Nanoscale Surface Engineering Research Articles

Silicon-Doped Graphene Oxide Quantum Dots as Efficient Nanoconjugates for Multifunctional Nanocomposites.

Graphene oxide quantum dots (GOQDs) hold great promise as a new class of high-performance carbonaceous nanomaterials due to their numerous functional properties, such as tunable photoluminescence (PL), excellent thermal and chemical stability, and superior biocompatibility. In this study, we developed a facile, one-pot, and effective strategy to engineer the interface of GOQDs through covalent doping with silicon. The successful covalent attachment of the silane dopant with pendant vinyl groups to the edges of the GOQDs was confirmed by an in-depth investigation of the structural and morphological characteristics. The Si-GOQD nanoconjugates had an average dimension of ∼8 nm, with a graphite-structured core and amorphous carbon on their shell. We further used the infrared nanoimaging based on scattering-type scanning near-field optical microscopy to unveil the spectral near-field response of GOQD samples and to measure the nanoscale IR response of its network; we then demonstrated their distinct domains with strongly enhanced near fields. The doping of Si atoms into the sp2-hybridized graphitic framework of GOQDs also led to tailored PL emissions. We then sought to explore the potential applications of Si-GOQDs on the surface of plastic films where poly(dimethylsiloxane) (PDMS) served as a bridge to tightly anchor the Si-GOQDs to the surface. The bi-layered coated films which were built with co-assembly of Si-GOQDs and PDMS contributed to suppressing the transmission of water molecules due to the generation of compact and less accessible passing sites, achieving a nearly twofold reduction in water permeability compared to the single-layered coated films. The nanoindentation and PeakForce quantitative nanomechanical mapping showed that Si-GOQD-coated substrates were softer and more deformable than those coated only with PDMS. The co-assembly of PDMS and Si-GOQDs yielded films that were less stiff than those made from PDMS alone. Our findings provided conceptual insights into the importance of nanoscale surface engineering of GOQDs in conferring excellent dispersibility and enhancing the performance of nanocomposite films.

Performance evaluation of metal photocathodes based on plasmonic nano-grating

An important class of photocathodes is metal photocathodes, which are used in various systems due to their rapid response time. However, they have low quantum efficiencies due to electron scattering and high photon reflectance losses. Nanoscale surface engineering and plasmonic capability are used to improve the performance and increase the quantum efficiency of metal photocathodes. Plasmonic technology is a good choice due to optical trapping and increased electric field at the surface of the structure. In this study, metal photocathodes Au, Ag, Al, and Cu with similar nano-grating surfaces are designed and exposed to photon radiation and reflected spectra are analyzed and compared using FDTD method. In the reflectance spectrum, surface plasmon polaritons are excited at specific wavelengths and reduce the light reflection from metal nano-grating surfaces. The resonance wavelength adjustment is investigated by changing the height of the nano-grating grooves. The quantum efficiencies of metal photocathodes are calculated and compared with each other based on the relations and equations. The quantum efficiencies of nano-grating metal photocathodes relative to the flat surfaces show that the quantum efficiencies of gold, silver, copper, and aluminum nano-grating increase by 56-fold, 35-fold, 32-fold, and 14-fold, respectively, higher than their flat surfaces during resonant wavelengths.

The Role of Biomaterials and Biocompatible Materials in Implant-Supported Dental Prosthesis.

The dental implant is one of the appropriate instances of the different dental materials and their application, which is the combined procedure of technology and science in physics, biomechanics, and surface chemistry from macroscale to nanoscale surface engineering and manufactured technologies. In recent decades, biomaterials in implant therapy promote bone response and biomechanical ability, which is long-term from surgical equipment to final prosthetic restoration. Biomaterials have a crucial role in rehabilitating the damaged structure of the tooth and supplying acceptable outcomes correlated with clinical performance. There are some challenges in implantation such as bleeding, mobility, peri-implant infections, and the solution associated with modern strategies which are regarded to biomaterials. Various materials have been known as promising candidates for coatings of dental implants which contain polyhydroxyalkanoates, calcium phosphate, carbon, bisphosphonates, hydroxyapatite, bone stimulating factors, bioactive glass, bioactive ceramics, collagen, chitosan, metal and their alloys, fluoride, and titanium/titanium nitride. It is pivotal that biomaterials should be biodegradable; for example, polyhydroxyalkanoates are biodegradable; also, they do not have bad effects on tissues and cells. Despite this, biomaterials have important roles in prosthetic conditions such as dental pulp regeneration, the healing process, and antibacterial and anti-inflammatory effects. In this review study, the role of biocompatible materials in dental implants is investigated in in vitro and in vivo studies.

