Change In Excitation Wavelength Research Articles

Employing Lactam Copolymerization Strategy to Effectively Achieve Pure Organic Room‐Temperature Phosphorescence in Amorphous State

Adv. Optical Mater. 2019, 7, 1901277 The authors regret that some of the spectral data in their manuscript were not correct as published with a minor problem. This correction provides an explanation of the origin of this problem along with the changes that have been made. The authors confirm that these minor changes do not affect the conclusions of the communication. By repeating the polymerization and measurement of PNVCL-BrHexene with newly-acquired and original reagent, we found that the original RTP emission peak of PNVCL-BrHexene at 568 nm was due to the impurity from the glassware used for polymerization while the newly-polymerized PNVCL-BrHexene exhibits only one emission peak at 479 nm with the emission maximum changing with the excitation wavelength just like PVP-BrHexene, which was considered as a minor peak of the previously reported PNVCL-BrHexene. We believe that this impurity was BrNpA monomer since the excitation, emission and absorption spectra (including fine structures) of PNVCL-BrNpA are similar to those of PNVCL-BrHexene reported previously. The fact that PNVCL, PNVCL-BrHexene and PNVCL-BA polymerized previously coincidentally contained this impurity (while other polymers did not) made us believe that the emission peaks at ca. 560 nm of these polymers originate from PNVCL units themselves. As the most important figure, Figure 2 has been corrected. The spectra of PNVCL-BrHexene and PNVCL-BA has been changed while those of PNVCL-BrNpA remains unchanged. Figure C1 in this correction corresponds to Figure 2 in the original communication. Table C1, which corresponds to Table 1 in the original communication, is also corrected for the photophysical data of PNVCL-BA, PNVCL-BrHexene and PNVCL. Please note that the data of PNVCL-BA is almost unchanged (except for the disappearance of the minor peak at ca. 560 nm which does not affect the excitation and emission peaks) and that the change of excitation wavelength is merely because the change of the relative intensity of the two excitation peaks. The colors described in the original communication are corrected. Scheme C1, corresponding to Scheme 1 in the original communication, is corrected for the color of PNVCL units. The corrected CIE coordinates of PNVCL-BA and PNVCL-BrHexene is (0.1591, 0.0790) and (0.1771, 0.2016), correspondingly. Figure C2 and Figure C3 correct the absorbance and excitation spectra for Figure S11 and Figure S13 in the original Supporting Information (SI), correspondingly. Although the X-ray powder diffraction (XRPD) and the GPC do not need to be corrected since it has nothing to do with the trace impurities, we remeasured these data for the new polymers. See Figure C4 and Table C2. Other subordinate figures, including Figures S15, S17, S18 and S19 in the original SI, are updated as following Figures S15, S17, S18 and S19.

One Stone, Two Birds: pH- and Temperature-Sensitive Nitrogen-Doped Carbon Dots for Multiple Anticounterfeiting and Multiple Cell Imaging.

Carbon dots (CDs) as new fluorescent materials with excellent fluorescence properties have shown enormous potential applications, especially in anticounterfeiting and cell imaging. Herein, nitrogen-doped CDs (NCDs) with excellent biocompatibility were prepared by a simple thermal sintering method. An extremely large red shift (∼130 nm) of the emission peak was observed when the excitation wavelength changes from 355 to 550 nm, indicating that NCDs are excellent fluorescent labeling materials for multiple cell imaging. On the other hand, NCDs showed obvious changes of emission intensity and peak position when the temperature increased from 223 to 323 K and the pH values changed from 1 to 13, respectively, which has been demonstrated by the "horse" pattern printed with NCD water-soluble fluorescent inks. The nontoxic NCDs dispersed in a multiple matrix are highly sensitive to excitation wavelength, temperature, and pH, indicating their great potential application in multiple anticounterfeiting and multiple cell imaging.

