Synthesis and characterizations of MoS2 nanoflowers and spectroscopic study of their interaction with bovine serum albumin.

Molybdenum disulfide nanoflowers (MoS2 NFs) were prepared by hydrothermal method. The prepared MoS2 NFs was characterized by SEM, TEM, XRD, specific surface areas, Raman and XPS. The characterization results show that the flower-like spherical MoS2 is composed of many ultra-thin nanosheets with an average diameter of about 300-400 nm. MoS2 NFs also exhibits excellent absorption and high fluorescence intensity. In order to explore the biological behavior of MoS2 NFs, the interaction between MoS2 NFs and bovine serum albumin (BSA) was studied by UV-Vis absorption, fluorescence, synchronous fluorescence spectra, and cyclic voltammetry. The results of absorption and fluorescence show that MoS2 NFs and BSA interact strongly through the formation of complexes. The Stern-Volmer constant and the quenching constant was calculated about 3.79×107 L mol-1 and 3.79×1015 L mol-1 s-1, respectively. The synchronous fluorescence implied that MoS2 in the complex may mainly bind to tryptophan residues of BSA. The cyclic voltammograms indicated that the addition of BSA makes electron reduction of MoS2 NFs more difficult than the corresponding free state. These experimental results clarified the effective transportation and elimination of MoS2 NFs in the body by binding to BSA, and can provide useful guideline for estimating MoS2 NFs as a drug carrier.

Detection of intracellular microRNA-21 for cancer diagnosis by a nanosystem containing a ZnO@polydopamine and DNAzyme probe.

MicroRNAs (miRNAs) are a series of single-stranded non-coding ribonucleic acid (RNA) molecules which associated closely with various human diseases. Efficient strategies for detecting miRNAs are of great significance to cancer diagnosis and prognosis. Here we provide a novel nanosystem that can be applied for the detection of miRNAs. The nanosystem consists of a single-stranded deoxyribonucleic acid (DNA) probe and a probe carrier. The DNA probe was designed based on a deoxyribozyme (DNAzyme) with several necessary functional sequences and two fluorescent dyes labeled at proper sites. The ZnO@polydopamine (ZnO@PDA) nanomaterial serves not only as a probe carrier, but also as a supplier of Zn2+ that can activate the DNAzyme. The DNA probe will undergo a conformation alteration induced by miRNA-21, which then trigger the DNAzyme catalyzed self-cleavage reaction with the assist of Zn2+ provided by ZnO decomposition under weak acid environment. A change of fluorescent color will occur due to the interruption of fluorescence resonance energy transfer between the two fluorescent dyes, and the dissociated miRNA-21 can repeatedly induce the above responses to amplify the fluorescence signal. The feasibility of the whole procedure was demonstrated by various experiments. This nanosystem showed a good selectivity towards miRNA-21, and under the optimal incubation time of 2 hours, a good linear relationship was obtained in a concentration range of 0.01-2.0 nM with a detection limit of 3.8 pM. In in vivo detection, an obvious fluorescence color change from red to green can be observed in the presence of miRNA-21. The results proved that this miRNA detection strategy has a broad application prospect in tumor diagnosis and miRNA related biological studies.

One-pot preparation of supramolecularly functionalized silver nanoparticles for surface plasmon resonance based dual-modal sensing of phytotoxic polychlorinated biphenyl.

Polychlorinated biphenyls (PCBs), as a member of persistent organic pollutants (POPs), have posed a risk to humans and the environment until today. The monitoring of phytotoxic PCB which is toxic to plants, is especially important for ecological early warning and pollution management. In this work, ß-cyclodextrin modified silver nanoparticles are prepared in a one-pot method, integrating the synthesis and surface modification in one step. The nanoparticles can supramolecularly immobilize 2,4,4'-trichlorobiphenyl (PCB 28) on their surface and construct a surface plasmon resonance-based nanosensor. Surface plasmon-resonance light scattering and surface-enhanced Raman scattering sensing of PCB 28 are realized using the nanosensor. The dual-modal sensing shows excellent performance for the potential practical monitoring of phytotoxic POPs in the plant and its growing environment.

Perylene tetra-(alkoxycarbonyl) derivative and its copper chelate for selective sensing of fluoride ions.