Nanoscale surface engineering of PdCo/Al2O3 catalyst via segregation for efficient purification of ethene feedstock

Surface engineering of bimetallic nanoparticles are crucial for harnessing the true catalytic potential. Herein, H2-induced segregation of palladium was employed to tune the surface structure of PdCo/Al2O3 catalysts with different Pd/Co atomic ratios. The composition dependency of segregation was demonstrated by XRD, XPS, and HAADF-STEM characterization. The results from in situ CO-FTIR analysis show that Pd ensemble sites were formed on Pd75Co25/Al2O3; while, isolated Pd sites were formed on Pd15Co85/Al2O3 after 700 °C hydrogen post-treatment. The post-treated catalysts exhibited significantly increased activity for acetylene selective hydrogenation due to Pd segregation on the surface. In addition, the Pd15Co85-700 catalyst displayed 88% ethene selectivity at ∼100% conversion of acetylene, which was related to the redispersion of Pd and Co during the H2 treatment. Kinetic analysis provided valuable insight into the nature of the active sites resulting from the surface segregation. The Pd15Co85-700 catalyst also showed favorable stability during 100 h reaction.

Directional Passive Transport of Microdroplets in Oil-Infused Diverging Channels for Effective Condensate Removal.

Condensation widely exists in nature and industry, and its performance heavily relies on the efficiency of condensate removal. Recent advances in micro-/nanoscale surface engineering enable condensing droplet removal from solid surfaces without extra energy cost, but it is still challenging to achieve passive transport of microdroplets over long distances along horizontal surfaces. The mobility of these condensate droplets can be enhanced by lubricant oil infusion on flat surfaces and frequent coalescence, which lead to fast growth but random motion of droplets. In this work, we propose a novel design of diverging microchannels with oil-infused surfaces to achieve controllable, long-distance, and directional transport of condensing droplets on horizontal surfaces. This idea is experimentally demonstrated with diverging copper and silicon microchannels with nanoengineered surfaces. Along these hierarchical surface structures, microdroplets condense on the top channel wall and submerge into microchannels owing to the capillary pressure gradient in infusing oil. Confined by the microchannel walls, the submerged droplets deform and maintain the back-front curvature difference, which enables the motion of droplets along the channel diverging direction. Subsequent droplet coalescences inside the channel further enhance this directional transport. Moreover, fast-moving deformed droplets transfer their momentum to downstream spherical droplets through the infusing oil. As a result, simultaneous passive transport of multiple droplets (20-400 μm) is achieved over long distances (beyond 7 mm). On these oil-infused surfaces, satellite microdroplets can further nucleate and grow on an oil-cloaked droplet, demonstrating an enlarged surface area for condensation. Our findings on passive condensate removal offer great opportunities in condensation enhancement, self-cleaning, and other applications requiring directional droplet transport along horizontal surfaces.

Performing DNA nanotechnology operations on a zebrafish.

Nanoscale engineering of surfaces is becoming an indispensable technique to modify membranes and, thus cellular behaviour. Here, such membrane engineering related was explored on the surface of a living animal using DNA nanotechnology. We demonstrate the immobilization of oligonucleotides functionalized with a membrane anchor on 2 day old zebrafish. The protruding single-stranded DNA on the skin of zebrafish served as a handle for complementary DNAs, which allowed the attachment of small molecule cargo, liposomes and dynamic relabeling by DNA hybridization protocols. Robust anchoring of the oligonucleotides was proven as DNA-based amplification processes were successfully performed on the outer membrane of the zebrafish enabling the multiplication of surface functionalities from a single DNA-anchoring unit and the dramatic improvement of fluorescent labeling of these animals. As zebrafish are becoming an alternative to animal models in drug development, toxicology and nanoparticles characterization, we believe the platform presented here allows amalgamation of DNA nanotechnology tools with live animals and this opens up yet unexplored avenues like efficient bio-barcoding as well as in vivo tracking.

Functionalized few-layer black phosphorus with super-wettability towards enhanced reaction kinetics for rechargeable batteries

Few-layer black phosphorus (BP) is a promising anode material for sodium ion batteries (SIBs) due to its high theoretical capacity and favorable layered structure. However, practical implementation is hindered by sluggish reaction kinetics and large volume change during de/sodiation process. Especially, combining BP with large portion of low-capacity carbonaceous materials is a common strategy to improve the Na storage properties, but leading to reduced specific capacity based on the overall mass of the whole electrode. To address these challenges, nanoscale surface engineering of few-layer BP is herein performed by homogeneously depositing horizontally aligned Poly(3, 4-ethylenedioxythiophene) (PEDOT) nanofibers on specially surface-modified BP nanosheets. Such material design could achieve simultaneously: (1) enhanced charge transfer kinetics and (2) super surface wettability with electrolyte. Benefiting from the unique functionalization, the reaction kinetics are greatly enhanced accordingly for both sodium and lithium storage. Our strategy sheds light on designing advanced electrodes for high-performance rechargeable batteries and other energy storage/conversion devices.

