Colloidal Flower‐Shaped Iron Oxide Nanoparticles: Synthesis Strategies and Coatings

The assembly of magnetic cores into regular structures may notably influence the properties displayed by a magnetic colloid. Here, key synthesis parameters driving the self‐assembly process capable of organizing colloidal magnetic cores into highly regular and reproducible multi‐core nanoparticles are determined. In addition, a self‐consistent picture that explains the collective magnetic properties exhibited by these complex assemblies is achieved through structural, colloidal, and magnetic means. For this purpose, different strategies to obtain flower‐shaped iron oxide assemblies in the size range 25–100 nm are examined. The routes are based on the partial oxidation of Fe(OH)₂, polyol‐mediated synthesis or the reduction of iron acetylacetonate. The nanoparticles are functionalized either with dextran, citric acid, or alternatively embedded in polystyrene and their long‐term stability is assessed. The core size is measured, calculated, and modeled using both structural and magnetic means, while the Debye model and multi‐core extended model are used to study interparticle interactions. This is the first step toward standardized protocols of synthesis and characterization of flower‐shaped nanoparticles.     

Polyacrylamide Nanoparticles with Visible and Near‐Infrared Autofluorescence

Nowadays, self‐fluorescent materials such as quantum dots are widely studied and applied in biomedical field. However, the biggest obstacle is biocompatibility. Here, a novel autofluorescent nanoparticle is constructed by crosslinking polyacrylamide nanoparticles (PAANPs) that contain ε‐poly‐l ‐lysine with glutaraldehyde (named fPAANPs). The nanoparticle has a mean size of about 16 nm, a zeta potential of about +16 mV, and strong visible and near‐infrared autofluorescence. The nanoparticle can be efficiently internalized into cells with high biocompatibility, the LC50 of which in RAW264.7, HepG2, and Hepa1‐6 cells is 6, 9, and 7.5 mg mL^?1, respectively. The nanoparticle shows no visible impact on the mice vitality even at a high intravenously administered dose (126 mg kg^?1). The autofluorescence of fPAANPs shows high stability, persistence, allowing long‐term dynamic imaging for 25 d in subcutaneous injections and 18 d in xenograft tumors in mice. The nanoparticle thus provides a self‐traceable nanomaterial that can be exploited as drug carrier and potential photodynamic therapy photosensitizer.     

Negative‐Imaging of Citrate Layers on Gold Nanoparticles by Ligand‐Templated Metal Deposition: Revealing Surface Heterogeneity

Surface heterogeneity of a metal nanoparticle is typically regarded as boundary defects and various crystalline facets. While organic capping ligands of a single type are assumed to be homogeneously distributed on the nanoparticle surface, heterogeneous surface coverage of citrate molecules on individual facets of gold nanoparticles (AuNPs) is revealed. Pt metallic clusters with 2 nm in diameter, epitaxially grown on the surface of AuNPs by chemical reaction and imaged by high‐resolution transmission electron microscopy, are utilized as negative‐imaging probes for densely packed adlayers where the underneath gold surface may not be accessible for Pt deposition. At pH > 5.0, citrate anions form only a loosely packed layer. At pH 4.5, citrates and citric acids form both loosely packed and densely packed layers that appear phase separated, and the densely packed domain as small as 5 nm × 5 nm is likely composed of fully protonated citric acids. IR spectra indicate that citric acid binds to a surface Au adatom through the oxygen atom of the central hydroxyl group, and similarly, citrate anions bind to Au adatoms through the carboxylate oxygen atom. This study also reveals the role of Au adatom in the adsorption of citrate species on the metallic surface of AuNPs.     

单分散银纳米颗粒的超声辅助制备及表面拉曼与荧光增强效应

以硝酸银和甲硼烷叔丁胺络合物分别为反应前驱物和还原剂,在油胺油酸体系中,利用超声辅助方法在室温下制备出粒径为3.4 nm的单分散银纳米颗粒．通过XRD、TEM和EDX对产物进行表征,结果显示产物具有典型的面心立方结构,单分散特征明显、尺寸分布均匀,且最可几尺寸为3.4 nm．超声反应时间、油胺和油酸的用量及其比例对银纳米晶的形貌和尺寸有重要影响,其中油胺溶剂的使用是控制单分散银纳米晶尺寸的关键．同时,研究显示单分散银纳米颗粒对罗丹明6G模型分子具有很强的拉曼增强效应;双光子荧光照片显示其具有很好的荧光增强效应．     