Two novel fluoride ion fluorescent probes (P1 and P2) containing perylene tetra-(alkoxycarbonyl) derivative (PTAC) and its copper chelate were designed and synthesized. The identification properties of the probes were studied by absorption and fluorescence methods. The results showed that the probes were highly selective and sensitive to fluoride ions. 1H NMR titration confirmed that the sensing mechanism involved the formation of H-bond between the O-H moiety and fluoride ions, and the coordination of copper ion could enhance the H-bond donor capacity of the receptor unit (O-H). The corresponding orbital electron distributions were calculated by density functional theory (DFT). In addition, fluoride ion can be easily detected by probe-coated Whatman filter paper without the need for expensive equipment. Until now, there have been few reports of such probes enhancing the capacity of the H-bond donor based on metal ion chelation. This study will contribute to the design and synthesis of novel sensitive perylene fluoride probes.

Molecular dynamics study of low molecular weight gel forming salt-triggered dipeptide.

Molecular dynamics simulation method was used to study the aggregation of Na and Ca salts in different concentrations of Naphthalene-dipeptide (2NapFF) solutions. The results show that high-valence Ca2+ triggers the formation of a gel at a certain dipeptide concentration, and the low-valence Na+ system follows the aggregation law of general surfactants. The results also show that hydrophobic and electrostatic forces are the main driving forces for the formation of dipeptide aggregates, and that hydrogen bonds do not play a major role in the formation of dipeptide solution aggregates. Hydrophobic and electrostatic effects are the main driving forces for the formation of gels in dipeptide solutions triggered by Ca2+. Electrostatic attraction drives Ca2+ to form a weak coordination with four oxygen atoms on two carboxyl groups, which causes the dipeptide molecules to form a gel with a branched network structure.

Visible-light photoelectrocatalysis/H2O2 synergistic degradation of organic pollutants by a magnetic Fe3O4@SiO2@mesoporous TiO2 catalyst-loaded photoelectrode.

In this paper, we describe a method for photoelectrocatalysis (PEC)/H2O2 synergistic degradation of organic pollutants with a magnetic Fe3O4@SiO2@mesoporous TiO2 (FST) photocatalyst-loaded electrode. At optimal conditions of pH 3.0, 2.25% H2O2, working electrode (fixed FST 30 mg) potential +0.6 V (vs. SCE), and 10 mg L-1 of all experimental pollutants, the FST PEC/H2O2 synergistic system exhibited high activity and stability for the removal of various organic pollutants under visible light with comparable degradation efficiencies, including MB (98.8%), rhodamine B (Rh B, 96.7%), methyl orange (MO, 97.7%), amoxicillin (AMX, 83.9%). Moreover, this system obtained TOC removal ratios of 83.5% (MB), 77.9% (Rh B), 80.2% (MO), 65.5% (AMX) within 8 min. The kinetic rate constants of the PEC/H2O2 synergistic system were nearly 53 and 1436 times higher than that of the PEC process and H2O2 photolysis under visible light, respectively. Furthermore, the main reactive oxidant species (˙OH, ˙O2 -) were studied and enhanced mechanisms of the photocatalytic-electro-H2O2 coupling system were proposed. This work brings new insights to efficiently purify organic pollutants by PEC coupled with peroxide under solar light illumination.

A novel colorimetric and fluorescent probe based on a core-extended perylene tetra-(alkoxycarbonyl) derivative for the selective sensing of fluoride ions.

A novel fluoride (F-) colorimetric and fluorescent probe (P1) based on a core-extended perylene tetra-(alkoxycarbonyl) (PTAC) derivative was developed. The probe exhibited high sensitivity and selectivity for distinguishing F- from other common anions through significant changes of the UV-Vis and fluorescence spectra. Job's plot analysis revealed that the stoichiometry of the P1-F- interaction is 1 : 1. The association constant between P1 and F- was estimated to be 9.7 × 102 M-1 and the detection limit of F- was about 0.97 µM. An approximately 76 nm red-shift in the absorption and fluorescent quenching response was observed when F- was associated with P1. The emission intensity (I 574) decreased linearly along with the F- concentration from 3 × 10-5 M to 2 × 10-4 M. The mechanism of intermolecular proton transfer (IPT) was deduced based on the changes in the absorption, fluorescence, electrochemistry, and 1H NMR titration spectra. The density functional theory (DFT) theoretical results of the P1-F- complex are in good agreement with the experimental results. The rapid detection of F- ions in the solid state and living cells was also studied.

