Formation Of Nanostructures Research Articles

Organic-Inorganic Copolymerization Induced Oriented Crystallization for Robust Lightweight Porous Composite.

Porous composites are important in engineering fields for their lightweight, thermal insulation, and mechanical properties. However, increased porosity commonly decreases the robustness, making a trade-off between mechanics and weight. Optimizing the strength of solid structure is a promising way to co-enhance the robustness and lightweight properties. Here, acrylamide and calcium phosphate ionic oligomers are copolymerized, revealing a pre-interaction of these precursors induced oriented crystallization of inorganic nanostructures during the linear polymerization of acrylamide, leading to the spontaneous formation of a bone-like nanostructure. The resulting solid phase shows enhanced mechanics, surpassing most biological materials. The bone-like nanostructure remains intact despite the introduction of porous structures at higher levels, resulting in a porous composite (P-APC) with high strength (yield strength of 10.5MPa) and lightweight properties (density below 0.22 gcm-3). Notably, the density-strength property surpasses most reported porous materials. Additionally, P-APC shows ultralow thermal conductivity (45 mWm-1k-1) due to its porous structure, making its strength and thermal insulation superior to many reported materials. This work provides a robust, lightweight, and thermal insulating composite for practical application. It emphasizes the advantage of prefunctionalization of ionic oligomers for organic-inorganic copolymerization in creating oriented nanostructure with toughened mechanics, offering an alternative strategy to produce robust lightweight materials.

Incorporating κ-carrageenan regulates the gel properties and structural characteristics of corn starch-soy protein isolate based ternary system

A thorough understanding of the interactions in the starch-protein-polysaccharide ternary system is essential for the development of highly stable hydrogel systems. In this work, the effects of different κ-carrageenan (KC) incorporation on the structure and sol-gel performance of the corn starch (CS)-soy protein isolate (SPI) composite system were investigated. As the KC incorporation was raised, the gelatinization temperature increased gradually, but the enthalpy value was reduced (lower system stability, from 9.14 J/g to 8.06 J/g). The structural results show that the higher content of KC decreased the smoothness of the network structure, increased the denseness of the ternary system, and hindered the formation of nanostructures and short-range ordered structures. However, the textural properties (hardness, chewiness, gumminess) and gel strength of the composite gels increased significantly with increasing KC content (from 65.53 g to 181.90 g). This could be due to the enhancement of hydrogen bonding between KC and amylose during the cooling process, forming more stable three-dimensional network structure. This work contributes to the design of multivariate starch-based gel foods.

A novel electrochemical immunosensor based on AuNPs/PNR/CS@MWCNTs-COOH for rapid detecting warning markers-BNP of heart failure caused by myocardial infarction

Heart failure (HF) is an insidious and dangerous disease that significantly impairs a patient’s quality of life and safety. It is not easy to detect in mild cases, and once it progresses to severe stages, deterioration can be rapid and challenging to reverse. Currently, early warning and prognostic risk assessment technologies are lacking, and there is an urgent need for precise early warning, risk assessment and diagnosis and treatment of HF at the cellular or molecular level. In this study, an electrochemical immunosensor based on AuNPs/PNR/CS@MWCNTs-COOH was prepared to detect brain natriuretic peptide (BNP), a biomarker for early warning of HF caused by myocardial infarction. Among them, the CS@MWCNTs-COOH nanocomposites and the polymerized neutral red (PNR) films on the electrode surface effectively enhanced the conductivity of the modified electrodes and significantly increased the specific surface area through the formation of three-dimensional nanostructures. AuNPs loaded on PNR/CS@MWCNTs-COOH provided a stable gold-ammonia bond for the specific antibody loading of BNP, facilitating the development of an electrochemical immunosensor with high selectivity for BNP detection. Furthermore, this work used cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) to improve aspects that influence the immunosensor’s analytical performance. Under ideal conditions, the immunosensor was tested for immunological qualities using differential pulse voltammetry (DPV), resulting in sensitive measurement of BNP concentration in undiluted serum samples.The peak current Ip of the response signal is linearly proportional to the LgCBNP in the range of 1.95 × 10−3 ng mL−1 to 8.0 ng mL−1, with a detection limit of 0.80 × 10−3 ng mL−1 (S/N=3). It can achieve highly sensitive identification and detection of trace BNP in complex biological samples and provide a convenient and efficient method for HF-related marker detection. Furthermore, it also can serve as a scientific basis and a new method for the development of early warning technology for HF and related pathological mechanism research.

