Morphology Of Metal Nanoparticles Research Articles

Recent Advances of Seed-Mediated Growth of Metal Nanoparticles: from Growth to Applications.

Unprecedented advances in metal nanoparticle synthesis have paved the way for broad applications in sensing, imaging, catalysis, diagnosis, and therapy by tuning the optical properties, enhancing catalytic performance, and improving chemical and biological properties of metal nanoparticles. The central guiding concept for regulating the size and morphology of metal nanoparticles is identified as the precise manipulation of nucleation and subsequent growth, often known as seed-mediated growth methods. However, since the growth process is sensitive not only to the metal seeds but also to capping agents, metal precursors, growth solution, growth/incubation time, reductants, and other influencing factors, the precise control of metal nanoparticle morphology is multifactorial. Further, multiple reaction parameters are entangled with each other, so it is necessary to clarify the mechanism by which each factor precisely regulates the morphology of metal nanoparticles. In this review, to exploit the generality and extendibility of metal nanoparticle synthesis, the mechanisms of growth influencing factors in seed-mediated growth methods aresystematically summarized. Second, a variety of critical properties and applications enabled by grown metal nanoparticles are focused upon. Finally, the current progress and offer insights on the challenges, opportunities, and future directions for the growth and applications of grown metal nanoparticles are reviewed.

DNA-Guided Metallization of Nanomaterials and Their Biomedical Applications.

Precise control of the structure of metallic nanomaterials is critical for the advancement of nanobiotechnology. As DNA (deoxyribonucleic acid) can readily modify various moieties, such as sulfhydryl, carboxyl, and amino groups, using DNA as a directing ligand to modulate the morphology of nanomaterials is a promising strategy. In this review, we focus on the use of DNA as a template to control the morphology of metallic nanoparticles and their biomedical applications, discuss the use of DNA for the metallization of gold and silver, explore the factors that influence the process, and outline its biomedical applications. This review aims to provide valuable insights into the DNA-guided growth of nanomaterials. The challenges and future directions are also discussed.

Enhanced room temperature gas sensing performance of ZnO with atomic-level Pt catalysts facilitated by the polydopamine mediator

The poor sensitivity of metal-oxide (MO) sensing material at room temperature can be enhanced by the modification of noble metal catalysts. However, the large size and uncontrollable morphology of metal nanoparticles (NPs) compromise the catalytic activity and selectivity. Downsizing metal NPs to the atomic level is a promising solution because it offers high activity and selectivity. Nevertheless, a facile and universal approach for stable loading atomic-level metal on MO-based sensing materials is still challenging. Herein, we present a strategy to construct synergetic coordination interface for uniform loading of atomic-level metal catalysts on MO-based gas-sensing materials using a difunctional mediator layer. In this work, atomically dispersed Pt catalysts are coordinately anchored on ZnO nanorods (NRs) using polydopamine (PDA) as a mediator. As a result, compared with pristine ZnO NRs, a six-fold enhanced response of 18,489% is achieved toward 100 ppm NO2 on 0.20 wt%Pt–ZnO@PDA-1.5 nm, and the selectivity is also promoted. Such sensitivity is higher than that of most reported noble metal-modified MO NO2-sensing materials. This work provides a simple and general strategy for building highly sensitive and selective gas-sensing materials using atomic-level noble metal catalyst.

Оптическая анизотропия пленок из поливилового спирта с металлическими наностержнями при одноосном растяжении

The possibility of obtaining macroscale anisotropic thin films from polyvinyl alcohol with included metal nanorods under uniaxial tension under conditions that do not lead to a change in the morphology of metal nanoparticles is shown. Silver and gold nanorods were obtained by directed growth from nuclei and then embedded in a polymer matrix based on polyvinyl alcohol. Initially isotropic films with absorption independent of the polarization of the probing light became anisotropic after stretching, which manifested itself in the dependence of the extinction spectra on the polarization of the probing radiation. The weakening of the longitudinal dipole plasmon resonance mode with the simultaneous enhancement of the transverse dipole plasmon resonance when the light polarization is rotated from 0 to 90 degree indicates the orientation of the nanorods in the film along the direction of its stretching. In addition to the change in absorption in the bands of dipole modes, a strong orientational dependence of absorption in the band of the quadrupole mode of the plasmon resonance of metal nanorods was found.

Formation of Island SERS Films on Surfaces of Track Membranes and Silicon Substrates

It is shown that metallic nano-island SERS-active layers can be created on the surfaces of porous track membranes made of polyethylene terephthalate and silicon substrates optimized for exciting laser radiation with wavelengths of 532 and 785 nm. Characteristic patterns of changes in the optical properties of SERS structures upon altering the morphology of metal nanoparticles on a substrate’s surface are established. Such structures can be used as SERS chips and highly sensitive filtering SERS elements in optical biosensors.

