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Self-organization facilitates the formation of specific structures as a result of constituent interactions. In this study, the bottom of a 600 nm hole array photoresist template, which was deposited with a hydrophobic atom transfer radical polymerization (ATRP) initiator, was wetted by treatment with oxygen plasma. After the removal of the photoresist template, ring patterns of the ATRP initiator were formed at the interface between the hydrophobic and wetting regions. Poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) was grafted from the ring array of the initiator to immobilize gold nanoparticles (AuNPs) as a uniform ring array on a silicon substrate via repeated swelling/shrinking cycles. The localized surface plasmon resonance (LSPR) peak of the PDMAEMA-AuNP hybrid ring (PAHR) red-shifted after 12 swelling/shrinking cycles. In comparison to gold nanoparticles, scalable gold nanorings can effectively develop a variety of nanostructures to design LSPR-based sensors and optimize the sensing accuracy and stability. To detect epithelial cell adhesion molecules (EpCAM) during the structural change from a ring to a disk, antiEpCAM was anchored onto the PAHR as a biosensor during swelling/shrinking. The coupling of antiEpCAM and EpCAM led to asymptotical convergence from rings to disks as well as blue shifts of the LSPR peaks. Linear correlation between the blue shift and EpCAM concentration showed a limit of detection of ∼27 pg mL

This Perspective highlights recent advances in linear and nonlinear spectral nanoimaging. The described developments are motivated by the need to characterize molecular and material systems noninvasively with nanometer spatial and femtosecond temporal resolution. Indeed, the ability to image and chemically characterize heterogeneous interfaces with joint nano-femto resolution is a prerequisite to advancing our fundamental understanding of processes as diverse as heterogeneous catalysis, microbial communication, and energy flow in pristine/defect-containing low-dimensional quantum materials, to name a few. We describe pioneering work and recent demonstrations of (non)linear optical nanoimaging and nanospectroscopy, with an emphasis on high spatial resolution measurements conducted under ambient laboratory conditions.

Design strategies of smart membranes for switchable gas separation performance.

Optical field localization at plasmonic tip-sample nanojunctions has enabled high-spatial-resolution chemical analysis through tip-enhanced linear optical spectroscopies, including Raman scattering and photoluminescence. Here, we illustrate that nonlinear optical processes, including parametric four-wave mixing (4WM), second-harmonic/sum-frequency generation (SHG and SFG), and two-photon photoluminescence (TPPL), can be enhanced at plasmonic junctions and spatiospectrally resolved simultaneously with few-nm spatial resolution under ambient conditions. Through a detailed analysis of our spectral nanoimages, we find that the efficiencies of the local nonlinear signals are determined by sharp tip-sample junction resonances that vary over the few-nanometer length scale. Namely, plasmon resonances centered at or around the different nonlinear signals are tracked through TPPL, and they are found to selectively enhance nonlinear signals with closely matched optical resonances.

We fabricated a mussel-inspired hemocompatible polycarbonate membrane (PC) modified by the cross-linking of chondroitin sulfate and caffeic acid polymer using CA-CS via a Schiff base and Michael addition reaction and named it CA-CS-PC. The as-fabricated CA-CS-PC membrane shows excellent hydrophilicity with a water contact angle of 0° and a negative surface charge with a zeta potential of -32 mV. The antiadhesion property of the CA-CS-modified PC membrane was investigated by enzyme-linked immunosorbent assay (ELISA), using human plasma protein fibrinogen adsorption studies, and proved to have excellent antiadhesion properties, because of the lower fibrinogen adsorption. In addition, the CA-CS-PC membrane also shows enhanced hemocompatibility. Finally, blood cell attachment tests of the CA-CS-PC membrane were observed by CLSM and SEM, and the obtained results proved that CA-CS-PC effectively resisted cell adhesion, such as platelets and leucocytes. Therefore, this work disclosed a new way to design a simple and versatile modification of the membrane surface by caffeic acid and chondroitin sulfate and apply it for cell adhesion.