Influence of high energy ion irradiation on structural, morphological and optical properties of high-k dielectric hafnium oxide (HfO2) thin films grown by atomic layer deposition

Abstract Modifications and resulting changes in various properties of nanocrystalline HfO2 high-k dielectric thin films with nominal thickness of 20 nm grown by atomic layer deposition technique on silicon and glass substrates were investigated as a function of swift heavy ions (SHI) irradiation. In the present work, our attention is to study the electronic excitation induced modifications in HfO2 thin films cause of formation of defects by 120 MeV Au9+(SHI) irradiation. For the same purpose, the annealed (500 °C) HfO2 thin films were irradiated with the varying fluence in the range of 1E11 to 1E13 ions/cm2. The virgin and irradiated representative HfO2 thin films were investigated by various techniques. The substantial root mean square (RMS) surface roughness (0.5–1 nm) and variation in grain size (40–52 nm) as a function of Au9+ ions irradiation were determined using atomic force microscope (AFM). The optical properties of HfO2 thin films were analyzed by measuring absorbance and transmission (54–62%) spectra in 200–700 nm wavelength range followed by calculation of optical band gap (Eg). The photoluminescence (PL) spectra obtained at excitation wavelength 220 nm indicate the formation of defects due to SHI irradiation. A change in excitation wavelength (220–260 nm) causes the shift in emission peaks towards higher wavelength. Structural investigations have been carried by Grazing Incidence X-ray Diffraction (GIXRD) techniques which reveal the variation in crystallite size as a function of different fluence. The results of a systematic XPS study of virgin and SHI irradiated samples shows the shifting of Hf 4f and O 1s peaks towards lower binding energy as compared to virgin sample. O K-edge XANES were performed to understand the ion-beam irradiation induced defect formation and their consequences on the electronic structure of HfO2 thin films. The obtained peaks in Rutherford backscattering spectrometry (RBS) affirm the existence of Hf and O elements and width of the peaks determine the sample thickness (20 nm).

Tuning the photoluminescence of large Ti3C2Tx MXene flakes

Ti3C2Tx MXene has been reported to be a metallic two-dimensional (2D) material with high conductivity, whereas its photoluminescence (PL) mechanism is still under debate. Herein, we demonstrate that large Ti3C2Tx MXene flakes exhibit tunable PL under ambient conditions. The as-prepared Ti3C2Tx MXene flakes emit blue, yellow-green and red light under different excitation wavelengths. Their PL emission wavelengths redshift as the excitation wavelength changes from violet to red light. Surface modification of the MXenes can further tune the PL peak wavelength into the near infrared region. Using density function theory (DFT) calculations, this excitation wavelength-dependent PL can be correlated to TiO2 defects that exist on the surface of Ti3C2Tx. Our study expounds on the optical properties of Ti3C2Tx MXene and is helpful for comprehensively understanding this novel material.

Influence of defect structure on colour tunability and magneto optical behaviour of WO3 nanoforms.

The present study reports the impact of thermal annealing on the structural, optical and magnetic properties of WO3 nanostructures, synthesized using an acid precipitation method by, employing various spectroscopic and magnetic measurements. The X-ray diffraction and Raman measurements confirmed the orthorhombic structure of as dried WO3·H2O and monoclinic structure of WO3 nanopowders annealed at or above 500 °C. The morphological characterization shows the formation of different microstructures like nanosheets, nanoplatelets and nanocuboids in the micro-scale with the variation of annealing temperatures. The optical band gap has been calculated using the Kubelka–Munk function. The room temperature photoluminescence (PL) spectra recorded at different excitation wavelengths show intense near ultraviolet (NUV) emission which might be due to the presence of localized states associated with oxygen vacancies, and the surface states in the conduction band. The emissions in visible region correspond to the structural defects such as oxygen vacancies present within the band gap and band to band transitions. The spectral chromaticity colour coordinates indicate that the light emitted from the prepared samples shows shift from violet to red region with the change of excitation wavelength. Magnetic measurements show decrease in room temperature ferromagnetism (FM) with annealing temperature. The X-ray absorption spectroscopy (XAS) measurements at O K-edge show the significant change in the W–O hybridizations. The decrease in PL intensity and ferromagnetic ordering with increase in annealing temperatures are directly correlated with the filling up of oxygen vacancies in the samples. The oxygen vacancies based F-Center exchange model is discussed to understand the origin of FM in WO3 nanostructures.