An overview of surface-enhanced Raman scattering substrates by pulsed laser deposition technique: fundamentals and applications.

Metallic nanoparticles (NPs), as an efficient substrate for surface-enhanced Raman scattering (SERS), attract much interests because of their various shapes and sizes. The appropriate size and morphology of metallic NPs are critical to serve as the substrate for achieving an efficient SERS. Pulsed laser deposition (PLD) is one of the feasible physical methods employed to synthesize metallic NPs with controllable sizes and surface characteristics. It has been recognized to be a successful tool for the deposition of SERS substrates due to its good controllability and high reproducibility in the manufacture of metallic NPs. This review provides an overview about the recent advances for the preparation of SERS substrates by PLD technique. The influences of parameters on the sizes and morphologies of metallic NPs during the deposition processes in PLD technique including laser output parameters, gas medium, liquid medium, substrate temperature, and properties of 3D substrate are presented. The applications of SERS substrates produced by PLD in the environmental monitoring and biomedical analysis are summarized. This knowledge could serve as a guideline for the researchers in exploring further applications of PLD technique in the production of SERS substrate.Graphical abstract

Influence of the Morphology of Metal Nanoparticles Deposited on Surfaces of Silicon Oxide on the Optical Properties of SERS Substrates

The possibility of adjusting the plasmon absorption of nanostructured SERS substrates to the wavelength of exciting laser radiation in the range of 530–620 nm is demonstrated. Characteristic patterns of changes in the optical properties of SERS substrates with changes in the morphology of metal nanoparticles on surfaces of silicon oxide are established.

An insight, at the atomic level, into the polarization effect in controlling the morphology of metal nanoclusters.

The polarization effect has been a powerful tool in controlling the morphology of metal nanoparticles. However, a precise investigation of the polarization effect has been a challenging pursuit for a long time, and little has been achieved for analysis at the atomic level. Here the atomic-level analysis of the polarization effect in controlling the morphologies of metal nanoclusters is reported. By simply regulating the counterions, the controllable transformation from Pt1Ag28(S-PhMe2)x(S-Adm)18−x(PPh3)4 (x = 0–6, Pt1Ag28-2) to Pt1Ag24(S-PhMe2)18 (Pt1Ag24) with a spherical configuration or to Pt1Ag28(S-Adm)18(PPh3)4 (Pt1Ag28-1) with a tetrahedral configuration has been accomplished. In addition, the spherical or tetrahedral configuration of the clusters could be reversibly transformed by re-regulating the proportion of counterions with opposite charges. More significantly, the configuration transformation rate has been meticulously manipulated by regulating the polarization effect of the ions on the parent nanoclusters. The observations in this paper provide an intriguing nanomodel that enables the polarization effect to be understood at the atomic level.

Engineering heterogenous catalysts for chemical CO2 utilization: Lessons from thermal catalysis and advantages of yolk@shell structured nanoreactors

The development of catalytic materials for the recycling CO2 through a myriad of available processes is an attractive field, especially given the current climate change. While there is increasing publication in this field, the reported catalysts rarely deviate from the traditionally supported metal nanoparticle morphology, with the most simplistic method of enhancement being the addition of more metals to an already complex composition. Encapsulated catalysts, especially [email protected] catalysts with hollow voids, offer answers to the most prominent issues faced by this field, coking and sintering, and further potential for more advanced phenomena, for example, the confinement effect, to promote selectivity or offer greater protection against coking and sintering. This work serves to demonstrate the current position of catalyst development in the fields of thermal CO2 reforming and hydrogenation, summarizing the most recent work available and most common metals used for these reactions, and how [email protected] catalysts can offer superior performance and survivability in thermal CO2 reforming and hydrogenation to the more traditional structure. Furthermore, this work will briefly demonstrate the bespoke nature and highly variable [email protected] structure. Moreover, this review aims to illuminate the spatial confinement effect and how it enhances [email protected] structured nanoreactors is presented.