Caution needs to be exercised in associating changes in plasmon-enhanced Raman spectra with chemical transformations. This is demonstrated through a detailed analysis of tip-enhanced Raman (TER) scattering from 4-mercaptopyridine (MPY) on gold. The substrate used consists of gold nanoplates atop a gold surface featuring heterogeneous grooves, all coated with a monolayer of MPY. The brightest spectra across the substrate exhibit features that can only be recovered by considering the generalized polarizability of oriented MPY molecules. The complex TER spectra we observe do not mark interfacial chemistry but rather multipolar TER scattering driven by local field gradients.

Membrane separation has been an efficient and energy saving technique in dealing with greenhouse gases, but the traditional membrane designs might not be able to handle the concomitant environmental pollution due to their fixed properties. Correspondingly, the use of an active-responsive smart membrane appears to be a new trend for membrane development in the coming future, which shows great potential to deal with the obstacles. In this research, we demonstrate a smart graphene-organic framework membrane to enable reversed electrical-switchable permselectivity in CO2 separation. The addition of polydopamine (PDA) to the polyvinylidene fluoride/Graphene (PVDF/G) membranes was done to (i) induce the β-phase of PVDF, since –NH2-functionalized graphene has specific interactions (dipole induced dipole interaction) between graphene-PDA and PVDF; (ii) modify the organic PVDF-inorganic graphene interface; and (iii) facilitate CO2 selective separation. Permeability and permselectivity was increased after applying voltage that resulted in the increase of gas permselectivity in response to the lowest applied voltage range (0–3 V) to the membrane. Digital image correlation method depicted the response of the membrane to voltage and proved that the membrane has high piezoelectric properties that is switchable. Furthermore, PALS studies confirmed the free volume and interlayers in the membrane. This membrane has unique properties because the pore changes from bimodal to single pore distribution.

Four-wave mixing at plasmonic tip-sample nanojunctions may be used to visualize plasmonic fields with sub-2 nm spatial resolution under ambient laboratory conditions. We illustrate the latter using a gold-coated atomic force microscopy probe irradiated with a pair of near-infrared femtosecond laser pulses and used to image plasmonic gold nanoplates and silver nanocubes. Through diagnostic polarization-dependent tip-only measurements, we illustrate that the four-wave mixing signal is localized to the tip apex. The apex-bound signal is further enhanced when the tip is located at specific locations near plasmonic nanoparticles. Overall, this work paves the way for visualizing chemical transformations as well as coherent electronic and vibrational dynamics with joint femtosecond temporal and few-nanometer spatial resolution under ambient conditions.

Water pollution has become a serious problem in aquatic ecology due to the oil spills and the consistent release of industrial pollutants, such as dyes. Herein, we report a simple method to fabricate superwetting caffeic acid (CA)-polyethyleneimine (PEI)-modified melamine sponges (CA-PEI-MS) for oil-in-water emulsion separation and dye adsorption. The as-fabricated CA-PEI-MS exhibited superhydrophilicity with an approximately zero water contact angel (WCA) and underwater superoleophobicity with an underwater oil contact angel (UWOCA) greater than 150°. The compressed CA-PEI-MS showed an excellent oil-in-water emulsion separation performance with a separation efficiency greater than 97% and a water flux of up to 25,480 L h−1 m−2 bar−1. The recyclability test was used to study the stability of the compressed CA-PEI-MS, after washing with acetone; the flux did not show any significant change during the 12-cycle separation test. The separation efficiency in every cycle was greater than 97%. Due to the availability of rich positive charged amino groups, the as fabricated CA-PEI-MS exhibited adsorption ability towards negatively charged dyes such as, rose bengal (RB) and direct red (DR) with 96% adsorption efficiency. Therefore, the as designed low-cost and eco-friendly preparation of CA-PEI-MS has a great potential for practical application as it shows high separation performances and excellent efficiency.

