A size controlled synthesis of CuS nano-particles in the protein cage,apoferritin

CuS compound semiconductor nanoparticles (NPs) were prepared in the 7 nm inner cavity of apoferritin, a cage-shaped protein composed of 24 subunits forming a cage-like structure, 12 nm in diameter. The average core diameter of the NPs synthesized in the apoferritin cavity was 5 nm with narrow size distribution. The synthesized NP cores were analyzed and confirmed by EDS, XRD and HR-TEM as hexagonal poly crystalline. The CuS NP core synthesis took 3 h and the synthesis manner was all-or-nothing core formation. This water-soluble and homogeneous CuS semiconductor NP has the potential to be used in the construction of nanostructures.     

Synthesis and characterization of core∕shell Fe(3)O(4)∕ZnSe fluorescent magnetic nanoparticles

We report on the successful preparation and characterization of fluorescent magnetic core∕shell Fe(3)O(4)∕ZnSe nanoparticles (NPs) with a spherical shape by organometallic synthesis. The 7 nm core∕3 nm shell NPs show good magnetic and photoluminescence (PL) responses. The observed PL emission∕excitation spectra are shifted to shorter wavelengths, compared to a reference ZnSe NP sample. A dramatic reduction of PL quantum yield is also observed. The temperature dependence of the magnetization for the core∕shell NPs shows the characteristic features of two coexisting and interacting magnetic (Fe(3)O(4)) and nonmagnetic (ZnSe) phases. Compared to a reference Fe(3)O(4) NP sample, the room-temperature Néel relaxation time in core∕shell NPs is three times longer.     

1D hierarchical CdS NPs/NiO NFs heterostructures with enhanced photocatalytic activity under visible light irradiation

One-dimensional (1D) hierarchically structured CdS nanoparticles (NPs)/NiO nanofibers (NFs) heterostructures with remarkable removal efficiency for diazo dye Congo red (CR) were fabricated by a stepwise synthesis process, which was involved a chemical bathing deposition combined with calcination, and a microwave-assisted wet chemical reaction. The crystal phases, morphologies, optical absorption properties, and adsorption/photocatalytic activity of as-prepared products were investigated by XRD, FESEM, TEM, high-resolution TEM (HRTEM), N₂ adsorption/desorption isotherms, UV–Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectrum respectively. The experimental results indicated that binary satellite- core CdS NPs/NiO NFs heterojunctions are comprised of n-type CdS NPs with size of 10–30 nm decorated onto 1D p-type NiO NFs with diameter of 60–180 nm and length up to microns, which are self-assembled by nanoparticles with 30–100 nm in size. The possible formation mechanism for satellite-core structured CdS/NiO heterojunction is proposed. Interestingly, the decolorization efficiency over CdS/NiO heterostructures reached up to 91.2% in removal of aqueous CR at high concentration within 40 min under visible light irradiation, which was approximately 5.2 and 3.8 times as high as that of pure CdS nanocrystals (NCs) and the mixture of NiO NFs and CdS NCs. Furthermore, the possible photocatalytic mechanism was also investigated. The as-designed hybrid CdS NPs/NiO NFs heterostructures exhibited improved photocatalytic activity, which is attributed to the enhancement of the visible light adsorption, the efficient separation of photogenerated electrons and holes, and the high adsorption capacity towards CR molecules, thereby displaying superior visible- light-driven photodegradation of CR in high concentration. This work may provide a green engineering heterojunction technology to develop the advanced multifunctional nanocomposites for their applications in wastewater purification.     

Photoluminescence properties of single crystalline ZnO/CdS core/shell one-dimensional nanostructures

ZnO/CdS core/shell one-dimensional nanostructures were synthesized using ZnO nanorod arrays as templates, which were fabricated by a vapor transport process. CdS shells with various thicknesses were epitaxially grown on the ZnO nanorod arrays by metal organic chemical vapor deposition. Selected area electron diffraction measurement revealed that both ZnO cores and CdS shells were single crystalline growing along the c-axis. The photoluminescence properties of the ZnO/CdS core/shell nanostructures were also varied with different CdS shell thicknesses. A carrier transition process from ZnO to CdS was assumed to induce the enhancement of CdS photoluminescence.     

