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• In-situ curing of the hierarchical structure of the ionic polymer gel encapsulated within ecoflex. • The GPE-TENG demonstrates high durability, sustaining heavy mechanical deformations and environmental stability. • The GPE-TENG exhibits outstanding energy harvesting capabilities with a peak power density of 0.36 W m−2. • The GPE-TENG showed superior strain sensing capabilities for monitoring human activities and rehabilitation progress. • A self-powered wearable touch panel is developed for demonstrating touch track/pattern recognition and user identification. Gel-based sensors for next generation touch panels have been acknowledged for their exceptional sensitivity and flexibility. However, these sensors typically depend on a metal grid connection, which is susceptible to structural deformation under heavy stress applications and necessitates external power. Here, we report a novel in-situ cured gel polymer electrode-based triboelectric nanogenerator (GPE-TENG) that is stretchable, semi-transparent, and durable, designed to enable a self-powered touch panel for intelligent touch perception. The in-situ curing of the hierarchical structure of the ionic polymer gel encapsulated within the ecoflex ensures robust adhesion of the ionic conductive polymer gel (PEO/LiTFSI) to the ecoflex layers, addressing the issue of delamination in TENG components under mechanical stress. As a result, the GPE-TENG demonstrates high durability, enduring under stretching of approximately 375 % and sustaining heavy mechanical deformations (under folding, twisting, and rolling) over a long period (approximately 2 months) without loss of functionality. Remarkably, the GPE-TENG exhibits outstanding energy harvesting capabilities with a peak power density of 0.36 W m-2. Notably, the GPE-TENG generates electrical signals through simple device stretching, thus serving as a self-powered wearable sensor for human activity monitoring. Moreover, a 9-digital arrayed (3 × 3) flexible, semi-transparent, and self-powered touch panel based on the GPE-TENG shows multifunctionality, including touch track/pattern recognition (i.e. touch and sliding mode) and a highly accurate (∼98 %) deep learning assisted smart biometric system for user identification. [ABSTRACT FROM AUTHOR]

Conductive electrodes in triboelectric nanogenerators (TENGs) typically use metal-based materials. However, such devices have limited flexibility and challenges in humid environments. To overcome this issue, we present a metal-free flexible TENG made from bifunctional carbon fiber paper that serves as both a conductive electrode and an efficient tribo-positive friction layer. The electrical performance of carbon fiber paper-based TENG (CFP-TENG) at 3 Hz demonstrated a peak-to-peak voltage of 109.1 V, a current of 10.8 μA, and a power density of ∼ 0.093 W/m2 at 7 MΩ external resistance. A 20 µF capacitor is also charged, and 38 light-emitting diodes (LEDs) arranged in the letter 'DGU' can be lighted. The CFP-TENG device's high flexibility allows it to sustain 12,000 repeated mechanical contact-separation cycles and fold, twist, and roll the device without degrading performance. In addition, the hydrophobic characteristic of carbon fiber ensures the improved moisture resistance of the CFP-TENG device compared to conventional copper electrodes. Furthermore, the CFP-TENG is successfully integrated into various human joints as a self-powered motion sensor for tracking real-time human activity monitoring, including finger motion detection, arm motion, walking, and running activities. A metal-free TENG based on bifunctional carbon fibers paves the way for energy- harvesting solutions and self-powered biomedical sensors. [Display omitted] • A metal-free flexible TENG was fabricated using a bifunctional carbon fiber paper. • A bifunctional carbon fiber paper serves as both a conductive electrode and an efficient tribo-positive friction layer. • The carbon fiber paper demonstrate excellent deformability, including folding, rolling, and twisting. • The CFP-TENG shows remarkable electrical performance even after 12,000 contact-separation cycles. • A self-powered motion sensor for tracking human activity was demonstrated. [ABSTRACT FROM AUTHOR]

Metal nanoparticles (NPs) fabricated by means of the solid state dewetting (SSD) approach are applicable in many optoelectronic, biomedical and catalytical applications. However, the fabrication of metallic NPs with the low diffusivity elements such as platinum (Pt) has been challenging for the well-defined configuration and uniformity due to the low diffusivity of Pt atoms and thus the optical properties suffer. In this paper, the evolution of well-defined configuration and improved uniformity of Pt NPs are demonstrated by the altered solid state dewetting (ASSD) approach using a sacrificial indium (In) layer. Upon annealing, the high diffusivity In atoms can lead to the formation of In-Pt alloy due to the inter-mixing at the interface and the dewetting process advances along with the enhanced diffusion of In-Pt alloy atoms. Eventually, well-defined Pt NPs are formed by means of complete desorption of In atoms by sublimation. By the control of In and Pt ratio in the bilayers with the fixed total thickness such as In4.5 nm/Pt1.5 nm, In3 nm/Pt3 nm, In1.5 nm/Pt4.5 nm, the isolated dome shaped Pt NPs of various size are demonstrated, which reflects the significant impact of In component in the dewetting process. The optical characterization of Pt NPs exhibits the formation of quadrupolar resonance and strong dipolar resonance bands in the UV and VIS regions respectively, which are tunable based on the morphology of Pt NPs. In specific, the dipolar resonance peaks demonstrate a red shifting behavior with the increment of size of Pt NPs and gradually become narrower along with the improvement of uniformity of Pt NPs. [ABSTRACT FROM AUTHOR]