Graphene possesses a set of unique physicochemical properties including exceptional mechanical, thermal, and electrical properties, making it an excellent candidate for constructing materials for a wide range of applications including the vast field of separation technology using membranes. Separation membranes based on graphene and its derivatives have shown satisfactory results over the years when applied to environmental systems such as wastewater treatment and gas purification, which is a great contribution in sustainable development. However, membrane separation research is generally performed using conventional membranes with fixed driving force and separation properties that suffer from fouling and decline in performance upon long-term use or when a change in the environmental conditions occur. These issues can be solved by employing an emerging technology that makes use of graphene and its derivatives combined with polymeric materials to construct stimuli-responsive or “smart” membranes that respond to the changes in their environment such as chemical cues, temperature, pressure, and external fields, and have a self-regulated separation performance due to reversible physicochemical properties. In this review, we present a report on the recent advancements on graphene-based separation technology including a concise discussion on the basic structure and properties of graphene and its derivatives, various membrane fabrication methods, and their employment on the different areas of membrane separation. More importantly, the main focus of this paper is to evaluate the design and utilization of graphene-based smart separation membranes.

Separation technology by using membranes is an effective choice for water treatment, but fouling is a significant problem for membrane applications. Recently, transition-metal dichalcogenide nanosh...

Quantifying the sensitivity limit of scattering-type scanning near-field optical microscopy (s-SNOM) in vibrational infrared imaging requires assembly of molecular systems with continuous variation...

Effective water use is currently a critical global challenge needed to prevent water shortages and has attracted significant research attention. The realization of solar-driven water evaporation by using effective converters has attracted considerable attention in recent years owing to its potential for seawater desalination and wastewater treatment. Consequently, this paper proposes a simple two-step method to prepare low-cost and self-floating photothermal converters from waste coffee grounds. First, the coffee grounds were carbonized at 1,000 °C to develop broadband absorption, and the carbonized coffee grounds were modified using hydrophobic silane to enhance the water-floatation property of the grounds. The prepared hydrophobic carbonized coffee grounds exhibited good performance for desalination and water purification under sunlight irradiation. The self-floatation ability, low cost, well solar evaporation performance, and easy preparation contribute to the promising potential of using hydrophobic carbonized coffee grounds infuture steps toward eco-friendly desalination procedures.

We revisit the reductive coupling of p-nitrothiophenol (NTP) to form dimercaptoazobenzene (DMAB), herein monitored through gap-mode tip-enhanced Raman spectroscopy (TERS) and nanoimaging. We employ a plasmonic Au probe (100 nm diameter at its apex) illuminated with a 633 nm laser source (50 μW/μm2 at the sample position) to image an NTP-coated faceted silver nanoparticle (∼70 nm diameter). A detailed analysis of the recorded spectra reveals that anionic NTP species contribute to the recorded spectral images, in addition to the more thoroughly described DMAB product. Notably, the signatures of the anions are more pronounced than those of the DMAB product under our present experimental conditions. Our results thus demonstrate that anions and their spectral signatures must be considered in the analysis of plasmon-enhanced optical spectra and images.

Whole grains are rich in nutrients. Microbial fermentation of grains increases their nutritional content and their antioxidant capacity. This study uses a mixed grain fermentation broth as a starter to ferment a mixture of eight grains: millet, wheat, sorghum, black rice, buckwheat, pear rice, black glutinous rice, and red quinoa. The fermentation was done for 13 weeks, to discern the quantitative changes in the concentration of amino acids, antioxidant capacity, GABA, glucuronic acid, ACE inhibition, total flavonoids and total phenols. After fermentation, the results indicated that the total phenols concentration increased by 2605%, total flavonoids increased by 1707%, ABTS radical scavenging capacity increased by 239%, DPPH radical scavenging capacity increased by 325%, GABA increased by 4810%, glucuronic acid increased by 4278%, and ACE inhibition activity increased by 69.28%.

