Green synthesis of copper oxide nanoparticles CuO NPs from Eucalyptus Globoulus leaf extract: Adsorption and design of experiments

The study is concerned with synthesizing copper oxide nanoparticles with leaf extract Eucalyptus Globoulus. The results of scanning electron microscopy (SEM) and dynamic light scattering (DLS) revealed that the green synthesized copper oxide nanoparticles are spherical and have a mean particle size of 88 nm, with a negative zeta potential of ?16.9 mV. The XRD graph showed the crystalline and monoclinic phases of CuO nanoparticles. The average crystalline size around 85.80 nm was observed by the Debye–Scherrer formula. The adsorption characteristics of the nano-adsorbents were investigated using methyl orange, and the adsorption efficiency at room temperature attained 95 mg/g. Copper oxide nanoparticles (CuO NPs) adsorb methyl orange dye most effectively at pH 4.5 when the dye is applied in quantities of 0.04 g/50 mL. Box–Behnken design (BBD) in response surface methodology (RSM) was used to optimize various process parameters, such as pH solution (X₁: 2 – 11), adsorbing dose (X₂: 0.01 – 0.08 g/L), [MO] dye concentration (X₃: 10 – 80 mg/L). Overall, the adjusted coefficient of determination (R²) value of 0.99 demonstrated that the used model was quite appropriate, and the chosen RSM was effective in optimization the decolorization conditions of MO.     

Small angle X-ray scattering study of surface modified tin oxide nanoparticles prepared by sol-gel route

The surface properties of SnO₂ nanoparticles were modified by grafting ionic (Tiron®_, (OH)₂C₆H₂(SO₃Na)₂·H₂O) or non-ionic (Catechol®_, C₆H₄-1,2-(OH)₂) capping molecules during aqueous sol-gel processing to improve the redispersibility of powdered xerogel. The effect of the amount of grafted organic molecules on the redispersibility of powders in aqueous solution at several basic pH values was studied. The nanostructural features of the colloidal suspensions were analyzed by small angle X-ray scattering (SAXS) measurements. Irrespective of the nature and amount of grafted molecules, complete redispersion was obtained in aqueous solution at pH = 13. The redispersion at pH = 11 results in a mixture of dispersed primary particles and aggregates. The proportion of well dispersed nanoparticles and aggregates (and their average size) can be tuned by the quantity of grafted ionic molecules.     

Adsorption of Cadmium on Titanium Dioxide Nanoparticles in Freshwater Conditions – A Chemodynamic Study

The adsorption of Cd onto two titanium dioxide nanoparticles (nTiO₂) with distinct crystalline phases and sizes was investigated in conditions that can be found in freshwater systems (I=0.01 M, pH 6.0–8.5). Cd dynamic speciation was assessed by two distinct electroanalytical techniques: absence of gradients and nernstian equilibrium stripping (AGNES) and scanned stripping chronopotentiometry (SSCP). With both NPs, 1 : 1 CdTiO₂ homogeneous and labile surface complexes are formed. To our knowledge this is the first study about the dynamic nature of the nTiO₂ surface complexes formed in the presence of Cd.     

The nido‐Cage⋅⋅⋅π Bond: A Non‐covalent Interaction between Boron Clusters and Aromatic Rings and Its Applications

Non‐covalent interactions involving multicenter multielectron skeletons such as boron clusters are rare. Now, a non‐covalent interaction, the nido‐cage???π bond, is discovered based on the boron cluster C₂B₉H₁₂^? and an aromatic π system. The X‐ray diffraction studies indicate that the nido‐cage???π bonding presents parallel‐displaced or T‐shaped geometries. The contacting distance between cage and π ring varies with the type and the substituent of the aromatic ring. Theoretical calculations reveal that this nido‐cage???π bond shares a similar nature to the conventional anion???π or π???π bonds found in classical aromatic ring systems. This nido‐cage???π interaction induces variable photophysical properties such as aggregation‐induced emission and aggregation‐caused quenching in one molecule. This work offers an overall understanding towards the boron cluster‐based non‐covalent bond and opens a door to investigate its properties.     