Alloy nanoparticles (NPs) can offer a wide range of opportunities for various applications due to their composition and structure dependent properties such as multifunctionality, electronic heterogeneity, site-specific response, and multiple plasmon resonance bands. In this work, the fabrication of self-assembled PdxAg1-x NPs alloy nanostructures with distinct size, density, shape, and composition is demonstrated via the solid-state dewetting of sputtered Pd/Ag thin films on c-plane sapphire. The initial stage of bilayer dewetting exhibits the nucleation of voids, followed by the expansion of voids and cluster breakdown and finally shape transformation along with the temperature control. Bilayer composition shows a substantial influence on the dewetting such that the overall dewetting is enhanced along with the increased Ag composition, i.e. Pd0.25Ag0.75 > Pd0.5Ag0.5 > Pd0.75Ag0.25. On the other hand, the size and density of NPs can be efficiently controlled by varying the initial thickness of bilayers. Reflectance peaks in UV and near-infrared (NIR) regions and a wide absorption band in the visible region arisen from the surface plasmon resonance are observed in reflectance spectra. The peak intensity depends on the composition of PdxAg1-x NPs and the NIR peaks gradually blue-shift with the size decrement. [ABSTRACT FROM AUTHOR]

Bimetallic nanostructures (BMNSs) have gained significant attention because of their multi-functionality, site-specific response and electronic heterogeneity along with the additional opportunities to tune physical and optical properties. In this paper, the systematic evolution of Au x Pd 1−x BMNS is thoroughly investigated in terms of morphological and optical properties through the solid state dewetting on c -plane sapphire. The bilayer composition and deposition order change are coherently tested along with the conventional growth parameter control. By the systematic control of annealing temperature, annealing duration and deposition thickness, the formation of various BMNSs demonstrate sharp distinctions at different Au x Pd 1−x compositions (x = 0.25, 0.50 and 0.75). In specific, the high Au percentage in the Au x Pd 1−x bilayers shows an enhanced dewetting due to the higher diffusivity and lower surface energy of Au atoms as compared to the Pd. Furthermore, the deposition order also induces a significant alteration on the dewetting process. Upon annealing, the evolution of BMNSs relies on the combination of atomic diffusion, inter-diffusion, alloying, surface and interface energy minimization and Rayleigh-like instability. Furthermore, the analysis of reflectance spectra demonstrates the development of the quadrupolar and dipolar resonance peaks, absorption band and their shift, induced by the localized surface plasmon resonance (LSPR) of various Au x Pd 1−x BMNSs. Specifically, the quadrupolar resonance peak is consistent ∼380 nm whereas the dipolar resonance peak and absorption dip are readily blue-shifted and narrowed along with the evolution of isolated and uniform BMNSs. [ABSTRACT FROM AUTHOR]

Multi-metallic alloy nanoparticles (NPs) can offer additional opportunities for modifying the electronic, optical and catalytic properties by the control of composition, configuration and size of individual nanostructures that are consisted of more than single element. In this paper, the fabrication of bimetallic Pd-Ag NPs is systematically demonstrated via the solid state dewetting of bilayer thin films on c-plane sapphire by governing the temperature, time as well as composition. The composition of Pd-Ag bilayer remarkably affects the morphology of alloy nanostructures, in which the higher Ag composition, i.e. Pd0.25Ag0.75, leads to the enhanced dewetting of bilayers whereas the higher Pd composition (Pd0.75Ag0.25) hinders the dewetting. Depending on the annealing temperature, Pd-Ag alloy nanostructures evolve with a series of configurations, i.e. nucleation of voids, porous network, elongated nanoclusters and round alloy NPs. In addition, with the annealing time set, the gradual configuration transformation from the elongated to round alloy NPs as well as size reduction is demonstrated due to the enhanced diffusion and sublimation of Ag atoms. The evolution of various morphology of Pd-Ag nanostructures is described based on the surface diffusion and inter-diffusion of Pd and Ag adatoms along with the Ag sublimation, Rayleigh instability and energy minimization mechanism. The reflectance spectra of bimetallic Pd-Ag nanostructures exhibit various quadrupolar and dipolar resonance peaks, peak shifts and absorption dips owing to the surface plasmon resonance of nanostructures depending on the surface morphology. The intensity of reflectance spectra is gradually decreased along with the surface coverage and NP size evolution. The absorption dips are red-shifted towards the longer wavelength for the larger alloy NPs and vice-versa. [ABSTRACT FROM AUTHOR]

The gradual evolution of Ag nanostructures in terms of the configuration, size, and density of via the solid state dewetting is demonstrated on GaN (0001) by the systematic control of annealing temperature and duration with various Ag film thickness. Upon the annealing between 150 and 700 °C with the 20 nm Ag film, the hillocks, voids, irregular, and round dome shaped Ag nanoparticles (NPs) are fabricated based on various growth mechanisms: i.e., thermal diffusion and sublimation as well as the surface energy minimization. On the other hand, along with the systematic control of annealing duration between 0 and 3600 s with 10 nm Ag film 700 °C, the Ag NPs show gradually decreased size and density based on the concurrent influence of the Ostwald's ripening and sublimation of Ag atoms. The Raman, photoluminescence, and reflectance spectroscopy of the resulting Ag NPs are characterized in accordance with the various morphology evolution of Ag nanostructures. [ABSTRACT FROM AUTHOR]

Nanoscale patterning of sapphires is a challenging task due to the high mechanical strength, chemical stability as well as thermal durability. In this paper, we demonstrate a gold droplet assisted approach of nano-hole fabrication on c -plane sapphire via a thermal treatment. Uniformly distributed nano-holes are fabricated on the sapphire surface guided by dome shaped Au nanoparticles (NPs) as catalysts and the patterning process is discussed based on the disequilibrium of vapor, liquid, solid interface energies at the Au NP/sapphire interface induced by the Au evaporation at high temperature. Followed by the re-equilibration of interface energy, transport of alumina from the beneath of NPs to the sapphire surface can occur along the NP/sapphire interface resulting in the formation of nano-holes. The fabrication of nano-holes using Au NPs as catalysts is a flexible, economical and convenient approach and can find applications in various optoelectronics. [ABSTRACT FROM AUTHOR]