Advances in the Synthesis and Long‐Term Protection of Zero‐Valent Iron Nanoparticles

Core@shell Fe@Fe₃O₄ nanoparticles (NPs) are synthesized via the thermal decomposition of iron pentacarbonyl (Fe(CO)₅) in the presence either of oleylamine (OAm) or a mixture of OAm and oleic acid (OA). The heterostructured nanocomposites formed do so by a postsynthetic modification of isolated Fe seeds. This proves the versatility of the coating procedure and represents a significant advantage over previous work with Co seeds owing to the higher magnetic susceptibility, reduced toxicity, and excellent biocompatibility of Fe. Furthermore, the latter system allows the synthetic methodology to be developed from a two‐pot scenario where seeds are isolated then coated, to an easier and more efficient direct one‐pot scenario. The two‐pot method yields proportionately larger cores. However, in both cases, the monodisperse product reveals a carbonaceous interface between the Fe core and oxide shell. Meanwhile for the one‐pot synthesis, the OA:OAm ratio influences both the morphology and dispersity of the product. This is interpreted in terms of competing interactions of the ligands with the iron precursor. Superparamagnetism (SPM) is observed, and microscopic studies reveal oxidative stability of the Fe(0) cores achieved by either method for >6 months. It is proposed that the carbonaceous interface is critical to this sustained oxidative stability.     

Recent Advancements in Ln‐Ion‐Based Upconverting Nanomaterials and Their Biological Applications

Upconversion nanoparticles (UCNPs) convert low‐energy infrared (IR) or near‐infrared (NIR) photons into high‐energy emission radiation ranging from ultraviolet to visible through a photon upconversion process. In comparison to conventional fluorophores, such as organic dyes or semiconductor quantum dots, lanthanide‐ion‐doped UCNPs exhibit high photostability, no photoblinking, no photobleaching, low cytotoxicity, sharp emission lines, and long luminescent lifetimes. Additionally, the use of IR or NIR for excitation in such UCNPs reduces the autofluorescence background and enables deeper penetration into biological samples due to reduced light scattering with negligible damage to the samples. Because of these attributes, UCNPs have found numerous potential applications in biological and medicinal fields as novel fluorescent materials. Different upconversion mechanisms commonly observed in UCNPs, various methods that are used in their synthesis, and surface modification processes are discussed. Recent applications of Ln‐UCNPs in the biological and medicinal fields, including in vivo and in vitro biological imaging, multimodal imaging, photodynamic therapy, drug delivery, and antibacterial activity, are also presented.     

In Vitro Evaluation of Non‐Protein Adsorbing Breast Cancer Theranostics Based on 19F‐Polymer Containing Nanoparticles

Eight fluorinated nanoparticles (NPs) are synthesized, loaded with doxorubicin (DOX), and evaluated as theranostic delivery platforms to breast cancer cells. The multifunctional NPs are formed by self‐assembly of either linear or star‐shaped amphiphilic block copolymers, with fluorinated segments incorporated in the hydrophilic corona of the carrier. The sizes of the NPs confirm that small circular NPs are formed. The release kinetics data of the particles reveals clear hydrophobic core dependence, with longer sustained release from particles with larger hydrophobic cores, suggesting that the DOX release from these carriers can be tailored. Viability assays and flow cytometry evaluation of the ratios of apoptosis/necrosis indicate that the materials are non‐toxic to breast cancer cells before DOX loading; however, they are very efficient, similar to free DOX, at killing cancer cells after drug encapsulation. Both flow cytometry and confocal microscopy confirm the cellular uptake of NPs and DOX‐NPs into breast cancer cells, and in vitro ¹⁹F‐MRI measurement shows that the fluorinated NPs have strong imaging signals, qualifying them as a potential in vivo contrast agent for ¹⁹F‐MRI.     

