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Aim: To ascertain the impact of shape and surface modification of anisotropic nanoparticles on the toxicity and photothermal efficiency toward cancerous cell lines. Methods: Gold nanobipyramids and nanostars surface modified with MUC1 aptamer were used in the current study to explore the toxicity and photothermal efficiency on MCF7 breast cancer cell lines via MTT assay. Results: Surface functionalization with MUC1 aptamer showed significant reduction in % cytotoxicity and increase in % specific internalization of nanostructures into MCF7 cell lines. Further, the photothermal studies accomplished at IC50 concentration for 6 h of treatment and laser exposure for 15 min reported that aptamer-conjugated nanobipyramids were more effective and specific toward MCF7 cell lines than aptamer-conjugated nanostars. Conclusion: This work establishes a platform for the development of tailored photoablation based gold nanostructures for in vivo studies. Article highlights The investigation on cytotoxic effects and photothermal efficiency of anisotropic spiked gold nanostructures are requisite. Gold Nanostars (GNS), nanobipyramids (GNB) possess exceptional tip-enhanced plasmonic characteristics. GNB and GNS were synthesized and surface modified with MUC1 aptamer. GNB and GNS exhibited photothermal conversion efficiency of 14.5 and 14.1%, respectively. GNB and GNS are much less cytotoxic after aptamer conjugation. Compared with aptamer-GNS, aptamer-GNB exhibited higher selective cellular internalization toward MCF7 cell lines. Photoablation studies revealed that MCF7 cell lines were more severely damaged by aptamer-GNB than by aptamer-GNS. [ABSTRACT FROM AUTHOR]

The introduction of dipoles on gold nanoparticle surfaces provides the formation of chain-like nanoparticle assemblies in solution under ambient conditions. Here, we present studies on influencing and controlling the strength of the induced dipole by thiols. Aromatic thiols lead to enhanced surface dipoles, where electron-donating functions can further increase the interaction. Thereby, particle–particle distances and chemical environment at the particle interface were manipulated, which resulted in different tunneling resistances Rg in these 1D structures. Here, Rg seemed to be mostly dominated by the interparticle distance rather than the type of ligand. Temperature-dependent current–voltage measurements of thiol-bearing nanoparticle chains revealed two different transport mechanisms. For temperatures <170 K, a thermally activated electron tunneling takes place, which depends on the charging energy Ec. Whereas for higher temperatures, a transition to an electron hopping process occurs determined by the involved thiol and nanoparticle shape. For structures with strong interparticle electronic coupling, the conduction mechanism is almost temperature-independent, which makes them promising candidates for highly sensitive chemiresistor sensors. [ABSTRACT FROM AUTHOR]

Gold nanostars have shown enormous potential as the main enablers of advanced applications ranging from biomedicine to sensing or catalysis. Their unique anisotropic structure featuring sharp spikes that grow from a central core offers enhanced optical capabilities and spectral tunability. Although several synthesis methods yield NSs of different morphologies and sizes up to several hundred nanometers, obtaining small NSs, while maintaining their plasmonic properties in the near-infrared, has proven challenging and elusive. Here, we show that Cu2+ addition during NS synthesis in polyvinylpyrrolidone/dimethylformamide generates more crystallographic defects and promotes the directional growth, giving rise to NSs with a larger number of much sharper spikes. They are also formed at smaller volumes, enabling the generation of ultrasmall nanostars, with a volume as small as 421 nm3 (i.e., 9.2 nm of volume-equivalent diameter), while maintaining a plasmon resonance in the near-infrared. To this end, we systematically evaluate the influence of synthesis parameters on the nanostar size and optical characteristics and demonstrate their properties for applications in catalysis, surface-enhanced Raman spectroscopy sensing, and hyperthermia. The ultrasmall nanostars show excellent attributes in all of them, leveraging their small size to enhance properties related to a higher surface-to-volume ratio or colloidal diffusivity. [ABSTRACT FROM AUTHOR]

The alignment of anisotropic nanoparticles in flow has been used for a range of applications such as the preparation of strong fibres and the assembly of in‐plane aligned 1D‐nanoobjects that are used for electronic devices, sensors, energy and biological application. Important is also the flow behaviour of nanoparticles that were designed for nanomedical applications such as drug delivery. It is widely observed that non‐spherical nanoparticles have longer circulation times and a more favourable biodistribution. To be able to understand this behaviour, researchers have turned to analyzing the flow of non‐spherical nanoparticles in the blood stream. In this review, an overview of microfluidic techniques that are used to monitor the alignment of anisotropic nanoparticles in solution will be provided, which includes analysis by small angle X‐ray scattering (SAXS) and polarized light microscopy. The flow of these nanoparticles in blood is then discussed as the presence of red blood cells causes margination of some nanoparticles. Using fluorescence microscopy, the extent of margination can be identified, which coincides with the ability of nanoparticles to adhere to the cells grown along the wall. While these studies are mainly carried out in vitro using blood, initial investigations in vivo were able to confirm the unusual flow of anisotropic nanoparticles. [ABSTRACT FROM AUTHOR]

Due to their low cost, high stability and low toxicity, metal oxide nanomaterials are widely used for applications in various fields such as electronics, cosmetics and photocatalysis. There is an increasing demand thereby for nanoparticles with highly defined properties, in particular a narrow particle size distribution and a well-defined morphology. Such products can be obtained under high control via bottom-up synthesis approaches. Although aqueous processes are largely found in literature, they often lead to particles with low crystallinity and broad size distribution. Thus, there has been a growing trend towards the use of non-aqueous and non-hydrolytic synthesis routes. Through variation of the reaction medium and the use of adequate additives, such non-aqueous systems can be tuned to adapt the product properties, and especially to yield anisotropic nanoparticles with peculiar shapes and even complex architectures. Anisotropic particle growth enables the exposure of specific facets of the oxide nanocrystal, leading to extraordinary properties such as enhanced catalytic activity. Thus, there is an increasing demand for anisotropic nanoparticles with tailored morphologies. In this review, the non-aqueous and non-hydrolytic synthesis of anisotropic metal oxide nanoparticles is presented, with a particular focus on the different parameters resulting in anisotropic growth to enable the rational design of specific morphologies. Furthermore, secondary phenomena occurring during anisotropic particle growth, such as oriented attachment mechanisms, will be discussed.