Hydrothermal synthesis of novel 1-aminoperylene diimide/TiO2/MoS2 composite with enhanced photocatalytic activity.

1-aminoperylene diimide/TiO2/MoS2 composite (NH2-PDI/TiO2/MoS2) with ordered structure was prepared by hydrothermal synthesis method. The composite was characterized by XRD, SEM, FTIR, XPS, BET, DRS, PL, EIS, Raman, photocurrent, and Mott-Schottky plots spectroscopy. The potential positions of the conduction and valence bands, and the band gap energy of the semiconductors were estimated. The composite exhibited higher photocatalytic activity compared with the mono-component systems. The apparent rate constants (k) were determined as 0.00616, 0.00352, 0.00738, 0.00517, 0.00752, and 0.00806 min-1 for TiO2, NH2-PDI, NH2-PDI/TiO2, MoS2, MoS2/TiO2, and NH2-PDI/TiO2/MoS2, respectively. The detection of radical scavengers confirmed that superoxide radicals, photogenerated holes, and photogenerated electrons were the main active substances for MB degradation. Between type II- heterojunction mechanism and Z-scheme mechanism, the latter could explain the enhanced photocatalytic activity of the composite better. The Z-scheme mechanism accumulates more electrons at CB level of NH2-PDI and hence generates more super oxide radicals.

Colorimetric and ratiometric fluorescent response for anthrax bio-indicator: A combination of rare earth MOF and rhodamine-derived dye.

Bacillus anthracis spores have a unique biomarker of calcium dipicolinate (CaDPA). In this work, we reported a composite nanostructure for the optical sensing of DPA, with Eu (III)-doped metal-organic framework (MOF) as supporting lattice, a rhodamine-derived dye as sensing probe, respectively. By means of XRD, IR, TGA and photophysical analysis, this composite structure was carefully discussed. It was found that rhodamine absorption and emission were enhanced by DPA, while Eu emission was quenched by DPA. As a consequence, two sensing skills were observed from this composite structure, which are colorimetric sensing based on absorption spectra and ratiometric fluorescent sensing based on emission spectra. Linear sensing response was observed for both sensing channels with a warning signal at DPA concentration higher than 140 µM. Good selectivity was confirmed with a low LOD value of 0.52 µM. The sensing mechanism was revealed as the combination of emission turn-on effect triggered by DPA-released protons and emission turn-off effect originated from electron-transfer from EuBTC to DPA. This composite structure showed its advantage of naked eye detection and two sensing skills with linear response.

Real roles of perylene diimides for improving photocatalytic activity.

Three novel visible-light-driven composite photocatalysts: five-membered O-heterocyclic annulated perylene diimide doped TiO2 (PDI-1/TiO2), 1-phenol-N,N'-dicyclohexyl perylene-3,4,9,10-tetracarboxylic diimide doped TiO2 (PDI-2/TiO2), and N,N'-dicyclohexyl perylene diimide doped TiO2 (PDI-3/TiO2), were synthesized using a hydrothermal synthesis method. The effects of introducing PDIs with different structures into TiO2 were evaluated by assaying the photodegradation rate of Methylene Blue (MB). The photoactivities of the PDI-1/TiO2 and PDI-2/TiO2 catalysts were better than that of PDI-3/TiO2. This is because the large surface area of PDI-1 nanorods and PDI-2 nanobelts extended the 1D charge carrier channel, which facilitated electron transfer to the TiO2 surface and improved the photocatalytic activity of the composites. The PDI-1/TiO2 composite showed the highest photoactivity, and the activity remained at 86.4% after four reuse cycles. The extended π-π stacking of self-assembled PDI-1 and the strong interactions between self-assembled PDI-1 and TiO2 played significant roles in accelerating charge transfer and decreasing recombination of photogenerated electron-hole pairs. The steric hindrance of the phenoxy substituent at the bay position of PDI-2 prevented the PDI-2 nucleus from contacting TiO2 and weakened the interaction between PDI-2 and TiO2, which further resulted in the low photoactivity of PDI-2/TiO2. This work provides a practical way to improve the performances of traditional organic and inorganic composite photocatalysts.

Efficient lead ion removal from water by a novel chitosan gel-based sorbent modified with glutamic acid ionic liquid.

