Major Role of Multiscale Entropy Evolution in Complex Systems and Data Science.

Complex systems are prevalent in various disciplines encompassing the natural and social sciences, such as physics, biology, economics, and sociology. Leveraging data science techniques, particularly those rooted in artificial intelligence and machine learning, offers a promising avenue for comprehending the intricacies of complex systems without necessitating detailed knowledge of underlying dynamics. In this paper, we demonstrate that multiscale entropy (MSE) is pivotal in describing the steady state of complex systems. Introducing the multiscale entropy dynamics (MED) methodology, we provide a framework for dissecting system dynamics and uncovering the driving forces behind their evolution. Our investigation reveals that the MED methodology facilitates the expression of complex system dynamics through a Generalized Nonlinear Schrödinger Equation (GNSE) that thus demonstrates its potential applicability across diverse complex systems. By elucidating the entropic underpinnings of complexity, our study paves the way for a deeper understanding of dynamic phenomena. It offers insights into the behavior of complex systems across various domains.

From multi-segmented to core/shell nanorods: morphology evolution in Fe-Au nanorods by tuning fabrication conditions.

Aiming to obtain hybrid magneto-plasmonic nanostructures, we have developed multisegmented and core/shell structured Fe-Au nanorods using template assisted electrochemical deposition. A facile method of tuning the growth pattern of multisegmented nanorods into core/shell structured is demonstrated. With a precise control of current density and deposition time, a brick-stacked wire like growth led to the formation of hollow nanotubes that could be further tuned to multilayered hollow nanotubes and core/shell structured nanorods. TEM imaging and STEM-EELS technique were used to explore the morphology, microstructure and the distribution of Au and Fe in the nanorods. The easy magnetization direction was found to be perpendicular to the nanorods' growth direction in the segmented nanorods. On the other hand, core/shell nanorods exhibited isotropic behavior. Our findings provide deeper insights into the fabrication of hybrid nanorods and the opportunity to tune the fabrication method to vary their morphology accordingly. Such studies will benefit design of hybrid nanorods with specific morphologies and physical properties and hence their integration into sensing, spintronics and other potential biomedical and technological applications.

Synthesis of Graphene Oxide from Sugarcane Dry Leaves by Two-Stage Pyrolysis.

Natural or synthetic graphite as precursors for the preparation of graphene oxide (GO) have constraints due to their limited availability, high reaction temperature for processing of synthetic graphite and higher generation cost. The use of oxidants, long reaction duration, the generation of toxic gases and residues of inorganic salts, the degree of hazard and low yield are some of the disadvantages of the oxidative-exfoliation methods. Under these circumstances, biomass waste usage as a precursor is a viable alternative. The conversion of biomass into GO by the pyrolysis method is ecofriendly with diverse applications, which partially overcomes the waste disposal problem encountered by the existing methods. In this study, graphene oxide (GO) is prepared from dry leaves of sugarcane plant through a two-step pyrolysis method using ferric (III) citrate as a catalyst, followed by treatment with conc. H2SO4. The synthesized GO is analyzed by UV-Vis., FTIR, XRD, SEM, TEM, EDS and Raman spectroscopy. The synthesized GO has many oxygen-containing functional groups (-OH, C-OH, COOH, C-O). It shows a sheet-like structure with a crystalline size of 10.08 nm. The GO has a graphitic structure due to the Raman shift of G (1339 cm-1) and D (1591 cm-1) bands. The prepared GO has multilayers due to the ratio of 0.92 between ID and IG. The weight ratios between carbon and oxygen are examined by SEM-EDS and TEM-EDS and found to be 3.35 and 38.11. This study reveals that the conversion of sugarcane dry leaves into the high-value-added material GO becomes realistic and feasible and thus reduces the production cost of GO.

Intrinsic efficiency limits in low-bandgap non-fullerene acceptor organic solar cells.

In bulk heterojunction (BHJ) organic solar cells (OSCs) both the electron affinity (EA) and ionization energy (IE) offsets at the donor-acceptor interface should equally control exciton dissociation. Here, we demonstrate that in low-bandgap non-fullerene acceptor (NFA) BHJs ultrafast donor-to-acceptor energy transfer precedes hole transfer from the acceptor to the donor and thus renders the EA offset virtually unimportant. Moreover, sizeable bulk IE offsets of about 0.5 eV are needed for efficient charge transfer and high internal quantum efficiencies, since energy level bending at the donor-NFA interface caused by the acceptors' quadrupole moments prevents efficient exciton-to-charge-transfer state conversion at low IE offsets. The same bending, however, is the origin of the barrier-less charge transfer state to free charge conversion. Our results provide a comprehensive picture of the photophysics of NFA-based blends, and show that sizeable bulk IE offsets are essential to design efficient BHJ OSCs based on low-bandgap NFAs.

