Magnetic M<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript>@N-C as heterogeneous catalysts for the catalytic oxidation of aniline solution with sulfate radicals

Metal nanoparticles have been combined with magnet metal–organic frameworks (MOFs) to afford new materials that demonstrate an efficient catalytic degradation, high stability, and excellent reusability in areas of catalysis because of their exceptionally high surface areas and structural diversity. Magnetic M _x O _y @N-C (M = Fe, Co, Mn) nanocrystals were formed on nitrogen-doped carbon surface by using 8-hydroxyquinoline as a C/N precursor. The Co@N-C, MnO@N-C, and Fe/Fe₂O₃@N-C catalysts were characterized by X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), N₂ adsorption/desorption, and X-ray photoelectron spectroscopy (XPS). The catalytic performances of catalysts were thoroughly investigated in the oxidation of aniline solution based on sulfate radicals (SO₄ ^?.) toward Fenton-like reaction. Magnetic M _x O _y @N-C exhibits an unexpectedly high catalytic activity in the degradation of aniline in water. A high magnetic M _x O _y @N-C catalytic activity was observed after the evaluation by aniline degradation in water. Aniline degradation was found to follow the first-order kinetics, and as a result, various metals significantly affected the structures and performances of the catalysts, and their catalytic activity followed the order of Co > Mn > Fe. The nanoparticles displayed good magnetic separation under the magnetic field.

Open image in new window

Graphical Abstract ?

     

Morphology and composition tailoring of Co<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript>3 − <Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>4</Subscript> nanoparticles

Nano-octahedra of cobalt ferrite Co _x Fe_3???xO₄ (1?≤?x?<?2), with a broad size distribution around 15–20 nm, were synthesized by a hydrothermal method using nitrates as precursors. For the first time, single-phased nano-octahedra of cobalt-rich ferrite Co _x Fe_3???xO₄ (x?=?1.5) were synthesized. The nano-octahedra are crystallized in a normal spinel structure, with tetrahedral sites occupied by Co²⁺. This specific octahedral shape was obtained with anionic, cationic, and nonionic surfactants. The nature of the surfactant influenced the chemical composition of the powder and the size of the nano-octahedra. The {100} truncation of the octahedra is more pronounced for the small particles. For the first time, single-phased nanoparticles with as much as x?=?1.8 cobalt were synthesized with ethylene glycol as solvent. These nanoparticles, around 8 nm in size, have no specific shape and possess a lacunar spinel structure similar to maghemite. The samples were characterized by X-ray diffraction, transmission electron microscopy, and energy-dispersive spectroscopy.

Open image in new window

Graphical abstract ?

     

Synthesis of Pd/Pt core/shell nanostructures with truncated-octahedral morphology toward formic acid oxidation

In this study, a simple one-pot method was adopted to synthetize Pd/Pt core/shell nanostructures with truncated-octahedral morphology. The morphology of the obtained Pd/Pt nanoparticles was characterized by transmission electron microscopy (TEM) and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). In addition, the composition was determined by energy-dispersive X-ray spectroscopy (EDS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the electric structures were studied by powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Based on the above results, it could be noticed that Pd/Pt core/shell nanostructures with truncated-octahedral morphology were produced, where the core consisted of Pd atoms and the shell consisted of Pt atoms. In order to test the catalytic properties of the prepared Pd/Pt nanoparticles, cyclic voltammetry (CV) was carried out in 0.5 M H₂SO₄ and 0.5 M H₂SO₄ + 1 M HCOOH. Compared with commercial Pt black, the Pd/Pt core/shell nanostructures with truncated-octahedral morphology exhibited higher activity and stability toward formic acid oxidation.

Open image in new window

Graphical abstract Pd/Pt core/shell nanostructures which exhibit excellent activity and stability are synthesized by a simple one-pot method

     

Synthesis,structure, and optical and photocatalytic properties of quasi-one-dimensional ZnO doped with Со<Subscript>3</Subscript>O<Subscript>4</Subscript> and carbon

One-dimensional nanocomposites Zn_1–x Co _x O_1–y С _у :nCo₃O₄ and solid solutions Zn_1–x Co _x O_1–y С _у , which are promising photocatalysts for the oxidation of toxic organic compounds in visible light, are obtained via the thermolysis of Zn_1–x Co _x (HCOO)(OCH₂CH₂O)_1/2 (0.1 ≤ x ≤ 0.5) precursor in a controlled gaseous atmosphere.     