Covalent organic polymer nanosheets (COPNs) endowed with porous networks and large surface areas in their structures offer great advantages over other materials in addressing environmental problems. In this study, fluorine-free superhydrophobic COPNs were designed and applied to selective dye absorption. Notably, COPNs selectively adsorb dyes with a high hydrophobic index (HI) and reject low HI dyes with maximum adsorption capacities of 361 and 263 mg/g for crystal violet and methylene blue, respectively. The adsorption isotherm model showed that the COPNs follow the Langmuir adsorption isotherm model and pseudo-second-order kinetics. Next, we explored the superhydrophobicity of the COPNs by in situ fabrication with melamine sponge (COPNs-MS), which incorporates the superhydrophobicity of COPNs [water contact angle (WCA) of150°] with the structure and flexibility of the MS skeleton. The COPNs-MS shows various oil-adsorbing properties with good adsorption capacity (from 60 to 120 g/g) and also effectively separates various surfactant-stabilized emulsions with a separation efficiency of over 99%. The as-fabricated COPNs-MS retains its superhydrophobicity in various solvents and hazardous conditions (WCA ≥ 150°) and exhibits good flame retardancy and excellent compression properties with excellent antifouling property due to the superhydrophobic COPN coating. Furthermore, COPNs-MS also demonstrates excellent recyclability because the strong COPN coating in the MS skeleton retains its hydrophobicity. Therefore, our fluorine-free superhydrophobic COPNs are not only capable of selective dye adsorption but also exhibit very good oil adsorption and surfactant-stabilized emulsion separation performance.

Localized surface plasmon resonances can increase the quantum efficiency of photon emitters through both absorption and spontaneous emission enhancement effects. Despite extensive studies, experime...

The separation of oily wastewater, specifically emulsions, is a crucial global issue. Possible strategies for the efficient separation of emulsified oil/water mixtures through sustainable and environmentally friendly materials have recently drawn considerable attention. In our study, we prepared superwetting water caltrop shell biochar (WCSB) via a top-lit-updraft carbonization procedure. The as-prepared WCSB was characterized by superhydrophilicity, underwater superoleophobicity, underoil superhydrophilicity, and underoil water adsorption ability. Because of its superwetting properties, WCSB was used for the separation of both surfactant-stabilized oil-in-water emulsions (SOIWEs) and surfactant-stabilized water-in-oil emulsions (SWIOEs) with very high fluxes (up to 74,700 and 241,000 L m

In this presentation, the molecular sensitivity of scattering-type near-field scanning optical microscopy (s-SNOM) will be demonstrated by imaging an organic thin film with thickness gradient that continuously vary from zero to over 200 nm on different substrates. We will then present recent s-SNOM experimental results that show phase separation and nanoscale pattern formation in thin films of blended polymers. The evolution of nanoscale domains and hierarchical patterns as a function of composition will be discussed. The results may help to understand the sensitivity of s-SNOM chemical imaging at the molecular “finger print” region of electromagnetic radiation and to realize the capability of the technique to resolve nanoscale domains and phase separation in multicomponent organic thin films.

We combine nanoindentation, herein achieved using atomic force microscopy-based pulsed-force lithography, with tip-enhanced Raman spectroscopy (TERS) and imaging. Our approach entails indentation and multimodal characterization of otherwise flat Au substrates, followed by chemical functionalization and TERS spectral imaging of the indented nanostructures. We find that the resulting structures, which vary in shape and size depending on the tip used to produce them, may sustain nano-confined and significantly enhanced local fields. We take advantage of the latter and illustrate TERS-based ultrasensitive detection/chemical fingerprinting as well as chemical reaction imaging-all using a single platform for nano-lithography, topographic imaging, hyperspectral dark field optical microscopy, and TERS.