The systematic control over the configuration, size, and density of Au nanostructures can directly improve or optimize the physical, chemical, and optoelectronic properties and thus the functionality in the related applications. In this work, we successfully demonstrate the systematic configurational transition of self-assembled Au nanostructures on c-plane GaN via the precise control of annealing temperature, deposition amount, and annealing duration. Depending on the control of annealing temperature, self-assembled Au vermiform-like nanostructures are fabricated and evolve into the faceted Au nanorods and Au hexagons with the minimization of overall surface energy based on the Volmer-Weber growth model. With the deposition amount control, the volume-dependent transition of Au nanostructure configurations from triangles to hexagons and then to polyhedral is clearly observed and discussed based on the combinational effects of growth kinetics and surface free energy distribution. The configurational transition from irregular Au clusters to faceted nanostructures is witnessed along with the incremental variation of annealing duration based on the Ostwald ripening. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zeolitic imidazolate framework nanocrystal decorated polyacrylonitrile nanofiber. • Triboelectric nanogenerator for self-powered visible light communication system. • Nanofibers provide a higher effective surface area for contact-electrification. • Remarkable electrical power output from nanofiber-based triboelectric nanogenerator. • Nanogenerator for the wireless control of home appliances and text messaging systems. We propose a zeolitic imidazolate framework (ZIF-8) nanocrystal decorated electrospun polyacrylonitrile (PAN) nanofiber as an efficient triboelectric positive material for the high-performance triboelectric nanogenerator (TENG) and demonstrate a self-powered visible light communication (VLC) system for wireless human-machine interactions. The PAN@ZIF-8 nanofibers provide a higher effective contact surface area that can contribute to the improvement of the total amount of generated charges. This can enable the energy harvesting performance of the PAN@ZIF-8 based TENG (PZ-TENG) to be increased more than 3 times compared to their individual PAN nanofibers and ZIF-8 crystal based TENG devices. Furthermore, we develop a PZ-TENG driven self-powered VLC system and utilize it for the wireless control of home appliances and text messaging systems. 3-bit binary codes are designed with two different mechanical activities (clicking '0′ and flapping '1′) for secure and wireless control of the home appliances (Fan, Humidifier, Bell, and Lamp) and to send a text message "HI DGU" on a mobile phone. The designed self-powered VLC system with advanced coding concepts can further enable remote personal identification, security defense, and smart home authentication and monitoring applications. [ABSTRACT FROM AUTHOR]

Porous GaN exhibits unique optoelectronic, chemical, and physical properties such as shift of band gap, increased surface area ratio, excellent chemical, mechanical, and thermal stability as well as efficient luminescence as compared to its bulk counterpart. Herein, we demonstrate a precise, efficient, and still cost-effective method of the fabrication of porous GaN through the enhanced GaN decomposition by using Au nanoparticles (NPs) as a catalyst, in which the size, density, and shape of the pores (nanoholes, NHs) can be precisely controlled. By the thermal annealing assisted with the Au NPs, the NHs are successfully fabricated, and the existence of Au NPs significantly accelerate the GaN decomposition at the interface between the NPs and GaN due to the Ga absorption by the Au NPs. We systematically study the formation mechanism of NHs assisted by the Au NPs by means of annealing temperature, duration, and Au deposition amount, and the results are systematically analyzed and discussed. [ABSTRACT FROM AUTHOR]

Metal nanoparticles (NPs) with controllable size, density and configuration can significantly enhance the energy conversion efficiency, detection sensitivity and catalytic activity as witnessed in various optoelectronic, optical sensing and electro-catalytic devices due to their shape and size dependent properties. In this work, we systematically investigate the evolution of the size, density and configuration of Pt nanostructures on sapphire (0 0 0 1). In particular, we have demonstrated four different configuration and evolution of Pt nanostructures with the systematic control of deposition amount (DA) based on the Volmer–Weber growth model in conjunction with the surface energy minimization mechanism, diffusion and coalescence. The various size and configuration of Pt nanostructures with respect to DA are (i) nucleation of mini-sized round shaped Pt NPs (1 ≤ DA ≤ 5 nm), (ii) growth of large sized Pt NPs (10 ≤ DA ≤ 15 nm), (iii) isolated irregular nanostructures (20 ≤ DA ≤ 30 nm) and (iv) coalesced Pt nanostructures (DA ≥ 40). On the other hand, with the increased dwelling time (DT), irregular Pt NPs are fabricated with the increased size and improved uniformity between 0 and 450 s of annealing. The growth of Pt NPs is saturated when the dwelling time reaches the critical value between 900 and 1800 s, which can be attributed to the Ostwald ripening. [ABSTRACT FROM AUTHOR]

Au nano-clusters and nanoparticles (NPs) have been widely utilized in various electronic, optoelectronic, and bio-medical applications due to their great potentials. The size, density and configuration of Au NPs play a vital role in the performance of these devices. In this paper, we present a systematic study on the self-assembled hexagonal Au voids, nano-clusters and NPs fabricated on GaN (0001) by the variation of annealing temperature and deposition amount. At relatively low annealing temperatures between 400 and 600°C, the fabrication of hexagonal shaped Au voids and Au nano-clusters are observed and discussed based on the diffusion limited aggregation model. The size and density of voids and nano-clusters can systematically be controlled. The self-assembled Au NPs are fabricated at comparatively high temperatures from 650 to 800°C based on the Volmer-Weber growth model and also the size and density can be tuned accordingly. The results are symmetrically analyzed and discussed in conjunction with the diffusion theory and thermodynamics by utilizing AFM and SEM images, EDS maps and spectra, FFT power spectra, cross-sectional line-profiles and size and density plots. [ABSTRACT FROM AUTHOR]