Surface engineering of Pd-based nanoparticles by gas treatment for oxygen reduction reaction

In many catalyst systems, including fuel cell applications, control of the catalyst surface composition is important for improving activity since catalytic reactions occur only at the surface. However, it is very difficult to modify the surface composition without changing the morphology of metal nanoparticles. Herein, carbon-supported Pd3Au1 nanoparticles with uniform size and distribution are fabricated by tert-butylamine reduction method. Pd or Au surface segregation is induced by simply heating as-prepared Pd3Au1 nanoparticles under CO or Ar atmosphere, respectively. Especially, CO-induced Pd surface segregation allows the alloy nanoparticles to have a Pd-rich surface, which is attributed to the strong CO binding energy of Pd. To demonstrate the change in surface composition of Pd3Au1 alloy catalyst with the annealing gas species, the oxygen reduction reaction performance is investigated and consequently, Pd3Au1 catalyst with the highest number of surface Pd atoms indicates excellent catalytic activity. Therefore, the present work provides insights into the development of metal-based alloys with optimum structures and surface compositions for various catalytic systems.

Study of the azo‐hydrazone tautomerism of Acid Orange 20 by spectroscopic techniques: UV–Visible, Raman, and surface‐enhanced Raman scattering

AbstractAcid Organge 20 is a synthetic monoazo dye, which molecular structure consists of a naphtol unit and a sulfonated benezene ring linked together by an azo chromophore group. As a phenylazonaphthol with the OH group in para position respect to the azo group, it undergoes an azo‐hydrazone tautomerism. In this work, the study of the preponderance of one tautomer over the other in different pH conditions was carried out by means of UV–Vis, Raman, and surface‐enhanced Raman scattering (SERS) spectroscopies. Raman spectra of powder and aqueous solutions of the dye were obtained at different excitation lines at the natural pH of the AO20 solutions. The best results were obtained at 633 nm, and the observed Raman bands suggested the presence of the hydrazone tautomer. The molecular structure and the theoretical Raman spectra of the two tautomers were calculated by density functional theory (DFT) methods. The obtained results were used for the assignment of the Acid Orange 20 vibrational modes. The SERS analysis of the dye solutions were carried out employing Ag nanostars, pH below and above 4.7, and excitation at 442, 532, and 633 nm. The hydrazone tautomer was prevalent in most conditions. The azo tautomer was only detected at pH ~ 5 under excitation with the 532 nm wavelength due to resonant Raman conditions. Finally, the effect of pH on the morphology of metal nanoparticles employed as SERS substrates was evaluated by TEM.

Crystallization of metallic nanoparticles on short DNA oligonucleotides in alkaline aqueous solution

Silver, zinc, and copper nanoparticles were reductively crystallized on thymine-containing single-stranded DNA decanucleotides, in aqueous solutions containing the corresponding metal ions and sodium borohydride, at 4 °C, pH 11.8, and 15 mM of NaCl. Iron nanoparticles were not formed under these conditions. Formation of aggregates was monitored by UV-Vis spectrophotometry, and characterized by scanning electron microscopy and dynamic light scattering. The absorption spectra for most Ag+-containing samples showed a major band centered around 425 nm and a shoulder between 500 and 600 nm, indicative of the presence of silver particles in a wide size distribution, in the 0.1–5 μm range. This was verified by micrographs and size distribution observed in scattering profiles. Silver-particle morphology indicates formation of cubic structures instead of spherical geometries. For the case of zinc and copper nanoparticles, quasi-spherical structures of approximately 100 nm were crystallized along the DNA chains by reduction reaction, and then released to the bulk solvent. Thymine residues show a higher effectiveness in nucleation of metallic cations in comparison to other DNA nucleobases, particularly in their deprotonated form, at high pH values. Adenines flanking central runs of deprotonable bases in the model oligonucletide chain affect the production of silver crystals on the DNA decamers. pH value and NaCl concentration have a significant effect on the production of silver particles, as alkaline and moderate-ionic-strength conditions are required to crystallize such structures. The tuning of size and morphology of metallic nanoparticles by the proper choice of oligonucleotide sequence and physical conditions may have interesting applications in the field of nanobiotechnology.

Enhancement of ethanol electrooxidation in half cell and single direct ethanol fuel cell (DEFC) using post-treated polyol synthesized Pt-Ru nano electrocatalysts supported on HNO3-functionalized acetylene black carbon