Compact broadband ( O, E, S, C, L & U bands) silicon TE-pass polarizer based on ridge waveguide adiabatic S-bends.

A compact, ultra-broadband and high-performance silicon TE-pass polarizer is proposed and demonstrated experimentally. It is based on partially-etched (ridge) waveguide adiabatic S-bends, input/output tapers and side gratings on a silicon-on-insulator (SOI) platform. A compact footprint and weak back reflections are obtained due to the bent waveguide and the tapers, respectively. An extremely high extinction ratio is achieved by scattering the undesired light in the slab section using the side gratings. The 3D FDTD simulations show a TE loss less than 0.3 dB and an extinction ratio greater than 30 dB over a 500 nm wavelength range (1200 nm to 1700 nm). Measured results show a high TM loss (> 35 dB) and a low TE insertion loss (< 1.5 dB), over a 200 nm wavelength range (1450 nm to 1650 nm). The measured TE loss is < 0.6 dB at a communication wavelength of 1550 nm. The footprint of the optimized design is 65 µm × 20 µm.

Enhanced photocatalytic hydrogen evolution from organic semiconductor heterojunction nanoparticles.

Photocatalysts formed from a single organic semiconductor typically suffer from inefficient intrinsic charge generation, which leads to low photocatalytic activities. We demonstrate that incorporating a heterojunction between a donor polymer (PTB7-Th) and non-fullerene acceptor (EH-IDTBR) in organic nanoparticles (NPs) can result in hydrogen evolution photocatalysts with greatly enhanced photocatalytic activity. Control of the nanomorphology of these NPs was achieved by varying the stabilizing surfactant employed during NP fabrication, converting it from a core-shell structure to an intermixed donor/acceptor blend and increasing H2 evolution by an order of magnitude. The resulting photocatalysts display an unprecedentedly high H2 evolution rate of over 60,000 µmol h-1 g-1 under 350 to 800 nm illumination, and external quantum efficiencies over 6% in the region of maximum solar photon flux.

Aqueous Zinc-Ion Storage in MoS2 by Tuning the Intercalation Energy.

Aqueous Zn-ion batteries present low-cost, safe, and high-energy battery technology but suffer from the lack of suitable cathode materials because of the sluggish intercalation kinetics associated with the large size of hydrated zinc ions. Herein we report an effective and general strategy to transform inactive intercalation hosts into efficient Zn2+ storage materials through intercalation energy tuning. Using MoS2 as a model system, we show both experimentally and theoretically that even hosts with an originally poor Zn2+ diffusivity can allow fast Zn2+ diffusion. Through simple interlayer spacing and hydrophilicity engineering that can be experimentally achieved by oxygen incorporation, the Zn2+ diffusivity is boosted by 3 orders of magnitude, effectively enabling the otherwise barely active MoS2 to achieve a high capacity of 232 mAh g-1, which is 10 times that of its pristine form. The strategy developed in our work can be generally applied for enhancing the ion storage capacity of metal chalcogenides and other layered materials, making them promising cathodes for challenging multivalent ion batteries.

TiO2-supported Pt single atoms by surface organometallic chemistry for photocatalytic hydrogen evolution.

A platinum complex, (CH3)2Pt(COD), is grafted via surface organometallic chemistry (SOMC) on morphology-controlled anatase TiO2 to generate single, isolated Pt atoms on TiO2 nano-platelets. The resulting material is characterized by FT-IR, high resolution scanning transmission electron microscopy (HRSTEM), NMR, and XAS, and then used to perform photocatalytic water splitting. The photocatalyst with SOMC-grafted Pt shows superior performance in photocatalytic hydrogen evolution and strongly suppresses the backwards reaction of H2 and O2 forming H2O under dark conditions, compared to the photocatalyst prepared by impregnation at the same Pt loading. However, single Pt atoms on this surface also rapidly coalesce into nanoparticles under photocatalytic conditions. It is also found that adsorption of CO gas at room temperature also triggers the aggregation of Pt single atoms into nanoparticles. A detailed mechanism is investigated for the mobility of Pt in the formation of its carbonyls using density functional theory (DFT) calculations.

