Response to "Critical Assessment of the Evidence for Striped Nanoparticles"

Stirling et al., (10.1371/journal.pone.0108482) presented an analysis on some of our publications on the formation of stripe-like domains on mixed-ligand coated gold nanoparticles. The authors shed doubts on some of our results however no valid argument is provided against what we have shown since our first publication: scanning tunneling microscopy (STM) images of striped nanoparticles show stripe-like domains that are independent of imaging parameters and in particular of imaging speed. We have consistently ruled out the presence of artifacts by comparing sets of images acquired at different tip speeds, finding invariance of the stipe-like domains. Stirling and co-workers incorrectly analyzed this key control, using a different microscope and imaging conditions that do not compare to ours. We show here data proving that our approach is rigorous. Furthermore, we never solely relied on image analysis to draw our conclusions; we have always used the chemical nature of the particles to assess the veracity of our images. Stirling et al. do not provide any justification for the spacing of the features that we find on nanoparticles: similar to 1 nm for mixed ligand particles and similar to 0.5 nm for homoligand particles. Hence our two central arguments remain unmodified: independence from imaging parameters and dependence on ligand shell chemical composition. The paper report observations on our STM images; none is a sufficient condition to prove that our images are artifacts. We thoroughly addressed issues related to STM artifacts throughout our microscopy work. Stirling et al. provide guidelines for what they consider good STM images of nanoparticles, such images are indeed present in our literature. They conclude that the evidences we provided to date are insufficient, this is a departure from one of the authors' previous article which concluded that our images were composed of artifacts. Given that four independent laboratories have reproduced our measurements and that no scientifically rigorous argument is presented to invalidate our STM images, and also given that Stirling et al. do not contest the quality of our recent STM images, we re-affirm that specific binary mixture of ligands spontaneously form features in their ligand shell that we describe as stripe-like domains similar to 1 nm in width

Synthesis and Characterization of Janus Gold Nanoparticles

When gold nanoparticles are coated with binary mixtures of dislike ligand molecules, separation in the ligand shell occurs; if the particles are smaller than a threshold size the separation is solely enthalpy driven leading to the spontaneous formation of Janus particles

Cryogenic electron tomography to determine thermodynamic quantities for nanoparticle dispersions

Here we present a method to extract thermodynamic quantities for nanoparticle dispersions in solvents. The method is based on the study of tomograms obtained from cryogenic electron tomography (cryoET). The approach is demonstrated for gold nanoparticles (diameter < 5 nm). Tomograms are reconstructed from tilt-series 2D images. Once the three-dimensional (3D) coordinates for the centres of mass of all of the particles in the sample are determined, we calculate the pair distribution function g(r) and the potential of mean force U(r) without any assumption. Importantly, we show that further quantitative information from 3D tomograms is readily available as the spatial fluctuation in the particles’ position can be efficiently determined. This in turn allows for the prompt derivation of the Kirkwood-Buff integrals with all their associated quantities such as the second virial coefficient. Finally, the structure factor and the agglomeration states of the particles are evaluated directly. These thermodynamic quantities provide key insights into the dispersion properties of the particles. The method works well both for dispersed systems containing isolated particles and for systems with varying degrees of agglomerations

Asian Pacific Society of Cardiology Consensus Statements on the Diagnosis and Management of Obstructive Sleep Apnoea in Patients with Cardiovascular Disease

Obstructive sleep apnoea (OSA) is strongly associated with cardiovascular disease (CVD). However, evidence supporting this association in the Asian population is scarce. Given the differences in the epidemiology of CVD and cardiovascular risk factors, as well as differences in the availability of healthcare resources between Asian and Western countries, an Asian Pacific Society of Cardiology (APSC) working group developed consensus recommendations on the management of OSA in patients with CVD in the Asia-Pacific region. The APSC expert panel reviewed and appraised the available evidence using the Grading of Recommendations Assessment, Development, and Evaluation system. Consensus recommendations were developed and put to an online vote. Consensus was reached when 80% of votes for a given recommendation were in support of ‘agree’ or ‘neutral.’ The resulting statements provide guidance on the assessment and treatment of OSA in patients with CVD in the Asia-Pacific region. The APSC hopes for these recommendations to pave the way for screening, early diagnosis and treatment of OSA in the Asia-Pacific region