Carbon Quantum Dot Surface-Engineered VO2Interwoven Nanowires: A Flexible Cathode Material for Lithium and Sodium Ion Batteries

The use of electrode materials in their powdery form requires binders and conductive additives for the fabrication of the cells, which leads to unsatisfactory energy storage performance. Recently, a new strategy to design flexible, binder-, and additive-free three-dimensional electrodes with nanoscale surface engineering has been exploited in boosting the storage performance of electrode materials. In this paper, we design a new type of free-standing carbon quantum dot coated VO2 interwoven nanowires through a simple fabrication process and demonstrate its potential to be used as cathode material for lithium and sodium ion batteries. The versatile carbon quantum dots that are vastly flexible for surface engineering serve the function of protecting the nanowire surface and play an important role in the diffusion of electrons. Also, the three-dimensional carbon cloth coated with VO2 interwoven nanowires assisted in the diffusion of ions through the inner and the outer surface. With this unique architecture, the carbon quantum dot nanosurface engineered VO2 electrode exhibited capacities of 420 and 328 mAh g(-1) at current density rate of 0.3 C for lithium and sodium storage, respectively. This work serves as a milestone for the potential replacement of lithium ion batteries and next generation postbatteries.

MoS2‐Quantum‐Dot‐Interspersed Li4Ti5O12 Nanosheets with Enhanced Performance for Li‐ and Na‐Ion Batteries

Rational nanoscale surface engineering of electroactive nanoarchitecture is highly desirable, since it can both secure high surface‐controlled energy storage and sustain the structural integrity for long‐time and high‐rate cycling. Herein, ultrasmall MoS2 quantum dots (QDs) are exploited as surface sensitizers to boost the electrochemical properties of Li4Ti5O12 (LTO). The LTO/MoS2 composite is prepared by anchoring 2D LTO nanosheets with ultrasmall MoS2 QDs using a simple and effective assembly technique. Impressively, such 0D/2D heterostructure composites possess enhanced surface‐controlled Li/Na storage behavior. This unprecedented Li/Na storage process provides a LTO/MoS2 composite with outstanding Li/Na storage properties, such as high capacity and high‐rate capability as well as long‐term cycling stability. As anodes in Li‐ion batteries, the materials have a stable specific capacity of 170 mAhg−1 after 20 cycles and are able to retain 94.1% of this capacity after 1000 cycles, i.e., 160 mAhg−1, at a high rate of 10 C. Due to these impressice performance, the presented 0D/2D heterostructure has great potential in high‐performance LIBs and sodium‐ion batteries.

Restructured graphene sheets embedded carbon film by oxygen plasma etching and its tribological properties

An oxygen plasma etching technique was introduced for improving the tribological properties of the graphene sheets embedded carbon (GSEC) film in electron cyclotron resonance plasma processing system. The nanostructural changing in the film caused by oxygen plasma etching was examined by transmission electron microscope, Raman spectroscopy and X-ray photoelectron spectroscopy, showing that the 3nm thick top surface layer was restructured with smaller graphene nanocrystallite size as well as higher sp3 bond fraction. The surface roughness, mechanical behavior and tribological properties of the original GSEC and oxygen plasma treated GSEC films were compared. The results indicated that after the oxygen plasma treatment, the average roughness decreased from 20.8±1.1nm to 1.9±0.1nm, the hardness increased from 2.3±0.1GPa to 2.9±0.1GPa, the nanoscratch depth decreased from 64.5±5.4nm to 9.9±0.9nm, and the wear life increased from 930±390 cycles to more than 15,000 frictional cycles. The origin of the improved tribological behavior was ascribed to the 3nm thick graphene nanocrystallite film. This finding can be expected for wide applications in nanoscale surface engineering.

Combined hydrophobicity and mechanical durability through surface nanoengineering.

This paper reports combined hydrophobicity and mechanical durability through the nanoscale engineering of surfaces in the form of nanorod-polymer composites. Specifically, the hydrophobicity derives from nanoscale features of mechanically hard ZnO nanorods and the mechanical durability derives from the composite structure of a hard ZnO nanorod core and soft polymer shell. Experimental characterization correlates the morphology of the nanoengineered surfaces with the combined hydrophobicity and mechanical durability, and reveals the responsible mechanisms. Such surfaces may find use in applications, such as boat hulls, that benefit from hydrophobicity and require mechanical durability.