In this work, we designed and prepared a hierarchically assembled 3D plasmonic metal-dielectric-metal (PMDM) hybrid nano-architecture for high-performance surface-enhanced Raman scattering (SERS) sensing. The fabrication of the PMDM hybrid nanostructure was achieved by the thermal evaporation of Au film followed by thermal dewetting and the atomic layer deposition (ALD) of the Al2O3 dielectric layer, which is crucial for creating numerous nanogaps between the core Au and the out-layered Au nanoparticles (NPs). The PMDM hybrid nanostructures exhibited strong SERS signals originating from highly enhanced electromagnetic (EM) hot spots at the 3 nm Al2O3 layer serving as the nanogap spacer, as confirmed by the finite-difference time-domain (FDTD) simulation. The PMDM SERS substrate achieved an outstanding SERS performance, including a high sensitivity (enhancement factor, EF of 1.3 × 108 and low detection limit 10−11 M) and excellent reproducibility (relative standard deviation (RSD) < 7.5%) for rhodamine 6G (R6G). This study opens a promising route for constructing multilayered plasmonic structures with abundant EM hotspots for the highly sensitive, rapid, and reproducible detection of biomolecules. [ABSTRACT FROM AUTHOR]

• A novel SERS sensing platform based on self-assembly arrays of porous AuAg NPs with nanogap is fabricated. • The intelligent SERS platform has demonstrated high sensitivity and multiplex sensing of R6G and CV molecules. • The SERS enhancement factor of ~7.8 × 106, RSD of<6.5% and LOD of 2.37 ×10−9 M concentration have been achieved. Designing and fabricating highly dense porous nanoparticles (p-NPs) arrays with nanogaps are crucial for ultra-sensitive surface-enhanced Raman scattering (SERS) detection as they can provide both abundant built-in and inter nanogap-induced hotspots. Here, we demonstrate highly sensitive multiplex-detection of organic dyes using SERS substrates with the self-assembly arrays of porous AuAg alloy (p-AuAg) NPs. The p-AuAg NPs were fabricated by a thermal dewetting method of very thin Au/Ag bilayers and a subsequent dealloying approach, which result in multiple built-in and inter nanogaps between the nano-granules with a porous structure and the adjacent NPs as well as excellent porosity and a high surface-to-volume ratio. The SERS substrates with p-AuAg NPs for the detection of Rhodamine 6 G (R6G) molecules exhibited an excellent enhancement factor of approximately 7.8 × 106, good reproducibility with relative standard deviation<6.5%, and limit of detection of dye molecules down to 2.37 × 10−9 M concentration in comparison with the AuAg alloy NPs. This is attributed to the generation of significant enhancement of electromagnetic field at the highly-dense built-in and inter nanogap in the self-assembly arrays of p-AuAg NPs, which is supported by the finite-difference time-domain (FDTD) simulation results. In addition to the detection of R6G molecules, the multiplex detection capability of R6G and crystal violet (CV) molecules at low concentrations for the p-AuAg NPs-based SERS substrates was also demonstrated. These findings present a potential pathway towards the development of an excellent SERS platform for practical applications such as bioscience, food, and environmental safety. [ABSTRACT FROM AUTHOR]

In this work, we develop a Ag@Al2O3@Ag plasmonic core–shell–satellite (PCSS) to achieve highly sensitive and reproducible surface-enhanced Raman spectroscopy (SERS) detection of probe molecules. To fabricate PCSS nanostructures, we employ a simple hierarchical dewetting process of Ag films coupled with an atomic layer deposition (ALD) method for the Al2O3 shell. Compared to bare Ag nanoparticles, several advantages of fabricating PCSS nanostructures are discovered, including high surface roughness, high density of nanogaps between Ag core and Ag satellites, and nanogaps between adjacent Ag satellites. Finite-difference time-domain (FDTD) simulations of the PCSS nanostructure confirm an enhancement in the electromagnetic field intensity (hotspots) in the nanogap between the Ag core and the satellite generated by the Al2O3 shell, due to the strong core–satellite plasmonic coupling. The as-prepared PCSS-based SERS substrate demonstrates an enhancement factor (EF) of 1.7 × 107 and relative standard deviation (RSD) of ~7%, endowing our SERS platform with highly sensitive and reproducible detection of R6G molecules. We think that this method provides a simple approach for the fabrication of PCSS by a solid-state technique and a basis for developing a highly SERS-active substrate for practical applications. [ABSTRACT FROM AUTHOR]

We demonstrate silver nanowire -network-film (AgNWNF)-coated soft polydimethyl siloxane (PDMS) substrates with wrinkled surfaces for use as stretchable SERS sensors. The AgNWNF-coated stretchable substrates showed strong SERS effects compared to those of Ag film-deposited substrates, which were likely attributed to the electromagnetic field enhancement induced by the relatively high density of hot spots in the AgNWNF. To investigate the stability of the stretchable SERS sensors, we examined the adhesion strength of AgNWNFs on the ultraviolet-ozone (UVO)-treated PDMS substrates, which was much stronger than the adhesion strength of AgNWNFs on the PDMS without prior UVO treatment. In addition, the strain-dependent SERS activity of the AgNWNF-coated stretchable sensor showed the detection of 10−7 M Rhodamine 6G (R6G) molecules despite the decreased Raman intensity under strain increased to 100%, resulting from the surface plasmon resonance tuning by the modulation of the active gap distance between neighboring AgNWs through the application of strain. This was further supported by finite-difference time domain (FDTD) numerical evaluation. Image 1 • The simple and low-cost fabrication of the stretchable SERS sensors based on the wrinkled PDMS substrates coated with the AgNWNFs. • The AgNWNFs-based SERS sensors exhibited the strain-dependent effect of surface plasmon resonance. • The strain-dependent SERS activity of FDTD evaluation of the stretchable sesnor were examined. [ABSTRACT FROM AUTHOR]

