Synthesis of Luminescent ZrO2:Eu3+ Nanoparticles and Their Holographic Sub‐Micrometer Patterning in Polymer Composites

Here, the facile synthesis of fluorescent ZrO₂:Eu³⁺ nanoparticles with luminescence quantum yield of up to 8.7% that can be easily dispersed in organic solvents and utilized for the preparation of organic/inorganic volume holographic gratings is presented. The nanoparticles are prepared through a one‐step solvothermal process resulting in spherical particles with a mean size of 4 nm that were highly crystalline directly after the synthesis, without any need for calcination treatment. Detailed luminescence studies of the nanoparticles as a function of Eu³⁺ content demonstrate that the dopant concentration and its site symmetry play an important role in the emissive properties and lifetime of the luminescent centers. It is shown that the luminescence quantum yield of the colloidal ZrO₂:Eu³⁺ nanoparticles increases with dopant concentration up to a critical concentration of 11 mol% while the luminescence lifetime is shortened from 1.8 to 1.4 ms. Holographic photopolymerization of suitable monomer mixtures containing the luminescent nanoparticles demonstrated the ability to inscribe volume Bragg gratings (refractive index contrast n₁ up to 0.011) with light‐emissive properties, evidencing the high suitability of this approach for the fabrication of tailored nanomaterials for elaborate and demanding applications.     

微乳液法制备BaYF_5:Eu~(2+)纳米粒子及光谱特性研究

采用微乳液法制备了BaYF5:Eu2+纳米微粒,并利用X射线衍射(XRD)、扫描电子显微镜(SEM)和光致发光光谱等手段进行了表征。XRD数据与标准卡片PDF#46-39很好吻合,利用谢乐公式计算所制备产物平均粒径在20 nm左右。SEM图谱显示所制备的纳米粒子为球形,且形貌规则,粒径分布比较均匀。BaYF5:Eu2+的发射光谱中存在一个300~410 nm的发射带,发射光谱最强峰为330 nm,对应于Eu2+的4f65d→4f7发射,与传统高温固相法所制多晶材料最强发射峰378 nm相比蓝移了48 nm;其激发光谱最强峰位于263 nm,与传统高温固相法所制多晶材料最强激发峰322 nm相比蓝移了59 nm。     

Generation of Monodisperse,Shape‐Controlled Single and Hybrid Core–Shell Nanoparticles via a Simple One‐Step Process

In nano‐biotechnology, optoelectronics, and energy research areas, various fabrication methods have been developed for hybrid nanoparticles. A method is developed here for fabricating highly monodisperse three‐dimensional hybrid nanoparticles using a unique top‐down method based on secondary sputtering lithography. Nanostructures that have been formed on a PEDOT sacrificial layer are transferred from the substrate to an aqueous solution in a process that could be used to successfully disperse a variety of nanoparticle shapes and hybrid nanoparticles. By this method, a fluorescent dye could be encapsulated within the fabricated hybrid nanoparticles for use in bio‐sensing and drug‐delivery applications     

One‐Step Hydrothermal Synthesis of 2D Hexagonal Nanoplates of α‐Fe2O3/Graphene Composites with Enhanced Photocatalytic Activity

There has been significant progress in the field of semiconductor photocatalysis, but it is still a challenge to fabricate low‐cost and high‐activity photocatalysts because of safety issues and non‐secondary pollution to the environment. Here, 2D hexagonal nanoplates of α‐Fe₂O₃/graphene composites with relatively good distribution are synthesized for the first time using a simple, one‐step, template‐free, hydrothermal method that achieves the effective reduction of the graphene oxide (GO) to graphene and intimate and large contact interfaces of the α‐Fe₂O₃ nanoplates with graphene. The α‐Fe₂O₃/graphene composites showed significantly enhancement in the photocatalytic activity compared with the pure α‐Fe₂O₃ nanoplates. At an optimal ratio of 5 wt% graphene, 98% of Rhodamine (RhB) is decomposed with 20 min of irradiation, and the rate constant of the composites is almost four times higher than that of pure α‐Fe₂O₃ nanoplates. The decisive factors in improving the photocatalytic performance are the intimate and large contact interfaces between 2D hexagonal α‐Fe₂O₃ nanoplates and graphene, in addition to the high electron withdrawing/storing ability and the highconductivity of reduced graphene oxide (RGO) formed during the hydrothermal reaction. The effective charge transfer from α‐Fe₂O₃ nanoplates to graphene sheets is demonstrated by the significant weakening of photoluminescence in α‐Fe₂O₃/graphene composites.     