Surface voltammetric dealloying investigation on PdCu/C electrocatalysts toward ethanol oxidation in alkaline media

Voltammetric dealloying is employed here to investigate the correlations between catalytic performance and surface composition and structure, taking ethanol oxidation reaction (EOR) on Pd-Cu alloy surface as a case study. First, home-made PdCu/C with a mean particle size of ca. 3.11?±?0.6 nm is dealloyed by repetitive potential cycling in 0.5 M H₂SO₄. With dealloying cycles rising, the Cu component is gradually leached out and the corresponding Pd/Cu atomic ratio gradually increases from ca. 2.1 to 4.0; meanwhile, SEM images display that Pd-rich porous shell is formed due to dealloying-induced surface structural rearrangement, being verified by the appearance of ear-like peaks at ??0.015 V (vs. SCE) in CVs collected in 0.5 M H₂SO₄; furthermore, XPS spectra indicate that core-level binding energies of Pd 3d_5/2 first positively shift to 336.1 eV and then oppositively move down to 334.9 eV, indicating that the d-band center of Pd composition is modulated by the dealloying treatment. Moreover, the voltammetric peak current densities for EOR follow the order of PdCu/C-DA15?>?as-prepared PdCu/C ??>?PdCu/C-DA30 ? commercial Pd/C ? PdCu/C-DA75, due to the modest downshift of Pd d-band center resulted by charge transfer and surface atomic rearrangement. In addition, the EOR durability gradually decays with the continuous loss of Cu, indicating that electro-oxidation of surface species also follows the so-called bi-functional mechanism. This work might provide some new insights into the catalysis enhancement by tuning the surface/interfacial structure of catalysts.

Open image in new window

Graphical abstract The voltammetric peak current densities for ethanol oxidation on home-made PdCu/C catalysts gradually decrease with the dealloying cycles rising, suggesting that the surface voltammetric dealloyment could effectively modulate the surface composition and structure, so as to tune the catalytic performance.

     

Thermosensitive polymer stabilized core-shell AuNR@Ag nanostructures as “smart” recyclable catalyst

Core-shell AuNR@Ag nanostructures were synthesized and surface-grafted with thermosensitive poly(N-isopropylacrylamide) to enhance stability and endow stimuli-responsive property. The AuNR cores showed average dimensions of 8-nm diameter and 33-nm length, while the anisotropic silver shells displayed 1–2 nm thin side and maximal 8 nm fat side. The obtained polymer-stabilized AuNR@Ag nanostructures as catalysts showed normal Arrhenius change of apparent rate constant, k _app, in catalyzed reaction between 20 and 30 °C, but displayed a decrease of k _app with respect to the temperature increasing between 32.5–40 °C, showing self-inhibition of the observed catalytic activity. Such “smart” self-inhibition of catalytic activity at enhanced temperature can be attributed to the thermosensitive response of the grafted polymer molecules and should be significant to control the reaction rate and avoid superheat for exothermic reactions. Such polymer-stabilized nanocatalyst also could be recovered and reused in the catalytic system.

Open image in new window

Graphical abstract Core-shell AuNR@Ag nanostructures were grafted with thermosensitive poly(N-isopropylacrylamide) and the obtained polymer-stabilized nanostructures as catalysts showed normal Arrhenius change of apparent rate constant, k _app, of catalyzed reaction between 20 and 30 °C, but displayed a decrease of k _app with respect to the temperature increasing between 32.5 and 40 °C. Such “smart” self-inhibition of catalytic activity at enhanced temperature should be significant to control the reaction rate and avoid superheat for exothermic reactions. The AuNR@Ag nanostructures could also be considered as recyclable catalysts.

     

Cu–CeO<Subscript>2</Subscript> nanocomposites: mechanochemical synthesis,physico-chemical properties,CO-PROX activity

Catalytic systems designated for preferential oxidation of CO in the presence of H₂ are prepared by ball milling of Cu and CeO₂, a simple and cheap one-step process to synthesize such catalysts. It is found that after 60 min of milling, a mixture of 8 wt.% Cu–CeO₂ powders exhibits CO conversion of 96% and CO selectivity of about 65% at 438 K. Two active oxygen states, which are not observed in case of pure CeO2, were detected in the nanocomposite lattice and attributed to the presence of Cu in surface sites as well as in subsurface bulk sites. Correspondingly, oxidation of CO to CO₂ was found to occur in a two-stage process with T _max ≈ 395/460 K, and oxidation of H₂ to H₂O likewise in a two-stage process with T _max ≈ 465/490 K. The milled powder consists of CeO₂ crystallites sized 8–10 nm agglomerated to somewhat larger aggregates, with Cu dispersed on the surface of the CeO₂ crystallites, and to a lesser extent present as Cu₂O.