Formation of CdS nanoparticles by gas-diffusion method in sol–gel derived ureasilicate matrix

CdS nanoparticles (NPs) were prepared by exposing a hybrid ureasilicate gel containing cadmium (II) ions to H₂S gas at room temperature. Additional component (tetraethoxysilane) was introduced during the synthesis in order to improve the mechanical properties of the host matrix. The obtained material was subsequently subjected to an annealing treatment under an argon atmosphere at temperatures that varied from 43 to 102 °C. The size of the embedded NPs increased with thermal annealing. The optical absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy (TEM) measurements confirmed the formation of CdS nanoparticles (NPs) exhibiting quantum confinement effect.     

Apoferritin-templated yttrium phosphate nanoparticle conjugates for radioimmunotherapy of cancers

We report a templated-synthetic approach based on protein-cage of apoferritin to prepare radionuclide nanoparticle (NP) conjugates. Non-radioactive yttrium (89Y) was used as a model target and surrogate for radioyttrium (90Y) to prepare the nanoparticle conjugate. The center cavity and multiple channel structure of apoferritin offer a fast and facile method to precipitate yttrium phosphate by diffusing yttrium and phosphate ions into the cavity of apoferritin, resulting a core-shell nanoparticle. The yttrium phosphate/apoferritin nanoparticle was functionalized with biotin for further application. The synthesized nanoparticle was characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). We found that the resulting nanoparticles were uniform in size, with a diameter of around 8 nm. We tested the pre-targeting capability of the biotin-modified yttrium phosphate/apoferritin nanoparticle conjugate with streptavidin-modified magnetic beads and with aid of streptavidin-modified fluorescein isothiocyanate (FITC) tracer. This work shows that an yttrium phosphate NP conjugate provides a fast, simple and efficient method to prepare radioactive yttrium conjugate for potential applications in radioimmunotherapy of cancer.     

Effective size-controlled synthesis and electrochemical characterization of ordered Pt nanopattern arrays from self-assembling block copolymer template

This work offers an effective size-controlled synthesis of platinum nanoparticle (Pt NP) arrays for electrocatalyst through self-assembled nanopatterns of block copolymers on titanium (Ti) wafers. Size, spacing and uniformity of Pt NP with loading of Pt to a minimum were investigated to be controlled and adjusted in order to improve the electrochemically active surface area (ECSA) and ECSA stability, and Pt concentration in copolymer/chloroplatinic acid (H₂PtCl₆) solution was verified to be one of the most important factors to control the arrays’ structure. In our case, the Pt NPs with predictable size of 5–16.5 nm could be obtained when the Pt concentration is larger than 0.05 mg ml^?1, which the dominant diameter is proved to be proportional to one-third power of the Pt concentration according to the linear relation of templates’ Pt/N mass ratio versus Pt concentration, and the Pt NPs remain highly ordered arrays with predictable spacing when the Pt concentration is larger than 0.125 mg ml^?1. Decrease in Pt concentration from 2 to 0.125 mg ml^?1 is an effective method to improve the ECSA and durability simultaneously. The Pt NP arrays exhibit not only a remarkable initial ECSA value of 106.2 m² g^?1, but also a pseudo-zero particle aggregation possibility during 3000-cycle voltammetry, which is attributed to the high Pt NP dispersion and the ordered arrays that improve the Pt utilization and lower the possibility of aggregation.     