• Fabrication of AgAuPt and AuPt NPs by the solid-state dewetting of Ag/Au/Pt tri-layers of various thickness. • Demonstration of individual nanoparticles of tri and bi-metallic alloy composite. • Demonstration of various LSPR bands, peak shift and absorption band evolution. • Demonstration of finite-difference time domain (FDTD) simulations for various ternary AgAuPt and binary AuPt NPs. In this work, various configurations, size, density and composition of AgAuPt and AuPt alloy NPs are demonstrated via the solid-state dewetting (SSD) of Ag/Au/Pt tri-layers on the transparent c-plane sapphire (0001) and the corresponding LSPR characteristics are thoroughly investigated along with the FDTD simulation. The SSD is adapted to convert the sputtered Ag/Au/Pt tri-layers into the definite alloy NPs based on the diffusion, interdiffusion and energy minimization process. The resulting AgAuPt and AuPt NPs demonstrate much stronger plasmonic characteristics as compared to their counterparts with the tunable LSPR bands in the UV and VIS regions along with the various plasmon resonance modes such as dipolar (DR), quadrupolar (QR), multipolar (MR) and higher order (HO). Furthermore, the Ag atom sublimation demonstrates a significant role in the dewetting process, which significantly alters the size, shape and composition of alloy NPs, giving a rise to the development of AuPt NPs. In specific, the LSPR response attenuates with the sublimation, however, as the AuPt NPs in this study are significantly improved in terms of composition and configuration, i.e. shape, size and spacing, the LSPR responses are much stronger and dynamic as compared to the pure Pt NPs on sapphire in the previous studies. [ABSTRACT FROM AUTHOR]

The modification and control of localized surface plasmon resonance (LSPR) properties of metallic nanoparticles (NPs) has become a vigorous research focus in various fields due to its wide range of applicability in various applications, which can be achieved by the control of surface morphology and elemental composition. In this paper, various configurations and compositions of AgPt and Pt NPs are demonstrated by the solid state dewetting using an auxiliary Ag layer on sapphire (0001) along with their strong dynamic LSPR properties. By the systematic control of Ag/Pt bilayer thickness and temperature, the interconnected AgPt nanoclusters at low temperature (<600 °C) and well-isolated pure Pt NPs at higher temperature (>650 °C) are obtained based on the enhanced diffusion, alloying, surface energy minimization and Ag sublimation. A strong LSPR response in the UV and VIS region is exhibited by the AgPt and Pt NPs depending on the alteration of size, shape, uniformity and elemental compositions. In particular, the AgPt NPs show the stronger plasmonic responses and it gradually attenuates with the sublimation of Ag atoms which results in the development of Pt NPs. In comparison with the previous study on the pure Pt NPs on sapphire, the Pt NPs in this study are significantly improved in terms of shape, size and spacing, whose LSPR responses are much stronger and dynamic. The auxiliary diffusion enhancement by Ag atoms leads to the rapid dewetting of AgPt NPs while the Ag sublimation assists the evolution of well-developed Pt NPs due to the vacancy creation and removal of material during mass transport. The tunability of surface morphologies and LSPR properties of AgPt and Pt NPs are systematically demonstrated by the methodical control of Ag/Pt bilayer thickness. • Fabrication of Ag x Pt 1-x and Pt NPs by the solid-state dewetting of Ag/Pt bi-layers with various alloy compositions. • Demonstration of improved LSPR response, peak shift and absorption band evolution. • Demonstration of finite-difference time domain simulations for various Ag x Pt 1-x and Pt NPs. • Systematic structural and optical characterizations of Ag x Pt 1-x and Pt NPs. [ABSTRACT FROM AUTHOR]

Multi-metallic alloy nanoparticles (MNPs) can offer valuable opportunities to meet the various demands of applications. MNPs consist of various noble metallic elements can combine diverse electronic, optical and catalytic properties in a single NP configuration, thus taking the advantage of each element. In this paper, the fabrication of tri- and quad- metallic alloy NPs with noble elements (Ag, Au, Pd and Pt) and the corresponding localized surface plasmon resonance (LPSR) properties are systematically demonstrated. Tri- and quad-metallic alloy NPs come in various size and configurations by the solid-state dewetting of Ag/Au/Pd/Pt quad-layers on sapphire (0001). Tri-metallic AuPdPt NPs are demonstrated by the systematic control of growth temperature along with the significant Ag atom sublimation. Strongly enhanced and tunable LPSR is exerted in the UV-VIS regions depending upon the size, configuration, spacing and elemental composition of the MNPs. The size dependent LSPR response of MNPs is discussed based on the absorption and scattering along with the excitation of dipolar, quadrupolar, high order and multipolar resonance modes. The MNPs exhibit much stronger and dynamic LSPR bands as compared with the monometallic Pt and Pd NPs with the comparable size and configurations. [ABSTRACT FROM AUTHOR]

Three-dimensional carbon nanofiber (3D-CNF)-supported hollow copper sulfide (HCuS) spheres were synthesized by the facile hydrothermal method. The morphology of the as-synthesized HCuS@3D-CNF composite clearly revealed that the 3D-CNFs act as a basement for HCuS spheres. The electrochemical performance of as-synthesized HCuS@3D-CNFs was evaluated by cyclic voltammetry (CV) tests, gravimetric charge–discharge (GCD) tests, and Nyquist plots. The obtained results revealed that the HCuS@3D-CNFs exhibited greater areal capacitance (4.6 F/cm2) compared to bare HCuS (0.64 F/cm2) at a current density of 2 mA/cm2. Furthermore, HCuS@3D-CNFs retained excellent cyclic stability of 83.2% after 5000 cycles. The assembled asymmetric device (HCuS@3D-CNFs//BAC) exhibits an energy density of 0.15 mWh/cm2 with a working potential window of 1.5 V in KOH electrolyte. The obtained results demonstrate that HZnS@3D-CNF nanoarchitectonics is a potential electrode material for supercapacitor applications. [ABSTRACT FROM AUTHOR]