Mesoporous Reduced Graphene Oxide as a High Capacity Cathode for Aluminum Batteries.

Research in the field of aluminum batteries has focused heavily on electrodes made of carbonaceous materials. Still, the capacities reported for these multivalent systems remain stubbornly low. It is believed that a high structural quality of graphitic carbons and/or specific surface areas of >1000 m2 g-1 are key factors to obtain optimal performance and cycling stability. Here an aluminum chloride battery is presented in which reduced graphene oxide (RGO) powder, dried under supercritical conditions, is used as the active cathode material and niobium foil as the current collector. With a specific surface area of just 364 m2 g-1 , the RGO enables a gravimetric capacity of 171 mAh g-1 at 100 mA g-1 and remarkable stability over a wide range of current densities (<15% decrease over 100 cycles in the interval 100-20000 mA g-1 ). These properties, up to now achieved only with much larger surface area materials, result from the cathode's tailored mesoporosity. The 20 nm wide mesopores facilitate the movement of the chloroaluminate ions through the RGO, effectively minimizing the inactive mass content of the electrode. This more than compensates for the ordinary micropore volume of the graphene powder.

Spark Plasma Sintering (SPS)-Assisted Synthesis and Thermoelectric Characterization of Magnéli Phase V6O11.

The Magnéli phase V6O11 was synthesized in gram amounts from a powder mixture of V6O11/V7O13 and vanadium metal, using the spark plasma sintering (SPS) technique. Its structure was determined with synchrotron X-ray powder diffraction data from a phase-pure sample synthesized by conventional solid-state synthesis. A special feature of Magnéli-type oxides is a combination of crystallographic shear and intrinsic disorder that leads to relatively low lattice thermal conductivities. SPS prepared V6O11 has a relatively low thermal conductivity of κ = 2.72 ± 0.06 W (m K)-1 while being a n-type conductor with an electrical conductivity of σ = 0.039 ± 0.005 (µΩ m)-1, a Seebeck coefficient of α = -(35 ± 2) µV K-1, which leads to a power factor of PF = 4.9 ± 0.8 × 10-5W (m K2)-1 at ∼600 K. Advances in the application of Magnéli phases are mostly hindered by synthetic and processing challenges, especially when metastable and nanostructured materials such as V6O11 are involved. This study gives insight into the complications of SPS-assisted synthesis of complex oxide materials, provides new information about the thermal and electrical properties of vanadium oxides at high temperatures, and supports the concept of reducing the thermal conductivity of materials with structural building blocks such as crystallographic shear (CS) planes.

Morphology control of anatase TiO2 for well-defined surface chemistry.

A specific allotrope of titanium dioxide (anatase) was synthesized both with a standard thermodynamic morphology ({101}-anatase) and with a highly anisotropic morphology ({001}-anatase) dominated by the {001} facet (81%). The surface chemistry of both samples after dehydroxylation was studied by 1H NMR and FT-IR. The influence of surface fluorides on the surface chemistry was also studied by 1H NMR, FT-IR and DFT. Full attribution of the IR spectra of anatase with dominant {001} facets could be provided based on experimental data and further confirmed by DFT. Our results showed that chemisorbed H2O molecules are still present on anatase after dehydroxylation at 350 °C, and that the type of surface hydroxyls present on the {001} facet is dependent on the presence of fluorides. They also provided general insight into the nature of the surface species on both fluorinated and fluorine-free anatase. The use of vanadium oxychloride (VOCl3) allowed the determination of the accessibility of the various OH groups spectroscopically observed.

Droop-free AlxGa1-xN/AlyGa1-yN quantum-disks-in-nanowires ultraviolet LED emitting at 337 nm on metal/silicon substrates.