Sulfur-rich carbon dots as a novel fluorescent imaging probe for distinguishing the pathological changes of mouse-bone cells

Nowadays, the florescent carbon dots (C-dots), as a type of heavy-metal-free nanomaterials, have been widely suggested for biological imaging, but attempts made for detecting and distinguishing bone-related diseases are still rarely reported by previous works. Here, a type of C-dots, featuring rich sulfur content and excellent bone cell affinity, is prepared by one-pot hydrothermal method. Various characterization techniques have been employed to study the structure and fluorescent properties of the sulfur C-dots, which include the X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), ultraviolet-visible (UV–vis) absorption, and fluorescence spectra. Our results show that the sulfur C-dots are featured with small particle size at ~4 nm and rich sulfur content as high as 24.85%, allowing the C-dots to exhibit excellent stability in the aqueous solution and good compatibility and affinity with bone cells. Moreover, we find the sulfur rich C-dots as the excitation wavelength changes from 270 nm to 460 nm can exhibit emission-tunable colors from blue, green and to yellow, showing a rich choice of fluorescent colors for cell imaging. Together with the advantages of low cytotoxicity behavior and sulfur-rich functionalized groups, the sulfur C-dots have been proposed to act as a fluorescent probe for detecting and distinguishing bone-related diseased cells where bone-related normal and diseased cells after incubated with sulfur rich C-dots are found to emit blue and yellow fluorescence upon excitation at 405 nm and 488 nm, respectively. Unlike previous works that are always reported to use the C-dots for cell imaging, here we have presented new application possibilities of C-dots for distinguishing the diseased cells from the normal cells.

Luminescence Properties and Decay Kinetics of Mn2+ and Eu3+ Co-Dopant Ions In MgGa2O4 Ceramics

Abstract The MgGa2O4 ceramics co-doped with Mn2+ and Eu3+ ions were synthesized via a high-temperature solid-state reaction technique. The samples with various Eu3+ concentrations were characterised using high-resolution photoluminescence (PL) spectroscopy. The PL spectra show weak matrix emission in a blue spectral region with dominant excitation band around 380 nm. Manganese ions are highly excited deeply in UV region and exhibit emission band peaked at 502 nm. The Eu3+ ions show characteristic f-f excitation and emission lines. The energy transfer between host defects and activator ions was observed. Luminescence decay curves of Mn2+ and Eu3+ emission showed complex kinetics with both Eu3+-ion concentration and excitation wavelength changes.

Dual color tuning in Ce3+‐doped oxyfluoride ceramic phosphor plate for white LED application

AbstractCeramic phosphor plates of cerium (Ce3+)‐doped oxyfluoride were fabricated by the solid‐state reaction method. These phosphors exhibit efficient emission, with the novel feature of color tuning by varying both the doping concentration and excitation wavelength. As the Ce3+ concentration increases, the excitation spectrum broadens by a factor of 1.6, and the excitation peak wavelength shifts from 390 to 435 nm, and there is a variation in excitation energy of ~ 10%. Luminescence spectrum of low Ce3+ concentration samples is tuned from blue to green with the change of excitation wavelength. The emission peak exhibits a shift of 58 nm into the red spectral region, varying the Ce3+ concentration from 0.05 to 0.1 mol%; whereas this shift is only 6 nm when Ce3+ content changes from 0.25 to 1 mol%. Photoluminescence (PL) quantum yield has achieved 76%. The crystal structure was examined using X‐ray diffraction to explain its possible influence on the redshift luminescence. A proof of concept of white LED was constructed using a 450 nm blue LED chip with an oxyfluoride phosphor plate, showing a luminous efficacy (LE) of 64 lm/W with a color rendering index of 74.

