Mixed micelles from methoxy poly(ethylene glycol)–polylactide and methoxy poly(ethylene glycol)–poly(sebacic anhydride) copolymers as drug carriers

mPEG–PLLA (poly l-lactic acid) is synthesized by ring-opening polymerization of lactide and conjugation with mPEG. Sebacic acid is modified with acetic anhydride and condensed with mPEG to form mPEG–PSA (poly sebacic anhydride). The micelles formed by mPEG–PLLA are characterized by slow degradation and low drug encapsulation efficiency; on the contrary, mPEG–PSA micelles are characterized by rapid degradation but high encapsulation efficiency. They can merge into spherical micelles (Φ = 140 nm) by self-assembly in water. The mixed micelles can successfully encapsulate a typical hydrophobic drug (curcumin), and significantly improve its solubility. Experimental results show that the mixed micelles have the features of high encapsulation efficiency and slow degradation.     

Sustained release of ibuprofen from polymeric micelles with a high loading capacity of ibuprofen in media simulating gastrointestinal tract fluids

Amphiphilic diblock copolymers with poly(ethylene glycol) as the hydrophilic block and a random copolymer of n-butyl methacrylate or styrene and (N,N-diethylamino)ethyl methacrylate as the hydrophobic block were prepared by atom transfer radical polymerization (ATRP). Ibuprofen, a model drug that contains a carboxylic group and hydrophobic moiety, was loaded into micelles formed from the amphiphilic diblock copolymers by a combination of ionic interaction and hydrophobic effect. The loading capacity of ibuprofen in the micelles reached 60%. Loaded ibuprofen was released in a sustained fashion into media simulating gastric fluid (pH 1.6, 2 h), small intestinal fluid (pH 7.4, 4 h), and colon fluid (pH 6.7, 18 h). Simulating the case of oral administration at 2 doses per day, loaded ibuprofen was released almost linearly against time after the second dose in media simulating human gastrointestinal tract fluids.     

A novel chromo- and fluorogenic dual responding H2PO4− receptor based on an azo derivative

A simple, novel anion receptor based on 4-hydroxy-3-(N-phenyl-thiourea-N′-nitrilo-methylidynyl)-azobenzene with hybrid –OH and thiourea binding sites was synthesized and characterized. Anion binding character was determined using visual inspection, UV–vis, fluorescence and ¹H NMR analyses. The addition of F^?, AcO^? and H₂PO₄^? resulted in a marked red shift of the charge-transfer absorbance band (Δλ = 140 nm, from 340 nm to 480 nm) accompanied by a color change from light yellow to orange.     

pH-Sensitive hydrogels formed by self-assembled amphiphilic triblock copolyelectrolytes

Results are reviewed of a recent extensive investigation of the behavior of self-assembled pH-sensitive triblock copolymers in aqueous solution. The hydrophilic central block was polyacrylic acid and the two hydrophobic end-blocks were statistical copolymers of n-butyl acrylate and acrylic acid containing 50 mol% acrylic acid units. The hydrophobicity of the end blocks could be modified by changing the degree of ionization of the acrylic acid units (α). The relationship between the pH and α was determined. Scattering techniques showed that flower-like micelles are formed that upon increasing concentration connect via bridging into larger aggregates and above a critical concentration into a percolating network. The rheology of the system is controlled by the exchange rate of the end-blocks between micelles and can be fine-tuned by varying the pH. The exchange rate increases exponentially with increasing α. As a consequence the system changes from a quasi-permanent hydrogel at pH < 4.5 to a free flowing liquid at pH > 5.5. The effect of the ionic strength on the structure and the rheology was found to be important only above 0.5 M.     