One‐Pot Synthesis of Dual Stimulus‐Responsive Degradable Hollow Hybrid Nanoparticles for Image‐Guided Trimodal Therapy

Exploiting exogenous and endogenous stimulus‐responsive degradable nanoparticles as drug carriers can improve drug delivery systems (DDSs). The use of hollow nanoparticles may facilitate degradation, and combination of DDS with photodynamic therapy (PDT) and photothermal therapy (PTT) may enhance the anticancer effects of treatments. Here, a one‐pot synthetic method is presented for an anticancer drug (doxorubicin [DOX]) and photosensitizer‐containing hollow hybrid nanoparticles (HNPs) with a disulfide and siloxane framework formed in response to exogenous (light) and endogenous (intracellular glutathione [GSH]) stimuli. The hollow HNPs emit fluorescence within the near‐infrared window and allow for the detection of tumors in vivo by fluorescence imaging. Furthermore, the disulfides within the HNP framework are cleaved by intracellular GSH, deforming the HNPs. Light irradiation facilitates penetration of GSH into the HNP framework and leads to the collapse of the HNPs. As a result, DOX is released from the hollow HNPs. Additionally, the hollow HNPs generate singlet oxygen (¹O₂) and heat in response to light; thus, fluorescence imaging of tumors combined with trimodal therapy consisting of DDS, PDT, and PTT is feasible, resulting in superior therapeutic efficacy. Thus, this method may have several applications in imaging and therapeutics in the future.     

Supercritical‐Fluid‐Assisted One‐Pot Synthesis of Biocompatible Core(γ‐Fe2O3)/Shell(SiO2) Nanoparticles as High Relaxivity T2‐Contrast Agents for Magnetic Resonance Imaging

Monodisperse iron oxide/microporous silica core/shell composite nanoparticles, core(γ‐Fe₂O₃)/shell(SiO₂), with a diameter of approximately 100 nm and a high magnetization are synthesized by combining sol–gel chemistry and supercritical fluid technology. This one‐step processing method, which is easily scalable, allows quick fabrication of materials with controlled properties and in high yield. The particles have a specific magnetic moment (per kg of iron) comparable to that of the bulk maghemite and show superparamagnetic behavior at room temperature. The nanocomposites are proven to be useful as T₂ MRI imaging agent. They also have potential to be used in NMR proximity sensing, theranostic drug delivery, and bioseparation.     

Rapid Synthesis of Amino Acid Polyoxometalate Nanotubes by One‐Step Solid‐State Chemical Reaction at Room Temperature

A novel and convenient method—solid‐state chemical reaction at room temperature—is reported for the synthesis of amino acid polyoxometalate nanotubes. As a convenient synthesis method for nanomaterials, it may open up a new pathway for the fabrication of organic–inorganic hybrid materials with nanotubular structure. Here, three novel tyrosine (Tyr) polyoxometalate nanotubes, (HTyr)₃PMo₁₂O₄₀ · 3H₂O, (HTyr)₃PW₁₂O₄₀ · 3H₂O, and (HTyr)₄SiW₁₂O₄₀ · 5H₂O are successfully synthesized via a one‐step solid‐state chemical reaction at room temperature. Elemental analysis confirms the rationality of composition for the samples. Infrared spectroscopy, X‐ray diffraction, and ³¹P magic‐angle spinning NMR results prove that the samples still possess Keggin‐type structures. Scanning and transmission electron microscopies suggest that the three samples are comprised of nanotubes with remarkably uniform shape and size, with diameters from 50 to 150 nm and lengths of up to several micrometers. Cyclic voltammograms of samples in 1 mol L^–1 H₂SO₄ indicate that three redox waves correspond to three two‐electron processes resulting from the reduction/oxidation of the heteropoly anion.     