Vibronic relaxation dynamics of o-dichlorobenzene in its lowest excited singlet state

Vibronic dynamics of o-dichlorobenzene in its lowest excited singlet state, S1, is investigated in real time by using femtosecond pump-probe method, combined with time-of-flight mass spectroscopy and photoelectron velocity mapping technique. Relaxation processes for the excitation in the range of 276–252 nm can be fitted by single exponential decay model, while in the case of wavelength shorter than 252 nm two-exponential decay model must be adopted for simulating transient profiles. Lifetime constants of the vibrationally excited S1 states change from 651 ± 10 ps for 276 nm excitation to 61 ± 1 ps for 242 nm excitation. Both the internal conversion from the S1 to the highly vibrationally excited ground state S0 and the intersystem crossing from the S1 to the triplet state are supposed to play important roles in de-excitation processes. Exponential fitting of the de-excitation rates on the excitation energy implies such de-excitation process starts from the highly vibrationally excited S0 state, which is validated, by probing the relaxation following photoexcitation at 281 nm, below the S1 origin. Time-dependent photoelectron kinetic energy distributions have been obtained experimentally. As the excitation wavelength changes from 276 nm to 242 nm, different cationic vibronic vibrations can be populated, determined by the Franck-Condon factors between the large geometry distorted excited singlet states and final cationic states.

Deep red aggregation-induced CPL emission behavior of four-component tunable AIE-active chiral polymers via two FRET pairs mechanism

Two four-component chiral polymers with two Förster resonance energy transfer (FRET) pairs incorporating chiral 1,1′-binaphthyl, 4,7- di(thiophen-2-yl)-2,1,3-benzothiadiazole (DTBT), tetraphenylethene (TPE) and fluorene moieties were designed and synthesized via one-pot two-step of Pd-catalyzed Sonogashira reaction and Suzuki reaction by changing different ratios of DTBT chromophore and AIE-active TPE group. Both chiral polymers exhibit large Stokes shift (257 nm) and tunable red aggregation-induced emission (AIE) response behavior via two intramolecular FRET pairs by changing excitation wavelength. Interestingly, the chiral polymer with lower ratio of DTBT (P-1) shows obvious aggregation-induced circularly polarized luminescence (AICPL) emission signals in deep red region (around 650 nm) and higher glum, which can reach as high as ±2.0 × 10-3 in THF-H2O mixtures.

Concurrent synthesis of nitrogen-doped carbon dots for cell imaging and ZnO@nitrogen-doped carbon sheets for photocatalytic degradation of methylene blue

Abstract The hybrid composite of ZnO nanoparticles decorated nitrogen-doped graphitic carbon sheets (ZnO@N-C) alongside nitrogen-doped carbon dots (N-CDs) were synthesized by the direct hydrothermal method of peach fruit juice and ZnO nanoparticles (ZnO NPs). The synthesized ZnO@N-C hybrid composite and N-CDs were thoroughly characterized by various physicochemical techniques including powder X-ray diffraction (PXRD), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray (EDX) spectroscopy, high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, and fluorescence spectroscopy. The ZnO NPs were dispersed in the graphitic carbon structure with an average size of 25 ± 5 nm. The chemical composition of C, O, N, and Zn within the ZnO@N-C hybrid composite exhibits enough graphitization. Methylene blue (MB)-degradation was estimated utilizing the ZnO@N-C hybrid composite, a maximum degradation efficiency of >95% was achieved in a neutral aqueous medium within 60 min under UV-light irradiation. This maximum efficiency allows estimating the contribution of the heterogeneous and homogeneity of ZnO@N-C hybrid composite which is responsible for the MB-degradation. Moreover, the economic natural biosource or bio-waste was employed for the synthesis of ZnO@N-C hybrid composite and displays an excellent photocatalytic degradation under UV-light irradiation which is an alternate for other carbon-based metal oxides. In addition, the resulting N-CDs were utilized as a fluorescence probe for cellular imaging, owing to their tremendous properties such as bright fluorescence with high quantum yield, excellent water solubility, and good biocompatibility. The N-CDs displays a multicolour fluorescence based on their changing of excitation wavelength and these multicolour fluorescence emissions offered a multicolour cellular imaging which could be applicable for real biological system in the near future.