Open image in new window

Graphical abstract ?

     

Preparation of metallic Pd nanoparticles using supercritical CO<Subscript>2</Subscript> deposition: An efficient catalyst for Suzuki cross-coupling reaction

Ligand-free palladium nanoparticles supported on multi-walled carbon nanotubes (Pd/MWCNT) were prepared by the supercritical carbon dioxide (scCO₂) deposition method using a novel scCO₂-soluble Pd organometallic complex as a precursor. The precursor with the perfluoroalkyl chain group was synthesized and identified by microanalytic methods. The deposition was carried out at the temperature of 363.15 K and pressure of 27.6 MPa CO₂. The prepared metallic nanoparticles were obtained with an average size of 2 nm. Pd/MWCNT was utilized as a heterogeneous catalyst in Suzuki cross-coupling reaction. The nanocatalyst was found very effective in Suzuki reaction and it could also be recovered easily from the reaction media and reused over several cycles without significant loss of catalytic activity under mild conditions.

Open image in new window

Graphical Abstract Pd/MWCNT was prepared by the scCO2 deposition method using a new synthesized perfluroalkylated vic-dioxime Pd complex as the precursor. The prepared nanoparticle was very effective as catalyst and reusable for Suzuki cross coupling reaction under mild conditions.

     

Extreme Electromechanical Characteristics and Microstructural Features of Ferro-Piezoceramics Based on Lead Titanate

Microstructural features and electrophysical parameters of a number of solid solutions based on PbTiO₃ are investigated. Solid solutions (Pb_{1–3/2x + z/2}Nd _x )(Ti_1–y–zMn _y Inz)O₃ and Pb_1–xCa _x Ti_1–y(W_1/2Co_1/2) _y O₃ with extreme values of the mechanical Q-factor and electromechanical anisotropy are chosen as the objects of investigation. The ferro-piezoceramic samples are obtained through conventional sintering and hot pressing. X-ray structural and microstructural studies are performed, and the complex elastic, dielectric, and piezoelectric parameters of experimental samples are measured. The frequency dependences of complex parameters of the experimental samples have been studied at frequencies of up to 40 MHz. It is established that the extreme values of the mechanical Q-factor and piezoelectric anisotropy of the investigated PbTiO₃-based solid solutions are due to microstructural features associated with the technological regimes of ferropiezoceramic fabrication.     

Highly active Pd/WO3-CNTs catalysts for formic acid electrooxidation and study of the kinetics

The new Pd/WO₃-CNTs catalysts are prepared for formic acid electrooxidation in direct formic acid fuel cells (DFAFCs). According to XRD, TEM, and HRTEM results, WO₃ particles are covered or overlapped with Pd particles, which have a uniform and narrow size distribution due to the highly dispersion of WO₃-CNTs. The electrochemical results show significantly enhanced electrocatalytic performances for formic acid oxidation on Pd/WO₃-CNTs catalysts, especially its dramatically improved stability and excellent tolerance to CO poisoning, which is mainly ascribed to the interaction between Pd and WO₃. Therefore, Pd/WO₃-CNTs catalysts show the great potential as less expensive and more efficient electrocatalyst for DFAFCs. Additionally, the kinetic parameters such as the charge transfer parameter and the diffusion coefficient of formic acid electrooxidation on 20 %Pd/20 %WO₃-CNTs were obtained.

The new Pd/WO₃-CNTs catalysts are prepared and studied in the oxidation of formic acid, and the significantly enhanced electrocatalytic performances, especially its dramatically improved stability and excellent tolerance to CO poisoning show great potential as less expensive and more efficient electrocatalyst for the direct formic acid fuel cells.     