Precise control over the configuration, size and density of Au nanoparticles (NPs) has offered an efficient route to enhance and optimize the performance and usability of various NP-based applications. In this study we successfully demonstrate precise control of the configuration, size and density of self-assembled Au nanostructures on 4H-SiC (0001) via systematic variation of the deposition amount, annealing temperature and duration. Depending on the deposition amount at a fixed annealing temperature and duration, the self-assembled Au NPs are successfully fabricated based on the Volmer–Weber growth model, and the NPs nucleate as round dome shapes and evolve into hexagonal nano-crystals with facet formation along with the increased deposition amounts. For the variation of annealing temperature, the Au nanostructures radically develop into two distinct regimes: i.e. irregular Au nano-mounds (regime I) between 400 and 700 °C based on the diffusion limited agglomeration (DLA) model and round dome-shaped droplets (DPs) (regime II) between 750 and 1000 °C. The dwelling time, size and density evolution of the round dome-shaped Au DPs are discussed based on the Ostwald ripening theory. [ABSTRACT FROM AUTHOR]

In recent years, there has been notable progress in developing advanced catalyst materials and improving the performance of Pt-based catalysts for the oxygen reduction reaction (ORR). ORR is pivotal for achieving high energy conversion efficiency in fuel cells and metal-air batteries. Despite extensive research, balancing the activity and stability of electrocatalysts remains challenging. Due to the high cost and limited availability of Pt, there's a focus on developing Pt alloys, hybrid catalysts, and nanostructured materials with enhanced catalytic activity and utilization using cost-effective methods. Hybridizing multiple active components with Pt shows promise for achieving synergistic effects and meeting high-performance targets set by the U.S. Department of Energy for 2025. This review aims to present recent advances and assess the significance of supported and support-free Pt-based electrocatalysts for ORR. It focuses on carbon, inorganic, and hybrid support materials, as well as support-free metal nanostructures, highlighting their key features and catalytic potential. This offers valuable insights into developing novel Pt-based hybrid electrocatalysts for superior ORR performance in energy conversion and storage applications. [Display omitted] • Assessing significance of supported & support-free Pt-based electrocatalysts for ORR. • Synergistic Pt hybridization overcomes material limitations for efficient electrocatalysis. • Insights on Pt-based hybrid electrocatalysts for superior ORR in energy conversion and storage. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

Multi-metallic alloy nanoparticles (NPs) can enable the advanced applications in the energy, biology, electronics, optics and catalysis due to their multi-functionality, wide tunable range and electronic heterogeneity. In this work, various mono-, bi- and tri-metallic nanostructures composed of Ag, Au and Pt are demonstrated on transparent c-plane sapphire (0001) substrates and the corresponding morphological and optical characteristics are thoroughly investigated. The resulting Pt and AuPt NPs in this study demonstrate much enhanced LSPR responses as compared to the pure Pt NPs from the previous studies, which was contributed by the synergistic effect of Au and Pt and improved surface morphology. These results are sharply distinct in terms of surface morphology and elemental variability from those obtained by the dewetting of monometallic Ag, Au and Pt films under the similar growth conditions, which is due to the distinct dewetting kinetics of the bi-layer and tri-layer films. These NPs exhibit strongly enhanced localized surface plasmon resonance (LSPR) bands in the UV-VIS wavelengths such as dipolar, quadrupolar, multipolar and higher order resonance modes depending upon the size and elemental composition of NPs. The LSPR bands are much stronger with the high Ag content and gradually attenuated with the Ag sublimation. Furthermore, the VIS region LSPR bands are readily blue shifted along with the reduction of NP size. The Ag/Pt bi-layers and Ag/Au/Pt tri-layers are systematically dewetted and transformed into various AgPt and AgAuPt nanostructures such as networked, elongated and semispherical configurations by means of enhanced surface diffusion, intermixing and energy minimization along with the temperature control. The sublimation of Ag atoms plays a significant role in the structural and elemental composition of NPs such that more isolated and semispherical Pt and AuPt NPs are evolved from the AgPt and AgAuPt NPs respectively. [ABSTRACT FROM AUTHOR]

Noble metallic nanoparticles (NPs) can exhibit valuable properties such as localized surface plasmon resonance (LSPR) and large surface to volume ratio, which can find various optoelectronic and catalytic applications. In this work, the improved configuration and uniformity of platinum (Pt) NPs are demonstrated by using a sacrificial indium (In) layer via the enhanced solid state dewetting of In-Pt bilayers on sapphire (0001). In a sharp contrast to the conventional dewetting of intrinsic Pt film, the introduction of In component can significantly enhance the global dewetting process and thus can result in the fabrication of well-defined Pt NPs with the improved uniformity. This can be due to the fact that In possess high diffusivity, low surface energy and low sublimation temperature. Upon annealing, the intermixing of In and Pt atoms can occur at the interface due to the inter-diffusion, which forms In-Pt alloy system. As a result, the overall diffusivity and dewetting degree of system can be significantly improved and this can produce more isolated, uniform and semispherical Pt NPs at much lower temperatures as compared to the pure Pt film dewetting. Conveniently, the In atoms preferentially can be removed from the NP matrix by the sublimation even at relatively low temperatures. These Pt NPs exhibit dynamic LSPR band in the UV-visible wavelength based on the excitation of dipolar, quadrupolar and higher order resonance modes. Specifically, the LSPR wavelength can be tuned between ~480 and 580 nm by the fabrication of small to large size Pt NPs with the distinct configuration and interparticle spacing. Furthermore, at a constant Pt thickness, the size, spacing and density of Pt NPs can be readily tuned by the control of In layer thickness. The introduction of sacrificial In component can enable an additional flexibility for the control of surface morphologies of metallic NPs with the low diffusivity materials. [ABSTRACT FROM AUTHOR]