Abstract The alignment of anisotropic nanoparticles in flow has been used for a range of applications such as the preparation of strong fibres and the assembly of in‐plane aligned 1D‐nanoobjects that are used for electronic devices, sensors, energy and biological application. Important is also the flow behaviour of nanoparticles that were designed for nanomedical applications such as drug delivery. It is widely observed that non‐spherical nanoparticles have longer circulation times and a more favourable biodistribution. To be able to understand this behaviour, researchers have turned to analyzing the flow of non‐spherical nanoparticles in the blood stream. In this review, an overview of microfluidic techniques that are used to monitor the alignment of anisotropic nanoparticles in solution will be provided, which includes analysis by small angle X‐ray scattering (SAXS) and polarized light microscopy. The flow of these nanoparticles in blood is then discussed as the presence of red blood cells causes margination of some nanoparticles. Using fluorescence microscopy, the extent of margination can be identified, which coincides with the ability of nanoparticles to adhere to the cells grown along the wall. While these studies are mainly carried out in vitro using blood, initial investigations in vivo were able to confirm the unusual flow of anisotropic nanoparticles.

By utilizing nanoparticles to upload and interact with several pharmaceuticals in varying methods, the primary obstacles associated with loading two or more medications or cargos with different characteristics may be addressed. Therefore, it is feasible to evaluate the benefits provided by co-delivery systems utilizing nanoparticles by investigating the properties and functions of the commonly used structures, such as multi- or simultaneous-stage controlled release, synergic effect, enhanced targetability, and internalization. However, due to the unique surface or core features of each hybrid design, the eventual drug–carrier interactions, release, and penetration processes may vary. Our review article focused on the drug's loading, binding interactions, release, physiochemical, and surface functionalization features, as well as the varying internalization and cytotoxicity of each structure that may aid in the selection of an appropriate design. This was achieved by comparing the actions of uniform-surfaced hybrid particles (such as core–shell particles) to those of anisotropic, asymmetrical hybrid particles (such as Janus, multicompartment, or patchy particles). Information is provided on the use of homogeneous or heterogeneous particles with specified characteristics for the simultaneous delivery of various cargos, possibly enhancing the efficacy of treatment techniques for illnesses such as cancer. [ABSTRACT FROM AUTHOR]

Abstract Anisotropic nanoparticles have attracted extensive attention due to their potential applications in material transport, energy storage, and biopharmaceutical. However, due to the inadequate understanding of microscopic particle formation, controllable asymmetric growth is still a great challenge. Herein, we report a facile emulsion‐assisted interfacial polymerization strategy for the synthesis of nitrogen‐doped porous carbon particles (NPCPs) with tunable anisotropic/isotropic architectures. During the synthesis process, we can form emulsion droplets with different nanostructures directionally through dual routes, thereby assisting and mediating the polymerization and growth process of the monomer to obtain poly‐diaminopyridine nanoparticles with various architectures. The corresponding NPCPs with tunable specific surface area (125–362 m2 g−1), nitrogen content (10%–14%), and diverse morphologies can be acquired by calcination under N2 atmosphere at 700 °C. The synergetic effect of abundant microporous structures and active nitrogen species content contributes to improve the physicochemical properties, while the unique anisotropic architecture increases the charge diffusion efficiency and enhances the high‐rate stability. Therefore, the resultant NPCPs electrode exhibits a specific capacitance up to 275 F g−1 at 0.2 A g−1 and surface‐area‐normalized capacitance of 83.0 μF cm−2, indicating a promising material for high‐performance supercapacitors.

One-dimensional anisotropic nanoparticles are of great research interest across a wide range of biomedical applications due to their specific physicochemical and magnetic properties in comparison with isotropic magnetic nanoparticles. In this work, the formation of iron oxides and oxyhydroxide anisotropic nanoparticles (ANPs) obtained by the co-precipitation method in the presence of urea was studied. Reaction pathways of iron oxide and oxyhydroxide ANPs formation are described based on of X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and pulse magnetometry studies. It is shown that a nonmonotonic change in the Fe3O4 content occurs during synthesis. The maximum content of the Fe3O4 phase of 47.4% was obtained at 12 h of the synthesis. At the same time, the reaction products contain ANPs of α-FeOOH and submicron isotropic particles of Fe3O4, the latter formation can occur due to the oxidation of Fe2+ ions by air-oxygen and Ostwald ripening processes. A subsequent increase in the synthesis time leads to the predominant formation of an α-FeOOH phase due to the oxidation of Fe3O4. As a result of the work, a methodological scheme for the analysis of iron oxide and oxyhydroxide ANPs was developed. [ABSTRACT FROM AUTHOR]