Y2O3:Yb,Tm and Y2O3:Yb,Ho powders for low-temperature thermometry based on up-conversion fluorescence

Recently, trivalent rare earth doped materials have received significant attention due to the strong temperature dependence of the fluorescence emission of these materials, which can be useful in temperature sensing. Here, we investigated Y₂O₃ ceramic powders doped with Yb³⁺ and co-doped with either Tm³⁺ or Ho³⁺. The powders were obtained via spray pyrolysis at 900 °C and additionally thermally treated at 1100 °C for 24 h. Structural characterization using X-ray powder diffraction confirmed the cubic bixbyte structure. Scanning electron microscopy (SEM) revealed that the particles exhibit a uniform spherical morphology. The up-conversion emissions were measured using laser excitation at 978 nm, resulting in the following transitions: blue emission in the range of 450–500 nm, weak red emission in the range of 650–680 nm and near infrared emission in the range of 765–840 nm for Tm³⁺, as well as green emission centered at 550 nm and weak near infrared emission at 755 nm for the Ho³⁺ ions. In addition, the temperature dependence of the fluorescence intensity ratios of different Stark components was analyzed in the range of 10–300 K. Significant temperature sensitivity was detected for several components, with the largest value of 0.097 K^?1 related to the intensity ratio of I₅₃₆ and I₇₇₂ emissions observed for the Y₂O₃:Yb,Ho powder.     

The effects of pulse repetition rate on the structural,surface morphological and UV photodetection properties of pulsed laser deposited Mg-doped ZnO nanorods

The Mg_0.05Zn_0.95O (MZO) nanorod array (NRA) films have been successfully grown onto SiO₂/ n-Si substrates by pulsed laser deposition (PLD) without any template or seed layer and the influence of pulse repetition rate (3 to 15 Hz) of a 248 nm KrF excimer laser on their crystallinity, surface morphology and UV photodetection properties were systematically investigated. All the samples show the hexagonal wurtzite phase with a preferential c-axis orientation and the optimum crystallization of the MZO NRAs occurs at 5 Hz. FE-SEM analysis revealed that the growth of MZO NRAs is strongly influenced by the pulse repetition rate. It was observed that the average film thickness increases almost linearly with the pulse repetition rate and the MZO nanorod arrays grown at 5 Hz exhibits best surface area. Moreover, the room temperature UV photodetection properties of the samples were investigated in metal–semiconductor–metal (MSM) planar configurations and are found to be strongly driven by the pulse repetition rate dependent crystalline and surface morphological features. The device current–voltage (I–V) characteristics were measured under dark and UV light conditions. Then, the photocurrent and responsivity were measured with the variation of optical power density and applied voltage, respectively. Transient photoresponse studies show an exceedingly stable and fast switching UV photoresponse for the photodetector having MZO nanorods grown at 5 Hz, which demonstrates highest responsivity of 17 mA/W upon 2 mW/cm² UV illumination (365 nm), at 5 V bias.     

A new copper(II) selective fluorescence probe based on naphthalimide: Synthesis,mechanism and application in living cells

A new fluorescence probe L based on naphthalimide has been synthesized for selective and quantitative detection of Cu^2 + in CH₃CN:H₂O (4:1, v/v) solution. L exhibited a strong green fluorescence. Upon addition of 2 equiv. of Cu^2 +, the fluorescence emission shows a steady and smooth decrease until a plateau is reached with a 30-fold quenching of fluorescence intensity. In the presence of Cu^2 +, the absorbance peak of L maximum at 466 nm decreased, and a new absorption band at 600 nm appeared. Under the identical conditions, other physiological and environmental important metal ions induced negligible spectroscopic changes. The 1:2 stoichiometry binding mode of L with Cu^2 + was supported by the Benesi–Hildebrand analysis and ESI-MS spectra studies. The detection limit for Cu^2 + was estimated to be 64 ppb. Fluorescence microscopy experiments showed that L has practical application in living cells.     

Blue emission of a 2D non-interpenetrated zinc coordination polymer constructed through saturated fatty acid ligand

We report a new non-interpenetrated 2D zinc coordination polymer, [Zn(AA)(BPHY)]_n (1) (H₂AA = adipic acid, BPHY = 1,2-bis(4-pyridyl)hydrazine), which is a mixed ligand complex. The solid-state sample of 1 exhibits tunable blue emission excited by UV light with the wavelengths from 320 nm to 380 nm. The luminescent mechanism of 1 has been studied by theoretical calculation.     