Three novel and highly effective AAIL-modified Chitosan (CS) adsorbents are presented. These three new CS-gels were prepared by an innovative synthetic method that uses amino acid ionic liquids (AA-ILs) to cross-link CS with, separately, glutamic acid, aspartic acid and alanine to give novel adsorbents Glu-AA-IL-CS (1), Asp-AA-IL-CS (2) and Ala-AA-IL-CS (3) respectively. The effectively incarcerating host-structures (1) - (3) were characterized by a whole range of techniques including FT-IR, SEM, EDS and XRD. The differences amongst novel adsorbents (1) - (3) with regard to their rate and efficiency of removal of Pb2+ from aqueous solutions are explained in terms of the different electronic, structural and steric features of the three amino acids. The glutamic acid variant (1) is clearly shown to be the best-performing adsorbent by experimental tests and data in combination with infrared spectroscopy. The behaviour of adsorbents (1) follows pseudo-second-order kinetics,and accord best with the Freundlich adsorption isotherm.

Self-assembly, optical and electrical properties of perylene diimide dyes bearing unsymmetrical substituents at bay position.

Perylene diimides (PDIs) are one class of the most explored organic fluorescent materials due to their high luminescence efficiency, optoelectronic properties, and ready to form well-tailored supramolecular structures. However, heavy aggregation caused quenching (ACQ) effect in solid state has greatly limited their potential applications. We have easily solved this problem by chemical modification of the PDI core with only phenoxy moietie at one of the bay position. In this paper, we report two perylene bisimides with small rigid substituents, 1- phenol -N, N'-dicyclohexyl perylene-3,4,9,10-tetracarboxylic diimide (PDI 1) and 1- p-chlorophenol-N, N'-dicyclohexyl perylene-3,4,9,10-tetracarboxylic diimide (PDI 2) possess both well defined organic nanostructures and high fluorescence quantum yield in the solid state. In contrast, 1-propanol-N, N'-dicyclohexyl perylene-3,4,9,10-tetracarboxylic diimide (PDI 3) bearing a straight chain only shown weak orange fluorescence. In addition, morphological inspection demonstrated that PDI 3 molecules easily form well-organized microstructures despite the linkage of the PDI core with a straight chain. The present strategy could provide a generic route towards novel and advanced fluorescent materials and these materials may find various applications in high-tech fields.

Novel fluorescent probes for the fluoride anion based on hydroxy-substituted perylene tetra-(alkoxycarbonyl) derivatives.

The fluoride anion (F-) sensing abilities of 1-hydroxyl-3,4,9,10-tetra (n-butoxyloxycarbonyl) perylene (probe 1) and 1-hydroxyl-mono-five-membered S-heterocyclic annulated tetra (n-butoxyloxycarbonyl) perylene (probe 2) were studied through visual detection experiments, UV-Vis, fluorescence, and 1H NMR titrations. The probes were sensitive and selective for distinguishing F- from other anions (Cl-, Br-, I-, SO4 -, PF6 -, H2PO4 -, BF4 -, ClO4 -, OH-, CH3COO-, and HPO4 2-) through a change of UV-Vis and fluorescence spectra. The absorption and fluorescence emission properties of the probes arise from the intermolecular proton transfer (IPT) process between a hydrogen atom on the phenolic O position of probe and the F- anion. The sensing mechanism was supported by theoretical investigation. Moreover, probe-based test strips can conveniently detect F- without any additional equipment, and they can be used as fluorescent probes for monitoring F- in living cells.

A water-soluble fluorescent pH probe based on perylene dyes and its application to cell imaging.

A fluorescent pH probe, N,N'-bi( l-phenylalanine amine)-perylene-3,4;9,10-dicarboxylic diimide (PDCDA) was synthesized and used for pH sensing in living cells. A significant fluorescence intensity change was observed over a pH range from 7.0 to 4.0. Electrostatic potential maps (MEP) suggested that the electronic repulsion between PDCDAs was increased by the high negative electrostatic potential which resulted in a high water solubility of PDCDA. PDCDA was successfully applied as a high-performance fluorochrome for living HeLa cell imaging. The results demonstrate that the probe PDCDA is a good candidate for monitoring pH fluctuations in living cells with good water solubility, low cytotoxicity, high fluorescence quantum yield and photostability.