Abstract Biomimetic nanostructures are attracting great interest because of their applications in mechanical engineering, optics, and biosciences. One of the most effective methods for fabricating nanostructures is forming particle arrays that have controlled shapes and placements. Herein, a novel self‐assembly method for forming vertically aligned arrays of anisotropic‐shaped particles is described. The particles can be vertically aligned with controlled spacing on substrates using a layer‐by‐layer method and thermal fusion. This method can be applied to particles of various shapes; for example, dumbbell‐shaped particles with an aspect ratio in the range of 1.2–1.9 and bullet‐shaped particles with an aspect ratio of two or more are aligned on substrates. From the results of the simulation of particle arrangement, the particles are oriented in the layer‐by‐layer process if they have anisotropy in terms of the shape, specific gravity, and surface charge of the particles. Furthermore, to make the particles stand upright, it is necessary to heat the particles at a temperature equal to or higher than the glass transition temperature of the polymer that covers the particles. This method is applicable to form broadband high aspect nanostructures, and the vertically aligned particle array shows good anti‐reflection properties and high transparency.

Non-specific binding (NSB) is one of the important issues in biosensing performance. Herein, we designed a strategy for removing non-specific binding including anti-mouse IgG antibody and bovine serum albumin (BSA) by utilizing anisotropic cadmium selenide tetrapods (CdSe TPs) in a vortex flow. The shear force on the tetrapod nanoparticles was increased by controlling the rotation rate of the vortex flow from 0 rpm to 1000 rpm. As a result, photoluminescence (PL) signals of fluorescein (FITC)-conjugated protein, anti-mouse IgG antibody-FITC and bovine serum albumin (BSA)-FITC, were reduced by 35% and 45%, respectively, indicating that NSB can be removed under vortex flow. In particular, simultaneous NSB removal and protein capture can be achieved even with mixture solutions of target antibodies and anti-mouse IgG antibodies by applying cyclic mode vortex flow on anisotropic CdSe TPs. These results demonstrate successfully that NSB can be diminished by rotating CdSe TPs to generate shear force under vortex flow. This study opens up new research protocols for utilization of anisotropic nanoparticles under vortex flow, which increases the feasibility of protein capture and non-specific proteins removal for biosensors. [ABSTRACT FROM AUTHOR]

Plasmonic metal nanoparticles are widely used for many applications due to their unique optical and chemical properties. Over the past decade, anisotropic metal nanoparticles have been explored for imaging, sensing, and diagnostic applications. The variations and flexibility of tuning the size and shape of the metal nanoparticles at the nanoscale made them promising candidates for biomedical applications such as therapeutics, diagnostics, and drug delivery. However, safety and risk assessment of the nanomaterials for clinical purposes are yet to be made owing to their cytotoxicity. The toxicity concern is primarily due to the conventional synthesis route that involves surfactants as a structure-directing agent and as a capping agent for nanoparticles. Wet chemical methods employ toxic auxiliary chemicals. However, the approach yields monodispersed nanoparticles, an essential criterion for their intended application and a limitation of the green synthesis of nanoparticles using plant extracts. Several biocompatible counterparts such as polymers, lipids, and chitosan-based nanoparticles have been successfully used in the synthesis of safe nanomaterials, but there were issues regarding reproducibility and yield. Enzymatic degradation was one of the factors responsible for limiting the efficacy. Hence, it is necessary to develop a safer and nontoxic route towards synthesizing biocompatible nanomaterials while retaining morphology, high yield, and monodispersity. In this regard, deep eutectic solvents (DESs) and carrageenan as capping agent for nanoparticles can ensure the safety. Carrageenan has the potential to act as antibacterial and antiviral agent, and adds enhanced stability to the nanoparticles. This leads to a multidimensional approach for utilizing safe nanomaterials for advanced biomedical and clinical applications.

By utilizing nanoparticles to upload and interact with several pharmaceuticals in varying methods, the primary obstacles associated with loading two or more medications or cargos with different characteristics may be addressed. Therefore, it is feasible to evaluate the benefits provided by co-delivery systems utilizing nanoparticles by investigating the properties and functions of the commonly used structures, such as multi- or simultaneous-stage controlled release, synergic effect, enhanced targetability, and internalization. However, due to the unique surface or core features of each hybrid design, the eventual drug–carrier interactions, release, and penetration processes may vary. Our review article focused on the drug’s loading, binding interactions, release, physiochemical, and surface functionalization features, as well as the varying internalization and cytotoxicity of each structure that may aid in the selection of an appropriate design. This was achieved by comparing the actions of uniform-surfaced hybrid particles (such as core–shell particles) to those of anisotropic, asymmetrical hybrid particles (such as Janus, multicompartment, or patchy particles). Information is provided on the use of homogeneous or heterogeneous particles with specified characteristics for the simultaneous delivery of various cargos, possibly enhancing the efficacy of treatment techniques for illnesses such as cancer.