Plasmonic Response of Ag‐ and Au‐Infiltrated Cross‐Linked Lysozyme Crystals

Metal‐infiltrated protein crystals form a novel class of bio‐nanomaterials of great interest for applications in biomedicine, chemistry, and optoelectronics. As yet, very little is known about the internal structure of these materials and the interconnectivity of the metallic network. Here, the optical response of individual Au‐ and Ag‐infiltrated cross‐linked lysozyme crystals is investigated using angle‐ and polarization‐dependent spectroscopy. The measurements unequivocally show that metallic inclusions formed inside the nanoporous solvent channels do not connect into continuous nanowires, but rather consist of ensembles of isolated spheroidal nanoclusters with aspect ratios as high as a value of four, and which exhibit a pronounced plasmonic response that is isotropic on a macroscopic length scale. Fluorescence measurement in the visible range show a strong contribution from the protein host, which is quenched by the Au inclusions, and a weaker contribution attributed to the molecule‐like emission from small Au‐clusters.     

Optical Properties of Quasi One‐Dimensional Chains of Gold Nanoparticles

Nanopores in alumina membranes can serve as reaction vessels for the generation of nanosized gold particles. In addition, they enable a quasi one‐dimensional arrangement of nanoparticles, the optical properties of which can easily be investigated due to their transparency in the visible and near ultraviolet (UV) regions. Gold colloids inside the pores were produced either by thermal decomposition of [Au₅₅(PPh₃)₁₂Cl₆] clusters or by loading the pores with preformed colloids. The clusters as well as the colloids were transferred into the pores by simple immersion, and if necessary supported by applying a vacuum. The [Au₅₅(PPh₃)₁₂Cl₆] clusters were decomposed over the temperature range of 100 to 800 °C, using pores of different diameters. Transmission electron microscopy (TEM) was used to investigate the resulting nanoparticles. At decomposition temperatures up to ca. 500 °C, no specific influence of pore size or temperature was observed: 4–5 nm colloids were formed. However, temperatures > 500 °C resulted in colloids of up to 10–11 nm being formed. The optical properties of these and of preformed gold colloids in the membranes were studied. The extinction spectra of the colloidal assemblies generated from clusters exhibited two absorption peaks, caused by excitation of the plasmon resonance along the long and the short axes of the wire‐like arranged particles. The optical extinctions were measured with unpolarized and polarized light (0 and 90°). Depending on the angle of polarization, the polarized light caused either a blue‐ or a red‐shift in the absorption maximum. Theoretical calculations, using the so‐called generalized Mie theory and Maxwell Garnet theory, confirmed the experimentally observed behavior of these gold/alumina nanocomposites.     

Doxorubicin Nanocarriers Based on Magnetic Colloids with a Bio‐polyelectrolyte Corona and High Non‐linear Optical Response: Synthesis,Characterization, and Properties

Magnetic drug nanocarriers are synthesized following an arrested mineralization of magnetic spinel iron oxides in the presence of the biopolymer of sodium carboxymethylcellulose. Based on the experimental results, the polyelectrolyte corona probably attains a brushlike configuration around the magnetic particles. The inner core of these colloids may be constituted of polymer‐associated nanocrystallites, forming nanogel colloids. The hybrid colloids are endowed with a high loading capacity for the anticancer agent doxorubicin and pronounced pH responsiveness. They also display a dramatic increase in non‐linear optical response as compared to previous studies of similar materials. Furthermore, as cell studies indicate, the blank nanocarriers are cytocompatible and the drug retains its activity after loading in the nanocarriers.     

One‐Pot Synthesis of Au25(SG)18 2‐ and 4‐nm Gold Nanoparticles and Comparison of Their Size‐Dependent Properties

