Graphene/chitosan nanoreactors for ultrafast and precise recovery and catalytic conversion of gold from electronic waste.

The extraction of gold (Au) from electronic waste (e-waste) has both environmental impact and inherent value. Improper e-waste disposal poses environmental and health risks, entailing substantial remediation and healthcare costs. Large efforts are applied for the recovery of Au from e-waste using complex processes which include the dissolution of Au, its adsorption in an ionic state and succeeding reduction to metallic Au. These processes themselves being complex and utilizing harsh chemicals contribute to the environmental impact of e-waste. Here, we present an approach for the simultaneous recovery and reduction of Au3+ and Au+ ions from e-waste to produce solid Au0 forms, thus skipping several technological steps. We develop a nanoscale cross-dimensional composite material via self-assembly of two-dimensional graphene oxide and one-dimensional chitosan macromolecules, capable of acting simultaneously as a scavenger of gold ions and as a reducing agent. Such multidimensional architecture doesn't require to apply any voltage for Au adsorption and reduction and solely relies on the chemisorption kinetics of Au ions in the heterogeneous GO/CS nanoconfinements and their chemical reduction on multiple binding sites. The cooperative phenomena in ionic absorption are responsible for the extremely high efficiency of gold extraction. The extraction capacity reaches 16.8 g/g for Au3+ and 6.2 g/g for Au+, which is ten times larger than any existing gold adsorbents can propose. The efficiency is above 99.5 wt.% (current limit is 75 wt.%) and extraction ability is down to very low concentrations of 3 ppm.

Diffusiophoretically Mediated Nanopatterning by Solvent Nanodroplets on Polystyrene Surfaces.

Dissolution is a ubiquitous process in nature and industry. However, due to technical difficulties, the detailed dissolution process at the nanoscale has seldom been captured experimentally. In this study, we investigated the dissolution dynamics in the confinement of toluene surface nanodroplets on polystyrene (PS) thin films in oversaturated toluene/water mixture solutions. This was achieved by adjusting the immersion durations from several minutes to 9 h. Dissolution takes place upon the deposition of nanodroplets on the PS surfaces, leading to the formation of surface nanostructures. Interestingly, we found that the induced nanostructures underwent complex morphological changes, from complex nanocraters with central bulges and/or multiple rims to simple nanocraters. We speculate that diffusiophoresis plays a key role in the formation of the complex nanocraters, as it facilitates the transportation of dissolved PS molecules inside the nanodroplets. We believe this finding not only enhances our understanding of dissolution dynamics at the nanoscale but also holds promise for applications in dissolution-based nanopatterning.

Graphene oxide-polyamine preprogrammable nanoreactors with sensing capability for corrosion protection of materials.

Corrosion is one of the major issues for sustainable manufacturing globally. The annual global cost of corrosion is US$2.5 trillion (approximately 3.4% of the world's GDP). The traditional ways of corrosion protection (such as barriers or inhibiting) are either not very effective (in the case of barrier protection) or excessively expensive (inhibiting). Here, we demonstrate a concept of nanoreactors, which are able to controllably release or adsorb protons or hydroxides directly on corrosion sites, hence, selectively regulating the corrosion reactions. A single nanoreactor comprises a nanocompartment wrapped around by a pH-sensing membrane represented, respectively, by a halloysite nanotube and a graphene oxide/polyamine envelope. A nanoreactor response is determined by the change of a signaling pH on a given corrosion site. The nanoreactors are self-assembled and suitable for mass-line production. The concept creates sustainable technology for developing smart anticorrosion coatings, which are nontoxic, selective, and inexpensive.

Laser Controlled Manipulation of Microbubbles on a Surface with Silica-Coated Gold Nanoparticle Array.