The growing need for developing new synthesis methods of plasmonic nanoparticles (PNPs) stems from their various applications in nanotechnology. As a result, a variety of protocols have been developed for the synthesis of PNPs of different shapes, sizes, and compositions. Though widely practiced, the chemical synthesis of PNPs demands stringent control over the experimental conditions, often employs environmentally hazardous chemicals for surface stabilization, and is frequently energy-intensive. Additionally, chemically obtained PNPs require subsequent surface engineering steps for various optoelectronic and biomedicine applications to minimize the toxic effects and render them useful for targeted drug delivery, sensing, and imaging. Considering the pressing need to develop environmentally-friendly technology solutions, "greener" methods of nanoparticle synthesis are gaining importance. Here, we report on the biological synthesis of plasmonic nanoparticles using bacterial metabolites. A peptide-based siderophore pyoverdine and a blue-green pigment pyocyanin obtained from a marine strain of Pseudomonas aeruginosa rapidly produced plasmonic nanoparticles of gold and silver in an aqueous environment. The morphology of plasmonic nanoparticles could be modulated by tuning the concentration of these metabolites and the reaction time. The exposure of pyoverdine to chloroauric acid resulted in anisotropic gold nanoparticles. On the other hand, pyocyanin produced a highly monodispersed population of gold nanoparticles and anisotropic silver nanoparticles. Biologically obtained gold and silver nanoparticles retained pyoverdine and pyocyanin on the nanoparticle surface and were stable for an extended period of time. The biologically obtained gold and silver plasmonic nanoparticles displayed potent anticancer activities against metastatic lung cancer cells. Biogenic nanoparticles were rapidly internalized by cancer cells in high quantity to affect the cellular organization, and karyoplasmic ratio, indicating the potential of these nanoparticles for cancer nanomedicine. [ABSTRACT FROM AUTHOR]

[Display omitted] This paper describes the synthesis of highly branched gold nanoparticles (AuNPs) through a facile seeded growth approach using poly(allylamine hydrochloride) (PAH) as shape inducing agent. The obtained branched AuNPs present highly tunable optical properties in the Vis-NIR region from ca. 560 nm to 1260 nm. We controlled the morphology, and therefore the optical response, of the NPs by either changing the gold salt to seeds ratio or by fine-tuning the solution pH. We proposed that the formation of size-dependent PAH-AuCl 4 - aggregates as demonstrated by dynamic light scattering measurements, together with pH-dependent gold salt speciation might be responsible for the branched morphology. Advanced electron microscopy techniques demonstrated the polycrystalline nature of the AuNPs and facilitated a better understanding of branched morphology. Additionally, the refractive index sensitivity estimated by the inflection point of the Localized Surface Plasmon Resonance (LSPR) band can be controlled by tuning the nanoparticle branching. Furthermore, the versatility of the PAH chemistry allowed the easy functionalization of the synthesized NPs. [ABSTRACT FROM AUTHOR]

Anisotropic Janus ("snowman") nanoparticles with a single protrusion are currently made via the solvent swelling‐induced method. Here, we demonstrate without the aid of toxic solvents a generally applicable method for the formation of anisotropic polymer nanoparticles directly in water by controlling polymer mobility through tuning its glass transition temperature (Tg). Spherical structures, formed immediately after the emulsion polymerization, transformed into uniform tadpoles (with head diameter ≈60 nm and tail length ≈130 nm) through the protrusion of a single cylindrical tail when cooled to a temperature above the Tg of the polymer. Cooling the spheres to below the Tg produced kinetically trapped kettlebell structures that could be freeze‐dried and rehydrated without any structural change. These unique kettlebells could transform into uniform tadpoles by heating above the Tg, representing a triggered and on‐demand structural reorganization. [ABSTRACT FROM AUTHOR]

Multifunctional magnetic nanocomposites based on mesoporous silica have a wide range of potential applications in catalysis, biomedicine, or sensing. Such particles combine responsiveness to external magnetic fields with other functionalities endowed by the agents loaded inside the pores or conjugated to the particle surface. Different applications might benefit from specific particle morphologies. In the case of biomedical applications, mesoporous silica nanospheres have been extensively studied while nanorods, with a more challenging preparation, have attracted much less attention despite the positive impact on the therapeutic performance shown by seminal studies. Here, we report on a sol–gel synthesis of mesoporous rodlike silica particles of two distinct lengths (1.4 and 0.9 μm) and aspect ratios (4.7 and 2.2) using Pluronic P123 as a structure-directing template and rendering ∼1 g of rods per batch. Iron oxide nanoparticles have been synthesized within the pores yielding maghemite (γ-Fe2O3) nanocrystals of elongated shape (∼7 nm × 5 nm) with a [110] preferential orientation along the rod axis and a superparamagnetic character. The performance of the rods as T2-weighted MRI contrast agents has also been confirmed. In a subsequent step, the mesoporous silica rods were loaded with a cerium compound and their surface was functionalized with fluorophores (fluorescamine and Cyanine5) emitting at λ = 525 and 730 nm, respectively, thus highlighting the possibility of multiple imaging modalities. The biocompatibility of the rods was evaluated in vitro in a zebrafish (Danio rerio) liver cell line (ZFL), with results showing that neither long nor short rods with magnetic particles caused cytotoxicity in ZFL cells for concentrations up to 50 μg/ml. We advocate that such nanocomposites can find applications in medical imaging and therapy, where the influence of shape on performance can be also assessed. [ABSTRACT FROM AUTHOR]

The growing need for developing new synthesis methods of plasmonic nanoparticles (PNPs) stems from their various applications in nanotechnology. As a result, a variety of protocols have been developed for the synthesis of PNPs of different shapes, sizes, and compositions. Though widely practiced, the chemical synthesis of PNPs demands stringent control over the experimental conditions, often employs environmentally hazardous chemicals for surface stabilization, and is frequently energy-intensive. Additionally, chemically obtained PNPs require subsequent surface engineering steps for various optoelectronic and biomedicine applications to minimize the toxic effects and render them useful for targeted drug delivery, sensing, and imaging. Considering the pressing need to develop environmentally-friendly technology solutions, “greener” methods of nanoparticle synthesis are gaining importance. Here, we report on the biological synthesis of plasmonic nanoparticles using bacterial metabolites. A peptide-based siderophore pyoverdine and a blue-green pigment pyocyanin obtained from a marine strain of Pseudomonas aeruginosa rapidly produced plasmonic nanoparticles of gold and silver in an aqueous environment. The morphology of plasmonic nanoparticles could be modulated by tuning the concentration of these metabolites and the reaction time. The exposure of pyoverdine to chloroauric acid resulted in anisotropic gold nanoparticles. On the other hand, pyocyanin produced a highly monodispersed population of gold nanoparticles and anisotropic silver nanoparticles. Biologically obtained gold and silver nanoparticles retained pyoverdine and pyocyanin on the nanoparticle surface and were stable for an extended period of time. The biologically obtained gold and silver plasmonic nanoparticles displayed potent anticancer activities against metastatic lung cancer cells. Biogenic nanoparticles were rapidly internalized by cancer cells in high quantity to affect the cellular organization, and karyoplasmic ratio, indicating the potential of these nanoparticles for cancer nanomedicine.