Green synthesis of carbon dots originated from Lycii Fructus for effective fluorescent sensing of ferric ion and multicolor cell imaging

Green, economical and effective method was developed for synthesis of fluorescent carbon dots (CDs), using one-pot hydrothermal treatment of Lycii Fructus. Optical and structural properties of the CDs have been extensively studied by UV–visible and fluorescence spectroscopic, x-ray diffraction (XRD) techniques, transmission electron microscopy (TEM) and high resolution TEM (HRTEM). Surface functionality and composition of CDs has been illustrated by Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS) spectra and elemental analysis. The fabricated CDs possess stable fluorescent properties. The fluorescent quantum yield of the CDs can reach 17.2%. The prepared CDs emitted a broad fluorescence between 415 and 545nm and their fluorescence was tuned by changing excitation wavelength. Meanwhile, the fluorescence intensity of the CDs could be significantly quenched by Fe3+ (turn-off). The CDs exhibit captivating sensitivity and selectivity toward Fe3+ with a linear range from 0 to 30μM and a detection limit of 21nM. The prepared CDs were successfully applied to the determination of Fe3+ in the urine samples, the water samples from the from the Yellow River and living HeLa (Henrietta Lacks) cells. Moreover, the low-toxicity and excellent biocompatibility of the CDs were evaluated through MTT assay on HeLa cells. The CDs were also employed as fluorescent probes for multicolor imaging of HeLa cells successfully.

Benzene expansion Janus GC base analogues: A detailed theoretical study

Density Functional Theory (B3LYP) and Time Dependent Density Functional Theory (TD-B3LYP) computations have been used to investigate the electronic structural and optical properties of the newly designed benzene expansion Janus GC bases (J-GC1, J-GC2 and J-GC3), and the effect of water solution and base pairing also has been considered. The results show that the benzene expansion J-GC bases can pair with G and C simultaneously to form stable H-bonded WC base pairs. The lowest absorption and emission wavelengths of J-GC1¡¢J-GC2 and J-GC3 are red shifted compared with J-GC due to the increase of effective conjugation length with the introduction of benzene. The oscillator strengths of J-GC1¡¢J-GC2 and J-GC3 are similar. The water solution greatly influences the properties of the excited states and the first excitation and emission wavelength changes in the range of 16–65nm. The water solution can increase the oscillator strengths of the absorption and emission spectra. The TD-B3LYP method predicts that the lowest excitation of J-GC3:C and J-GC2:G are charge transfer states, while the other base pairs present local transitions on the J-GC base moieties. The first excitation wavelengths of these local transition base pairs change in the range of 6–18nm indicating that H-bonding interaction can influence the first excitation energy.

Novel flexible coaxial nanoribbons arrays to help achieve tuned and enhanced simultaneous multicolor luminescence–electricity–magnetism trifunctionality

Flexible color-tunable coaxial nanoribbons array endowed with electricity and magnetism is obtained via coaxial electrospinning. Every single coaxial nanoribbon is composed of Fe3O4 nanoparticles (NPs)/polyaniline(PANI)/polymethylmethacrylate (PMMA) conductive-magnetic bifunctional core and [Eu(TTA)3(TPPO)2+Tb(TTA)3(TPPO)2]/PMMA [TTA = 2-Thenoyltrifluoroacetone radical, TPPO = tris(N,N-tetramethylene)phosphoric acid triamide] insulative-photoluminescent shell. In the coaxial nanoribbons array, the fluorescent color is adjustable in the range of green–yellow–red via modulating the mass ratios of RE(TTA)3(TPPO)2, (RE = Eu, Tb), PANI and Fe3O4 NPs, and changing excitation wavelength. The coaxial nanoribbons array possesses more excellent luminescent performance than the counterpart composite nanoribbons array. For the core of coaxial nanoribbons, the highest electrical conductivity reaches 3.152 × 10−2 S cm−1. Magnetism and electricity of the coaxial nanoribbons array can be tuned. Design philosophy and fabrication method provide a novel and facile strategy toward other nanomaterials with multifunctionality.