Currently the AlGaN-based ultraviolet (UV) solid-state lighting research suffers from numerous challenges. In particular, low internal quantum efficiency, low extraction efficiency, inefficient doping, large polarization fields, and high dislocation density epitaxy constitute bottlenecks in realizing high power devices. Despite the clear advantage of quantum-confinement nanostructure, it has not been widely utilized in AlGaN-based nanowires. Here we utilize the self-assembled nanowires (NWs) with embedding quantum-disks (Qdisks) to mitigate these issues, and achieve UV emission of 337 nm at 32 A/cm2 (80 mA in 0.5 × 0.5 mm2 device), a turn-on voltage of ~5.5 V and droop-free behavior up to 120 A/cm2 of injection current. The device was grown on a titanium-coated n-type silicon substrate, to improve current injection and heat dissipation. A narrow linewidth of 11.7 nm in the electroluminescence spectrum and a strong wavefunctions overlap factor of 42% confirm strong quantum confinement within uniformly formed AlGaN/AlGaN Qdisks, verified using transmission electron microscopy (TEM). The nitride-based UV nanowires light-emitting diodes (NWs-LEDs) grown on low cost and scalable metal/silicon template substrate, offers a scalable, environment friendly and low cost solution for numerous applications, such as solid-state lighting, spectroscopy, medical science and security.

Plasma-Assisted Synthesis of NiCoP for Efficient Overall Water Splitting.

Efficient water splitting requires highly active, earth-abundant, and robust catalysts. Monometallic phosphides such as Ni2P have been shown to be active toward water splitting. Our theoretical analysis has suggested that their performance can be further enhanced by substitution with extrinsic metals, though very little work has been conducted in this area. Here we present for the first time a novel PH3 plasma-assisted approach to convert NiCo hydroxides into ternary NiCoP. The obtained NiCoP nanostructure supported on Ni foam shows superior catalytic activity toward the hydrogen evolution reaction (HER) with a low overpotential of 32 mV at -10 mA cm-2 in alkaline media. Moreover, it is also capable of catalyzing the oxygen evolution reaction (OER) with high efficiency though the real active sites are surface oxides in situ formed during the catalysis. Specifically, a current density of 10 mA cm-2 is achieved at overpotential of 280 mV. These overpotentials are among the best reported values for non-noble metal catalysts. Most importantly, when used as both the cathode and anode for overall water splitting, a current density of 10 mA cm-2 is achieved at a cell voltage as low as 1.58 V, making NiCoP among the most efficient earth-abundant catalysts for water splitting. Moreover, our new synthetic approach can serve as a versatile route to synthesize various bimetallic or even more complex phosphides for various applications.

An Oxygen-Insensitive Hydrogen Evolution Catalyst Coated by a Molybdenum-Based Layer for Overall Water Splitting.

For overall water-splitting systems, it is essential to establish O2 -insensitive cathodes that allow cogeneration of H2 and O2 . An acid-tolerant electrocatalyst is described, which employs a Mo-coating on a metal surface to achieve selective H2 evolution in the presence of O2 . In operando X-ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O2 gas permeation, impeding contact with active Pt. Photocatalytic overall water splitting proceeded using MoOx /Pt/SrTiO3 with inhibited water formation from H2 and O2 , which is the prevailing back reaction on the bare Pt/SrTiO3 photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membraneless electrolysis and photocatalysis.

Periodic Mesoporous Organosilica Nanoparticles with Controlled Morphologies and High Drug/Dye Loadings for Multicargo Delivery in Cancer Cells.

Despite the worldwide interest generated by periodic mesoporous organosilica (PMO) bulk materials, the design of PMO nanomaterials with controlled morphology remains largely unexplored and their properties unknown. In this work, we describe the first study of PMO nanoparticles (NPs) based on meta-phenylene bridges, and we conducted a comparative structure-property relationship investigation with para-phenylene-bridged PMO NPs. Our findings indicate that the change of the isomer drastically affects the structure, morphology, size, porosity and thermal stability of PMO materials. We observed a much higher porosity and thermal stability of the para-based PMO which was likely due to a higher molecular periodicity. Additionally, the para isomer could generate multipodal NPs at very low stirring speed and upon this discovery we designed a phenylene-ethylene bridged PMO with a controlled Janus morphology. Unprecedentedly high payloads could be obtained from 40 to 110 wt % regardless of the organic bridge of PMOs. Finally, we demonstrate for the first time the co-delivery of two cargos by PMO NPs. Importantly, the cargo stability in PMOs did not require the capping of the pores, unlike pure silica, and the delivery could be autonomously triggered in cancer cells by acidic pH with nearly 70 % cell killing.

Biodegradable Oxamide-Phenylene-Based Mesoporous Organosilica Nanoparticles with Unprecedented Drug Payloads for Delivery in Cells.