Microbubble generation and manipulation play critical roles in diverse applications such as microfluidic mixing, pumping, and microrobot propulsion. However, existing methods are typically limited to lateral movements on customized substrates or rely on specific liquids with particular properties or designed concentration gradients, thereby hindering their practical applications. To address this challenge, this paper presents a method that enables robust vertical manipulation of microbubbles. By focusing a resonant laser on hydrophilic silica-coated gold nanoparticle arrays immersed in water, plasmonic microbubbles are generated and detach from the substrates immediately upon cessation of laser irradiation. Using simple laser pulse control, it can achieve an adjustable size and frequency of bubble bouncing, which is governed by the movement of the three-phase contact line during surface wetting. Furthermore, it demonstrates that rising bubbles can be pulled back by laser irradiation induced thermal Marangoni flow, which is verified by particle image velocimetry measurements and numerical simulations. This study provides novel insights into flexible bubble manipulation and integration in microfluidics, with significant implications for various applications including mixing, drug delivery, and the development of soft actuators.

Association of the tissue infiltrated and peripheral blood immune cell subsets with response to radiotherapy for rectal cancer.

BACKGROUND: Tumor microenvironment plays pivotal roles in carcinogenesis, cancer development and metastasis. Composition of cancer immune cell subsets can be inferred by deconvolution of gene expression profile accurately. Compositions of the cell types in cancer microenvironment including cancer infiltrating immune and stromal cells have been reported to be associated with the cancer outcomes markers for cancer prognosis. However, rare studies have been reported on their association with the response to preoperative radiotherapy for rectal cancer. METHODS: In this paper, we deconvoluted the immune/stromal cell composition from the gene expression profiles. We compared the composition of immune/stromal cell types in the RT responsive versus nonresponsive for rectal cancer. We also compared the peripheral blood immune cell subset composition in the stable diseases versus progressive diseases of rectal cancer patients with fluorescence-activated cell sorting from our institution. RESULTS: Compared with the non-responsive group, the responsive group showed higher proportions of CD4+ T cell (0.1378 ± 0.0368 vs. 0.1071 ± 0.0373, p = 0.0215), adipocytes, T cells CD4 memory resting, and lower proportions of CD8+ T cell (0.1798 ± 0.0217 vs. 0.2104 ± 0.0415, p = 0.0239), macrophages M2, and preadipocytes in their cancer tissue. The responsive patients showed a higher ratio of CD4+/CD8+ T cell proportions (mean 0.7869 vs. 0.5564, p = 0.0210). Consistently, the peripheral blood dataset showed higher proportion of CD4+ T cells and higher ratio of CD4+/CD8+ T cells, and lower proportion of CD8+ T cells for favorable prognosis. We validated these results with a pooled dataset of GSE3493 and GSE35452, and more peripheral blood data, respectively. Finally, we imported these eight cell features including eosinophils and macrophage M1 to Support Vector Machines and could predict the pre-radiotherapy responsive versus non-responsive with an accuracy of 76%, ROC AUC 0.77, 95% confidential interval of 0.632-0.857, better than the gene signatures. CONCLUSIONS: Our results showed that the proportions of tumor-infiltrating subsets and peripheral blood immune cell subsets can be important immune cell markers and treatment targets for outcomes of radiotherapy for rectal cancer.

Droplet plume emission during plasmonic bubble growth in ternary liquids.

Plasmonic bubbles are of great relevance in numerous applications, including catalytic reactions, micro/nanomanipulation of molecules or particles dispersed in liquids, and cancer therapeutics. So far, studies have been focused on bubble nucleation in pure liquids. Here we investigate plasmonic bubble nucleation in ternary liquids consisting of ethanol, water, and trans-anethole oil, which can show the so-called ouzo effect. We find that oil (trans-anethole) droplet plumes are produced around the growing plasmonic bubbles. The nucleation of the microdroplets and their organization in droplet plumes is due to the symmetry breaking of the ethanol concentration field during the selective evaporation of ethanol from the surrounding ternary liquids into the growing plasmonic bubbles. Numerical simulations show the existence of a critical Marangoni number Ma (the ratio between solutal advection rate and the diffusion rate), above which the symmetry breaking of the ethanol concentration field occurs, leading to the emission of the droplet plumes. The numerical results agree with the experimental observation that more plumes are emitted with increasing ethanol-water relative weight ratios and hence Ma. Our findings on the droplet plume formation reveal the rich phenomena of plasmonic bubble nucleation in multicomponent liquids and help to pave the way to achieve enhanced mixing in multicomponent liquids in chemical, pharmaceutical, and cosmetic industries.