Modulating low-temperature interfacial polymerization with NaHCO3 for high-performance ultrathin nanofiltration membranes

Conventional interfacial polymerization (IP) encounters significant challenges in achieving the desired nanofiltration (NF) membrane structure, owing to uncontrolled diffusion and ultrafast polymerization. Our study introduced carbonates into the low-temperature interfacial polymerization (LTIP) process to precisely regulate the diffusion of amine monomers and polymerization kinetics. Carbonates in the aqueous phase restrict the diffusion of amine monomers while promoting the generation of nanobubbles. Further utilization of the low-temperature oil phase not only retards polymerization but also facilitates the formation of foam nanostructures in the polyamide layer. Density functional theory calculations and molecular dynamics simulations revealed the mechanisms underlying the regulation of amine monomer diffusion and gas-bubble release by carbonates and LTIP. The fabricated membrane has a smoother, ultrathin separation layer while maintaining a high permeability of 35.0 L·m−2·h−1·bar−1 (nearly doubled compared with the pristine membrane) and high Na2SO4 rejection of 99.5 %. This study confirms the practicality of the carbonate-modulated LTIP strategy.

Synthesis and evaluation of novel urethane macromonomers for the formulation of fracture tough 3D printable dental materials

3D printing of materials which combine fracture toughness, high modulus and high strength is quite challenging. Most commercially available 3D printing resins contain a mixture of multifunctional (meth)acrylates. The resulting 3D printed materials are therefore brittle and not adapted for the preparation of denture bases. For this reason, this article focuses on toughening by incorporation of triblock copolymers in methacrylate-based materials. In a first step, three urethane dimethacrylates with various alkyl spacer length were synthesized in a one-pot two-step synthesis. Each monomer was combined with 2-phenoxyethyl methacrylate as a monofunctional monomer and a polycaprolactone-polydimethylsiloxane-polycaprolactone triblock copolymer was added as toughener. The formation of nanostructures via self-assembly was proven by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The addition of the triblock copolymer resulted in a strong increase in fracture toughness for all mixtures. The nature of the urethane dimethacrylate had a significant impact on fracture toughness and flexural strength and modulus of the cured materials. Most promising systems were also investigated via dynamic fatigue propagation da/dN measurements, confirming that the toughening also works under dynamic load. By carefully selecting the length of the urethane dimethacrylate spacer and the amount of block copolymer, materials with the desired physical properties could be efficiently formulated. Especially the formulation containing the medium alkyl spacer length (DMA2/PEMA) and 5 wt% BCP1 (block copolymer), exhibits excellent mechanical properties and high fracture toughness.

How substrate surface area and surface curvature determine kinetics and titanate formation during non-hydrothermal alkali treatment of titanium microspheres