We describe biodegradable mesoporous hybrid nanoparticles (NPs) in the presence of proteins and their applications for drug delivery. We synthesized oxamide phenylene-based mesoporous organosilica nanoparticles (MON) in the absence of a silica source which had remarkably high organic content and high surface areas. Oxamide functions provided biodegradability in the presence of trypsin model proteins. MON displayed exceptionally high payloads of hydrophilic and hydrophobic drugs (up to 84 wt %), and a unique zero premature leakage without the pore capping, unlike mesoporous silica. MON were biocompatible and internalized into cancer cells for drug delivery.

Tunable Nanocarrier Morphologies from Glycopolypeptide-Based Amphiphilic Biocompatible Star Copolymers and Their Carbohydrate Specific Intracellular Delivery.

Nanocarriers with carbohydrates on the surface represent a very interesting class of drug-delivery vehicles because carbohydrates are involved in biomolecular recognition events in vivo. We have synthesized biocompatible miktoarm star copolymers comprising glycopolypeptide and poly(ε-caprolactone) chains using ring-opening polymerization and "click chemistry". The amphiphilic copolymers were self-assembled in water into morphologies such as nanorods, polymersomes, and micelles with carbohydrates displayed on the surface. We demonstrate that the formation of nanostructure could be tuned by chain length of the blocks and was not affected by the type of sugar residue. These nanostructures were characterized in detail using a variety of techniques such as TEM, AFM, cryogenic electron microscopy, spectrally resolved fluorescence imaging, and dye encapsulation techniques. We show that it is possible to sequester both hydrophobic as well as hydrophilic dyes within the nanostructures. Finally, we show that these noncytotoxic mannosylated rods and polymersomes were selectively and efficiently taken up by MDA-MB-231 breast cancer cells, demonstrating their potential as nanocarriers for drug delivery.

Transmission electron microscopy of mercury metal.

Transmission electron microcopy (TEM) analysis of liquid metals, especially mercury (Hg), is difficult to carry out because their specimen preparation poses a daunting task due to the unique surface properties of these metals. This paper reports a cryoTEM study on Hg using a novel specimen preparation technique. Hg metal is mixed with water using sonication and quenched in liquid ethane cryogen. This technique permits research into the morphological, phase and structural properties of Hg at nanoscale dimensions.

Transmission electron microscopy of carbon-coated and iron-doped titania nanoparticles.

We present a study on the properties of iron (Fe)-doped and carbon (C)-coated titania (TiO2) nanoparticles (NPs) which has been compiled by using x-ray diffraction (XRD), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS). These TiO2 NPs were prepared by using the flame synthesis method. This method allows the simultaneous C coating and Fe doping of TiO2 NPs. XRD investigations revealed that the phase of the prepared NPs was anatase TiO2. Conventional TEM analysis showed that the average size of the TiO2 NPs was about 65 nm and that the NPs were uniformly coated with the element C. Furthermore, from the x-ray energy dispersive spectrometry analysis, it was found that about 8 at.% Fe was present in the synthesized samples. High-resolution TEM (HRTEM) revealed the graphitized carbon structure of the layer surrounding the prepared TiO2 NPs. HRTEM analysis further revealed that the NPs possessed the crystalline structure of anatase titania. Energy-filtered TEM (EFTEM) analysis showed the C coating and Fe doping of the NPs. The ratio of L3 and L2 peaks for the Ti-L23 and Fe-L23 edges present in the core loss electron energy loss spectroscopy (EELS) revealed a +4 oxidation state for the Ti and a +3 oxidation state for the Fe. These EELS results were further confirmed with XPS analysis. The electronic properties of the samples were investigated by applying Kramers-Kronig analysis to the low-loss EELS spectra acquired from the prepared NPs. The presented results showed that the band gap energy of the TiO2 NPs decreased from an original value of 3.2 eV to about 2.2 eV, which is quite close to the ideal band gap energy of 1.65 eV for photocatalysis semiconductors. The observed decrease in band gap energy of the TiO2 NPs was attributed to the presence of Fe atoms at the lattice sites of the anatase TiO2 lattice. In short, C-coated and Fe-doped TiO2 NPs were synthesized with a rather cost-effective and comparatively easily scalable method. The presented analysis enables us to predict the excellent efficiency of these NPs for solar-cell and photo-catalysis applications.