Ultraviolet and visible Raman spectroscopies of the graphitic BCx phases

Ultraviolet (UV) Raman and visible Raman spectroscopies were applied to study the graphitic BC_x (g-BC_x) phases. The Raman spectra of the g-BC_x phases excited with UV laser at 244 nm have one main peak: a G peak (approximately at 1590 cm^? 1), and do not have the D peak (around 1350 cm^? 1) characteristic for Raman spectra of disordered graphitic phases. The D peak can be detected in all g-BC_x phases when green (534 nm) or near-infrared (785 nm) lasers are used for Raman scattering excitation. The positions of the G and D peaks were found to be independent (within the experimental errors) of the B/C ratio. The pattern of the peaks in UV Raman spectra of g-BC_2.1 phase indicates that the additional peaks centered at 1089 cm^? 1 should be assigned to the E_g mode of B₄C vibration rather than to the T mode characteristic to amorphous graphite. The high signal-to-noise (S/N) ratio and lack of fluorescence of the UV Raman spectra allow an accurate measure of bandwidth and frequency of the G peaks.     

Synthesis,characterization and kinetics properties of chromium(III) complex [Cr(3-HNA)(en)2]Cl · H2O · CH3OH

The reaction of chromium(III) chloride, 3-hydroxy-2-naphthoic acid (3-HNA) and ethylenediamine (en) led to the formation of complex [Cr(3-HNA)(en)₂]Cl · H₂O · CH₃OH, Bis(ethylenediamine-κ²N,N′)(3-hydroxy-2-naphthoic acid-κ²O,O′) chromium(III) monochloride monohydrate monomethanol. The kinetics of transfer of Cr(III) from the title compound to the low-molecular-mass chelator EDTA and to the iron-binding protein apoovotransferrin (apoOTf) were carried out by means of UV–Visible (UV–Vis) and fluorescence spectra in 0.01 M Hepes at pH 7.4. The second-order rate constants were calculated, respectively. The results show that Cr(III) can be transferred from the complex to apoovotransferrin.     

A novel cobalt(II) acylpyrazolonate complex with intermolecular hydrogen bond: Synthesis,structure and properties

A new cobalt complex, [Co(L)₂·(H₂O)₂](HL = 4-hexanoyl-3-methyl-1-phenyl-1H -pyrazol-5(4H)-one), was synthesized by us. The complex was characterized by single crystal X-ray diffraction, IR, UV, fluorescence spectra and thermogravimetric analysis. The results of characterization showed that the crystal is monoclinic system with crystal parameters: a = 15.2439(12) Å, b = 7.4101(6) Å, c = 15.7381(18) Å, and Z = 2, S = 1.074. It was found that the Co²⁺ is located in the inversion center of the complex. The Co(II) had an ideal octahedral coordination environment with four oxygen atoms of HL ligands in the equatorial plane and two water molecules in axial positions. The complex exhibits yellow emission as the result of the fluorescence from the intraligand emission excited state.     

Deposition of silver nanoparticles on single wall carbon nanotubes via a self assembled block copolymer micelles

We demonstrate a facile route to decorate the surface of networked single walled carbon nanotubes (SWNTs) with silver nanoparticles (Ag NPs). The method is based on utilization of either spherical poly(styrene-b-4vinylpyridine) (PS-b-P4VP) or cylindrical poly(styrene-b-acrylic acid) (PS-b-PAA) copolymer micelles capable of stabilizing nanotubes in solution and subsequently forming a thin and uniform block copolymer/SWNTs composite film upon spin coating. The selective doping of silver acetate into either P4VP or PAA domains in a thin composite film, followed by thermal treatment, results in the formation of Ag NPs in the cores of micelles. Further heat treatment at 500 °C sufficiently high for degrading both block copolymers allows us to fabricate a thin SWNTs network in which Ag NPs are efficiently deposited on the surface of nanotubes. A sharp surface plasmon absorption band around 400 nm of the networked SWNTs with Ag NPs confirms the presence of Ag NPs with narrow distribution in their size.     