Periodic bouncing of a plasmonic bubble in a binary liquid by competing solutal and thermal Marangoni forces.

The physicochemical hydrodynamics of bubbles and droplets out of equilibrium, in particular with phase transitions, display surprisingly rich and often counterintuitive phenomena. Here we experimentally and theoretically study the nucleation and early evolution of plasmonic bubbles in a binary liquid consisting of water and ethanol. Remarkably, the submillimeter plasmonic bubble is found to be periodically attracted to and repelled from the nanoparticle-decorated substrate, with frequencies of around a few kilohertz. We identify the competition between solutal and thermal Marangoni forces as the origin of the periodic bouncing. The former arises due to the selective vaporization of ethanol at the substrate's side of the bubble, leading to a solutal Marangoni flow toward the hot substrate, which pushes the bubble away. The latter arises due to the temperature gradient across the bubble, leading to a thermal Marangoni flow away from the substrate, which sucks the bubble toward it. We study the dependence of the frequency of the bouncing phenomenon from the control parameters of the system, namely the ethanol fraction and the laser power for the plasmonic heating. Our findings can be generalized to boiling and electrolytically or catalytically generated bubbles in multicomponent liquids.

Laser photonic nanojets triggered thermoplasmonic micro/nanofabrication of polymer materials for enhanced resolution.

Micro/nanofabrication of polymer materials is of interest for micro/nanofluidic systems. Due to the optical diffraction limit, it remains a challenge to achieve nanoscale resolution fabrication using an ordinary continuous-wave laser system. In this study, we therefore propose a laser photonic nanojet-based micro/nanofabrication method for polymer materials using a low-power and low-cost continuous-wave laser. The photonic nanojets were produced using glass microspheres. Moreover, a thermoplasmonic effect was employed by depositing a gold layer beneath the polymer films. By applying the photonic nanojet triggered thermoplasmonics, sub-micrometer surface structures, as well as their arrays, were fabricated with a laser power threshold value down to 10 mW. The influences of the microsphere diameters, and thicknesses of gold layers and polymer films on the fabricated microstructures were systematically investigated, which aligns well with the finite-difference time-domain simulation results.

Plasmonic Microbubble Dynamics in Binary Liquids.

The growth of surface plasmonic microbubbles in binary water/ethanol solutions is experimentally studied. The microbubbles are generated by illuminating a gold nanoparticle array with a continuous wave laser. Plasmonic bubbles exhibit ethanol concentration-dependent behaviors. For low ethanol concentrations (fe) of ≲67.5%, bubbles do not exist at the solid-liquid interface. For high fe values of ≳80%, the bubbles behave as in pure ethanol. Only in an intermediate window of 67.5% ≲ fe ≲ 80% do we find sessile plasmonic bubbles with a highly nontrivial temporal evolution, in which as a function of time three phases can be discerned. (1) In the first phase, the microbubbles grow, while wiggling. (2) As soon as the wiggling stops, the microbubbles enter the second phase in which they suddenly shrink, followed by (3) a steady reentrant growth phase. Our experiments reveal that the sudden shrinkage of the microbubbles in the second regime is caused by a depinning event of the three-phase contact line. We systematically vary the ethanol concentration, laser power, and laser spot size to unravel water recondensation as the underlying mechanism of the sudden bubble shrinkage in phase 2.