Titanium surface nanostructuring using alkali treatment gains significant attention in a wide range of fields, such as biomaterials, (photo)catalysis, (metal/ion) sorption, CO2 capture, electrochromism and sodium-ion batteries. Even though the physicochemical properties and application potentials of the surface nanostructures are fairly well understood, there is still debate about their exact formation mechanism, limiting knowledge based structural control through altered synthesis conditions. Moreover, this knowledge is largely focused on hydrothermal synthesis conditions, whereas non-hydrothermal conditions might provide benefits towards industrial application. Also the impact of substrate properties, rather than chemical reaction conditions, on the nanostructure formation is only limitedly reported in literature. This work reveals new fundamental knowledge of non-hydrothermal alkali treatment of titanium, using microspheres by implementing, for the first time, in-situ hydrogen measurement during alkali treatment in combination with the ex-situ determination of the sodium and oxygen content in the recovered alkali treated samples, providing critical information on the role of dissolution apart from the precipitation process. The effect of surface area and surface curvature on the dissolution and precipitation process, and the resulting impact on the physicochemical properties of the obtained titanate layer is studied. This shows the much larger impact on dissolution in contrast to precipitation, knowledge that is lacking in literature, but important when implementing alkali surface nanostructuring on complex (e.g. 3D printed) substrates, and considering the prospective shift from lab-scale to industry. The Ti dissolution step was found to be mainly controlled by the total surface area, while the rate determining step was found to be the titanate precipitation, not influenced by either surface area or particle size.The changes in oxygen content in the samples after transformation of titanate into TiO2 provided a novel method for its quantification. The microspheres were analysed chemically (Raman), structurally (XRD) and morphologically (SEM, MIP), screening the effect of surface area, particle size and reaction time on the growth behaviour of the titanate layer. The porous layer structurally corresponds to Na2Ti2O4(OH)2 for all evaluated conditions, with pores in the range of 10–600 nm. Increasing surface area and particle size results in local and non-uniform titanate growth, while titanate nanowire and strut formation between the microspheres were enhanced by reduced microsphere size and prolonged reaction times.

Tuning the stability of DNA tetrahedra with base-stacking interactions.

DNA nanotechnology relies on programmable anchoring of regions of single-stranded DNA through base pair hybridization to create nanoscale objects such as polyhedra, tubes, sheets, and other desired shapes. Recent work from our lab measured the energetics of base-stacking interactions and suggested that terminal stacking interactions between two adjacent strands could be an additional design parameter for DNA nanotechnology. Here, we explore that idea by creating DNA tetrahedra held together with sticky ends that contain identical base pairing interactions but different terminal stacking interactions. Testing all 16 possible combinations, we found that the melting temperature of DNA tetrahedra varied by up to 10 °C from altering a single base stack in the design. These results can inform stacking design to control DNA tetrahedra stability in a substantial and predictable way. To that end, we show that a 4 bp sticky end with weak terminal stacking does not form stable tetrahedra, while strengthening the stacks confers high stability with a 46.8 ± 1.2 °C melting temperature, comparable to a 6 bp sticky end with weak stacking. The results likely apply to other types of DNA nanostructures and suggest that terminal stacking interactions play an integral role in formation and stability of DNA nanostructures.

Ultra-small one-dimensional rice-like CoMoO4 nanorods as a promising pseudocapacitive electrode for high-performance supercapacitors

The demand for sustainable energy sources increases as society progresses. Supercapacitors possess a long lifespan, have a high power density, are ecologically sound, and have the ability to rapidly charge and discharge. Among the several binary transition metal oxides (BTMOs), metal molybdates (AMoO4) are notable for their significant redox activity, widespread availability, affordability, and small ecological footprint. The exceptional theoretical capacitance of CoMoO4, resulting from the presence of active cobalt ions, distinguishes it from other materials. However, the synthesis of CoMoO4 in nanostructured forms presents a challenge. This study introduces a straightforward one-pot solvothermal technique for producing ultra-small, one-dimensional (1D) rice-like CoMoO4 nanorods. The electrochemical performance of rice-like CoMoO4 nanorods as a supercapacitor electrode material was thoroughly investigated, along with larger CoMoO4 nanorods made using the hydrothermal process for comparison. The structural, morphological, and surface characteristics of the rice-like CoMoO4 nanorods were comprehensively examined. The nanorods, formed like rice grains, exhibited exceptional ability to store electric charge, with an outstanding specific capacitance of 1608.8 F g−1. They demonstrated remarkable cycling stability, retaining 96 % of their capacitance after numerous charge and discharge cycles, indicating their durability and reliability. The nanorods also exhibited a high rate capability of 71 %, which is crucial for applications that demand quick energy delivery. This capability enables the nanorods to maintain considerable capacitance even at higher charge-discharge rates. The results indicate that rice-like CoMoO4 nanorods can be used as a material in supercapacitors.