We interrogate para-mercaptobenzoic acid (MBA) molecules chemisorbed onto plasmonic silver nanocubes through tip-enhanced Raman (TER) spectral nanoimaging. Through a detailed examination of the spectra, aided by correlation analysis and density functional theory calculations, we find that MBA chemisorbs onto the plasmonic particles with at least two distinct configurations: S- and CO2-bound. High spatial resolution TER mapping allows us to distinguish between the distinct adsorption geometries with a pixel-limited (

Gradient properties facilitate the correlation of chemical and physical features of particles on the structure and adherent fate. Herein, performance enhancement is explored by particle gradient assembly patterning (PGAP) formed with magnetic field gradient (MFG) by magnetolithography (ML) in the electrochemiluminescence (ECL) measurement. Magnetic Fe3O4 nanoparticles were selected as nanocarriers and coated with a SiO2 layer for immobilization of primary antibodies. CdTe quantum dots with protein G coatings were selected as signal labels and conjugated with secondary antibodies. Magnetized 500-nm pillar, 1 μm- and 3 μm-line arrays of nickel were placed behind the working electrode modifying the sandwich-structured ECL immunosensor to form various PGAPs. A performance enhancement of ca. 2.4 times was observed when comparing the PGAP-free immunosensor to the researched gradient immunosensor, formed with a magnetized 3 μm-line array of nickel. This concludes that the sensitivity of an ECL immunosensor has been enhanced due to PGAP properties. When the immunosensor with PGAP properties was used to quantify human serum albumin, it exhibited a wide linear range (10–480 ng/mL), and a limit of detection of 10 ng/mL. PGAP properties, formed with MFG by ML, provides a simple method to improve the ECL performance.

In this study, two different types of hybrid porous organic polymers (POPs), polyhedral oligomeric silsesquioxane tetraphenylpyrazine (POSS-TPP) and tetraphenylethene (POSS-TPE), were successfully synthesized through the Friedel&minus, Crafts polymerization of tetraphenylpyrazine (TPP) and tetraphenylethene (TPE), respectively, with octavinylsilsesquioxane (OVS) as node building blocks, in the presence of anhydrous FeCl3 as a catalyst and 1,2-dichloroethane at 60 &deg, C. Based on N2 adsorption and thermogravimetric analyses, the resulting hybrid porous materials displayed high surface areas (270 m2/g for POSS-TPP and 741 m2/g for POSS-TPE) and outstanding thermal stabilities. Furthermore, as-prepared POSS-TPP exhibited a high carbon dioxide capacity (1.63 mmol/g at 298 K and 2.88 mmol/g at 273 K) with an excellent high adsorption capacity for iodine, reaching up to 363 mg/g, compared with the POSS-TPE (309 mg/g).

Quantum well intersubband polaritons are traditionally studied in large scale systems, over many wavelengths in size. In this presentation, we demonstrate that it is possible to detect and investigate intersubband polaritons in a single subwavelength nanoantenna in the IR frequency range. We observe polariton formation using a scattering-type near-field microscope and nano-FTIR spectroscopy. We will discuss near-field spectroscopic signatures of plasmonic antennae with and without coupling to the intersubband transition in quantum wells located underneath the antenna. Evanescent field amplitude spectra recorded on the antenna surface show a mode anti-crossing behavior in the strong coupling case. We also observe a corresponding strong-coupling signature in the phase of the detected field. We anticipate that this near-field approach will enable explorations of strong and ultrastrong light-matter coupling in the single nanoantenna regime, including investigations of the elusive effect of ISB polariton condensation.

Classical versus quantum plasmons are responsible for the recorded signals in non-contact-mode versus contact-mode tip-enhanced Raman spectroscopy (TERS) and lead to distinct observables. Under otherwise identical experimental conditions, we illustrate the concept through tapping- and contact-mode TERS mapping of chemically functionalized silver nanocubes. Whereas molecular charging, chemical transformations, and optical rectification are prominent observables in contact-mode TERS, the same effects are suppressed using tapping-mode feedback. In effect, this work demonstrates that nanoscale physical and chemical processes can be accessed and/or suppressed on demand in the TERS geometry. The advantages of tapping-mode TERS are otherwise highlighted with the latter in mind.