High‐Performance UV Protective Waterborne Polymer Coatings Based on Hybrid Graphene/Carbon Nanotube Radicals Scavenging Filler

Ultraviolet (UV) degradation is one of the most important challenges of waterborne coatings in exterior applications. One of the ways to address this issue is addition of radical scavenging species within the polymer matrix. Herein, hybrids of graphene (G) and multiwall carbon nanotubes (CNTs) in different ratios are used as radical scavenging species. Evaluated by electron paramagnetic resonance spectroscopy, it is found that the hybrid made of G/CNTs in ratio of 10:1 efficiently captures and quenches the free radicals. The waterborne polymer composites containing 1 wt% of hybrid G/CNT are synthesized by in situ miniemulsion free radical polymerization using a water soluble initiator. However, due to excellent efficiency to capture free radicals, the polymerization performed using water soluble initiators in the presence of 10:1 G/CNT filler is hindered. This is resolved by physical separation of the free radicals and the scavenging materials within different phases by use of oil soluble initiator. The resulting polymer composites, beside having excellent mechanical resistance, present exceptional stability under accelerated aging conditions during 400 h, suppressing almost completely the UV photodegradation. This is attributed to the efficient radical scavenging of the G/CNTs hybrid filler distributed within polymer matrix, resulting in high‐performance UV protective waterborne composite coatings.     

Self‐Assembled Fluorescent and Antibacterial GHK‐Cu Nanoparticles for Wound Healing Applications

GHK‐Cu is demonstrated with the abilities to improve wound healing, accelerate anti‐inflammatory activity, and repair DNA damage. However, the instability of the GHK‐Cu in biological fluids is always a big challenge for its long‐term and efficient function at the target site. Therefore, the self‐assembled GHK‐Cu nanoparticles (GHK‐Cu NPs) are investigated in this work to solve the instability issue. The crystalline nanostructure within the GHK‐Cu nanoparticles offers them visible and near‐infrared fluorescent properties. With the excellent self‐assembly performance, the antibacterial properties of GHK‐Cu NPs are demonstrated using E. coli and S. aureus. The L929 dermal fibroblast cells are utilized to prove the good biocompatibility and enhanced wound healing applications of GHK‐Cu NPs. This study could pave the way for the design and elaboration of a new class of fluorescent peptides with various biological functions in biomedical applications.     

Metal–Polymer Hybrid Nanoparticles for Correlative High‐Resolution Light and Electron Microscopy

The combination of fluorescence microscopy and electron microscopy promises a deeper insight into the ultrastructural features of cell organelles, e.g., after drug administration. Both methods complement each other and provide, as a correlative approach, a keen insight into the fate of nanoparticles within the cell. Moreover, it represents a promising tool to determine alterations of the cellular environment as a response to particle uptake. However, the availability of suitable correlative markers is mandatory for such correlative approaches. In this contribution, the utilization of poly(ethylene imine) based metal–polymer hybrid particles labeled with small gold nanoparticles and Rhodamine B facilitating the observation of the particles by means of fluorescence as well as by transmission electron microscopy is suggested. Correlative light and electron microscopy is used to study uptake and intracellular fusion processes of endosomal/lysosomal structures.     

Long‐Term Colloidal and Chemical Stability in Aqueous Media of NaYF4‐Type Upconversion Nanoparticles Modified by Ligand‐Exchange

Surface capping is an essential component of nanoparticles as it provides access to their outstanding properties in the real world. Upconversion nanoparticles are predominantly interesting for use in biological environments, due to their excellent optical properties such as the conversion of near‐infrared excitation light into emissions in the visible or UV range of the spectrum, high photostability, and the absence of any intermittence. One of the most efficient upconversion nanoparticles, consisting of lanthanide doped NaYF₄, suffers from limited stability in aqueous media. This study investigates a set of five types of surface coatings, ranging from small ligands to polymers of different charge and different coordinating groups, on monodisperse 28 ± 0.9 nm sized NaYF₄(Yb,Er) nanoparticles modified by a two‐step ligand exchange mediated by NOBF₄. Information on the long‐term chemical and colloidal stability for highly diluted aqueous dispersions of these particles is acquired by transmission electron microscopy, dynamic light scattering, and luminescence spectroscopy. The findings are of importance for the development of probes and labels based on upconversion nanoparticles for biological applications.     