CdS:Mn nanorods: solvothermal synthesis and properties

Manganese (0.05-9 mol.%) doped CdS nanorods were synthesized via solvothermal route using ethylenediamine (En) and a mixture of En and water as the solvents. The diameters and the lengths of the doped CdS nanorods varied from 40-100 nm and 600-2500 nm, respectively, with change in the composition of the solvents. The broad photoluminescence (PL) emission from the undoped CdS nanorods centered at approximately 535 nm is found to be blue shifted to 516 nm with the incorporation of Mn in the CdS crystal structure. Also increase in the intensity of the PL was noticed in the Mn doped CdS nanorods for both the solvent systems. Maximum PL intensity was observed for 1 mol.% Mn in case of En system and for 0.5 mol.% Mn in case of En/water system, above which quenching occurred as a result of Mn-Mn clustering. EPR study revealed six-line hyperfine splitting for low Mn concentration in both solvent systems. Increase in the Mn concentration caused EPR signal broadening due to Mn-Mn clustering.     

Structural and optical properties of CdS thin films prepared by chemical bath deposition at different ammonia concentration and S/Cd molar ratios

CdS thin films were prepared by chemical bath deposition technique using the precursors of SC(NH₂)₂, CdCl₂, NH₄Cl, NH₃·H₂O and deionized water. The obtained thin films were characterized by scanning electron microscopy, X-ray diffraction, energy dispersive spectrometer, UV–VIS specrophotometry and photoluminescence spectroscopy. The morphology, structural and optical properties of CdS thin films were investigated as a function of ammonia concentration and S/Cd molar ratios in precursors. The results reveal that morphology of CdS films change from flake like into spherical particle like, crystal structure from wurtzite structure to zinc blende structure, S/Cd atom ratios in CdS thin films increase and optical band gap E _g decrease with increasing ammonia concentration in precursors. The room temperature photoluminescence spectrum of CdS thin films shows a strong peak at about 500 nm and a weak peak at about 675 nm.     

CdSe/Cd(x)Zn1-xS core/shell nanocrystals: core morphology and luminescent property

CdSe cores with rod (an aspect ratio of 1.8, d-5 nm) and spherical (an aspect ratio of 1, d-5 nm) morphologies were fabricated by two kinds of organic approaches through adjusting growth processes. Because of large difference of size and morphology, two kinds of cores revealed different absorption spectra. However, these cores exhibited almost same photoluminescence (PL) spectra with a red-emitting PL peak of around 625 nm. This is ascribed that they have a similar size in diameter. A graded Cd(x)Zn1-xS shell of larger band gap was grown around CdSe rods and spheres using oleic acid as a capping agent. Based on the growth kinetics of CdS and ZnS, interfacial segregation was created to preferentially deposit CdS near the core, providing relaxation of the strain at the core/shell interface. For spherical CdSe cores, the homogeneous deposition of the Cd(x)Zn1-xS shell created spherical core/shell nanocrystals (NCs) with a size of 7.1 nm in diameter. In the case of using CdSe cores with rod morphology, the anisotropic aggregation behaviors of CdS monomers on CdSe rods led to the size (approximately 10 nm in diameter) of spherical CdSe/Cd(x)Zn1-xS core/shell NCs with a small difference to the length of the CdSe rod (approximately 8.9 nm). The resulting spherical core/shell NCs created by the rod and spherical cores exhibited almost same PL peak wavelength (652 and 653 nm for using rod and spherical cores, respectively), high PL efficiency up to 50%, and narrow PL spectra (36 and 28 nm of full with at half maximum of PL spectra for the core/shell NCs with CdSe spheres and rods, respectively). These core/shell NCs provide an opportunity for the study of the evolution of PL properties as the shape of semiconductor NCs.     

