Enhancing the photodynamic therapy efficacy of black phosphorus nanosheets by covalently grafting fullerene C60

Few-layer black phosphorus (BP) nanosheets show potential application in biomedicine such as photodynamic therapy (PDT), and are therefore commonly used in anticancer therapy and nanomedicine due to being relatively less invasive. However, they suffer from low ambient stability and poor therapeutic efficacy. Herein, C₆₀ was covalently grafted onto the edges of BP nanosheets, and the resultant BP-C₆₀ hybrid was applied as a novel endocytosing photosensitizer, resulting in not only significantly enhanced PDT efficacy relative to that of the pristine BP nanosheets, but also drastically improved stability in a physiological environment, as confirmed by both in vitro and in vivo studies. Such improved stability was due to shielding effect of the stable hydrophobic C₆₀ molecules. The enhanced PDT efficacy is interpreted from the photoinduced electron transfer from BP to C₆₀, leading to the promoted generation of ˙OH radicals, acting as a reactive oxygen species (ROS) that is effective in killing tumor cells. Furthermore, the BP-C₆₀ hybrid exhibited low systemic toxicity in the major organs of mice. The BP-C₆₀ hybrid represents the first BP-fullerene hybrid nanomaterial fulfilling promoted ROS generation and consequently enhanced PDT efficacy.

Covalently grafting C₆₀ molecules onto black phosphorus (BP) nanosheets improves their tumor inhibition rate from 36.6% to 88.2%.     

Improving the flame retardancy of PET fabric by photo-induced grafting

Photo-induced surface grafting with glycidyl methacrylate (GMA) as monomer in association with a pad-curing treatment by using a flame retardant (FR) solution which contains 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP) and sulfamic acid (H₂NSO₃H) has been used to improve the fire performance of PET fabric in this study. The effects of initiator concentration, monomer concentration and the irradiation time on the grafting percentage were investigated. The chemical structure of grafted surface of the PET fabric was characterized by an attenuated total reflection-infrared (ATR-IR) spectroscopy. The fire performance was evaluated by the LOI and the vertical flammability tests, and the results indicate that the photo grafting treatment could improve the flame retardancy and dripping resistance of PET fabric. Thermal behaviour of treated PET fabric samples was investigated by thermogravimetric (TG) and differential scanning calorimetric (DSC). The morphology of the sample char residue was also investigated by scanning electron microscope (SEM).     

Graft polymerization of styrene initiated by covalently bonded peroxide groups on silica

The graft polymerization of styrene initiated by immobilized peroxide groups was investigated. Three different types of modification reactions were used to introduce peroxide groups which are directly attached onto the surface of two different silica supports. Silanol groups were chlorinated using thionyl chloride or tetrachlorosilane. In another reaction pathway 1,3,5-benzenetricarbonyl chloride enabled the introduction of free acid chloride residues bonded onto the surface of silica. tert-Butyl hydroperoxide (TBHP) was used to transform the chlorosilyl and the acid chloride groups into peroxide residues. In a further reaction step the covalently bonded peroxides initiated the polymerization of styrene to form grafted polystyrene directly attached onto the silica support. Solid-state 13C CP/MAS NMR spectroscopy, and thermogravimetric and scanning electron microscope measurements enabled a clear structure and property elucidation of the different bonded phases. The highest amount of grafted polystyrene was achieved employing the acid chloride synthesis pathway with silica-gel, whereas modification of spherical silica only led to minor amounts of grafted polymer. The results contribute to the evolving need to understand particle surface modifications and may have positive impact on development of new HPLC stationary phases for improved elutant resolution.     

Radical grafting of carbon surfaces with alkylic groups by mediated oxidation of carboxylates

The mediated oxidation of tetrabutylammonium acetate and 4-nitrophenylacetate was carried out in acetonitrile on glassy carbon electrodes. It is discussed that direct oxidation of aliphatic carboxylates, which give rise to a carbocationic chemistry, cannot induce covalent grafting of the carbon surface, however surface grafting is possible by using ferrocene derivatives as electron transfer mediators. Density functional theory has been used to model a radical grafting involving methyl groups. In addition semiempirical calculations have been performed for 4-nitrobenzyl additions, and a new anchoring pattern, is proposed. Coverage factors have been calculated for both kinds of radicals. Both, experimental and theoretical results support the covalent attachment of methyl groups on the carbon surface and the formation of a highly compact monolayer which does not allow the permeation of reversible redox molecules as small as the molecular oxygen.     

Displacement reactions of covalently attached organosilicon monolayers on Si

The covalently attached monolayers of alkylsilanes (R(CH(3))(2)SiX) on Si undergo complete displacement by the solutions of different organosilanes (R'(CH(3))(2)SiX). By varying the reaction time, the degree of displacement can be controlled offering a convenient method for the preparation of surfaces with mixed functionalities (R and R').     