Graphene quantum dots coated VO2 arrays for highly durable electrodes for Li and Na ion batteries.

Nanoscale surface engineering is playing important role in enhancing the performance of battery electrode. VO2 is one of high-capacity but less-stable materials and has been used mostly in the form of powders for Li-ion battery cathode with mediocre performance. In this work, we design a new type of binder-free cathode by bottom-up growth of biface VO2 arrays directly on a graphene network for both high-performance Li-ion and Na-ion battery cathodes. More importantly, graphene quantum dots (GQDs) are coated onto the VO2 surfaces as a highly efficient surface "sensitizer" and protection to further boost the electrochemical properties. The integrated electrodes deliver a Na storage capacity of 306 mAh/g at 100 mA/g, and a capacity of more than 110 mAh/g after 1500 cycles at 18 A/g. Our result on Na-ion battery may pave the way to next generation postlithium batteries.

Gold nanograin microelectrodes for neuroelectronic interfaces

Neuroelectronic interfaces are imperative in investigating neural tissues as electrical signals are the main information carriers in the nervous system and metal microelectrodes have been widely used for recording and stimulation of nerve cells. For high performance microelectrodes, low tissue-electrode interfacial impedance and high charge injection limits are essential and nanoscale surface engineering has been utilized to meet the requirements for microelectrodes. We report a single-cell sized microelectrode, which has unique gold nanograin structures, using a simple electrochemical deposition method. The fabricated microelectrode had a sunflower shape with 1-5 (m of micropetals along the circumference of the microelectrode and 500 nm nanograins at the center. The nanograin electrodes had 69-fold decrease of impedance and 10-fold increase in electrical stimulation capability compared to unmodified flat gold microelectrodes. The recording and stimulation performance of nanograin electrodes was tested using dissociated rat hippocampal neuronal cultures. Noise levels were extremely low (2.89 μV(rms) ) resulting in high signal-to-noise ratio for low-amplitude action potentials (18.6-315 μV). Small biphasic current pulses (20-60 μA) could evoke action potentials from neurons nearby electrodes. This new nanostructured neural electrode may be applicable for the development of cell-based biosensors or clinical neural prosthetic devices.

Nanoscale Surface Engineering of Cuprous Oxide Crystals: The Function of Chloride

Nanoscale Surface Engineering of Cuprous Oxide Crystals: The Function of Chloride

Nanoscale Surface Engineering with Deformation-Resistant Core–Shell Nanostructures

Nano-textured surfaces (NTSs) can reduce adhesion and friction and thus have potential to increase the reliability of micro-electro-mechanical systems and nano-electro-mechanical systems. However, deformation of the nanotextures severely limits the effectiveness of using NTSs. This article presents a novel concept of nano-surface-engineering by texturing the surface with core–shell nanostructures to produce deformation-resistant nanotextures. The NTSs were produced by thermal evaporation of Al on Si substrates to form Al nanostructures and then depositing amorphous silicon on top of Al by plasma-enhanced chemical vapor deposition. Friction and deformation of the NTSs were studied using a TriboIndenter and a scanning electron microscope. The results show that the novel NTS significantly reduced the coefficients of friction of the surface without any detectable plastic deformations of the nanotextures even after heavy scratches.

Stimuli‐Sensitive Polymers

Stimuli‐Sensitive Polymers

Nanoscale surface engineering of PDMS by embedding vertical nanosheets of materials

This paper describes an innovative, low cost and time effective nano-engineering process dedicated to macroelectronics and lab-on-a-chip applications. It consists of the fabrication of vertical nanosheets self-standing on a silicon template, and their embedding in polydimethylsiloxane (PDMS) by a mechanical release during the peel-off of the cured polymer. We demonstrate for the first time the embedding of a multi-stack composed of Au/SiO 2/Au nanosheets in PDMS and discussed in details the influence of each process parameters on the nanosheet composition and dimension. Since the embedded materials are hydrophilic, the formation of micro droplets was observed by condensation of the water vapor, leading to a self-alignment of those micro droplets onto the functional PDMS surface.

Single-Atom Extraction by Scanning Tunneling Microscope Tip Crash and Nanoscale Surface Engineering

We report a novel atom extraction mechanism from the native substrate by means of a scanning tunneling microscope tip crash on a Ag(111) surface at 5 K. Individual atoms are scattered on the surface when a silver coated tip is dipped into the substrate at low tunneling biases. Quantitative analyses reveal that the mechanical energy supplied by the tip crash dominates the atom extraction process. Application of this procedure is demonstrated by constructing quantum structures using the extracted atoms on an atom-by-atom basis.

Nanoscale surface engineering of LN and LT by a chemical etching

Nanoscale surface engineering of LN and LT by a chemical etching