Single w/o microemulsion templating of CdS nanoparticles

We report the synthesis of monodispersed CdS nanoparticle with tunable size by controlling the reaction aging time in a single water in oil (w/o) microemulsion system. The w/o microemulsion system consists of nonionic surfactant poly (oxyethylene)₅ nonyl phenol ether (NP5), poly (oxyethylene)₁₀ nonyl phenol ether (NP10), cyclohexane and aqueous solution (cadmium salt and thioacetamide). Thioacetamide (TAA) has been utilized as a source for slow release of sulfur ions in the in situ synthesis of CdS. UV-Visible spectra shows obvious blue shift for the CdS nanoparticles as compared to the bulk material due to quantum size effect. CdS nanoparticle size depends on the reaction aging time where longer reaction aging time yields bigger particles. CdS nanoparticles growth behaviour as a function of reaction aging time in the microemulsion system was characterized by UV-Visible spectroscopy. The particle growth follows a power law with an exponential in the order of 0.17. Energy Filter Transmissions Electron Microscopy (EFTEM) reveals monodispersed CdS nanoparticles with standard deviation, less than 8%.     

Directed self-assembly of nanogold using a chemically modified nanopatterned surface

Electron-beam lithography (EBL) was used to define an aminosilane nanopatterned surface in order to electrostatically self-assemble gold nanoparticles (Au NPs). The chemically modified nanopatterned surfaces were immersed into a Au NP solution to allow the Au NPs to self-assemble. Equilibrium self-assembly was achieved in only 20 min. The number of Au NPs that self-assembled on an aminosilane dot was controlled by manipulating the diameters of both the Au NPs and the dots. Adding salt to the Au NP solution enabled the Au NPs to self-assemble in greater numbers on the same sized dot. However, the preparation of the Au NP solution containing salt was sensitive to spikes in the salt concentration. These spikes led to aggregation of the Au NPs and non-specific deposition of Au NPs on the substrate. The Au NP patterned surfaces were immersed in a sodium hydroxide solution in order to lift-off the patterned Au NPs, but no lift-off was observed without adequate physical agitation. The van der Waals forces are too strong to allow for lift-off despite the absence of electrostatic forces.     

Bottom-up photonic crystal cavities formed by patterned III-V nanopillars

We report on the formation and optical properties of bottom-up photonic crystal (PC) cavities formed by III-V nanopillars (NPs) via catalyst-free selective-area metal-organic chemical vapor deposition on masked GaAs substrates. This method of NP synthesis allows for precise lithographic control of NP position and diameter enabling simultaneous formation of both the photonic band gap (PBG) region and active gain region. The PBG and cavity resonance are determined by independently tuning the NP radius r, pitch a, and height h in the respective masked areas. Near-infrared emission at 970 nm is achieved from axial GaAs/InGaAs heterostructures with in situ passivation by laterally grown InGaP shells. To achieve out-of-plane optical confinement, the PC cavities are embedded in polydimethylsiloxane (PDMS) and removed from the growth substrate. Spatially and spectrally resolved 77 K photoluminescence demonstrates a strong influence of the PBG resonance on device emission. Resonant peaks are observed in the emission spectra of PC cavities embedded in PDMS.     

WO3 Nanofiber‐Based Biomarker Detectors Enabled by Protein‐Encapsulated Catalyst Self‐Assembled on Polystyrene Colloid Templates

A novel catalyst functionalization method, based on protein‐encapsulated metallic nanoparticles (NPs) and their self‐assembly on polystyrene (PS) colloid templates, is used to form catalyst‐loaded porous WO₃ nanofibers (NFs). The metallic NPs, composed of Au, Pd, or Pt, are encapsulated within a protein cage, i.e., apoferritin, to form unagglomerated monodispersed particles with diameters of less than 5 nm. The catalytic NPs maintain their nanoscale size, even following high‐temperature heat‐treatment during synthesis, which is attributed to the discrete self‐assembly of NPs on PS colloid templates. In addition, the PS templates generate open pores on the electrospun WO₃ NFs, facilitating gas molecule transport into the sensing layers and promoting active surface reactions. As a result, the Au and Pd NP‐loaded porous WO₃ NFs show superior sensitivity toward hydrogen sulfide, as evidenced by responses (R_air/R_gas) of 11.1 and 43.5 at 350 °C, respectively. These responses represent 1.8‐ and 7.1‐fold improvements compared to that of dense WO₃ NFs (R_air/R_gas = 6.1). Moreover, Pt NP‐loaded porous WO₃ NFs exhibit high acetone sensitivity with response of 28.9. These results demonstrate a novel catalyst loading method, in which small NPs are well‐dispersed within the pores of WO₃ NFs, that is applicable to high sensitivity breath sensors.     