Interaction of phospholipase C with liposome: A conformation transition of the enzyme is critical and specific to liposome composition for burst hydrolysis and fusion in concert

Phospholipase C (PLC)1 is known to help the pathogen B. cereus entry to the host cell and human PLC is over expressed in multiple cancers. Knowledge of dynamic activity of the enzyme PLC while in action on membrane lipids is essential and helpful to drug design and delivery. In view of this, interactions of PLC with liposome of various lipid compositions have been visualized by testing enzyme activity and microenvironments around the intrinsic fluorophores of the enzyme. Overall change of the protein's conformation has been monitored by fluorescence spectroscopy and circular dichroism (CD). Liposome aggregation and fusion were predicted by increase in turbidity and vesicle size. PLC in solution has high fluorescence and exhibit appreciable shift in its emission maxima, upon gradual change in excitation wavelength towards the red edge of the absorption band. REES fluorescence studies indicated that certain Trp fluorophores of inactive PLC are in motionally restricted compact/rigid environments in solution conformation. PLC fluorescence decreased in association with liposome and Trps loosed rigidity where liposome aggregation and fusion occurred. We argue that the structural flexibility is the cause of decrease of fluorescence, mostly to gain optimum conformation for maximum activity of the enzyme PLC. Further studies deciphered that the enzyme PLC undergoes change of conformation when mixed to LUVs prepared with specific lipids. CD data at the far-UV and near-UV regions of PLC in solution are in excellent agreement with the previous reports. CD analyses of PLC with LUVs, showed significant reduction of α-helices, increase of β-sheets; and confirmed dramatic change of orientations of Trps. In case of liposome composed of lipid raft like composition, the enzyme binds very fast, hydrolyze PC with higher rate, exhibit highest structural flexibility and promote vesicle fusion. These data strongly suggest marked differences in conformation transition induced PLC activation and liposome fusion on the lipid composition.

N, B-doped carbon dots as a sensitive fluorescence probe for Hg2 + ions and 2,4,6-trinitrophenol detection for bioimaging

Nitrogen and boron co-doped carbon dots (BCNDs1–3) were prepared from three kinds of borate via a facile hydrothermal method. The as-prepared BCNDs did not shift with the change of excitation wavelength and possess good water dispersibility, strong fluorescence emission with high fluorescent quantum yield of 29.01%, 51.42%, 68.28%, respectively. Subsequently, these BCNDs were exploited as excellent Hg2+ ion and 2,4,6-trinitrophenol (TNP) probe. The efficient selective detection of Hg2+ can be attributed to non-radiative electron/hole recombination annihilation through an effective electron transfer process and the detection of TNP can be attributed to the fluorescence resonance energy transfer process (FRET). The results show that the BCNDs2 is the most sensitive fluorescence probe for Hg2+ ions and TNP detection as low as Hg2+ 7.3nM and TNP 0.35μM compared with BCNDs1 and BCNDs3. The as-prepared BCNDs possess the advantages of good selectivity, fast response and a broad linear detection. They were applied to sensing and imaging of human umbilical vein endothelial cells, showing low cytotoxicity and good biocompatibility.

Atomic Oxygen Tailored Graphene Oxide Nanosheets Emissions for Multicolor Cellular Imaging.

Graphene oxide (GO) has been widely used as a fluorescence quencher, but its luminescent properties, especially tailor-made controlling emission colors, have been seldom reported due to its heterogeneous structures. Herein, we demonstrated a novel chemical oxidative strategy to tune GO emissions from brown to cyan without changing excitation wavelength. The precise tuning is simply achieved by varying reaction times of GO nanosheets in piranha solution, but there is no need for complex chromatography separation procedures. With increasing reaction times, oxygen content on the lattice of GO nanosheets increased, accompanied by the diminution of their sizes and sp(2) conjugation system, resulting in an increase of emissive carbon cluster-like states. Thereby, the luminescent colors of GO were tuned from brown to yellow, green, and cyan, and its fluorescent quantum yields were enhanced. The obtained multicolored fluorescent GO nanosheets would open plenty of novel applications in cellular imaging and multiplex encoding analysis.