A Tetrameric Cage with D2h Symmetry through Alkyne Metathesis

Shape‐persistent covalent organic polyhedrons (COPs) with ethynylene linkers are usually prepared through kinetically controlled cross‐coupling reactions. The high‐yielding synthesis of ethynylene‐linked rigid tetrameric cages via one‐step alkyne metathesis from readily accessible triyne precursors is presented. The tetrameric cage contains two macrocyclic panels and exhibits D_2h symmetry. The assembly of such a COP is a thermodynamically controlled process, which involves the initial formation of macrocycles as key intermediates followed by the connection of two macrocycles with ethynylene linkages. With a large internal cavity, the cage exhibits a high binding selectivity toward C₇₀ (K=3.9×10³ L mol^?1) over C₆₀ (no noticeable binding).     

Liquid crystalline formulations containing modified surface TiO2 nanoparticles obtained by sol–gel process

Titanium dioxide (TiO₂) is an inorganic compound used as sunscreen in cosmetic/pharmaceutical formulations as a way to prevent the skin cancer. In this work we have used surface modified titania nanoparticles obtained by thermo-reversible sol?Cgel transition showing transparency in the range of temperature typical for sunscreen use (between 20 and 45?°C). The goal of this work was to develop and characterize liquid crystalline cosmetic formulations containing surface modified titania nanoparticles. We have analyzed the citotoxicity of the nanoparticles, their zeta potential and the liquid crystalline phase behavior of the formulations. The violet crystal assay has shown no citotoxicity associated to the presence of surface modified groups on the two cell lines tested, human keratinocytes and fibroblasts, presenting more than 70% of cell viability for all analyzed nanoparticles. The zeta potential measurements revealed a negative charged surface for TiO₂ nanoparticles at pH values in the range of 6.5?C7.0, preventing the aggregation and maintaining the final transparency of the liquid crystalline sunscreen formulations. The polarized light microscopy, associated to SAXS, have shown the presence of liquid crystalline phases both with and without TiO₂ nanoparticles. The charged surface of TiO₂ nanoparticles maintains the stability of the formulations and the liquid crystalline structure. This renders this system a good candidate for being used simultaneously as sunscreen and as controlled release system of anti cancer drugs.     

Encapsulation of Metalloporphyrins in a Self‐Assembled Cubic M8L6 Cage: A New Molecular Flask for Cobalt–Porphyrin‐Catalysed Radical‐Type Reactions

The synthesis of a new, cubic M₈L₆ cage is described. This new assembly was characterised by using NMR spectroscopy, DOSY, TGA, MS, and molecular modelling techniques. Interestingly, the enlarged cavity size of this new supramolecular assembly allows the selective encapsulation of tetra(4‐pyridyl)metalloporphyrins (M^II(TPyP), M=Zn, Co). The obtained encapsulated cobalt–porphyrin embedded in the cubic zinc–porphyrin assembly is the first example of a catalytically active encapsulated transition‐metal complex in a cubic M₈L₆ cage. The substrate accessibility of this system was demonstrated through radical‐trapping experiments, and its catalytic activity was demonstrated in two different radical‐type transformations. The reactivity of the encapsulated Co^II(TPyP) complex is significantly increased compared to free Co^II(TPyP) and other cobalt–porphyrin complexes. The reactions catalysed by this system are the first examples of cobalt–porphyrin‐catalysed radical‐type transformations involving diazo compounds which occur inside a supramolecular cage.     

Host–Guest Recognition and Fluorescence of a Tetraphenylethene‐Based Octacationic Cage

We report the synthesis and characterization of a three‐dimensional tetraphenylethene‐based octacationic cage that shows host–guest recognition of polycyclic aromatic hydrocarbons (e.g. coronene) in organic media and water‐soluble dyes (e.g. sulforhodamine 101) in aqueous media through CH???π, π–π, and/or electrostatic interactions. The cage?coronene exhibits a cuboid internal cavity with a size of approximately 17.2×11.0×6.96 ų and a “hamburger”‐type host–guest complex, which is hierarchically stacked into 1D nanotubes and a 3D supramolecular framework. The free cage possesses a similar cavity in the crystalline state. Furthermore, a host–guest complex formed between the octacationic cage and sulforhodamine 101 had a higher absolute quantum yield (Φ_F=28.5 %), larger excitation–emission gap (Δλ_ex‐em=211 nm), and longer emission lifetime (τ=7.0 ns) as compared to the guest (Φ_F=10.5 %; Δλ_ex‐em=11 nm; τ=4.9 ns), and purer emission (Δλ_FWHM=38 nm) as compared to the host (Δλ_FWHM=111 nm).     