Low Scattering Microstrip Antenna Based on Broadband Artificial Magnetic Conductor Structure.

In this summary, we have suggested a new technique in which destructive interference principle is incorporated into a chessboard like a reflective screen, and the proposed antenna realizes a remarkable in-band and also out-of-band backscattered energy reduction by using a metasurface (MS). Two different MS unit cells are designed to provide the resonant frequency with a zero-degree reflection phase. Metasurface unit cells are configured in a chessboard-like reflector screen to achieve the reflection phase difference of 180° ± 37° over a broadband range of frequencies to redirect the scattering field into four quadrants. It is implemented to reduce the backscattered energy level of the microstrip antenna, which is based on destructive interference principle. The simulations indicate that the proposed antenna possesses significant backscattered energy reduction from 6 GHz to 16 GHz in both x- and y- polarization and also -10 dB backscattering reduction at antenna working band (7.4-7.8 GHz) is covered. Moreover, the radiation performance is preserved well and artificial magnetic conductor (AMC) unit cells work at different frequencies which are not influenced on the radiation properties. The bistatic performance of the antenna at different frequencies is also presented. Measurements and simulations of the fabricated design coincide well and the proposed design is verified and validated successfully.

Plasmonic Bubble Nucleation and Growth in Water: Effect of Dissolved Air.

Under continuous laser irradiation, noble metal nanoparticles immersed in water can quickly heat up, leading to the nucleation of so-called plasmonic bubbles. In this work, we want to further understand the bubble nucleation and growth mechanism. In particular, we quantitatively study the effect of the amount of dissolved air on the bubble nucleation and growth dynamics, both for the initial giant bubble, which forms shortly after switching on the laser and is mainly composed of vapor, and for the final life phase of the bubble, during which it mainly contains air expelled from water. We found that the bubble nucleation temperature depends on the gas concentration: the higher the gas concentration, the lower the bubble nucleation temperature. Also, the long-term diffusion-dominated bubble growth is governed by the gas concentration. The radius of the bubbles grows as R(t) ∝ t 1/3 for air-equilibrated and air-oversaturated water. In contrast, in partially degassed water, the growth is much slower since, even for the highest temperature we achieve, the water remains undersaturated.

Entrapment and Dissolution of Microbubbles Inside Microwells.

The formation and evolution of immersed surface micro- and nanobubbles are essential in various practical applications, such as the usage of superhydrophobic materials, drug delivery, and mineral flotation. In this work, we investigate the entrapment of microbubbles on a hydrophobic surface, structured with microwells, when water flow passes along, and the subsequent microbubble dissolution. At entrapment, the microbubble is initially pinned at the edge of the microwell. At some point, the three-phase contact line detaches from one side of the edge and separates from the wall, after which it further recedes. We systematically investigate the evolution of the footprint diameter and the contact angle of the entrapped microbubbles, which reveals that the dissolution process is in the constant contact angle mode. By varying the gas undersaturation level, we quantify how a high gas undersaturation enhances the dissolution process, and compare with simplified theoretical predictions for dissolving bubbles on a plane surface. We find that geometric partial blockage effects of the diffusive flux out of the microbubble trapped in the microwell lead to reduced dissolution rates.

Automated image segmentation-assisted flattening of atomic force microscopy images.

Atomic force microscopy (AFM) images normally exhibit various artifacts. As a result, image flattening is required prior to image analysis. To obtain optimized flattening results, foreground features are generally manually excluded using rectangular masks in image flattening, which is time consuming and inaccurate. In this study, a two-step scheme was proposed to achieve optimized image flattening in an automated manner. In the first step, the convex and concave features in the foreground were automatically segmented with accurate boundary detection. The extracted foreground features were taken as exclusion masks. In the second step, data points in the background were fitted as polynomial curves/surfaces, which were then subtracted from raw images to get the flattened images. Moreover, sliding-window-based polynomial fitting was proposed to process images with complex background trends. The working principle of the two-step image flattening scheme were presented, followed by the investigation of the influence of a sliding-window size and polynomial fitting direction on the flattened images. Additionally, the role of image flattening on the morphological characterization and segmentation of AFM images were verified with the proposed method.