A one‐pot synthesis of glutathione (denoted as ‐SG) capped gold nanoparticles, including Au₂₅(SG)₁₈ (ca. 1 nm in diameter) 2‐ and 4‐nm particles is reported. These nanoparticles are isolated by methanol‐induced precipitation with a controlled amount of added methanol. Except for their particle size, these nanoparticles have an identical chemical composition (i.e., gold and ‐SG content), synthetic history, and surface conditions, which allows for precise comparison of their size‐dependent properties, in particular the magnetic property as this could be attributed to contamination by trace iron impurities. Specifically, the structure, optical, and magnetic properties of these gold nanoparticles are compared. A trend from non‐fcc (fcc = face centered cubic) Au₂₅(SG)₁₈ nanoclusters (ca. 1 nm) to 2‐ and 4‐nm fcc‐crystalline Au nanocrystals is revealed. The Au₂₅(SG)₁₈ nanoparticles resemble molecules and exhibit multiple optical absorption peaks ascribed to one‐electron transitions, whereas the 4‐nm nanoparticles exhibit surface plasmon resonance at around 520 nm related to the collective excitation of conduction electrons upon optical excitation. The transition from the non‐fcc cluster state to the fcc crystalline state occurs at around 2 nm. Interestingly, both 2‐ and 4‐nm particles exhibit paramagnetism, whereas the Au₂₅(SG)₁₈ (anionic) clusters are diamagnetic. The information attained on the evolution of the properties of nanoparticles from nanoclusters to fcc‐structured nanocrystals is of major importance and provides insight into structure—property relationships.     

Synthesis and Assembly of Gold Nanoparticles in Quasi‐Linear Lysine–Keggin‐Ion Colloidal Particles

The formation of fiber‐like colloidal particles of the amino acid lysine complexed with Keggin ions is demonstrated. The lysine–phosphotungstic acid (PTA) colloidal particles act as excellent templates for the synthesis and assembly of gold nanoparticles wherein the lysine‐PTA complex acts as a UV‐switchable reducing agent for gold ions. This novel bio‐organic–inorganic template shows excellent potential as a regulated nanoreactor for application in programmed nanoparticle synthesis and assembly in a single step.     

Novel Triclosan‐Bound Hybrid‐Silica Nanoparticles and their Enhanced Antimicrobial Properties

The design and synthesis of novel hybrid‐silica nanoparticles (NPs) containing the FDA‐approved antimicrobial triclosan (Irgasan) covalently linked within the inorganic matrix for its controlled, slow release upon interaction, is reported. The NPs are in the range of 130 ± 30 nm in diameter, with a smooth and spherical morphology. Characterization of the hybrid‐silica NPs containing triclosan, namely T‐SNPs, and their appropriate linkers is accomplished by microscopic and spectroscopic techniques. Preliminary antimicrobial activity is studied through bacterial‐growth experiments. The T‐SNPs are found to be superior in killing bacteria, as compared with the free biocide.     

Preparation‐Condition Dependence of Hybrid SiO2‐Coated CdTe Nanocrystals with Intense and Tunable Photoluminescence

When aqueously prepared CdTe nanocrystals (NCs) are coated with a SiO₂ shell containing Cd ions and a sulfur source, they show a drastic increase in photoluminescence (PL) efficiency with a significant red shift and spectral narrowing after reflux. This is ascribed to the creation of a hybrid structure characterized by the formation of CdS‐like clusters in the vicinity of the NCs in the SiO₂ shell. Since these clusters are close to the NCs, their effective size increases to reduce the quantum size effect. The dependences of the PL properties on the preparation conditions are systematically investigated. The PL efficiency increases from 28% to 80% in the best case with a red shift of 80 nm. The PL behaviors differ from those of normal CdTe NCs and include less temperature quenching and longer PL lifetime. The SiO₂ coating enables bioconjugation with IgG without deterioration of PL efficiency, making hybrid NCs amenable for bioapplication.     

Single Step Preparation of Novel Hydrophobic Composite Films for Low‐k Applications

Composite films with low dielectric constants (k) containing micro‐ and mesopores are synthesized from precursor solutions for the preparation of mesoporous silica and ethanolic suspensions of silicalite‐1 nanoparticles. The material contains silicalite‐1 nanoparticles (include nanocrystals and nanoslabs/intermediates) embedded in a randomly oriented matrix of highly porous mesoporous silica. Micropores result from the incorporated silicalite‐1 nanoparticles, while decomposition of the porogen F127 leads to additional mesopores. The porosity of the composite films increases from 9 to 60% with the increase in porogen loading, while in parallel the elastic modulus and hardness decrease. The elastic moduli of the films are in the range of 13–20 GPa. Hydrophobic surfaces of the composite films are obtained by introducing methyl triethoxysilane during the preparation of both precursor solutions, leading to the incorporation of ? CH₃ groups in the final composite films. These methyl groups are stable up to at least 500 °C. A low k value of approximately 2 is observed for films cured at 400 °C in N₂ flow, which is ideal for removing templates without decomposing methyl groups. Due to the intrinsic hydrophobicity of the material, post‐silylation is not required rendering the composite films attractive candidates for future low k materials.     