DNA interaction and cytotoxic activity of copper complex based on tridentate hydrazone derived ligand and nitrogen donor heterocycle

Tetra coordinated copper(II) complex of formula [Cu(L¹)(imid)] is synthesized using imidazole and a tridentate O,N,O hydrazone ligand L¹ prepared by condensation of 1,1,1-trifluoropentanedione and 4-chlorobenzhydrazide. The ligand and complex are characterized by UV–Visible, FTIR, NMR, mass and single crystal XRD techniques. DNA binding mode is assessed by UV absorption, fluorescence spectral and circular dichroism studies. Based on the results, it is observed that complex has preferred intercalative mode of binding with DNA. The binding constant, K_b, was found to be 4.02 ± 0.09 × 10⁴ M^− 1. Thermodynamic parameters such as ΔH, ΔS and ΔG obtained from acridine orange fluorescence displacement assay revealed that the hydrophobic and hydrogen bonding interactions are playing a major role in the binding pattern. In addition, cytotoxicity of the complex towards MCF-7 breast cancer cell line has also been assessed.     

Synthesis,structural characterization,opto-electrical properties of Ir(III) complexes with imidazolium-based carbene ligands

A series of Ir(III) complexes with N–heterocyclic carbenes (NHC) ligands (1–3) were synthesized and characterized. The opto-electrical properties of these complexes were investigated spectroscopically, electrochemically and theoretically. All complexes exhibit ligand-based ¹π,π* transitions in the UV region, ¹MLCT absorption in the UV region, and weak low energy ³π, π* transition in visible region. These complexes all exhibit blue phosphorescence at both room temperature and 77 K, which is dominated by ³π,π* character. DFT calculation results indicate their lowest unoccupied molecular orbitals (LUMO) from − 0.47 to − 0.33 eV and the highest occupied molecular orbitals (HOMO) from − 4.97 to − 5.33 eV. The opto-electrical properties can be influenced drastically by NHC ligands, which would be useful for rational design of optical functional materials.     

Synthesis,photophysical and photochemical studies of benzophenone based novel monomeric and polymeric photoinitiators

Four novel benzophenone-containing photoinitiators (monomers PI-1 and PI-2 and their polymers PPI-1 and PPI-2) were prepared from alkyl α-hydroxymethacrylates. PI-1 was synthesized from reaction of tert-butyl α-bromomethacrylate and 4-hydroxybenzophenone followed by cleavage of tert-butyl groups using trifluoroacetic acid. PI-2 was synthesized from reaction of ethyl α-bromomethacrylate and 3-benzoylbenzoic acid. Thermal polymerization of PI-1 and PI-2 was performed using 2,2′-azobis(isobutyronitrile). PI-1 and PPI-1 show UV absorption (289 and 294 nm) which are red-shifted compared to benzophenone (252 nm), PI-2 (255 nm) and PPI-2 (252 nm). All of the photoinitiators give phosphorescence emissions from their n–π* states. The photopolymerizations of triethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate and hexanediol diacrylate initiated by PI-1, PI-2, PPI-1, PPI-2 and benzophenone were studied by photo-differential scanning calorimeter using N,N-dimethyl-p-toluidine as coinitiator. Polymeric photoinitiators were found to have higher efficiencies than benzophenone and monomeric ones. Photopolymerization results are also compared to that of an alkyl α-hydroxymethacrylate-based photoinitiator previously reported by us; and the influence of monomer structure on polymerization efficiency is discussed.     