Structural and magnetic studies of core-shell and hollow nanoparticles

Nanoparticles can self-assemble or be directed to assemble into ordered structures, as determined from balance of forces acting upon them. In Chapter I, the concept of self-assembly and directed assembly is introduced followed by a discussion on surface and interparticle forces. Externally applied fields are particularly useful in directed assembly, and can be magnetic, electric, or optical forces in origin. In this chapter, we investigate methods leading to the directed assembly of cobalt nanoparticle rings around gold nanowires (nano-rotaxanes), and show that both dielectrophoretic and electrophoretic forces can be used to create such nanoscale heterostructures. Surfaces and material interfaces often play a significant role in governing the magnetic properties of nanoparticles. In Chapter II, we study the magnetic behaviors of core-shell Fe@Fe3O4 and hollow Fe 3O4 nanoparticles and reveal an unusual exchange-bias effect related to interfacial frozen spins. Hysteresis measurements of core–shell particles at 5 K after field cooling exhibit a large loop shift associated with unidirectional anisotropy, whereas Fe3O4 hollow nanoparticles support much smaller shifts. Both core–shell and hollow particles exhibit sharp demagnetization jumps at low fields associated with a sudden switching of shell moments. Temperature-dependent magnetizations of core–shell particles at high field show a deviation between field cooling and zero field cooling curves below 30 K, suggesting the presence of frozen spins at the interface. These frozen interfacial spins play an important role in mediating the exchange coupling between the ferromagnetic core and ferrimagnetic shell. We have also explored several experimental conditions that affect the relative intensity of the interfacial frozen spins such as temperature, repeated measuring field cycling, and age-dependent oxidation. With respect to nanoparticle synthesis, transitional-metal nanoparticles are often prepared by solvothermal routes or by the reduction of ionic salts. In chapter III, we show that TOPO has the potential to mediate the solvothermal synthesis of Co nanoparticles via a redox coupling process. The viability of the redox coupling is established by using TOP to convert Co-oleate into Co nanoparticles. Co nanoparticles synthesized from this route can then be coated with a thin shell of iron oxide, and further transformed into hollow cobalt ferrite nanoparticles upon heating or irradiation by a TEM electron beam. The transformation is accompanied by an enlargement of particle size, and is affected by environmental factors. Magnetic studies revealed that hollow cobalt ferrite nanoparticles possess higher blocking temperatures than their parent core–shell Co@FexOy nanoparticles. In Chapter IV, ultrathin Au nanowires (d\u3c2 nm) with extremely high aspect ratio were synthesized by reduction of Au(III) in oleylamine (OAm), and carefully analyzed by a combination of HRTEM and STM studies. While the nanowires are highly crystalline with apparent growth along the \u3c111\u3e direction, some segments are marked with amorphous defects, which we postulate to be an ionic Au(I)-OAm complex. The growth mechanism is proposed as template nucleation and anisotropic growth, in conjunction with oriented attachment

Supplementing probiotics during early stages of mud crab (Scylla paramamosain) culture under various rearing systems

The study aimed to improve megalopa and crablets production of mud crab, Scylla paramamosain, through dietary supplementation of probiotics and locally available diets under various rearing systems. The results concluded that the probiotic-enriched live food fed until the late zoeal stage in a green water culture system increased the megalopa production. Megalopa fed live Acetes resulted in increased survival. However, the production of crablets and not megalopa, was compromised when green water culture was employed

A review of molecular phase separation in binary self-assembled monolayers of thiols on gold surfaces

Binary self-assembled monolayers (SAMs) on gold surfaces have been known to undergo molecular phase separation to various degrees and have been subject to both experimental and theoretical studies. On gold nanoparticles in particular, binary SAMs ligand shells display intriguing morphologies. Consequently, unexpected behaviors of the nanoparticles with respect to their biological, chemical, and interfacial properties have been observed. It is critical that the phase separation of binary SAMs be understood at both molecular and macroscopic level to create, and then manipulate, the useful properties of the functionalized surfaces. We look into the current understanding of molecular phase separation of binary SAMs on gold surfaces, represented by Au(111) flat surfaces and Au nanoparticles, from both theoretical and experimental aspects. We point out shortcomings and describe several research strategies that will address them in the future