Hydrophobic modification of cellulose nanocrystal via covalently grafting of castor oil

Hydrophobic cellulose nanocrystals (CNs) have been prepared by grafting isocyanate-terminated castor oil, a kind of natural vegetable oil, onto their surface. The existence of castor oil component in the modified cellulose nanocrystals was verified by Fourier transform infrared spectroscopy, solid-state ¹³C NMR spectra and X-ray photoelectron spectroscopy. At the same time, X-ray diffraction and transmission electron micrographs further proved that the crystalline structure and large aspect ratio of cellulose nanocrystals were essentially preserved after chemical grafting. Furthermore, the surface of modified cellulose nanocrystals appeared to be hydrophobic as indicated by contact angle measurements. The value of the polar component of surface energy decreased from 21.5 mJ/m² to almost zero via grafting castor oil. These novel hydrophobic castor oil-grafted cellulose nanocrystals appear as valuable alternatives to formulate bionanocomposites with non-polar polymers for optimized performances.     

XPS/EXAFS study of cycleability improved LiMn2O4 thin film cathodes prepared by solution deposition

The influence of Sn substitution in LiMn₂O₄ thin films as a cathode has been studied via solution deposition to improve the electrochemical performance of thin film lithium batteries. LiSn_0.025Mn_1.95O₄ thin films showed the most promising performance, i.e. a high capacity retention of 77% at 10 C after the 500th cycle, due to the increased average Mn valence state. The thin films of LiSn_x/2Mn_2?xO₄ (x ? 0.10) showed significant precipitation of SnO₂ and SnO after the cycling evaluation.     

Yolk-shell Si/C composites with multiple Si nanoparticles encapsulated into double carbon shells as lithium-ion battery anodes

The conceptual design of yolk-shell structured Si/C composites is considered to be an effective way to improve the recyclability and conductivity of Si-based anode materials. Herein, a new type of yolk-shell structured Si/C composite(denoted as TSC-PDA-B) has been intelligently designed by rational engineering and precise control. In the novel structure, the multiple Si nanoparticles with small size are successfully encapsulated into the porous carbon shells with double layers benefiting from the strong etching effect of HF. The TSC-PDA-B product prepared is evaluated as anode materials for lithium-ion batteries(LIBs).The TSC-PDA-B product exhibits an excellent lithium storage performance with a high initial capacity of 2108 mAh g~(-1) at a current density of 100 mA g~(-1) and superior cycling performance of 1113 mAh g~(-1) over 200 cycles. The enhancement of lithium storage performance may be attributed to the construction of hybrid structure including small Si nanoparticles, high surface area, and double carbon shells, which can not only increase electrical conductivity and intimate electrical contact with Si nanoparticles, but also provide built-in buffer voids for Si nanoparticles to expand freely without damaging the carbon layer.The present findings can provide some scientific insights into the design and the application of advanced Si-based anode materials in energy storage fields.     

Improving the catalytic activity of nickel-containing anodes for the oxidation of alcohols

Looking for ways to improve the catalytic activity of a Ni anode during the oxidation of alcohols in basic medium, we tested the action of amino compounds as Ni-complexing agents. We have discovered a significant increase in the effective rate of oxidation of alcohols to the corresponding carboxylic acids in the presence of amino compounds. The activating effect of amino compounds (AEAC) became the basis for the industrial method to produce the carboxylic acid diaceton-2-keto-L-gulonic acid (DAG), an intermediate in the synthesis of vitamin C. The DAG electrosynthesis at stainless steel (StS) anodes with a capacity of 1,500?t/year/production line was developed. The application of the electrochemical method allowed drastically reducing the wastes and resulted in significant economy effects. Operation during 10 years showed good anode corrosion resistance, stability, and safety of the process. There are other possible AEAC applications, in particular, for increasing the sensitivity of ROH sensors. The possibility of using the AEAC effect for improving the efficiency of direct alcohol fuel cells (DAFC) with Ni-containing systems is also discussed.     

Thermotropic copolyamides from polyethyleneglycol bis(4-carboxyphenyl)ethers with different oxyethylene units

Copolymerizations of polyethyleneglycol bis(4-carboxyphenyl)ethers (PEG_n) with different n values were found to significantly lower the anisotropic transition temperature (T_m) of the copolymers produced, and the thermotropic copolyamides of thermally more stable nematic phases were obtained. The effect was investigated in terms of PEG_m/PEG_n molar ratios, the number of oxyethylene units, and the even—odd character of the flexible segment. Several modes of copolymerization were carried out to investigate the effect of monomer (PEG_n sequence on T_m. By these copolymerizations thermally stable copolyamides even from p-phenylenic diamines such as methyl-p-phenylenediamine and p-phenylenediamine were obtained. © 1993 John Wiley & Sons, Inc.     