Synthesis of Zn doped black TiO2 nanoparticles for degradation of 2, 4, 6 tri-chloro-phenol under visible light

A modified sol-gel method was used for synthesis of zinc doped black TiO₂ nanoparticles. The modified sol-gel synthesised catalyst was utilised for degradation of 2, 4, 6 tri-chloro-phenol under visible light irradiation. The catalyst was characterized using XRD, SEM, TEM, BET and DRS analysis. The nanoparticles were crystalline in nature and in anatase phase. The size of zinc doped black TiO₂ nanoparticles was 5 nm. The synthesised nanoparticles were mesoporous in nature and the specific surface area was found to be 34.15 m²/g. The band gap energy of zinc black TiO₂ nanoparticles was found to be 2.73 eV. The point of zero charge of zinc doped black TiO₂ nanoparticles was 6.7. The maximum degradation of 2, 4, 6 tri-chloro-phenol using 2 mol% zinc doped black TiO₂ was found to be 95%.     

Calcium Phosphate Hybrid Nanoparticles: Self‐Assembly Formation,Characterization, and Application as an Anticancer Drug Nanocarrier

Calcium phosphate hybrid nanoparticles (CaP‐HNPs) have been synthesized in aqueous solution through self‐assembly by using two oppositely charged polyelectrolytes (poly(diallyldimethylammonium chloride) (PDADMAC) and poly(acrylate sodium) (PAS)) as dual templates. First, the PAS/Ca²⁺ and PDADMAC/PO₄^3? complexes form through electrostatic interactions and then two complexes self‐assemble into CaP‐HNPs after mixing them together. The as‐prepared CaP‐HNPs exhibit a spherical morphology with a narrow size distribution, good dispersibility, and high colloidal stability in water. The CaP‐HNPs are explored as a nanocarrier for the anticancer drug docetaxel (Dtxl). The CaP‐HNPs show excellent biocompatibility, high drug‐loading capacity, pH‐sensitive drug‐release behavior, and high anticancer effect after being loaded with Dtxl. Therefore, the as‐prepared CaP‐HNPs are promising drug nanocarriers for cancer therapy.     

Host–Guest Recognition and Fluorescence of a Tetraphenylethene-Based Octacationic Cage

We report the synthesis and characterization of a three-dimensional tetraphenylethene-based octacationic cage that shows host–guest recognition of polycyclic aromatic hydrocarbons (e.g. coronene) in organic media and water-soluble dyes (e.g. sulforhodamine 101) in aqueous media through CH⋅⋅⋅π, π–π, and/or electrostatic interactions. The cage⊃coronene exhibits a cuboid internal cavity with a size of approximately 17.2×11.0×6.96 ų and a “hamburger”-type host–guest complex, which is hierarchically stacked into 1D nanotubes and a 3D supramolecular framework. The free cage possesses a similar cavity in the crystalline state. Furthermore, a host–guest complex formed between the octacationic cage and sulforhodamine 101 had a higher absolute quantum yield (Φ_F=28.5 %), larger excitation–emission gap (Δλ_ex-em=211 nm), and longer emission lifetime (τ=7.0 ns) as compared to the guest (Φ_F=10.5 %; Δλ_ex-em=11 nm; τ=4.9 ns), and purer emission (Δλ_FWHM=38 nm) as compared to the host (Δλ_FWHM=111 nm).     

Stabilization of pH‐Sensitive mPEG–PH–PLA Nanoparticles by Stereocomplexation Between Enantiomeric Polylactides

Methoxy poly(ethylene glycol)–poly(L ‐histidine)–poly(lactide) (mPEG₄₅–PH₃₀–PLA₈₂) triblock copolymers self‐assemble into nanoparticles by sterocomplexation. The properties of the stereocomplex nanoparticles including morphology, stability, and biocompatibility are investigated. The results reveal that the stereocomplexation between PLLA and PDLA segments could prevent the aggregation of the nanoparticles when the pH value is around 6.8. The mean diameter of the stereocomplex nanoparticles is stabilized at about 100 nm when the pH values are changed from 7.9 to 5.0. The cytotoxicity of the stereocomplex nanoparticles is evaluated, and the results demonstrate that the stereocomplexation could decrease the cytotoxicity of the PDLA segments.     