Metallic nanostructures can find various applications such as in optoelectronic devices, nanostructure synthesis and catalytic applications and their applicability vary depending on their size, density and configuration dependent properties. In this paper, the dimensional and configurational evolution of self-assembled palladium (Pd) nanostructures is systematically studied on c -plane sapphire with the control of annealing temperature (AT) and annealing duration with the initial Pd layers of various thicknesses. Depending on the AT, two distinct growth regimes are observed based on the concurrent effect of surface diffusion, surface energy minimization and Pd sublimation: i.e. (i) agglomeration of Pd nano-clusters from voids (500 < AT ≤ 650 °C) and (ii) round nanoparticle (NP) fabrication (650 °C < AT ≤ 900 °C). At 950 °C, due to the sublimation of Pd atoms, substantial decrease in the NP dimension is witnessed and results in the ring patterns around the NPs. Additional investigation is performed at 950 °C to reveal the annealing duration effect on the NP evolution. Due to the dual effect of the Oswald ripening and atom sublimation, initially the dimension of NPs is grown and then gradually decays along with the duration, resulting in an inverted ‘V’ pattern evolution in diameter and height. Moreover, the evolution of optical properties such as absorption band and average reflectance are studied with the corresponding reflectance spectra as a function of wavelength over UV, visible and NIR region. The Raman spectra analysis depicts the variation of lattice vibration peak intensity and position based on the surface morphology of the Pd nanostructures. [ABSTRACT FROM AUTHOR]

Metallic nanostructures (NSs) have been widely adapted in various applications and their physical, chemical, optical and catalytic properties are strongly dependent on their surface morphologies. In this work, the morphological and optical evolution of self-assembled Pt nanostructures on c-plane sapphire (0001) is demonstrated by the control of annealing temperature and dwelling duration with the distinct thickness of Pt films. The formation of Pt NSs is led by the surface diffusion, agglomeration and surface and interface energy minimization of Pt thin films, which relies on the growth parameters such as system temperature, film thickness and annealing duration. The Pt layer of 10 nm shows the formation of overlaying NPs below 650°C and isolated Pt nanoparticles above 700°C based on the enhanced surface diffusion and Volmer-Weber growth model whereas larger wiggly nanostructures are formed with 20 nm thick Pt layers based on the coalescence growth model. The morphologies of Pt nanostructures demonstrate a sharp distinction depending on the growth parameters applied. By the control of dwelling duration, the gradual transition from dense Pt nanoparticles to networks-like and large clusters is observed as correlated to the Rayleigh instability and Ostwald ripening. The various Pt NSs show a significant distinction in the reflectance spectra depending on the morphology evolution: i.e. the enhancement in UV-visible and NIR regions and the related optical properties are discussed in conjunction with the Pt NSs morphology and the surface coverage. [ABSTRACT FROM AUTHOR]

Silver (Ag) nanostructures demonstrate outstanding optical, electrical, magnetic, and catalytic properties and are utilized in photonic, energy, sensors, and biomedical devices. The target application and the performance can be inherently tuned by control of configuration, shape, and size of Ag nanostructures. In this work, we demonstrate the systematical fabrication of various configurations of Ag nanostructures on sapphire (0001) by controlling the Ag deposition thickness at different annealing environments in a plasma ion coater. In particular, the evolution of Ag particles (between 2 and 20 nm), irregular nanoclusters (between 30 and 60 nm), and nanocluster networks (between 80 and 200 nm) are found be depended on the thickness of Ag thin film. The results were systematically analyzed and explained based on the solid-state dewetting, surface diffusion, Volmer–Weber growth model, coalescence, and surface energy minimization mechanism. The growth behavior of Ag nanostructures is remarkably differentiated at higher annealing temperature (750 °C) due to the sublimation and temperature-dependent characteristic of dewetting process. In addition, Raman and reflectance spectra analyses reveal that optical properties of Ag nanostructures depend on their morphology. [ABSTRACT FROM AUTHOR]

Silver (Ag) nanostructures have demonstrated the feasibility of being utilized in various optoelectronic, catalytic, biomedical, and sensor devices due to their excellent surface plasmon resonance characteristics. The geometrical structure, spacing, and spatial arrangement of nanostructures are crucial for controlling the properties and device performance. Herein, we demonstrate the fabrication of various configurations of self-assembled Ag nanostructures on GaN (0001) by the systematic control of deposition thickness and annealing duration. The surface morphology evolution is thoroughly investigated, and the corresponding influence on optical properties is probed. The evolution of Ag nanostructures in response to thermal annealing is described based on the dewetting of thin films, Volmer-Weber growth model, coalescence growth, and surface energy minimization mechanism. For the deposition amount variation between 1 and 100 nm, the Ag nanostructures show gradual morphological transitions such as small nanoparticles (NPs) to enlarged NPs between 1 and 7 nm, elongated nanostructures to cluster networks between 10 and 30 nm, and void evolution with layered nanostructures between 40 and 100 nm. In addition, the annealing duration effect has been studied between 0 and 3600 s, where the Ag nanostructures exhibit the evolution of network-like, elongated and isolated irregular shapes, ascribed to Ostwald's ripening along with Ag sublimation. Furthermore, corresponding Raman, photoluminescence, and reflectance spectra reveal the morphology-dependent behaviors and are discussed based on the phonon, emission band, scattering, absorption, and surface plasmon effect. [ABSTRACT FROM AUTHOR]