Red Emissive Biocompatible Nanoparticles from Tetraphenylethene‐Decorated BODIPY Luminogens for Two‐Photon Excited Fluorescence Cellular Imaging and Mouse Brain Blood Vascular Visualization

BODIPY (4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene) is an emissive chromophore in solutions but suffers from fluorescence quenching when aggregated due to its flat molecular conformation and small Stokes shift. To create aggregate‐state emissive BODIPY luminogens, tetraphenylethene (TPE), which is a popular luminogen with intriguing aggregation‐induced emission (AIE) characteristic, is introduced as periphery to a methylated BODIPY core. Three TPE‐BODIPY adducts are synthesized and characterized, and their photophysical properties and electronic structures are investigated. The incorporation of AIE‐active TPE units alleviates aggregation‐caused quenching of BODIPY core, furnishing emissive nanoparticles based on TPE‐BODIPY adducts. Significantly, the two‐photon absorption (TPA) and two‐photon excited fluorescence (TPEF) properties are improved as more TPE units are attached. The luminogens with 3TPE units (3TPE‐BODIPY) shows the strongest TPA and TPEF in the wavelength range of 750–830 nm, with cross‐section values of 264 and 116 GM at 810 nm, respectively. Red emissive nanoparticles with a Stokes shift of 60 nm and a fluorescence quantum yield of 16% are attained by encapsulating 3TPE‐BODIPY with 1,2‐sistearoyl‐sn‐glycero‐3‐phosphoethanolamine‐N‐[methoxy(polyethylene glycol)‐2000]. The nanoparticles are biocompatible and function well in TPEF cellular imaging and mouse brain blood vascular visualization.     

Colloidal Nanoparticles: Formation of Large 2D Arrays of Shape‐Controlled Colloidal Nanoparticles at Variable Interparticle Distances (Part. Part. Syst. Charact. 1/2013)

A method for the production of homogeneous layers of nanoparticles of arbitrary shape is presented. The method relies on a ligand exchange with a functionalized polymer and a subsequent self‐assembly of a thin film on the substrates. The interparticle distances in the layer can be adjusted by the length of the polymer. In the case of spherical particles, the approach yields quasi‐hexagonal structures; in the case of anisotropic particles, the minimum distance between adjacent particles is controlled. Regular arrangements of the nanoparticles covering areas of several square centimeters are achieved.     

Preparation,Characterization and Optimization of Egg Albumin Nanoparticles as Low Molecular‐Weight Drug Delivery Vehicle

Protein nanoparticles have been recognized as carriers to deliver low molecular‐weight drugs, anticancer drug, DNA, vaccines, oligonucleotides, peptides and etc. The purpose of this research was preparation of Egg Albumin (EA) nanoparticle with suitable size/size distribution and good surface properties for drug delivery application based on simple coacervation method along with optimization of the nanoparticles by employing Taguchi method. Several synthesis parameters were examined to characterize their impacts on nanoparticle size and topography. These variables were including temperature, EA concentration, desolvating agent volume, pH value and agitation speed. In addition, size and morphology of prepared nanoparticles were analyzed by photon correlation spectroscopy (PCS) as well as atomic force microscopy (AFM). As result of Taguchi analysis in this research, desolvating agent volume and pH were most influencing factors on particle size. The minimum size of nanoparticles (～51 nm) were obtained at Temperature 55 °C, 30 mg/ml EA concentration, desolvating agent volume 50 ml, agitation speed of 500 rpm and pH 4. The mechanistic of optimum conditions for preparing protein nanoparticles from Egg Albumin for the first time and their characterization as delivering nano system are discussed.     

Photoswitchable Fluorescent Liquid Crystal Nanoparticles and Their Inkjet‐Printed Patterns for Information Encrypting and Anti‐Counterfeiting

Liquid crystal nanoparticles (LCNPs) with desirable multifunctionality are catching increasing attention due to their promising applications in various fields. However, reversible photoswitchable fluorescent LCNPs are not reported until now. Here, the first example of water‐dispersible, reversibly phototunable fluorescent LCNPs prepared through a miniemulsion polymerization technique is presented. The LCNPs mainly consist of an aggregation‐induced emission enhancement (AIEE)‐active dicyanodistyrylbenzene‐based monomer, a LC cross‐linking monomer, and a dithienylethene (DAE) derivative as a photochromic molecular switch. The fluorescence of the resultant LCNPs can be switched reversibly between bright (ON) and dark (OFF) states with a high contrast and excellent repeatability upon alternating irradiation of 365 nm UV light and visible light (λ > 450 nm). This observation could be attributed to ring‐opening/ring‐closing photoisomerization of the DAE structure on the basis of an intraparticle fluorescence resonance energy transfer process between the AIEE‐active monomer and DAE derivative. More importantly, the potential for aqueous dispersion of the photoswitchable fluorescent LCNPs as a security ink for information encryption and anti‐counterfeiting is further demonstrated. The results demonstrate that the reversible photoswitchable fluorescent LCNPs as multifunctional nanomaterials exhibit promising applications in photonic fields.     