Synthesis,characterization, and in vitro toxicity evaluation of upconversion luminescence NaLuF4:Yb3+/Tm3+ nanoparticles suitable for medical applications

Synthesis, characterization, and in vitro toxicity evaluation of upconversion luminescence NaLuF₄:Yb³⁺/Tm³⁺ nanoparticles (UCLNPs) are reported in the current study. Initially, the synthesized lanthanide trifluoroacetate (Ln(OOCCF₃)₃) precursor was used to fabricate NaLuF₄ nanoparticles doped with Yb³⁺ and Tm³⁺ metal ions. The nanoparticles were coated with calcium carbonate (CaCO₃) after removing the hydrophobic species on them to enhance their biocompatibility. The in vitro methylthiazolyldiphenyl-tetrazoliumbromide (MTT) test was used to evaluate the toxicity of synthesized NaLuF₄:Yb³⁺/Tm³⁺ nanoparticles (NLF-5) on L929 mouse fibroblast cell lines. The transmission electron microscopy image showed that the particle size of NaLuF₄:Yb³⁺/Tm³⁺ was 32 nm. The synthesized NLF-5 nanoparticles have both α-cubic and β-hexagonal crystalline structures that provided a superb near-infrared-to-near-infrared upconversion luminescence signal when excited at 980 nm. MTT test results show that the death of L929 fibroblast cells was observed only at concentrations above 250 μg/mL of NaLuF₄:Yb³⁺/Tm³⁺ nanoparticles. In addition, with an increase in patrol time of 24, 48, and 72 hr, cell toxicity increased significantly, while the coated nanoparticles did not have any toxic effects. The synthesized nanoparticles could be used as a suitable material for medical applications due to their small particle size, high photoluminescence emission intensity, and low toxicity.     

Lactic acid based sol–gel process of Ag nanoparticles and crystalline phase control of Ni particles in aqueous sol–gel process

Nickel and silver particles were prepared by using sol–gel auto-combustion method under N₂ atmosphere where lactic acid was applied as chelating agent. The synthesis of nickel particles was carried out at various pH conditions (2–7), resulting in the face-centered-cubic or hexagonal-close-packed crystalline nickel phase. The morphology and structure of synthesized nickel particles and silver nanoparticles were characterized by X-ray diffraction, transmission electron microscope, energy dispersive X-Ray spectroscopy and differential scanning calorimetry-thermogravimetric analysis. The results show that the spherical Ag nanoparticles with diameters in the range of 18–27 nm and narrow size distribution can be obtained by this sol–gel process.     

Transition Metal Complexes of a Salen–Fullerene Diad: Redox and Catalytically Active Nanostructures for Delivery of Metals in Nanotubes

A covalently‐linked salen–C₆₀ (H₂L) assembly binds a range of transition metal cations in close proximity to the fullerene cage to give complexes [M(L)] (M=Mn, Co, Ni, Cu, Zn, Pd), [MCl(L)] (M=Cr, Fe) and [V(O)L]. Attaching salen covalently to the C₆₀ cage only marginally slows down metal binding at the salen functionality compared to metal binding to free salen. Coordination of metal cations to salen–C₆₀ introduces to these fullerene derivatives strong absorption bands across the visible spectrum from 400 to 630 nm, the optical features of which are controlled by the nature of the transition metal. The redox properties of the metal–salen–C₆₀ complexes are determined both by the fullerene and by the nature of the transition metal, enabling the generation of a wide range of fullerene‐containing charged species, some of which possess two or more unpaired electrons. The presence of the fullerene cage enhances the affinity of these complexes for carbon nanostructures, such as single‐, double‐ and multiwalled carbon nanotubes and graphitised carbon nanofibres, without detrimental effects on the catalytic activity of the metal centre, as demonstrated in styrene oxidation catalysed by [Cu(L)]. This approach shows promise for applications of salen–C₆₀ complexes in heterogeneous catalysis.     

Effect of Hydrothermal on the Crystalline Phase and Morphology of Manganese Oxide Nanocrystals

The effect of hydrothermal on the crystalline phase and morphology of manganese oxide nanocrystals was studied. The Mn₃O₄ nanoparticles were transformed into γ‐MnOOH nanowires after hydrothermal treatment. The pH plays an important role in the transformation of crystalline phases. The whole nanowires of γ‐MnOOH were formed at pH 8 and pH 9 while the crystalline phase of Mn₃O₄ was still remained in the mixture of Mn₃O₄ and γ‐MnOOH at pH 10.     