Highly dispersed Pt-Ru nano electrocatalysts supported on functionalized acetylene black carbon (CAB) were synthesized by a modified polyol reduction route followed by post treatment under three different conditions. The synthesized Pt-Ru/CAB-syn electrocatalysts after post treatment were designated as Pt-Ru/CAB-H2-RT when treated under H2 atmosphere at room temperature of 40 °C, and Pt-Ru/CAB-H2-160 when treated under H2 atmosphere at 160 °C and Pt-Ru/CAB-Air-160 when treated under air at 160 °C, respectively. The post treatment of synthesized electrocatalyst modified the crystallographic and morphological structures of the synthesized electrocatalysts which enhanced the electrocatalytic activity for ethanol electrooxidation. The physical characteristics of the post-treated electrocatalysts were recorded using XRD, SEM-EDX and TEM techniques. The XRD and TEM analyses revealed that the synthesized electrocatalysts have particle size in nano range with narrow size distribution. The electrochemical study of synthesized electrocatalysts were evaluated via cyclic voltammetry and chronoamperometry revealed that the Pt-Ru/CAB-H2-RT electrocatalyst is the most active exhibit towards ethanol electrooxidation in comparison to that of Pt-Ru/CAB-H2-160, Pt-Ru/CAB-Air-160 and commercial Pt-Ru/C electrocatalysts. In DEFC performance test at a temperature of 40 °C, the obtained power density (9.15 mW/cm2) using the synthesized Pt-Ru/CAB-H2-RT as anode electrocatalyst was higher than that of Pt-Ru/CAB-Air-160 (5.79 mW/cm2), Pt-Ru/CAB-H2-160 (6.84 mW/cm2) and commercial Pt-Ru/C (7.86 mW/cm2) electrocatalysts with same anode electrocatalyst loading of 1 mg/cm2 and 2 M ethanol fuel. The maximum OCV of 0.737 V and power density of 16.23 mW/cm2 at 0.317 V with a current density of 51.2 mA/cm2 were obtained using Pt-Ru/CAB-H2-RT electrocatalyst as anode at a cell temperature of 80 °C. The enhanced and superior performance of Pt-Ru/CAB-H2-RT electrocatalyst after post treatment could be attributed to well alloyed microstructure and highly dispersed surface morphology of metal nanoparticles.

A Nature-Inspired, Flexible Substrate Strategy for Future Wearable Electronics.

Flexibility plays a vital role in wearable electronics. Repeated bending often leads to the dramatic decrease of conductivity because of the numerous microcracks formed in the metal coating layer, which is undesirable for flexible conductors. Herein, conductive textile-based tactile sensors and metal-coated polyurethane sponge-based bending sensors with superior flexibility for monitoring human touch and arm motions are proposed, respectively. Tannic acid, a traditional mordant, is introduced to attach to various flexible substrates, providing a perfect platform for catalyst absorbing and subsequent electroless deposition (ELD). By understanding the nucleation, growth, and structure of electroless metal deposits, the surface morphology of metal nanoparticles can be controlled in nanoscale with simple variation of the plating time. When the electroless plating time is 20 min, the normalized resistance (R/R0 ) of as-made conductive fibers is only 1.6, which is much lower than a 60 min ELD sample at the same conditions (R/R0 ≈ 5). This is because a large number of unfilled gaps between nanoparticles prevent metal films from cracking under bending. Importantly, the Kelvin problem is relevant to deposited conductive coatings because metallic cells have a honeycomb-like structure, which is a rationale to explain the relationships of conductivity and flexibility.

Discovery of and Insights into DNA "Codes" for Tunable Morphologies of Metal Nanoparticles.

The discovery and elucidation of genetic codes has profoundly changed not only biology but also many fields of science and engineering. The fundamental building blocks of life comprises of four simple deoxyribonucleotides and yet their combinations serve as the carrier of genetic information that encodes for proteins that can carry out many biological functions due to their unique functionalities. Inspired by nature, the functionalities of DNA molecules have been used as a capping ligand for controlling morphology of nanomaterials, and such a control is sequence dependent, which translates into distinct physical and chemical properties of resulting nanoparticles. Herein, an overview on the use of DNA as engineered codes for controlling the morphology of metal nanoparticles, such as gold, silver, and Pd-Au bimetallic nanoparticles is provided. Fundamental insights into rules governing DNA controlled growth mechanisms are also summarized, based on understanding of the affinity of the DNA nucleobases to various metals, the effect of combination of nucleobases, functional modification of DNA, the secondary structures of DNA, and the properties of the seed employed. The resulting physical and chemical properties of these DNA encoded nanomaterials are also reviewed, while perspectives into the future directions of DNA-mediated nanoparticle synthesis are provided.

Fabrication of Metal Nanostructures on DNA Templates.