Magnetic interactions in chromium adsorption on silicene

Silicon is a material with well established technological applications. Thus, obtaining this material in nanostructured form increases its possibility of integration in the current technology. Silicene, a two-dimensional allotrope of silicon, has a natural compatibility with current silicon-based technology. In this work we use density-functional theory to identify the electronic and magnetic properties of chromium atoms on monolayer and bilayer silicene. We investigate several properties of chromium in silicene, such as dopant solubility limits, site preference for adsorption and charge transfer. We find that magnetization depends on key parameters such as buckling, interlayer distance and adsorption site. Chromium intercalated in silicene bilayers showed a very interesting relation between the buckling of silicene and the total magnetic moment. The larger is the buckling the smaller is the magnetic moment. Our results demonstrate that it is possible to manipulate the magnetic properties of silicene by changing chromium concentration, adsorption site and structural parameters of the host material.

Development of Potential Electrocatalyst: Highly Multiporous WO3–rGO Nanocomposites for Enhancing Electrocatalytic Oxygen Evolution Reactions

AbstractThe development of sustainable energy technologies, such as fuel cells and metal–air batteries, necessitates the use of a highly efficient electrocatalyst for the oxygen evolution process. The fabrication of WO3–rGO nanocomposites results in the formation of a multiporous nanostructure. The catalytic activity of highly multiporous WO3–rGO nanocomposites containing multiporous nanostructures is shown to be significant. The catalyst has the potential to facilitate highly reactive anodic oxygen reactions, hence augmenting the synergistic impact of interfacial charge transfer and the porous structure of WO3–rGO nanocomposites. The findings of this work indicate that the use of WO3–rGO nanocomposites as electrocatalysts exhibits a considerable overpotential value of 350 mV, a Tafel slope of 67 mV dec−1, good stability, roughness factor, and turnover frequency for the process of oxygen evolution in real‐world scenarios.

Elucidating nanostructural organization and photonic properties of butterfly wing scales using hyperspectral microscopy.

Biophotonic nanostructures in butterfly wing scales remain fascinating examples of biological functional materials, with intriguing open questions with regard to formation and evolutionary function. One particularly interesting butterfly species, Erora opisena (Lycaenidae: Theclinae), develops wing scales that contain three-dimensional photonic crystals that closely resemble a single gyroid geometry. Unlike most other gyroid-forming butterflies, E. opisena develops discrete gyroid crystallites with a pronounced size gradient hinting at a developmental sequence frozen in time. Here, we present a novel application of a hyperspectral (wavelength-resolved) microscopy technique to investigate the ultrastructural organization of these gyroid crystallites in dry, adult wing scales. We show that reflectance corresponds to crystallite size, where larger crystallites reflect green wavelengths more intensely; this relationship could be used to infer size from the optical signal. We further successfully resolve the red-shifted reflectance signal from wing scales immersed in refractive index liquids with varying refractive index, including values similar to water or cytosol. Such photonic crystals with lower refractive index contrast may be similar to the hypothesized nanostructural forms in the developing butterfly scales. The ability to resolve these fainter signals hints at the potential of this facile light microscopy method for in vivo analysis of nanostructure formation in developing butterflies.

Photo-annealed electrospun TiO2 nanofibers as ion-storage layer for self-rechargeable Zn-based electrochromic energy storage device

Developing a self-rechargeable transparent electrochromic energy storage device (EESD) is highly demanding for advancing electrochromic technology and energy harvesting capabilities. In this study, we introduce a room-temperature photo-annealing method to fabricate electrospun titanium oxide (TiO2) nanofibers, serving as an ion-storage layer (ISL) on the counter electrode. By monitoring the composition and morphology of the precursor before and after ultraviolet/ozone irradiation, we confirm the formation of oxide nanostructures in electrospun TiO2 nanofibers, which enhances ion transport in the fabricated EESDs. The structural and surface properties of the photo-annealed ISL are comprehensively analyzed using various characterization techniques. Enhanced electrochromic performances are evidenced through cyclic voltammetry, spectroelectrochemical measurements, and charge storage assessments. The Zn-based EESDs with ISL (ISL Zn-EESDs) display rapid electrochemical kinetics, high charge-storing capacities, and long lifespans, with open-circuit potential of 1.2 V, optical contrast of 77 %, discharge capacity of 92 mA h/g, coloration efficiency of 58.63 cm2/C, and 99.9 % efficiency retention up to 250 cycles in both flat and bent states. Furthermore, the practical viability of the ISL Zn-EESDs is demonstrated by powering an LED lamp for several minutes. This approach highlights the potential of ISL Zn-EESDs for developing flexible smart windows, opening up a range of promising applications.

