was 6–33 μM and detection limit was 0.145 μM. In addition, the CDs-Cu2+ system shows excellent glutathione (GSH) turn-on detection in the range of 19–52 μM, where a red-shift to 650 nm and 700 nm was observed and the maximum value of F/F0 is 5.8. Reasonable quenching mechanism was speculated to be the combination of static and dynamic quenching. Cytotoxicity measurements displayed good biocompatibility of CDs and cell viability was higher than 83% even under the highest concentration of CDs.