Metal nanoarchitectures fabrication based on DNA assembly has attracted a good deal of attention. DNA nanotechnology enables precise organization of nanoscale objects with extraordinary structural programmability. The spatial addressability of DNA nanostructures and sequence-dependent recognition allow functional elements to be precisely positioned; thus, novel functional materials that are difficult to produce using conventional methods could be fabricated. This review focuses on the recent development of the fabrication strategies toward manipulating the shape and morphology of metal nanoparticles and nanoassemblies based on the rational design of DNA structures. DNA-mediated metallization, including DNA-templated conductive nanowire fabrication and sequence-selective metal deposition, etc., is briefly introduced. The modifications of metal nanoparticles (NPs) with DNA and subsequent construction of heterogeneous metal nanoarchitectures are highlighted. Importantly, DNA-assembled dynamic metal nanostructures that are responsive to different stimuli are also discussed as they allow the design of smart and dynamic materials. Meanwhile, the prospects and challenges of these shape-and morphology-controlled strategies are summarized.

A Universal Platform for the Electrodeposition of Ligand-Free Metal Nanoparticles from a Water-in-Oil Emulsion System

Prodigious resources are currently being devoted to control the size and morphology of metal nanoparticles (NPs). Several homogeneous chemical and photochemical techniques exist for the synthesis o...

Growth of Nanoparticles with Desired Catalytic Functions by Controlled Doping-Segregation of Metal in Oxide

The size and morphology of metal nanoparticles (NPs) often play a critical role in defining the catalytic performance of supported metal nanocatalysts. However, common synthetic methods struggle to produce metal NPs of appropriate size and morphological control. Thus, facile synthetic methods that offer controlled catalytic functions are highly desired. Here we have identified a new pathway to synthesize supported Rh nanocatalysts with finely tuned spatial dimensions and controlled morphology using a doping-segregation method. We have analyzed their structure evolutions during both the segregation process and catalytic reaction using a variety of in situ spectroscopic and microscopic techniques. A correlation between the catalytic functional sites and activity in CO2 hydrogenation over supported Rh nanocatalysts is then established. This study demonstrates a facile strategy to design and synthesize nanocatalysts with desired catalytic functions.

Probing nanostructured materials using X‐ray fluorescence analysis

Dispersion of metal nanoparticles on flat surfaces has attracted considerable interest in many technological applications. Numerous advantages of functionalized patterned nanostructures especially in medical physics, chemistry, biology, and semiconductor quantum dot applications have rapidly driven the growth of this field in the last two decades. In particular, for applications involving biomedical imaging, the nanoparticles have attracted perhaps the greatest attention as these materials provide a direct interface at the subcellular length scale. Reliable characterization methods are thus often needed to infer their detailed structural properties such as average particle size, particle shape, internal structure, surface morphology, distribution of particles, and their chemical composition. As a nondestructive probe, X‐ray fluorescence measurements at grazing incidence provide sensitive information about the physical and chemical nature of the nanoparticles over the large surface area of a substrate. Herein, we demonstrate the potential capabilities of the X‐ray fluorescence technique for reliable and precise determination of surface morphology of metal nanoparticles, dispersed on a flat surface. Our results show that X‐ray standing wave assisted fluorescence measurements are markedly sensitive to the nature of dispersion of nanoparticles on a substrate surface. We have analyzed different types of nanostructured materials; e.g. a W thin film structure and Au nanoparticles deposited on a Si surface. The average size of the Au nanoparticles estimated, using X‐ray standing wave fluorescence analysis, was found to closely agree with the atomic force microscopy measurements. The inherent features of the X‐ray fluorescence technique permit us to analyze distribution of all kinds of metal and metalloid nanoparticles on a flat surface. Copyright © 2017 John Wiley & Sons, Ltd.

WITHDRAWN: Microscopy study, structural and optical properties correlated with the morphology of metallic nanoparticles embedded in synthetic sapphire

Abstract This work reports on the electron microscopy analysis of the structure and morphology of gold nanoparticles produced by ion implantation, as well as their relationship to their optical properties. Gold nanoparticles are usually spherical and formed beneath the surface of a dielectric matrix. In this experiment, the matrix was sapphire. After high-energy Si ion irradiation, the gold nanoparticles were elongated into prolate spheroids. Since the nanoparticles are embedded in a dielectric matrix, secondary electron imaging in a JEOL JSM-7800F at low voltage did not allow their analysis. This work proposes an analysis using backscattered electron imaging in a field emission scanning electron microscope at higher voltages (20 kV) in order to explore the morphology of the embedded nanoparticles. The samples were observed by cross-sectional view as well as a top view of the surface of the sapphire matrix for exploration and recognition of their morphology, dimensions, distribution, and composition. The analysis was extended with Rutherford backscattering spectrometry, X-ray diffraction, and optical extinction spectroscopy. The nanoparticles exhibited structural and optical properties correlated directly to the morphology observed by microscopy. The beam interaction with the sample and the conditions used were simulated in the CASINO code, from which the depth of exploration with the conditions used in field emission scanning electron microscopy were estimated.