Hydrogel nanoparticles covered by neuroligin-2-derived peptide-protected <Emphasis Type="Italic">β</Emphasis> cells under oxidative stress and increase their proliferation

Protein complexes that mediate secretion and adhesion are located on the plasma membrane of pancreatic β cells. Neuroligins and their binding partners, the neurexins, are among these complexes. β cell maturation and physiologically regulated insulin secretion, as a response to high levels of blood glucose, are dependent on their three-dimensional (3D) arrangement. Both insulin secretion and the proliferation rates of β cells dramatically increase when β cells are co-cultured with clusters of a member of the neuroligin family: NL-2. A membranal protein, such as NL-2, has very limited drugability owing to its low biostability and bioavailability. Thus, based on in silico modeling, a short NL-2 peptide (HSA-28), which was able to mimic NL-2-positive effects on β cells, was designed, as we described in previous publication. However, the peptide was active only as a cluster, created by the covering the maghemite (γ-Fe₂O₃)-based nanoparticles (NPs) with limited biocompatibility. In this brief communication, we will show that conjugation of HSA-28 to biocompatible hydrogel NPs exhibits an impressive protective effect on INS-1E β cells under oxidative stress and induces their proliferation rate via augmentation of PDX1 nuclear translocation. The diameter of coated by the peptide NPs was 206?±?63 nm (DLS) and 114?±?27 nm (cryo-TEM). This significant change in size can be explained by the very hydrophilic character of the proteinoid NPs, inducing adsorption of many water molecules on their surface, which are accounted only by the DLS. The ability of biocompatible hydrogel NPs to prevent apoptosis and increase β cell mass might be used for developing novel β cell protective therapies.

Open image in new window

Graphical abstract Effect of covered by bioactive peptide NPs on PDX1 nuclei translocation.

     

A Raman study of lattice vibrations in II–VI semiconductors doped with 3<Emphasis Type="Italic">d</Emphasis> elements

Room-temperature Raman spectra were obtained for powder samples of Zn_1?xNixSe and Zn_1?yCr_ySe compounds and for a single-crystal Zn_1?xNi_xSe (x = 0.0025) sample in the temperature range 5–140 K. The results obtained are interpreted in terms of large-scale lattice shear strains induced by 3d elements in these solid solutions.     

Ordered phases of lithium nickelite Li<Subscript>1−<Emphasis Type="Italic">x</Emphasis>−<Emphasis Type="Italic">z</Emphasis></Subscript>Ni<Subscript>1+<Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript>

A symmetry analysis of ordering in lithium nickelite Li_1?x?zNi_1+xO₂ (Li_1?x?z□_yNi_1+xO₂) was performed with regard to the substitution of Li and Ni atoms and the occurrence of structural vacancies □ in the metal sublattice. For all the ordered phases, the k ₉ ⁽³⁾ ray of the Lifshitz {k₉} star is present in the order-disorder transition channel. This ray determines the consecutive alternation of atomic planes filled with only Ni atoms or only Li atoms and vacancies in the \([1\bar 11]_{B1} \) direction. It was shown that the rhombohedral ordered LiNiO₂ phase is formed in the defect-free lithium nickelite, whereas a family of three monoclinic Li₃□Ni₄O₈ (C2/m space group) and Li₂□Ni₃O₆ (C2/m and C2 space groups) superstructures arises as the concentration of structural vacancies increases. For all the superstructures, the order-disorder phase-transition channels were determined and the distribution functions of Li and Ni atoms have been calculated. The long-range order parameters describing each superstructure were found as functions of the Li_{1?x? z}Ni_1+xO₂ composition.     

Effects of electron tunneling in photophysics of quantum-sized luminescent nanosilicon

The paper deals with the processes of photoburning and dark recovery of the photoluminescence (PL) yield of a “core-shell”-type hybrid nanoparticles Si/SiO _x (npSi/SiO _x ) after exposure to laser light with a wavelength of 405 nm and power density of 0.05–1 W/cm². The PL of npSi/SiO _x occurs after excitation of nanocrystalline Si core and subsequent energy transfer to the luminescent oxygen-deficient centers (ODC) in the SiO _x shell of a nanoparticle. These photoburning effects linearly depend on the power density of the exciting laser light, and the dynamics of the photoburning of PL is significantly non-exponential: the burning rate strongly drops during the exposure. The stop of laser exposure of npSi/SiO _x is accompanied by a slow dark recovery of the quantum efficiency of PL up to its initial level. We have demonstrated the possibility of controlling the photosensibility of npSi/SiO _x through changing the electron affinity of the environment. We have also proposed a physical mechanism that explains the observed photoburning and subsequent dark recovery of npSi/SiO _x PL based on the existence of “traps” for electrons residing in the SiO _x shell, where the electrons come as a result of tunneling from the excited ODC. The limiting time for this process is the lifetime of PL of ODC ranging from 10^?5 to 10^?4 s. The drop of the burning rate during exposure is caused by a strong difference in tunneling probabilities for different pairs of “ODC-trap”. The dark back tunneling of an electron from a trap to the original ODC occurs significantly (7–10 orders of magnitude) slower than the direct tunneling due to higher energy barrier.