We revisit the reductive coupling of

Discharged wastewater is known to contain insoluble oils, soluble pollutants (organic dyes), and metal ions from industry, which can lead to serious ecological problems. Inspired by the strong adhesion behavior of marine mussels to surfaces, polymers have been developed to mimic this behavior. More specifically, such polymers have been applied in the coating of membrane substrates to obtain multifunctional materials for the absorption of wastewater pollutants. In this study, superwettable cotton-based materials for wastewater treatment were constructed by modifying cotton fiber (CF) with caffeic acid (CA) and chitosan (CHI). The as-prepared CA-CHI-CF materials exhibited superhydrophilicity (i.e., a water contact angle of ~ 0°) and underwater superoleophobicity (i.e., an underwater oil contact angle ≥ 160°). Notably, the compressed CA-CHI-CF exhibited an excellent oil-in-water emulsion separation performance, i.e., a flux up to 50,050 L h−1 m−2 bar−1 under 0.1 bar pressure, and a separation efficiency > 99.9%. Interestingly, due to the advantages of the amino, carboxyl, and hydroxyl groups offered by caffeic acid and chitosan, CA-CHI-CF showed excellent adsorption capabilities for cationic dyes (>99%) and heavy metal ions (>99%). To demonstrate the applicability of our system, a benchmark separation experiment was conducted, namely the separation of dye- and metal ion-spiked emulsions. CA-CHI-CF was found to separate all target pollutants from the solution simultaneously. CA-CHI-CF also exhibited a good biocompatibility and biodegradability, thereby confirming its great potential for practical applications.

A flower-like Bi2WO6-Bi2O3 photocatalyst was prepared by a two-step process, including an ionic liquid-assisted solvothermal step and calcination. The effects of the ionic liquids and calcination on the morphology, property, and photocatalytic performance of Bi2WO6-based photocatalysts were studied. The addition of ionic liquids during the preparation of Bi2WO6 based-materials lead to increased sizes of photocatalysts and the formation of more petal sheets in the flower-like microspheres. The results of XRD, XPS, and TEM confirm that Bi2WO6-Bi2O3 photocatalysts formed after the calcination treatment of Bi2WO6 photocatalyst in an air atmosphere. The Bi2WO6-Bi2O3 flower-like photocatalyst exhibits better photocatalytic H2 production activity than the Bi2WO6 photocatalyst. The improved activity of the Bi2WO6-Bi2O3 photocatalysts was attributed to their enhanced light absorption, increased surface area, matched band structure, and the inhibited recombination of the photogenerated charge carriers.

Oil spills and oily industrial wastewater contain insoluble toxic organic molecules, which are harmful to the environment and human health. The preparation of separation membranes with favorable superwettability is crucial for oil-contaminated water treatment. In this study, we prepared a membrane from carbon nanotubes (CNTs), tannic acid (TA), and polyvinylpyrrolidone (PVP) via a green method, without using organic solvents. This membrane exhibited superhydrophilicity and underwater superoleophobicity, along with excellent self-cleaning and anti-fouling properties towards highly viscous crude oil. Furthermore, the CNT/TA/PVP membrane exhibited excellent oil/water separation performance, with very high permeation flux values of up to 7570 and 2634 L m−2 h−1 bar−1for surfactant-free and -stabilized oil-in-water emulsions, respectively. Remarkably, we separated a stabilized crude oil-in-water emulsion using the CNT/TA/PVP membrane. Moreover, these CNT/TA/PVP membranes were resilient under oil accumulation at intermittent pressure during oil/water separation, maintaining a high flux. The high performance of this CNT/TA/PVP membrane, and its green, low-energy, cost-effective preparation, indicate considerable potential for practical applications.