Characterization of Ligand Shell for Mixed-Ligand Coated Gold Nanoparticles

Gold nanoparticles owe a large number of their properties to their ligand shell. Indeed, many researchers routinely use mixtures of ligand molecules for their nanoparticles to impart complex property sets. It has been shown that the morphology of ligand shells (e.g., Janus, random, stripelike) leads to specific properties. Examples include wettability, solubility, protein nonspecific adsorption, cell penetration, catalysis, and cation-capturing abilities. Yet, it remains a great challenge to evaluate such morphologies in even the most fundamental terms such as dimension and shape. In this Account, we review recent progress in characterization techniques applicable to gold nanoparticles with ligand shells composed of mixed ligands. We divide the characterization into three major categories, namely, microscopy, spectroscopy, and simulation. In microscopy, we review progresses in scanning tunneling microscopy (STM), atomic force microscopy (AFM), and scanning/transmission electron microscopy. In spectroscopy, we mainly highlight recent achievements in nuclear magnetic resonance (NMR), mass spectrometry (MS), small angle neutron scattering (SANS), electron spin resonance (EPR), and adsorption based spectroscopies. In simulation, we point out the latest results in understanding thermodynamic stability of ligand shell morphology and emphasize the role of computer simulation for helping interpretation of experimental data. We conclude with a perspective of future development

(a) STM image of a sample of nanoparticles imaged in phenyl octane. This image is taken from reference [5] (Moglianetti et al. Scanning Tunneling Microscopy and Small Angle Neutron Scattering Study of Mixed Monolayer Protected Gold Nanoparticles in Organic Solvents. Chem. Sci. 2014, 5, 1232–1240; http://dx.doi.org/10.1039/C3SC52595C) where a full description of the image and of the sample can be found. Reproduced by permission of the Royal Society of Chemistry. All rights reserved. (b) Same image as the one shown in (a) with curvature removed using the same procedure described in reference [1], this is done so to highlight the features on the nanoparticles it should be noted the alignment of these features across many particles.

<p>(a) STM image of a sample of nanoparticles imaged in phenyl octane. This image is taken from reference [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135594#pone.0135594.ref005" target="_blank">5</a>] (Moglianetti et al. Scanning Tunneling Microscopy and Small Angle Neutron Scattering Study of Mixed Monolayer Protected Gold Nanoparticles in Organic Solvents. Chem. Sci. 2014, 5, 1232–1240; <a href="http://dx.doi.org/10.1039/C3SC52595C" target="_blank">http://dx.doi.org/10.1039/C3SC52595C</a>) where a full description of the image and of the sample can be found. Reproduced by permission of the Royal Society of Chemistry. All rights reserved. (b) Same image as the one shown in (a) with curvature removed using the same procedure described in reference [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135594#pone.0135594.ref001" target="_blank">1</a>], this is done so to highlight the features on the nanoparticles it should be noted the alignment of these features across many particles.</p

(a and b) 1D PSD plots for STM topography images of nanoparticles imaged with feedback loop oscillations induced. Plots in (a) are for images at 1.03 μm/s and in (b) are at 1.55 μm/s. (c and d) representative images for the images analyzed in (b) taken with the integral gain of 1 and 1.8, respectively. (e) Plot for the trend for the spacing corresponding to the frequency at the main peak in the PSD plots shown in (a, black) and (b, red). In the case of (a) we see minimal dependence on gain; in (b) we observe a weak dependence after the gain of 1.5, where the PSD plot show a start of loss of tracking. In any case the change in spacing measured is only ~ 0.2 nm (20% of the smallest spacing measured at this speed). We should highlight that the vast majority of our images are at speeds below 1.0 μm/s and are obtained currently at gains below 0.5 while historically at gains below 1, hence is a regime where in our microscope there is no dependence of the measured spacing on gains.

<p>(a and b) 1D PSD plots for STM topography images of nanoparticles imaged with feedback loop oscillations induced. Plots in (a) are for images at 1.03 μm/s and in (b) are at 1.55 μm/s. (c and d) representative images for the images analyzed in (b) taken with the integral gain of 1 and 1.8, respectively. (e) Plot for the trend for the spacing corresponding to the frequency at the main peak in the PSD plots shown in (a, black) and (b, red). In the case of (a) we see minimal dependence on gain; in (b) we observe a weak dependence after the gain of 1.5, where the PSD plot show a start of loss of tracking. In any case the change in spacing measured is only ~ 0.2 nm (20% of the smallest spacing measured at this speed). We should highlight that the vast majority of our images are at speeds below 1.0 μm/s and are obtained currently at gains below 0.5 while historically at gains below 1, hence is a regime where in our microscope there is no dependence of the measured spacing on gains.</p