Open image in new window

Graphical abstract Dark recovery of photoluminescence efficiency of Si nanoparticles following laser burning in three surrounding media differing in electron affinity

     

The magnetization reversal in CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/CoFe<Subscript>2</Subscript> granular systems

The temperature-dependent field cooling (FC) and zero-field cooling (ZFC) magnetizations, i.e., M _FC and M _ZFC, measured under different magnetic fields from 500 Oe to 20 kOe have been investigated on two exchange–spring CoFe₂O₄/CoFe₂ composites with different relative content of CoFe₂. Two samples exhibit different magnetization reversal behaviors. With decreasing temperature, a progressive freezing of the moments in two composites occurs at a field-dependent irreversible temperature T _irr. For the sample with less CoFe₂, the curves of ?d(M _FC ? M _ZFC)/dT versus temperature T exhibit a broad peak at an intermediate temperature T ₂ below T _irr , and the moments are suggested not to fully freeze till the lowest measuring temperature 10 K. However, for the ?d(M _FC ? M _ZFC)/dT curves of the sample with more CoFe₂, besides a broad peat at an intermediate temperature T ₂, a rapid rise around the low temperature T ₁~15 K is observed, below which the moments are suggested to fully freeze. Increase of magnetic field from 2 kOe leads to the shift of T ₂ and T _irr towards a lower temperature, and the shift of T ₂ is attributable to the moment reversal of CoFe₂O₄.

Open image in new window

Graphical abstract CoFe₂O₄/CoFe₂ composites with different relative content of CoFe₂ were prepared by reducing CoFe₂O₄ in H₂ for 4 h (S4H) and 8 h (S8H). The temperature-dependent FC and ZFC magnetizations, i.e., M _FC and M _ZFC, under different magnetic fields from 500 Oe to 20 kOe have been investigated. Two samples exhibit different magnetization reversal behaviors. With decreasing temperature, a progressive freezing of the moments in two composites occurs at field-dependent irreversible temperature T _irr. For the S4H sample, the curves of ?d(M _FC ? M _ZFC)/dT versus temperature T exhibit a broad and field-dependent relaxing peak at T ₂ below T _irr (figure a), and the moments were suggested not to fully freeze till the lowest measuring temperature 10 K. However, for the S8H sample, it exhibits the reentrant spin-glass state around 50 K, as evidenced by a peak in the M _FC curve (inset in figure b) and as a result of the cooperative effects of the random anisotropy of CoFe₂O₄, exchange–spring occurring at the interface of CoFe₂O₄ and CoFe₂ together with the inter-particle dipolar interaction (figure c); in ?d(M _FC ? M _ZFC)/dT curves, besides a broad relaxing peat at T ₂, a rapid rise around the low-temperature T ₁~15 K is observed, below which the moments are suggested to fully freeze. Increase of magnetic field from 2 kOe leads to the shift of T ₂ and T _irr towards a lower temperature, and the shift of T ₂ is attributable to the moment reversal of CoFe₂O₄.

     

Construction of Ag/AgCl nanostructures from Ag nanoparticles as high-performance visible-light photocatalysts

A combined strategy of in situ oxidation and assembly is developed to prepare Ag/AgCl nanospheres and nanocubes from Ag nanoparticles under room temperature. It is a new facile way to fabricate Ag/AgCl with small sizes and defined morphologies. Ag/AgCl nanospheres with an average size of 80 nm were achieved without any surfactants, while Ag/AgCl nanocubes with a mean edge length of 150 nm were obtained by introduction of N-dodecyl-N,N-dimethyl-2-ammonio-acetate. The possible formation mechanism involves the self-assembly of AgCl nanoparticles, Ostwald ripening and photoreduction of Ag⁺ into Ag⁰ by the room light. The as-prepared Ag/AgCl nanospheres and nanocubes exhibit excellent photocatalytic activity and stability toward degradation of organic pollutants under visible-light irradiation. It is demonstrated that Ag/AgCl nanocubes display enhanced photocatalytic activity in comparison with Ag/AgCl nanospheres due to the more efficient charge transfer. This work may pave an avenue to construct various functional materials via the assembly strategy using nanoparticles as versatile building blocks.

