Size and isotopic ratio measurements of individual nanoparticles by a continuous ion-monitoring method using Faraday detectors equipped on a multiple collector-ICP-mass spectrometer

We investigated the analytical capability of high-gain Faraday detectors equipped on a multiple collector-ICP-mass spectrometer (MFC-ICP-MS) in performing both size and isotopic ratio measurements on individual silver nanoparticles (Ag NPs)....

Formation of planar plasmon microstructures by dry aerosol printing

Optical properties and microstructure of samples formed by dry aerosol printing are studied. Silver nanoparticles flat layers of two types were formed on substrates surfaces and were investigated by a spectrophotometer, a scanning electron microscope, and a transmission electron microscope. It is shown that all microstructures support plasmon resonance on individual nanoparticles with the Q factor depending both on the width of the nanoparticles size distribution in the aerosol and on their tendency to agglomeration and aggregation.

Tracking Brownian motion in three dimensions and characterization of individual nanoparticles using a fiber-based high-finesse microcavity

The dynamics of nanosystems in solution contain a wealth of information with relevance for diverse fields ranging from materials science to biology and biomedical applications. When nanosystems are marked with fluorophores or strong scatterers, it is possible to track their position and reveal internal motion with high spatial and temporal resolution. However, markers can be toxic, expensive, or change the object’s intrinsic properties. Here, we simultaneously measure dispersive frequency shifts of three transverse modes of a high-finesse microcavity to obtain the three-dimensional path of unlabeled SiO2 nanospheres with 300 μs temporal and down to 8 nm spatial resolution. This allows us to quantitatively determine properties such as the polarizability, hydrodynamic radius, and effective refractive index. The fiber-based cavity is integrated in a direct-laser-written microfluidic device that enables the precise control of the fluid with ultra-small sample volumes. Our approach enables quantitative nanomaterial characterization and the analysis of biomolecular motion at high bandwidth.

Clustering in thin silver films upon heating

The kinetics of the formation of silver clusters Ag from nanoscale continuous films of Ag on the surface of silicate glass and composite structures from films of Ag with carbon in the form of a continuous film and individual nanoparticles upon annealing in air at temperatures up to 670K is investigated. In the course of the work, the dependences of the surface morphology of silver clusters and absorption spectra in the visible wavelength range were obtained by the methods of atomic force microscopy and optical spectrophotometry.

Self-regulated co-assembly of soft and hard nanoparticles

Controlled self-assembly of colloidal particles into predetermined organization facilitates the bottom-up manufacture of artificial materials with designated hierarchies and synergistically integrated functionalities. However, it remains a major challenge to assemble individual nanoparticles with minimal building instructions in a programmable fashion due to the lack of directional interactions. Here, we develop a general paradigm for controlled co-assembly of soft block copolymer micelles and simple unvarnished hard nanoparticles through variable noncovalent interactions, including hydrogen bonding and coordination interactions. Upon association, the hairy micelle corona binds with the hard nanoparticles with a specific valence depending exactly on their relative size and feeding ratio. This permits the integration of block copolymer micelles with a diverse array of hard nanoparticles with tunable chemistry into multidimensional colloidal molecules and polymers. Secondary co-assembly of the resulting colloidal molecules further leads to the formation of more complex hierarchical colloidal superstructures. Notably, such colloidal assembly is processible on surface either through initiating the alternating co-assembly from a micelle immobilized on a substrate or directly grafting a colloidal oligomer onto the micellar anchor.

Ab initio thermodynamics reveals the nanocomposite structure of ferrihydrite

Ferrihydrite is a poorly crystalline iron oxyhydroxide nanomineral that serves a critical role as the most bioavailable form of ferric iron for living systems. However, its atomic structure and composition remain unclear due in part to ambiguities in interpretation of X-ray scattering results. Prevailing models so far have not considered the prospect that at the level of individual nanoparticles multiple X-ray indistinguishable phases could coexist. Using ab initio thermodynamics we show that ferrihydrite is likely a nanocomposite of distinct structure types whose distribution depends on particle size, temperature, and hydration. Nanoparticles of two contrasting single-phase ferrihydrite models of Michel and Manceau are here shown to be thermodynamically equivalent across a wide range of temperature and pressure conditions despite differences in their structural water content. Higher temperature and water pressure favor the formation of the former, while lower temperature and water pressure favor the latter. For aqueous suspensions at ambient conditions, their coexistence is maximal for particle sizes up to 12 nm. The predictions inform and help resolve different observations in various experiments.

Wide-field photothermal reflectance spectroscopy for single nanoparticle absorption spectrum analysis

Photothermal imaging is useful for detecting individual nanoparticles and obtaining the absorption spectra. This study presents a wide-field photothermal reflectance spectroscopy technique achieved by incorporating a pump beam, a probe beam, and a charge-coupled device (CCD) camera into a commercial microscopic setup. The presented design does not require precise alignment between the pump and the probe beams and enables the observation of numerous individual nanoparticles during image acquisition. Despite the use of a simple imaging processing method, i.e., a four-bucket method using a CCD camera, sufficient sensitivity for the spectral imaging of a single gold nanorod (20 nm diameter and 84 nm length) is demonstrated. Numerous individual nanoparticles within a wide field of view (240 μm × 180 μm) are detected in an image captures at an imaging measurement speed of 0.02 mm2 min−1. Furthermore, the proposed photothermal reflectance spectroscopy technique can detect the variation in the absorption peak of the measured spectra depending on the aspect ratio of individual nanoparticles within a spectral resolution of 1 nm.

On the Fly” Characterization of YbIII:ErIII Co-Doped Upconversion Nanoparticle Nonlinear Optical Response from Single-Particle Trajectories

<p> Spectroscopic characterization of individual nanoparticles is essential for understanding their structure-property relationship and for applications. Upconversion nanoparticles (UCNPs) in condensed phases can undergo both nonlinear optical and stochastic dynamics when interacting with near-infrared sources. By integrating optical trapping microspectroscopy, stochastic dynamics and light-matter interactions experiments and simulations, in the present work we study how individual trajectories of YbIII:ErIII co-doped UCNPs can be used to perform “on the fly” characterization of their nonlinear optical power-law response upon near-infrared excitation. We illustrate the methodology in the case of freely diffusing and optically trapped UCNPs as well as with particles bound to the substrate. The approach presented in this work can be applied to UCNPs with varying composition and morphological features, particularly in single-particle studies.</p>