Multifunctional Nanoparticle@MOF Core–Shell Nanostructures

Controllable integration of inorganic nanoparticles (NPs) and metal–organic frameworks (MOFs) is leading to the creation of many new multifunctional materials. In this Research News, an emerging type of core–shell nanostructure, in which the inorganic NP cores are encapsulated by the MOF shells, is briefly introduced. Unique functions originating from the property synergies of different types of inorganic NP cores and MOF shells are highlighted, and insight into their future development is suggested. It is highly expected that this Research News could arouse research enthusiasm on such NP@MOF core–shell nanostructures, which have great application potential in devices, energy, the environment, and medicine.     

Effect of inorganic shells on luminescence properties of ZnS:Ag nanoparticles

The hydrothermally synthesized Ag-doped ZnS (ZnS:Ag) nanoparticles have been coated with inorganic shells by a chemical precipitation method. The ZnS:Ag/ZnS, ZnS:Ag/CdS, and ZnS:Ag/ZnO core–shell nanoparticles with different thickness of ZnS, CdS, and ZnO shells have been prepared. The effects of shells on the luminescence properties of ZnS:Ag cores have been investigated through the photoluminescence (PL) spectra and luminescence stabilities of products. In the core–shell nanoparticles involved here, the ZnO shell can most significantly enhance the luminescence of ZnS:Ag cores. The 450 nm emission intensity of ZnS:Ag/ZnO nanoparticles is up to 125 % of that of ZnS:Ag nanoparticles. However, the ZnO shell can hardly influence the luminescence stability under ultraviolet irradiation. The ZnS shell can only increase the luminescence of ZnS:Ag cores to some extent, but it can improve the luminescence stability under ultraviolet irradiation. Although the CdS shell can improve the luminescence stability to some extent, it quenches the luminescence of ZnS:Ag nanoparticles dramatically.     

CdSe/Cd1−x Zn x S core/shell quantum dots with tunable emission: growth and morphology evolution

We demonstrate an organic synthesis to fabricate hydrophobic core/shell CdSe/Cd_1?x Zn _x S quantum dots (QDs) with tunable photoluminescence (PL) between green and red at relatively low temperature using trioctylphosphine S reacted directly with cadmium and zinc acetate. A seeded growth strategy was used for preparing large CdSe cores. Large CdSe cores revealed a rod-like morphology while small one exhibited a spherical shape. Being coated with a Cd_1?x Zn _x S shell on spherical CdSe cores with an average size of 3.9 nm in diameter, core/shell QDs exhibited a cubic morphology (a length of 5 nm). In contrast, the core/shell QDs created using a small core (3.3 nm in diameter) show a spherical morphology. Namely, the anisotropic aggregation behavior of CdS monomers on CdSe cores occurs when the rod-like core is coated with a Cd_1?x Zn _x S shell. CdS interlayer plays an important role for such morphology evolution because all CdSe cores with a pure ZnS shell exhibited a spherical morphology. The PL properties of CdSe/Cd_1?x Zn _x S core/shell QDs depended strongly on the size and morphology of the cores. The QDs revealed a narrow and tunable PL spectrum. It is believed that this facile strategy can be extended to synthesize other core–shell QDs at low temperature.     