Aqueous reductive dechlorination of chlorinated ethylenes with tetrakis(4-carboxyphenyl)porphyrin cobalt

The catalytic dechlorination of chlorinated ethylenes by 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin cobalt ((TCPP)Co), a cobalt complex structurally similar to vitamin B12, was studied. It was found to have superior aqueous-phase dechlorination activity on chlorinated ethylenes (CEs) relative to vitamin B12. Bimolecular rate constants for the degradation of CEs by (TCPP)Co of 250, 24, 0.24, and 1.5 M(-1) s(-1) were found for perchloroethylene (PCE), trichloroethylene (TCE), cis-dichloroethylene (cDCE), and trans-dichloroethylene (tDCE), respectively. Through kinetic analysis, the rate laws for PCE and TCE were determined to be first order in substrate and catalyst, and PCE degradation was shown to be sensitive to the concentration of the titanium citrate bulk reductant and pH. The importance of the Co(I) oxidation state on dehalogenation was studied with UV-vis absorbance spectroscopy, a variety of reducing agents, and cyclic voltammetry. Evidence of chlorovinyl complexes as potential catalytic cycle intermediates was obtained through the preparation of (TPP)Co(trans-C2H2Cl) and the observation of (TPP)Co(C2HCl2) and (TCPP)Co(C2HCl2) by mass spectrometry. The X-ray crystal structure of (TPP)Co(trans-C2H2Cl) is reported.     

5,10,15,20-四(4-羧基苯基)卟啉的微波合成

利用微波加热法,由5,10,15,20-四(4-甲氧羰基苯基)卟啉水解合成了四(4-羧基苯基)卟啉,并对反应条件进行了探讨。结果表明：以吡啶为溶剂,氢氧化钾为催化剂,以65W的微波功率辐射30rnin,可使5,10,15,20-四(4．甲氧羰基苯基)卟啉完全水解。反应时间是传统加热法用时的1/48。     

Improving the lower detection limit of potentiometric sensors by covalently binding the ionophore to a polymer backbone

The lower detection limit of polymeric membrane ion-selective electrodes (ISEs) is impaired by zero-current ion fluxes through the organic phase. This adverse effect is largely eliminated by covalently attaching the ionophore to a polymer backbone. To this purpose, the Pb²⁺-selective ligand, 4-tert-butylcalix[4] arene-tetrakis(N,N′-dimethylthioacetamide) is substituted on its upper rim by a diol derivative which is subsequently copolymerized with poly(tetrahydrofuran)diol and 2,2,4-trimethylhexamethylene diisocyanate to the corresponding polyurethane. By measurements on sandwich membranes, it is shown that through binding the ionophore to the polymer, the mobility of Pb²⁺ in the ISE membrane is strongly reduced. As a consequence, the response range of such an ISE is extended by several orders of magnitude. This is the case even when using an internal electrolyte that with an ISE based on a mobile ionophore leads to strong deviations from the linear response because of ion uptake from the sample into the membrane or ion release from the membrane into the sample. With a conventional inner filling solution of 10⁻¹ M Pb(NO₃)₂, a lower detection limit of 1.7×10⁻⁹ M Pb²⁺ has been achieved in the presence of 10⁻⁴ M Na⁺.     

Formation of uniform ferrocenyl-terminated monolayer covalently bonded to Si using reaction of hydrogen-terminated Si(111) surface with vinylferrocene/n-decane solution by visible-light excitation

Electrochemically active self-assembled monolayers (SAM) have been successfully fabricated with atomic-scale uniformity on a silicon (Si)(111) surface by immobilizing vinylferrocene (VFC) molecules through Si-C covalent bonds. The reaction of VFC with the hydrogen-terminated Si (H-Si)(111) surface was photochemically promoted by irradiation of visible light on a H-Si(111) substrate immersed in n-decane solution of VFC. We found that aggregation and polymerization of VFC was avoided when n-decane was used as a solvent. Voltammetric quantification revealed that the surface density of ferrocenyl groups was 1.4×10(-10) mol cm(-2), i.e., 11% in substitution rate of Si-H bond. VFC-SAMs were then formed by the optimized preparation method on n-type and p-type Si wafers. VFC-SAM on n-type Si showed positive photo-responsivity, while VFC-SAM on p-type Si showed negative photo-responsivity.     