The synthesis of magnetite (Fe3O4) nanorods using reverse co-precipitation of Fe3+ and Fe2+ ions in the presence of a static magnetic field is reported in this work. The phase composition and crystal structure of the synthesized material were investigated using electron diffraction, Raman spectroscopy, and transmission electron microscopy. It was shown that the morphology of the reaction product strongly depends on the amount of OH− ions in the reaction mixture, varying from Fe3O4 nanorods to spherical Fe3O4 nanoparticles. Fe3O4 nanorods were examined using high-resolution transmission electron microscopy proving that they are single-crystalline and do not have any preferred crystallographic orientation along the axis of the rods. According to the data obtained a growth mechanism was proposed for the rods that consists of the dipole–dipole interaction between their building blocks (small hexagonal faceted magnetite nanocrystals), which are formed during the first step of the reaction. The study suggests a facile, green and controllable method for synthesizing anisotropic magnetic nanoparticles in the absence of stabilizers, which is important for further modification of their surfaces and/or incorporation of the nanoparticles into different media.

One-dimensional anisotropic nanoparticles are of great research interest across a wide range of biomedical applications due to their specific physicochemical and magnetic properties in comparison with isotropic magnetic nanoparticles. In this work, the formation of iron oxides and oxyhydroxide anisotropic nanoparticles (ANPs) obtained by the co-precipitation method in the presence of urea was studied. Reaction pathways of iron oxide and oxyhydroxide ANPs formation are described based on of X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and pulse magnetometry studies. It is shown that a nonmonotonic change in the Fe3O4 content occurs during synthesis. The maximum content of the Fe3O4 phase of 47.4% was obtained at 12 h of the synthesis. At the same time, the reaction products contain ANPs of α-FeOOH and submicron isotropic particles of Fe3O4, the latter formation can occur due to the oxidation of Fe2+ ions by air-oxygen and Ostwald ripening processes. A subsequent increase in the synthesis time leads to the predominant formation of an α-FeOOH phase due to the oxidation of Fe3O4. As a result of the work, a methodological scheme for the analysis of iron oxide and oxyhydroxide ANPs was developed.

In this work, the successful synthesis of spherical (sCuONPs) and rod-like (CuONRs) copper oxide nanoparticles was reported. Several microscopic and spectroscopic techniques were used to confirm the different morphologies (spherical and rod-like) and also different diameter sizes. Copper metal within nanomaterials had different oxidation states (Cu0, Cu+, and Cu2+) as was confirmed by X-ray photoelectron spectroscopy (XPS). The optical properties of the synthesized nanoparticles were investigated, and their reactive oxygen radical species (ROS) generation was confirmed using UV–vis spectroscopy. Copper oxide nanoparticles catalytically converted H2O2 to form ROS (HO●−, HOO●−, or O2●−). ROS generation was confirmed using UV–vis spectroscopy and 1,3-diphenylbenzofuran (DPBF, as a radical quencher) and also using electron paramagnetic resonance (EPR) spectroscopy and 2,2,6,6-tetramethylpiperidine (TEMP) as a spin trap. UV–vis spectroscopy was further used to monitor a blue color development when copper oxide nanoparticles were mixed with 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2). The color changes were confirmed by UV–vis spectra with absorption maxima at 370 nm and 652 nm and naked eye for blue color development. Oxidase enzymes produce hydrogen peroxide as by-product and this property was used for the detection of biological analytes. Glucose and glucose oxidase (GOx) enzyme were used as model bioanalytical system. Copper oxide nanorods were successfully synthesized and characterized their surface properties using various techniques. The nanoparticles exhibited excellent catalytic properties towards converting hydrogen peroxide to reactive oxygen radical species (ROS). The catalytic properties were confirmed using UV–vis (DPBF, radical scavenger) and EPR spectroscopy (TEMP, spin trap). The radicals could oxidize TMB to blue products visible to the naked eye as further proof of ROS generation. [ABSTRACT FROM AUTHOR]

Understanding the role of shape-directing substances is crucial for the controllable preparation of anisotropic nanostructures through solution growths. Herein, we report a comparative investigation about the morphologies and structures of Au nanoparticles (Au NPs) synthesized using two different capping agents (hexadecyltrimethylammonium chloride (CTAC) and polyvinylpyrrolidone (PVP)) with/without the addition of iodide salts. The study manifests a synergistic effect of shape-directing agents on the growth pathways and shape formation. Depending on the specific use of surfactants/polymers, the iodide additives can promote the growth of prismatic anisotropic nanoparticles or lead to the shape evolution from irregular to quasi-spherical configurations. The effect of iodide additives and organic capping agents (CTAC and PVP) on the formation of shape anisotropy was systematically investigated through UV-vis spectroscopy and transmission electron microscopy characterizations of Au nanoparticles synthesized via a one-pot seedless growth approach. The study revealed a combined role of shape-directing substances (iodide additives and organic capping agents) on the crystallization processes of Au nanoparticles. [ABSTRACT FROM AUTHOR]