Syntheses, crystal structures and luminescence properties of lanthanide-based coordination polymers constructed from a functionalized terpyridyl carboxylate ligand

Six families of new lanthanide coordination polymers, [Ln2(L)6(H2O)2]n·3nH2O (Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6), Ho (7), Er (8), Yb (9)), [Pr2(L)2(ox)2(H2O)4]n·9nH2O (10), [Pr2(L)2(glu)2(H2O)2]n (11), [Er2(L)2(glu)2]n (12), [Nd2(L)2(adip)2]n (13), [Ln2(L)2(1,2-bdc)2(H2O)2]n (Ln = Eu (14), Gd (15), Er (16)), (HL = 4′-(2-carboxyphenyl)-4,2′:6′,4′′-terpyridine, H2ox = oxalic acid, H2glu = glutaric acid, H2adip = adipic acid, H2(1,2-bdc) = benzene-1,2-dicarboxylic acid) were synthesized under hydrothermal conditions and characterized by elemental analysis, IR and single crystal X-ray diffraction. Compounds 1–9 are isomorphic 1D chain structures based on binuclear Ln(III) units. Compound 10 is a 1D chain, where L− ligands dangle on two sides of the Pr-ox zigzag chain. Compounds 11 and 12 exhibit distinct 2D-layer structures consisting of Ln2(COO)4 binuclear units. Compound 13 displays an appealing 3D network structure, where the auxiliary ligand H2adip plays a significant role in the self-assembly process. Compounds 14–16 present a 1D-chain structure which is extended to a 2D-supramolecular framework by means of weak interactions. The diverse structures further verify the potential of HL ligand in the preparation of coordination polymers with new structures and properties. The effects of auxiliary ligands and coordination modes of HL ligand on the crystal architectures are discussed. The solid-state luminescence and thermal stabilities of compounds 1–16 also were studied. Based on the luminescent properties, we have designed and constructed successfully a series of doped-lanthanide MOF by adjusting the co-doping ratio of Eu(III) and Tb(III) into the same framework as that of 1–9. Interestingly, the luminescent colors of the Eu(III)-doped Tb(III) compounds can be tuned with change of excitation wavelength. Moreover, white-light emission was achieved on excitation at 330 nm.

Luminescent monolayer MoS2 quantum dots produced by multi-exfoliation based on lithium intercalation

An effective multi-exfoliation method based on lithium (Li) intercalation has been demonstrated for preparing monolayer molybdenum disulfide (MoS2) quantum dots (QDs). The cutting mechanism of MoS2 QDs may involve the complete breakup around the defects and edges during the reaction of LixMoS2 with water and its following ultrasonication process. The multiply exfoliation make the MoS2 fragile and easier to break up. After the third exfoliation, a large number of monolayer MoS2 QDs is formed. The as-prepared MoS2 QDs show photoluminescence (PL) inactive due to the existence of 1T phase. After heating treatment, the PL intensity excited at 300nm is enhanced by five times. The MoS2 QDs solution has an excitation-dependent luminescence emission which shifts to longer wavelengths when the excitation wavelength changes from 280nm to 370nm. The optical properties are explored based on the quantum confinement and edge effect.

Liquid nitrogen-assisted synthesis of fluorescent carbon dots from Blueberry and their performance in Fe3+ detection

Fluorescent carbon dots (C-dots) were synthesized by a facile method containing liquid N2 treatment and centrifuge processes. The photophysical properties of the C-dots in an aqueous solution were examined at various conditions such as concentration, temperature, pH and excitation wavelength by using UV–vis absorption, fluorescence and time-resolved fluorescence spectroscopies. The C-dots emitted a broad fluorescence between approximately 350–550nm and their fluorescence was tuned by changing excitation wavelength. The as-prepared C-dots were applied to Fe3+ detection from aqueous solution. Spectroscopic data revealed that the as-prepared C-dots were used to detect Fe3+ in the range of 12.5μM to 100μM as a fluorescence sensor.