Ratiometric pH-nanosensors based on rhodamine-doped silica nanoparticles functionalized with a naphthalimide derivative

This paper describes the preparation of two-dye-doped silica nanoparticles for ratiometric pH measurements in the biologically relevant pH-range. While a rhodamine derivative is embedded in a silica core and used as the reference, a pH-sensitive naphthalimide dye is immobilized on the previously amino-functionalized core through two different approaches. Either the naphthalimide’s carboxylic group is activated to a succinimidyl-ester to form an amide bond or the system can be built up via solid-phase organic synthesis in only two steps. Both types of nanosensors are characterized in terms of morphology (dynamic light scattering, transmission electron microscopy) and optical properties (steady-state fluorescence spectroscopy). In terms of application, e.g. reproducibility and handling of the synthesis, the first approach gave very good results with respect to size and size distribution and a pK_a value of 6.55 was found that is comparable to the free indicator dye in solution. The solid-phase organic synthesis method proves the possibility of covalent immobilization of naphthalimides to amino-functionalized surfaces, showing the stability of the polymeric substrate and achieving comparable results for pH sensing.     

Synthesis of nickel metal nanoparticles via a chemical reduction of nickel ammine and alkylamine complexes by hydrazine

Nickel nanoparticles were prepared from their coordination compounds, such as [Ni(NH₃)₆]Cl₂, [Ni(N₂H₄)₂Cl₂], [Ni(HNEt₂)₆]Cl₂, and [Ni(H₂NBu)₆]Cl₂ in aqueous solution by chemical reduction. The reaction of nickel ammine and alkylamine complexes with hydrazine monohydrate as a reducing agent was carried out at 90 °C and pH = 10–12. Depending on the influencing parameters such as oxidizing agent, pH, and temperature, the hydrazine reaction can be carried out in different pathways. The chemical reduction method is a simple procedure and also is the best one in the controlling of composition, size, and shape of Ni powder. The reduction of nickel complexes into the metallic Ni powder occurs via the dissociation of complexes and reduction by hydrazine in alkaline solution. Therefore, complexing agents have the most effect on the reduction reaction. The results show that, when the ligands in complexes were changed from ammine to diethylamine and butylamine, respectively, the crystalline size and morphology of nickel metal nanoparticles are changed. The chemical reduction of nickel complexes into metallic nickel can be accompanied with a change in the crystalline system. The pure nickel crystalline has a face-centered cubic structure. The nickel nanoparticles were characterized using IR spectroscopy, X-ray powder diffraction, scanning electron microscopy and vibrating sample magnetometer analyses.     

Covalently Assembled Dipeptide Nanospheres as Intrinsic Photosensitizers for Efficient Photodynamic Therapy in Vitro

Monodispersed diphenylalanine‐based nanospheres with excellent biocompatibility are fabricated through a facile covalent reaction‐induced assembly. Interestingly, the nanospheres exhibit red autofluorescence. Most importantly, such assembled dipeptide nanospheres can serve as intrinsic photosensitizer to convert O₂ to singlet oxygen (¹O₂). Thus, photodynamic therapy in vitro can be achieved effectively. The versatile strategy could be extended to other biomolecules containing a primary amine group for the fabrication of potential intrinsic photosensitizers.     

Self‐assembly of N‐carboxyethylchitosan near the isoelectric point

For the first time the possibility to obtain nanostructures by self‐assembly of chitosan polyampholytic derivative was demonstrated. The self‐assembly of N‐carboxyethylchitosan (CECh) took place only near its isoelectric point (pH 5.0–5.6). Out of the pH range 5.0–5.6, CECh aqueous solutions behaved as real solutions. Dynamic light scattering and atomic force microscopy analyses revealed that spherically shaped or rod/worm‐like nanosized assemblies were formed depending on the polymer molar mass, pH value, and polymer concentration. CECh of two different molar masses was studied in concentrations ranging from 0.01 to 0.1 mg/mL. The structures from CECh of weight‐average molar mass (M_w ) 4.5 × 10³ g/mol were spherical regardless the pH and polymer concentration. In contrast, CECh of high molar mass (HMMCECh, M_w = 6.7 × 10⁵ g/mol) formed self‐assemblies with spherical shape only at pH 5.0 and 5.6. At pH 5.2 spherical nanoparticles were obtained only at polymer concentration 0.01 mg/mL. The mean hydrodynamic diameter (D_h) of the obtained nanoparticles was in the range from 30 to 980 nm. On increasing the concentration, aggregation of the nanoparticles appeared, and at HMMCECh concentration 0.1 mg/mL, rod/worm‐like structures were obtained. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6712–6721, 2008