Non-specific binding (NSB) is one of the important issues in biosensing performance. Herein, we designed a strategy for removing non-specific binding including anti-mouse IgG antibody and bovine serum albumin (BSA) by utilizing anisotropic cadmium selenide tetrapods (CdSe TPs) in a vortex flow. The shear force on the tetrapod nanoparticles was increased by controlling the rotation rate of the vortex flow from 0 rpm to 1000 rpm. As a result, photoluminescence (PL) signals of fluorescein (FITC)-conjugated protein, anti-mouse IgG antibody-FITC and bovine serum albumin (BSA)-FITC, were reduced by 35% and 45%, respectively, indicating that NSB can be removed under vortex flow. In particular, simultaneous NSB removal and protein capture can be achieved even with mixture solutions of target antibodies and anti-mouse IgG antibodies by applying cyclic mode vortex flow on anisotropic CdSe TPs. These results demonstrate successfully that NSB can be diminished by rotating CdSe TPs to generate shear force under vortex flow. This study opens up new research protocols for utilization of anisotropic nanoparticles under vortex flow, which increases the feasibility of protein capture and non-specific proteins removal for biosensors.

Anisotropic metal nanoparticles (NPs), such as high-aspect-ratio Au nanorods (NRs), play an important role for applications in photocatalysis, sensing, and drug delivery because of their adjustable plasmon resonances. Their performance for these applications can be further improved by fine-tuning their morphologies. Achieving desired NP architectures requires insight into their formation mechanisms. Here, liquid-phase transmission electron microscopy is used to directly follow the overgrowth of Au NR seeds into nanoarrows (NAs) with fourfold symmetric wings along the sides. Adding thiol molecules like L-cysteine to the growth solution can lead to the formation of NAs with periodic prismatic teeth instead of the straight side wings. These observations suggest that this transition is controlled by binding of L-cysteine to the NR surface, which in turn, slows down the metal deposition rate, switching the overgrowth from the kinetically to thermodynamically controlled process. Furthermore, simulations demonstrate that these prismatic teeth enhance the NPs' plasmonic properties. The study describes how thiol additives control the morphological evolution of metal NPs, which is important for the fabrication of NPs with tailored shapes for a broad range of applications. [ABSTRACT FROM AUTHOR]

Abstract We report an efficient, seed‐mediated method for the synthesis of gold nanotriangles (NTs) which can be used for controlled self‐assembly. The main advantage of the proposed synthetic protocol is that it relies on using stable (over the course of several days) intermediate seeds. This stability translates into increasing time efficiency of the synthesis and makes the protocol experimentally less demanding (‘fast addition’ not required, tap water can be used in the final steps) as compared to previously reported procedures, without compromising the size and shape monodispersity of the product. We demonstrate high reproducibility of the protocol in the hands of different researchers and in different laboratories. Additionally, this modified seed‐mediated method can be used to produce NTs with edge lengths between ca. 45 and 150 nm. Finally, the high ‘quality’ of NTs allows the preparation of long‐range ordered assemblies with vertically oriented building blocks, which makes them promising candidates for future optoelectronic technologies.

Silver nanoparticles (AgNPs) are incredibly versatile nanostructures that present a broad spectrum of applications, from nanomedicine to advanced optoelectronic materials. All AgNP properties strongly depend on nanoparticle size and shape. However, controlling these parameters in a cost-effective way is still a challenge. In this scenario, this study presents a modification of a classical two-step seed-mediated synthesis for photoinduced control of the morphology and optical properties of AgNP under low-intensity light-emitting diode (LED) irradiation in the presence of citrate as the sole additive. The LED irradiation wavelength determines the final morphology of these particles because of the shape dependence of the AgNP plasmon spectrum. Kinetics of photochemical transformation were monitored by electronic absorption, transmission electron microscopy, and X-ray diffraction studies. Data fitting revealed that particle growth follows an unusual two-step photoinduced mechanism that includes (i) a photoinduced fusion of AgNP and (ii) a light-driven autocatalytic anisotropic growth along a favorable silver crystal axis following the Finke–Watzky kinetic model. The proposed mechanism highlights the importance of interweaving both crystallographic and surface chemistry arguments in order to discern the overall mechanism of nanoparticle growth. Therefore, the presented methodology allows obtaining very complex metallic nanostructures using a simple and low-cost methodology aiming the development of size-controllable nanoparticles for optical and (photo)-catalytic applications. [ABSTRACT FROM AUTHOR]

Aim: To study the difference in biodistribution of gold nanoprisms (NPr) and nanorods (NR), PEGylated to ensure colloidal stability. Materials & methods: Surface changes were studied for nanoparticles in different media, while the biodistribution was quantified and imaged in vivo. Results: Upon interaction with the mouse serum, NR showed more abrupt changes in surface properties than NPr. In the in vivo tests, while NPr accumulated similarly in the spleen and liver, NR showed much higher gold presence in the spleen than in liver; together with some accumulation in kidneys, which was nonexistent in NPr. NPr were cleared from the tissues 2 months after administration, while NR were more persistent. Conclusion: The results suggest that the differential biodistribution is caused by size-/shape-dependent interactions with the serum. [ABSTRACT FROM AUTHOR]