Improving polylactide/starch biocomposites by grafting polylactide with acrylic acid--characterization and biodegradability assessment

In this article, the properties of a polylactide and starch composite (PLA/starch) and an acrylic acid grafted polylactide and starch composite (PLA-g-AA/starch) were compared. The composite containing PLA-g-AA was found to have much better dispersion and homogeneity of starch in the polymer matrix than the composite containing PLA, indicating better compatibility between the two phases. Better mechanical and thermal properties of the PLA-g-AA/starch composite, notably an increase in tensile strength and elongation at breakpoint, evidenced its superiority to the PLA/starch composite. Furthermore, the lower viscosity of PLA-g-AA/starch makes it easier to process than PLA/starch. Weight loss on exposure to a soil environment over a period of three months showed that the starch in the composites was almost completely biodegradable, even at a high degree of substitution (60 wt.-% starch). After three months in soil, a reduction in the mechanical properties of the blends was observed, especially in those with higher starch contents.     

Preparation, structure, and imaging of luminescent SiO2 nanoparticles by covalently grafting surfactant-encapsulated europium-substituted polyoxometalates

A novel route to the preparation of luminescent silica nanoparticles and coloration for living cells was demonstrated in this article. A europium-substituted polyoxometalate was encapsulated by a hydroxyl-group-terminated double-chain quaternary ammonium cation through an ion replacement process, yielding an organic-inorganic complex with core-shell structure bearing hydroxyl groups located at the periphery. The introduction of -OH groups not only increased the solubility of the complex in polar solvents but also caused it to embed into the inner matrix of silica nanoparticles covalently and be well-dispersed through an in situ sol-gel reaction with tetraethyl orthosilicate. Elemental analysis and spectral characterization confirmed the formation of prepared complexes with the anticipated chemical composition. Scanning and transmission electron microscopy images illustrated the size change of luminescent nanoparticles with smooth surfaces and well-dispersed polyoxometalate complexes inside of the silica matrix. X-ray photonic spectra and ζ-potential measurements revealed the chemical association between the silica matrix and the complex. Luminescent spectral characterization indicated the well-retained photophysical property of Eu-substituted polyoxometalate in silica nanoparticles. The surface amino-modified silica nanoparticles were applied to cell coloration, and the dyed Hela cells were observed through laser confocal fluorescence microscopy.     

Surface modification of hydroxyapatite nanocrystals by grafting polymers containing phosphonic acid groups

A novel approach for the surface modification of hydroxyapatite (HAp) nanocrystals is described by grafting polymerization of vinyl phosphonic acid (VPA) using a redox initiating system in an aqueous media. Fourier transform infrared (FT-IR) and XRD analyses confirmed the modification reaction on HAp surfaces. Inductively coupled plasma mass spectroscopy (ICP MS) showed that the Ca/P molar ratio decreased from 1.67 to 1.36 with increasing the feed VPA amount. Zeta potentials of unmodified HAp and modified HAp in phosphate-buffered saline (PBS) solutions (pH 7.4, ionic strength = 10 mM) were negative and decreased with increasing the amount of grafted PVPA. Transmission electron microscopy (TEM) measurements and time-dependent phase monitoring indicated that the colloidal stability of modified HAp over unmodified HAp in water dramatically increased and tended to exist as single nanocrystals without aggregation.     

Functionalization of mesoporous MCM-41 with aminopropyl groups by co-condensation and grafting: a physico-chemical characterization

This work reports on the synthesis and characterization of NH₂-MCM-41, a well-known hybrid material commonly used in biomedical and biotechnological applications, based on mesoporous silica and aminopropyl functionalities. Samples were prepared by post-synthesis grafting and by one-pot co-condensation methods, to achieve a relatively high organic loading (around 12% wt), and were characterized in terms of porosity, thermal stability and distribution of the aminopropyl moieties in the silica framework. The results suggest that grafting brings about an almost complete consumption of surface silanols, with structurally defined functional groups mainly located inside the material pores. In contrast, co-condensation results in lower surface area and thermal stability, with ink-bottle-like pores. This suggests that the aminopropyl groups are not only linked to the pores inner surface but could be located in the pore walls or at their entrance.     

Sorption behavior of vanadium on silica gel modified with tetrakis(4-carboxyphenyl)porphyrin.

Tetrakis(4-carboxyphenyl)porphyrin (TCPP) has been loaded on aminopropyl-silica gel by physical adsorption and by direct immobilization through formation of an amide bond to obtain chelating sorbents. These sorbents have been studied for preconcentration and separation of vanadium prior to its determination by atomic absorption spectrometry. Several parameters, such as sorption capacity of the chelating resin, pH for retention of V(IV) and V(V), volume of sample and eluent, were evaluated. Both vanadium species sorbed on TCPP-modified resin could be eluted using 2 mol L(-1) nitric acid solution. The recovery values were > 94% and preconcentration factor of 160 was obtained. For speciation analysis, cyclohexane-1,2-diaminetetraacetic acid (CDTA) was added to the sample for complexation of vanadium(IV), which was not retained on the microcolumn. The proposed method was examined for reference standard materials (TM-25.2 and CAAS-3) as well as for river water samples.