Open image in new window

Graphical abstract A combined strategy of in situ oxidation and assembly was developed to construct Ag/AgCl nanospheres and nanocubes from Ag nanoparticles, which exhibited highly photocatalytic activity and good stability for degrading methyl orange under visible light irradiation.

     

Josephson effects in unconventional heavy fermion superconductors

We discuss the Josephson effect for pairing states which break crystal symmetries in addition to gauge symmetry. We consider theE _1g andE _2u models for the low-temperature phase ofUPt ₃, with order parameters Δ(E _1g )～p _z (p _x +ip _y ) and Δ(E _2u )～p _z (p _x +ip _y )². We report calculations of Josephson critical currents, taking into account the effects of depairing at the interface. For singlet-triplet junctions the critical current is non-zero only for spin-orbit, spin-flip tunneling, and is found to be much smaller than the Ambegaokar-Baratoff value even when the spin-orbit tunneling amplitude is comparable to the spin-independent amplitude.     

Polar Phase of Superfluid <Superscript>3</Superscript>He: Dirac Lines in the Parameter and Momentum Spaces

The time reversal symmetric polar phase of the spin-triplet superfluid ³He has two types of Dirac nodal lines. In addition to the Dirac loop in the spectrum of the fermionic Bogoliubov quasiparticles in the momentum space (p _x , p _y , p _z ), the spectrum of bosons (magnons) has Dirac loop in the 3D space of parameters—the components of magnetic field (H _x ,H _y ,H _z ). The bosonic Dirac system lives on the border between the type-I and type-II.     

ZnSe core and ZnSe@ZnS core-shell quantum dots as platform for folic acid sensing

This report demonstrates a quantum dot (QD)-based selective and fast sensor platform for detection of folic acid (FA). This electrochemical platform provides a good linear relation between the anodic and cathodic peak currents (i _pa and i _pc ) in the FA concentration range of 12 to 96 nM, and the minimum detection limit (MDL) achieved was 10 nM. As an extension, absorbance and fluorescence methods were also used for the detection of FA in solutions. Core-shell QDs provided better binding than core-only ZnSe quantum dots, and showed twofold increment in binding constant. A detailed comparative evaluation of the three methods (absorbance, fluorescence, and electrochemical) is presented vis-a-vis real samples. Therefore, in principle absorbance and fluorescence spectroscopy can also be used for detecting folic acid with high selectivity and sensitivity. The MDL can be extended to be 4–7 nM level by using fluorescence and absorbance spectroscopy. FA metabolism occurs in the intestine, where the pH conditions are basic. Hence, sensing of FA under physiological conditions is relevant, which was achieved in our case. Earlier methods have reported sensing under acidic or neutral pH conditions. Considering the importance of folic acid in physiology, the significance of the present study can be hardly stressed.

Open image in new window

Graphical abstract Interaction of ZnSe and ZnSe@ZnS QDs with Folic acid

     

Effect of alkyl chain lengths on the assemblies of magnetic nanoparticles coated with multi-functional thiolactone-containing copolymer

This work presents the synthesis of magnetite nanoparticle (MNP) coated with poly(N,N-diethylaminoethyl methacrylate)-b-poly(N-isopropyl acrylamide-st-thiolactone acrylamide) (PDEAEMA-b-P(NIPAAm-st-TlaAm) copolymer and its use in controlled drug release and bio-conjugation. TlaAm units in the copolymer were ring-opened with various alkyl amines to form thiol groups (-SH), followed by thiol-ene coupling reactions with acrylamide-coated MNP and then quaternized to obtain cationic copolymer-MNP assemblies (the size <?200 nm/cluster). The use of alkyl amines having various chain lengths (e.g., 1-propylamine, 1-octylamine, or 1-dodecylamine) in the nucleophilic ring-opening reactions of the thiolactone rings affected their magnetic separation ability, water dispersibility, and release rate of doxorubicin model drug. In all cases, when increasing the temperature, they showed a thermo-responsive behavior as indicated by the decrease in hydrodynamic size and the accelerated drug release rate. These copolymer-MNP assemblies could be used as a novel platform with thermal-triggering controlled drug release and capability for adsorption with any negatively charged biomolecules.

Open image in new window

Graphical abstract MNP coated with multi-functional PDEAEMA-b-P(NIPAAm-st-TlaAm) copolymer and its proposed drug release