A versatile generation of plasmonic nanoparticle dimers for surface-enhanced Raman scattering (SERS) is presented by combining a DNA origami nanofork and spherical and nonspherical Au or Ag nanoparticles. Combining different nanoparticle species with a DNA origami nanofork to form DNA origami nanoantennas (DONAs), the plasmonic nanoparticle dimers can be optimized for a specific excitation wavelength in SERS. The preparation of such nanoparticle dimers is robust enough to enable the characterization of SERS intensities and SERS enhancement factors of dye-modified DONAs on a single dimer level by measuring in total several thousands of dimers from five different dimer designs, each functionalized with three different Raman reporter molecules and measured at four different excitation wavelengths. Based on these data, SERS enhancement factor (EF) distributions have been determined for each dimer design and excitation wavelengths. The structures and measurement conditions with the highest EFs are suitable for single-molecule SERS (SM-SERS), which is realized by placing single dye molecules into hot spots. We demonstrate that the probability of placing single molecules in a strongly enhancing hot spot for SM-SERS can be increased by using anisotropic nanoparticles with several sharp edges, such as nanoflowers. Combining a Ag nanoparticle with a Au particle in one dimer structure allows for a broadband excitation covering almost the whole visible range. The most versatile plasmonic dimer structure for SERS combines a spherical Ag nanoparticle with a Au nanoflower. Employing the discontinuous Galerkin time domain method, we numerically investigate the bare, symmetric dimers with respect to spectral and near-field properties, showing that, indeed, the nanoflowers induce multiple hot spots located at the edges which surpass the intensity of the spherical dimers, indicating the possibility for SM-SERS. The presented DONA structures and SERS data provide a robust basis for applying such designs as versatile SERS tags and as substrates for SM-SERS measurements.

The truncated singular value decomposition (TSVD) is applied to extract the underlying 2D correlation functions from small‐angle scattering patterns. The approach is tested by transforming the simulated data of ellipsoidal particles and it is shown that also in the case of anisotropic patterns (i.e. aligned ellipsoids) the derived correlation functions correspond to the theoretically predicted profiles. Furthermore, the TSVD is used to analyze the small‐angle X‐ray scattering patterns of colloidal dispersions of hematite spindles and magnetotactic bacteria in the presence of magnetic fields, to verify that this approach can be applied to extract model‐free the scattering profiles of anisotropic scatterers from noisy data. [ABSTRACT FROM AUTHOR]

Abstract Gold nanostar@reduced graphene oxide (GNS@rGO) nanocomposite was used as a catalyst in a chemiluminescence (CL) reaction. Composites with different sizes of gold nanostars were prepared without any surfactant, and characterized by transmission electron microscopy, UV–visible, FT-IR and Raman spectroscopy. We showed that GNS@rGO can strongly enhance the intensity of luminol ‑ sodium periodate CL system and the larger the GNS size, the greater the enhancing effect. This effect results from the unique catalytic action of GNS@rGO, which leads to the acceleration of reactive oxygen species generation. We also found that a remarkable increase in the CL intensity of GNS@rGO-luminol-NaIO 4 system occurs in the presence of glutathione (GSH). Based on this observation, a simple and highly sensitive CL probe was developed for detection of GSH. Under the optimum conditions, the calibration curve exhibits a linear range from 1.0 nM to 1.0 μM for GSH with a detection limit of 0.2 nM. The developed method was applied to the detection of GSH in human plasma samples. Graphical abstract Unlabelled Image Highlights • Gold nanostar@reduced graphene oxide was used as a catalyst in chemiluminescence. • CL intensity of luminol-periodate reaction is significantly enhanced by GNS@rGO. • Larger nanostars with sharper and more branches exhibit greater catalytic effect. • A sensitive and selective CL probe was developed for detection of glutathione. [ABSTRACT FROM AUTHOR]

We report an efficient, seed‐mediated method for the synthesis of gold nanotriangles (NTs) which can be used for controlled self‐assembly. The main advantage of the proposed synthetic protocol is that it relies on using stable (over the course of several days) intermediate seeds. This stability translates into increasing time efficiency of the synthesis and makes the protocol experimentally less demanding ('fast addition' not required, tap water can be used in the final steps) as compared to previously reported procedures, without compromising the size and shape monodispersity of the product. We demonstrate high reproducibility of the protocol in the hands of different researchers and in different laboratories. Additionally, this modified seed‐mediated method can be used to produce NTs with edge lengths between ca. 45 and 150 nm. Finally, the high 'quality' of NTs allows the preparation of long‐range ordered assemblies with vertically oriented building blocks, which makes them promising candidates for future optoelectronic technologies. [ABSTRACT FROM AUTHOR]

Abstract In this work a non-aggregated colorimetric probe for detection of chemotherapeutic drug, 6–thioguanine (6-TG), is introduced. It is based on the protective effect of 6-TG on silver nanoprisms (AgNPRs) against the iodide-induced etching reaction. Iodide ions can attack the corners of AgNPRs and etch them, leading to the morphological transition from nanoprisms to nanodiscs. As a consequence, the solution color changes from blue to pink. However, in the presence of 6-TG, due to its protective effect on the corners of AgNPRs, I− ions cannot etch the prisms and the blue color of solution remains unchanged. Using this effect, selective sensor was designed for detection of 6–TG in the range of 2.5–500 μg L−1, with a detection limit of 0.95 μg L−1. Since with varying the concentration of 6-TG in this range, the color variation from pink to blue can be easily observed, the designed sensing scheme can be used as a colorimetric probe. The method was used for analysis of human plasma samples. Graphical Abstract Unlabelled Image Highlights • Ag nanoprism-based colorimetric sensor was developed for detection of thioguanine. • Thioguanine protects Ag nanoprisms from iodide-induced etching. • Color change and wavelength shift occur in nanoprism-iodide solution. • The probe was applied for analysis of human plasma samples. [ABSTRACT FROM AUTHOR]