Preparation and characterization of fluorescent hyperbranched polyether

A new kind of fluorescent hyperbranched polymers was prepared by an end-capping approach, i.e., the hyperbranched poly(hydroxyl ether) was end capped with p-N,N-dimethylaminobenzaldehyde. The resulting polymers fluoresce yellow-green in solid and in solution. The maximum excitation and emission wavelengths in ethanol are 310 ± 10 and 360 ± 10 nm, respectively. Hyperbranched polyethers with various densities of chromophore groups showed different fluorescence intensities at the same concentration of chromophore groups. The fluorescent hyperbranched polyether with a high density of chromophore groups can form intramolecular excimers. The fluorescence signal of the resulting polymer increases with pH and passes through a maximum at 7.2–8.5 and then decreases gradually. Furthermore, the peak at 360 nm shifts to 405 nm with increasing pH. The fluorescence can be quenched by transition metal cations such as Cu²⁺ and Fe³⁺, while the alkali and alkaline earth metal cations and Ni²⁺ and Co²⁺ have little effect on the fluorescence intensity.     

Fluorescence resonance energy transfer sensor between quantum dot donors and neutral red acceptors and its detection of BSA in micelles

Bovine serum albumin in micelles was effectively detected by a fluorescence resonance energy transfer -based molecular sensor using CdTe quantum dots as energy donors and neutral red as energy acceptors. The fluorescence resonance energy transfer efficiency was enhanced by the construction of cetyltrimethylammonium bromide micelles, which significantly reduced the distance between the donor and the acceptor. The results indicated that the addition of the albumin easily leads to the fluorescence quenching of CdTe-neutral red fluorescence resonance energy transfer due to the formation of CdTe-albumin complexes which have weak affinity to CdTe and repels the dyes from CdTe surface. The fluorescence intensity of the CdTe-neutral red sensor quenched with the increasing concentration of albumin. The linear range of albumin was from 0.4 × 10⁻³ to 11.00 × 10⁻³ g L⁻¹. The detection limit was 0.13 g L⁻¹.     

Influence of ultrasonic treatment on the structure and emulsifying properties of peanut protein isolate

Effects of ultrasonic treatment on emulsifying properties and structure of peanut protein isolate (PPI) were evaluated by analysis of particle size distribution, protein surface hydrophobicity, SDS-PAGE, circular dichroism spectra and environmental scanning electron microscopy. The emulsifying properties of the PPI were found to be improved by ultrasonic treatment. The mean particle size decreased from 474.7 nm to 255.8 nm while the molecular weight remained unaffected. The results of intrinsic fluorescence spectroscopy and surface hydrophobicity indicated that ultrasonic treatment induced tertiary structural changes of the proteins in PPI. Emulsifying activity index and emulsion stability index were found to be correlated fairly well with surface hydrophobicity (H₀) (r = 0.712 and r = 0.668, respectively).     

Luminescence properties of a thermal-responsive organogel to various metal cations

A new gelator (L) containing Schiff base, benzoimidazol and naphthayl moieties was synthesized and its self-assembly was investigated in various solvents. Gelation test revealed that it could form a thermal-responsive gel in ethylene glycol (GL) or the mixture solution of ethylene glycol and DMF. Different fluorescence behaviors were observed upon adding different metal ions. The addition of Mg^2 + maintained the gelating ability of L, meanwhile the Mg^2 +-ion-mediated organogel in ethylene glycol can enhance the fluorescence of GL. The addition of Al^3 + can destroy GL and lead to a state transition from gel to clear solution; the solution can give a brilliant blue emission excited at 365 nm UV. Interestingly, the luminescence of GL increased sharply at first but decreased finally. The fluorescence of GL was quenched when other metal cations were added.     

Plant mediated green biosynthesis of silver nanoparticles using Vitex negundo L. extract

In the present study silver nanoparticles (Ag-NPs) were synthesized from aqueous silver nitrate through a biosynthetic route using water extract of Vitex negundo L. extract which acted as a reductant and stabilizer agents, simultaneously. Formations of Ag/V. negundo were determined by UV–vis spectroscopy where surface plasmon absorption maxima can be observed at 423–432 nm. The XRD analysis shows that the Ag-NPs are of face centered cubic structure. TEM images show the well dispersed of Ag-NPs with average particle size less than 20 nm. The FT-IR spectrum indicates the presence of V. negundo in capping with silver nanoparticles.