A CO2-tunable plasmonic nanosensor based on the interfacial assembly of gold nanoparticles on diblock copolymers grafted from gold surfaces.

A general stepwise strategy for the fabrication of CO2-tunable plasmonic nanosensors was described for the first time, based on gold surface functionalization by CO2-responsive poly(N,N-diethylaminoethyl methacrylate) (PDEAEMA) brushes via a surface-initiated atom transfer radical polymerization (SI-ATRP) method, then the extremity of PDEAEMA was functionalized by linking the polyacrylamide (PAAm) brushes via ATRP, where they were assembled with gold nanoparticles (AuNPs) efficiently by altering the deposition time. The swelling-shrinking states of the PDEAEMA brushes can be tuned just by passing CO2 and N2 through a solution alternately. The unique plasmonic surface-enhanced Raman scattering (SERS) sensing properties of these stimulable substrates were investigated using 4-mercaptophenol (4MPh) as a molecular probe. When alternating CO2 and N2 bubbling in the water solution, the reversible switching of the SERS signals was complete. By in situ contact-mode atomic force microscopy, the thickness of the polymer layer was observed to be 26 nm in CO2 saturated water, and after N2 bubbling to remove CO2 it decreased to 15 nm, causing the AuNPs to move near to the gold surface. Meanwhile, the distance between the nearby AuNPs becomes smaller, and the surface coverage (φ) of the AuNPs increased from 27% to 35%. The reported CO2-responsive plasmonic nanosensor provided a dynamic SERS platform, with reversible regulation for electromagnetic coupling between the AuNPs and the gold surface, and between nearby AuNPs.

Robust nanobubble and nanodroplet segmentation in atomic force microscope images using the spherical Hough transform.

Interfacial nanobubbles (NBs) and nanodroplets (NDs) have been attracting increasing attention due to their potential for numerous applications. As a result, the automated segmentation and morphological characterization of NBs and NDs in atomic force microscope (AFM) images is highly awaited. The current segmentation methods suffer from the uneven background in AFM images due to thermal drift and hysteresis of AFM scanners. In this study, a two-step approach was proposed to segment NBs and NDs in AFM images in an automated manner. The spherical Hough transform (SHT) and a boundary optimization operation were combined to achieve robust segmentation. The SHT was first used to preliminarily detect NBs and NDs. After that, the so-called contour expansion operation was applied to achieve optimized boundaries. The principle and the detailed procedure of the proposed method were presented, followed by the demonstration of the automated segmentation and morphological characterization. The result shows that the proposed method gives an improved segmentation result compared with the thresholding and circle Hough transform method. Moreover, the proposed method shows strong robustness of segmentation in AFM images with an uneven background.

Entrapment of interfacial nanobubbles on nano-structured surfaces.

Spherical-cap-shaped interfacial nanobubbles (NBs) forming on hydrophobic surfaces in aqueous solutions have extensively been studied both from a fundamental point of view and due to their relevance for various practical applications. In this study, the nucleation mechanism of spontaneously generated NBs at solid-liquid interfaces of immersed nanostructured hydrophobic surfaces is studied. Depending on the size and density of the surface nanostructures, NBs with different size and density were reproducibly and deterministically obtained. A two-step process can explain the NB nucleation, based on the crevice model, i.e., entrapped air pockets in surface cavities which grow by diffusion. The results show direct evidence for the spontaneous formation of NBs on a surface at its immersion. Next, the influence of size and shape of the nanostructures on the nucleated NBs are revealed. In particular, on non-circular nanopits we obtain NBs with a non-circular footprint, demonstrating the strong pinning forces at the three-phase contact line.