Novel Synthesis and Characterization of Doxycycline‐Loaded Gold Nanoparticles: The Golden Doxycycline for Antibacterial Applications

Doxycycline (DOXY) is a tetracycline antibiotic with a potent antibacterial activity against a wide variety of bacteria. One potential strategy to enhance the penetration and the antibacterial activity of antibiotics is the use of nanotechnology. In this work, an innovative synthesis of stable PEGylated‐gold nanoparticles (PEG‐AuNPs) loaded with DOXY is reported. As far as it is known, this is the first report on the combination of DOXY with AuNPs as polymeric complex. The obtained nanoparticles are fully characterized by transmission electron microscopy, dynamic light scattering, zeta‐potential, and UV–vis and Raman spectroscopy. The stability and sustained activity of the drug in nanoparticles is determined on a panel of Gram‐positive and Gram‐negative bacteria in comparison with the native form of the drug. This combined therapeutic agent restores the susceptibility of DOXY and shows an antibacterial activity against major human pathogens.     

Metal–Organic Framework Supported Palladium Nanoparticles: Applications and Mechanisms

Heterogeneous palladium (Pd)‐based catalysts are extensively applied to improve the catalytic performance and/or expand the reaction scope in many catalytic processes, involving the cross‐coupling, hydrogenation, reduction, and oxidation reactions. Among them, metal–organic framework (MOF)‐supported Pd nanoparticles (Pd NPs) are becoming the most popular one for their excellent catalytic performance and reusable property. To motivate the development of this technology, the applications of MOF‐supported Pd NPs (Pd NPs/MOFs) in heterogeneous catalysis are critically summarized herein, including the hydrogenation reduction of nitro‐ and polyunsaturated compounds, synthesis of carbon–carbon (C? C) bonds compounds, chromium (Cr(VI)) reduction, dehalogenation, alcohol oxidation, CO₂ conversion, and CO oxidation. The influences of base, solvents, electron character of substitutes, and type of halogen on the catalytic performance are comprehensively discussed. Finally, the application prospects of Pd NPs/MOFs and existing shortcomings in the catalytic field are proposed.     

Monodisperse Polypyrrole Nanoparticles Prepared via γ‐Ray Radiolysis of Water: An Efficient Near‐Infrared Photothermal Agent for Cancer Therapy

Biosafe nanoparticles with strong near‐infrared (NIR) light photothermal conversion effect can bring effective hyperthermia as one of the promising approaches in cancer therapy. In this work, a new facile and green preparation method of polypyrrole (PPy) nanoparticles based on ⁶⁰Co γ‐ray radiation on a simple air‐saturated strong acidic aqueous solution of pyrrole (pH ≤ 1) is studied. According to the MCAP‐FACSIMILE simulation on the concentrations of the radiolysis products of water at the presence of H⁺ and O₂, the main strong oxidative radiolysis products · OH and H₂O₂ rapidly induce the polymerization of pyrrole. The size of the prepared PPy nanoparticles is about several tens of nanometers and can be controlled by the pH, the concentration of the stabilizer poly(vinyl alcohol), and the absorbed dose rate (the amount of energy absorbed per unit mass of the irradiated material within per unit of time). The PPy nanoparticles show rapid and remarkable NIR (808 nm) photothermal conversion efficiency up to 40.1% in water. Furthermore, the in vitro and in vivo experiments confirm that the prepared PPy nanoparticles exhibit enough strong NIR photothermal effect in tumor cells (4T1 and HeLa) and show a promising prospect as the NIR photothermal agent for the future cancer therapy.     

Phosphonated Polyethylenimine‐Coated Nanoparticles: Size‐ and Zeta‐Potential‐Adjustable Nanomaterials

Novel partially phosphonated polyethylenimine polymers are developed in order to control the modification of nanoparticle (NP) surfaces. This polymer is built by an accessible one‐step process. The numerous phosphonate functions assume both a strong covalent anchoring on metal oxide NPs and a modulation of electric charges, while amino groups are associated with dispersion preservation and subsequent biofunctionalization. The zwitterionic nanomaterials obtained display a good stability toward pH and ionic strength. According to the selected percentage of phosphonation and the polymer size, zeta potential, and diameter of the particles are controlled.