The control over the configuration, size, and density of Au nanoparticles (NPs) has offered a promising route to control the spatial confinement of electrons and photons, as a result, Au NPs with a various configuration, size and density are witnessed in numerous applications. In this work, we investigate the evolution of self-assembled Au nanostructures on 4H-SiC (0001) by the systematic variation of annealing temperature (AT) with several deposition amount (DA). With the relatively high DAs (8 and 15 nm), depending on the AT variation, the surface morphology drastically evolve in two distinctive phases, i.e. (I) irregular nano-mounds and (II) hexagonal nano-crystals. The thermal energy activates adatoms to aggregate resulting in the formation of self-assembled irregular Au nano-mounds based on diffusion limited agglomeration at comparatively low annealing temperature, which is also accompanied with the formations of hillocks and granules due to the dewetting of Au films and surface reordering. At high temperature, hexagonal Au nano-crystals form with facets along {111} and {100} likely due to anisotropic distribution of surface energy induced by the increased volume of NPs. With the small DA (3 nm), only dome shaped Au NPs are fabricated along with the variation of AT from low to elevated temperature. [ABSTRACT FROM AUTHOR]

A unique UV photodetector architecture of MoS 2 /ZnO/HNPs is explored for the enhanced UV photo-response. The hybrid configuration offers greatly improved localized surface plasmon resonance (LSPR) and sufficient absorption as well as efficient transmittance of 2-D transition metal dichalcogenide MoS 2 nanoflakes. [Display omitted] • Demonstration of novel hybrid photodetector architecture of MoS 2 /ZnO/HNP for the significantly increased photocurrent. • Detailed explanation for photocurrent enhancement mechanism by the FDTD simulation. • Detailed morphological, elemental and current–voltage (I-V) study. • Systematic comparison and demonstration of the superior photoresponse. A unique ultraviolet (UV) photodetector architecture of MoS 2 /ZnO/HNP is explored and significantly increased photocurrent (I ph) of 4 × 10−3 A is demonstrated under the 385 nm illumination of 54.9 mW/mm2 at 10 V. This leads to the superior device performance factors: i.e., photoresponsivity of 21,111 mA/W, detectivity of 7.9 × 1011 jones and EQE of 6,800 %. These device performance factors confirm that the proposed photodetector configuration is superior as compared to the similar versions of ZnO-based UV photodetectors. The hybrid MoS 2 /ZnO/HNP architecture is constructed by the 2-D transition metal dichalcogenide MoS 2 nanoflakes, wide-bandgapZnO quantum dots (QDs) and plasomonic PdAg hybrid nanoparticles (HNPs). The increased I ph is related to the hot carrier injection through the strongly improved localized surface plasmon resonance (LSPR) by the PdAg HNPs and additional photo carriers from the 2-D MoS 2 nanoflakes on top of the original photo-induced carriers in the ZnO QD layer. The PdAg HNPs are fabricated by a unique two-step solid-state dewetting (SSD) technique, having the core-shelled PdAg NPs with the high-density small background Ag NPs. This HNP configuration offers very high-density hot spots and significantly improved LSPR. The photocurrent enhancement of MoS 2 /ZnO/HNP architecture is systematically studied by the finite-difference time-domain (FDTD) simulations. [ABSTRACT FROM AUTHOR]

Hybrid metal-oxide (MO)/metal nanostructures (MNSs) have been appealing in widespread optoelectronic devices due to their strong and tunable plasmonic activity encompassing selective scattering and absorption of wavelength depending upon the surface morphology and surrounding dielectric environment. In this paper, the various MO/Au NSs hybrid thin-films are fabricated via the solid-state-dewetting growth of Au NSs and sol-gel deposition of MO top-layers including ZrO x , CeO x , YO x and AlO x. Over 450% enhancements in maximum absorption are observed along with the peak redshift of 168 nm for the series of MO/Au NS films. The overall plasmonic properties undergo three regimes by the systematical control of film morphology: (I) Rapid enhancement, (II) Slow enhancement and (III) Decay. The optical evolution is correspondingly investigated with the assistant of finite-different time-domain (FDTD) calculation. This work may give an aid to the photo-electronic applications, such as photovoltaics, sensing and surface enhanced Raman scattering, based on hybrid MNSs especially on control of their plasmonic properties. Unlabelled Image • Metallic oxide (MO)/Au nanoparticle (NPs) hybrid films with ZrO x , CeO x , YO x , and AlO x • Over 450% enhancement in NP absorption with a simultaneous maximum redshift of 168 nm • Accurate morphological modeling and spectral calculation via FDTD • Promising for surface functionalization in optical and optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this paper, the modified solid-state dewetting (MSSD) of well-defined and various uniform Pt nanostructures is demonstrated by the auxiliary diffusion enhancement. The MSSD utilizes the introduction of metallic indium (In) layers with high diffusivity in between sapphire and platinum (Pt) layer, through which the global diffusion and dewetting of metallic atoms can be significantly enhanced. Subsequently, the In atoms can be sublimated from the NP matrix, resulting in the formation of pure Pt NPs. By the systematic control of In and Pt bi-layer thickness, various areal density, size and configuration of Pt NPs are demonstrated. The In2 nm/Pt2 nm bilayers establish very small and highly dense NPs throughout the temperature range due to the early maturation of growth. Intermediate size of NPs is demonstrated with the In45 nm/Pt15 nm bilayers with the much improved interparticle spacings by annealing between 650 and 900 °C for 450 s. Finally, the In30 nm/Pt30 nm bilayers demonstrate the widely connected network-like nanostructures. In addition, the finite difference time domain (FDTD) simulation is employed to exploit the local electric field distributions at resonance wavelengths. The dewetting characteristics of In/Pt bilayers is systematically controlled by the modifications of layer thickness and annealing temperature and is systematically described based on the diffusion of atoms, Rayleigh instability and surface energy minimization mechanism. The optical properties demonstrate dynamic and widely tunable localized surface plasmon resonance (LSPR) responses depending upon the various surface morphologies of Pt nanostructures. [ABSTRACT FROM AUTHOR]