One‐Step Solvent‐Free Synthesis and Characterization of Zn1−xMnxSe@C Nanorods and Nanowires

The carbon‐encapsulated, Mn‐doped ZnSe (Zn_1−xMn_xSe@C) nanowires, nanorods, and nanoparticles are synthesized by the solvent‐free, one‐step RAPET (reactions under autogenic pressure at elevated temperature) approach. The aspect ratio of the nanowires/nanorods is altered according to the Mn/Zn atomic ratio, with the maximum being observed for Mn/Zn = 1:20. A 10–20 nm amorphous carbon shell is evidenced from electron microscopy analysis. The replacement of Zn by Mn in the Zn_1−xMn_xSe lattice is confirmed by the hyperfine splitting values in the electron paramagnetic resonance (EPR) experiments. Raman experiments reveal that the Zn_1−xMn_xSe core is highly crystalline, while the shell consists of disordered graphitic carbon. Variable‐temperature cathodoluminescence measurements are performed for all samples and show distinct ZnSe near‐band‐edge and Mn‐related emissions. An intense and broad Mn‐related emission at the largest Mn alloy composition of 19.9% is further consistent with an efficient incorporation of Mn within the host ZnSe lattice. The formation of the core/shell nanowires and nanorods in the absence of any template or structure‐directing agent is controlled kinetically by the Zn_1−xMn_xSe nucleus formation and subsequent carbon encapsulation. Mn replaces Zn mainly in the (111) plane and catalyzes the nanowire growth in the [111] direction.     

Surfactant‐Free One‐Step Synthesis of Dual‐Functional Polyurea Microcapsules: Contact Infection Control and Drug Delivery

Surface functionalized polyurea microcapsules (MCQ) are synthesized in one step. Dimethyl‐dodecyl‐(5‐hydroxy‐pentyl)‐ammonium bromide (DAB), a hydroxyl‐end‐capped quaternary ammonium salt, is synthesized and adopted as a new surfmer for the synthesis of MCQ. It is confirmed by fluorescein adsorption that DAB is covalently bonded to MCQ. The so‐formed MCQ possess dual‐functionality: contact infection control and sustained drug delivery. Agar diffusion antimicrobial tests confirm successful inhibition of multi‐drug‐resistant E. coli by MCQ alone instead of by leaching of free quaternary ammonium salts. Furthermore, few E. coli colonies survive on an agar plate coated with 3–4 layers of MCQ. Dissolution tests show a typical first‐order release profile of courmarin‐1, a model dye, from MCQ.     

Synthesis and Properties of Plasmonic Boron‐Hyperdoped Silicon Nanoparticles

Electronic properties of silicon, the most important semiconductor material, are controlled through doping. The range of achievable properties can be extended by hyperdoping, i.e., doping to concentrations beyond the nominal equilibrium solubility of the dopant. Here, hyperdoping is achieved in a laser pyrolysis reactor capable of providing nonequilibrium conditions, where doping is governed by kinetics rather than thermodynamics. High resolution scanning transmission electron microscopy (TEM) with energy‐dispersive X‐ray spectroscopy shows that the boron atom distribution in the hyperdoped nanoparticles is relatively uniform. The hyperdoped nanoparticles demonstrate tunable localized surface plasmon resonance (LSPR) and are stable in air for periods of at least one year. The hyperdoped nanoparticles are also stable upon annealing at temperatures up to 600 °C. Furthermore, boron hyperdoping does not change the diamond cubic crystal structure of silicon, as demonstrated in detail by high flux synchrotron X‐ray diffraction and pair distribution function (PDF) analysis, supported by high‐resolution TEM analysis.