Phosphine-free synthesis of high-quality reverse type-I ZnSe/CdSe core with CdS/Cd(x)Zn(1 - x)S/ZnS multishell nanocrystals and their application for detection of human hepatitis B surface antigen

Highly photoluminescent (PL) reverse type-I ZnSe/CdSe nanocrystals (NCs) and ZnSe/CdSe/CdS/Cd(x)Zn(1 - x)S/ZnS core/multishell NCs were successfully synthesized by a phosphine-free method. By this low-cost, 'green' synthesis route, more than 10 g of high-quality ZnSe/CdSe/CdS/Cd(x)Zn(1 - x)S/ZnS NCs were synthesized in a large scale synthesis. After the overgrowth of a CdS/Cd(x)Zn(1 - x)S/ZnS multishell on ZnSe/CdSe cores, the PL quantum yields (QYs) increased from 28% to 75% along with the stability improvement. An amphiphilic oligomer was used as a surface coating agent to conduct a phase transfer experiment, core/multishell NCs were dissolved in water by such surface modification and the QYs were still kept above 70%. The as-prepared water dispersible ZnSe/CdSe/CdS/Cd(x)Zn(1 - x)S/ZnS core/multishell NCs not only have high fluorescence QYs but also are extremely stable in various physiological conditions. Furthermore, a biosensor system (lateral flow immunoassay system, LFIA) for the detection of human hepatitis B surface antigen (HBsAg) was developed by using this water-soluble core/multishell NCs as a fluorescent label and a nitrocellulose filter membrane for lateral flow. The result showed that such ZnSe/CdSe/CdS/Cd(x)Zn(1 - x)S/ZnS core/multishell NCs were excellent fluorescent labels to detect HBsAg. The sensitivity of HBsAg detection could reach as high as 0.05 ng ml( - 1).     

Fluorescent polymeric nanoparticles: aggregation and phase behavior of pyrene and amphotericin B molecules in nanoparticle cores

The state of aggregation of compounds, especially drugs, in the cores of nanoparticles (NPs) formed by rapid precipitation is a significant unresolved issue. The state can control the dissolution kinetics from the NP, bioavailability, and chemical stability of the compound. A block-copolymer-directed rapid precipitation process is used to form ≈100 nm NPs comprising mixtures of hydrophobic species including fluorescent probe molecules. Fluorescence measurements are used to probe the state of aggregation and dynamics of rearrangement of pyrene (Py), Hostasol Yellow (HosY), and amphotericin B (AmpB) in NP cores. The Flory-Huggins theory of mixing is used to predict the miscibility or phase separation of the fluorophores from the host NP core material (polystyrene, cholesterol, or polycaprolactone). For Py, excimer fluorescence shows an initial microphase separation in the polystyrene core. Over time the Py redistributes more uniformly with a decrease in excimer and increase in monomer fluorescence. The Flory-Huggins theory predicts the miscibility. For HosY, the fluorescence quenching is not time-dependent, thus indicating stability of the microphase-separated fluorophores, which is consistent with the Flory-Huggins theory calculations. For the drug compound AmpB, the amphiphilic character of the molecule creates unusual "anti-Ostwald" ripening behavior in which the size distribution decreases and narrows over time, and the fluorescence demonstrates an increased ordering in the NP core over time--opposite to the behavior observed for Py.     

Synthesis of water-soluble core/shell CdS/ZnS nanoparticles at room temperature under ultrasonic irradiation: Potential for human serum detection

Water soluble semiconductor nanoparticles (NPs) of CdS are prepared at room temperature (~295 K) and under short time ultrasonic irradiation. We present the effect of ultrasonic irradiation on the formation of CdS NPs, and the data is explained by a growth law. It is found that the growth is governed by surface diffusion at the solid–liquid interface. CdS NPs are easily coated with relatively wide bandgap semiconductor ZnS. The interaction of core/shell CdS/ZnS NPs with a different amount of lyophilisates of human serum is studied by means of the absorption spectrum and zeta potential.