A sensitive fluorescent analytical method for the detection of dopamine (DA) was developed based on surface-enhanced Tb(III)/La(III) co-luminescence using silver nanoflowers (AgNFs). Anisotropic AgNFs show strong surface-enhanced fluorescence effect owing to the abundant sharp tips. Tb(III)/La(III)-DA complexes mainly bind to the sharp tips of AgNFs and thus shorten the distance between the complexes. The shortened distance gives rise to obvious surface-enhanced Tb(III)/La(III) co-luminescence effect. In this work, AgNFs offer many superior properties, such as enhanced intrinsic green fluorescence of Tb(III) (λex/λem = 310/546 nm), increased fluorescence lifetime, and improved energy transfer efficiency. Under the optimum conditions, the fluorescence intensity is linearly correlated with the concentration of DA in the range of 0.80–10 nM (R2 = 0.9970), and the detection limit is 0.34 nM (S/N = 3). The fluorescent nanoprobe was successfully applied to the determination of DA in human serum samples with recoveries ranging from 99.1 to 102.6%. Graphical abstract [ABSTRACT FROM AUTHOR]

Montmorillonite (MMT) based anisotropic magnetic nanoparticles (Fe 3 O 4 /APTES/MMT) with high anisotropy and reliable magnetism were prepared by using Fe 3 O 4 as magnetic nanoparticles and γ-aminopropyltriethoxysilane (ATPES) as modifier. The characterization indicated that the interactions between Fe 3 O 4 nanoparticles and MMT in Fe 3 O 4 /APTES/MMT were stronger than that of directly deposited on to MMT (Fe 3 O 4 -MMT) because APTES was chemically bonded to both Fe 3 O 4 and MMT. Fe 3 O 4 /APTES/MMT had a greater Ms value (25.16 emu/g) than Fe 3 O 4 -MMT (23.71 emu/g). Also, ultrasonication was used to test the interactions between Fe 3 O 4 and MMT. With 30 min of ultrasonication, the amount of Fe 3 O 4 nanoparticles on the surface of Fe 3 O 4 /APTES/MMT was more than that of Fe 3 O 4 -MMT, and Fe 3 O 4 /APTES/MMT had a faster magnetic response to a magnetic field than that of Fe 3 O 4 -MMT because of enhanced interactions between Fe 3 O 4 and MMT in Fe 3 O 4 /APTES/MMT. In addition, Fe 3 O 4 nanoparticles were densely immobilized onto Fe 3 O 4 /APTES/MMT with a smaller average diameter, and the distribution of Fe 3 O 4 nanoparticles on the surface of MMT was more uniform than that of Fe 3 O 4 -MMT. Fe 3 O 4 /APTES/MMT possessed stable and high magnetism, in ease of orientation and recycling in the magnetic field, and this makes it a promising candidate as anisotropic nanoparticles for use in preparing anisotropic inorganic/polymer composites and anisotropic adsorbents used in wastewater treatment. Finally, the mechanism of ATPES-modified magnetic MMT was investigated. [ABSTRACT FROM AUTHOR]

Abstract: Reconfigurable hybrid nanoparticles made by decorating flexible polymer shells on rigid inorganic nanoparticle cores can provide a unique means to build stimuli‐responsive functional materials. The polymer shell reconfiguration has been expected to depend on the local core shape details, but limited systematic investigations have been undertaken. Here, two literature methods are adapted to coat either thiol‐terminated polystyrene (PS) or polystyrene‐poly(acrylic acid) (PS‐b‐PAA) shells onto a series of anisotropic gold nanoparticles of shapes not studied previously, including octahedron, concave cube, and bipyramid. These core shapes are complex, rendering shell contours with nanoscale details (e.g., local surface curvature, shell thickness) that are imaged and analyzed quantitatively using the authors' customized analysis codes. It is found that the hybrid nanoparticles based on the chosen core shapes, when coated with the above two polymer shells, exhibit distinct shell segregations upon a variation in solvent polarity or temperature. It is demonstrated for the PS‐b‐PAA‐coated hybrid nanoparticles, the shell segregation is maintained even after a further decoration of the shell periphery with gold seeds; these seeds can potentially facilitate subsequent deposition of other nanostructures to enrich structural and functional diversity. These synthesis, imaging, and analysis methods for the hybrid nanoparticles of anisotropically shaped cores can potentially aid in their predictive design for materials reconfigurable from the bottom up. [ABSTRACT FROM AUTHOR]

Self-assembly of nanoparticles into superlattices can be used to create hierarchically structured materials with tailored functions. We have used the surface sensitive quartz crystal microbalance with dissipation monitoring (QCM-D) technique in combination with video microscopy (VM) to obtain time-resolved information on the mass increase and rheological properties of evaporation-induced self-assembly of nanocubes. We have recorded the frequency and dissipation shifts during growth and densification of superlattices formed by self-assembly of oleic acid capped, truncated iron oxide nanocubes and analyzed the time-resolved QCM-D data using a Kelvin-Voigt viscoelastic model. We show that the nanoparticles first assemble into solvent-containing arrays dominated by a viscous response followed by a solvent-releasing step that results in the formation of rigid and well-ordered superlattices. Our findings demonstrate that QCM-D can be successfully used to follow self-assembly and assist in the design of optimized routes to produce well-ordered superlattices. [ABSTRACT FROM AUTHOR]