Biomedical Utility of Non-Enzymatic DNA Amplification Reaction: From Material Design to Diagnosis and Treatment.

Nucleic acid nanotechnology has become a promising strategy for disease diagnosis and treatment, owing to remarkable programmability, precision, and biocompatibility. However, current biosensing and biotherapy approaches by nucleic acids exhibit limitations in sensitivity, specificity, versatility, and real-time monitoring. DNA amplification reactions present an advantageous strategy to enhance the performance of biosensing and biotherapy platforms. Non-enzymatic DNA amplification reaction (NEDAR), such as hybridization chain reaction and catalytic hairpin assembly, operate via strand displacement. NEDAR presents distinct advantages over traditional enzymatic DNA amplification reactions, including simplified procedures, milder reaction conditions, higher specificity, enhanced controllability, and excellent versatility. Consequently, research focusing on NEDAR-based biosensing and biotherapy has garnered significant attention. NEDAR demonstrates high efficacy in detecting multiple types of biomarkers, including nucleic acids, small molecules, and proteins, with high sensitivity and specificity, enabling the parallel detection of multiple targets. Besides, NEDAR can strengthen drug therapy, cellular behavior control, and cell encapsulation. Moreover, NEDAR holds promise for constructing assembled diagnosis-treatment nanoplatforms in the forms of pure DNA nanostructures and hybrid nanomaterials, which offer utility in disease monitoring and precise treatment. Thus, this paper aims to comprehensively elucidate the reaction mechanism of NEDAR and review the substantial advancements in NEDAR-based diagnosis and treatment over the past five years, encompassing NEDAR-based design strategies, applications, and prospects.

Enhancing Corrosion Resistance of Titanium Alloys via Hydrothermal Etching: Nanostructure Formation under Varied Temperature Conditions

Enhancing Corrosion Resistance of Titanium Alloys via Hydrothermal Etching: Nanostructure Formation under Varied Temperature Conditions

Photocatalytic, antioxidant, and antibacterial activities of biocompatible MgO flake-like nanostructures created using Piper betle leaf extract

In this study, biocompatible magnesium oxide (MgO) nanostructures were synthesized using an aqueous solution of Piper betle leaf methanolic extract. The color change during the synthesis process, i.e., colorless to dark brown solution, indicates the formation of MgO nano structures which is further confirmed through UV–Visible spectrum that exhibited characteristic absorption band at 329 nm. Results obtained from morphological analysis reveal that MgO nano flakes (MgO NFs) are present as triangular and polyhedral shapes having an average size ranging between 150 and 200 nm with clear lattice fringes. Secondary metabolites were clearly identified from the FTIR spectrum, and they helped in reduction and stabilization during the synthesis of MgO NFs. The XRD pattern displayed Braggs planes of (111), (220), (220), (311), and (222) with a face centered cubic (FCC) structure, which was further confirmed from the SAED pattern using HRTEM analysis. The as-synthesized MgO NFs manifested profound antimicrobial activity against gram positive as well as gram-negative bacteria with favorable biocompatibility. Furthermore, methylene orange dye was degraded almost completely (98.36 %) in the presence of MgO NFs photo catalysts within 1 h of sunlight illumination. In addition, MgO NFs displayed high level of antioxidant properties with recorded IC50 value of 15.89 μg/ml.

Recent progress of high-energy density supercapacitors based on nanostructured nickel oxides

With the progressive demand of portable devices and hybrid electronic vehicles, relevant energy storage options are one of the most important practical necessities. Supercapacitors may play a key role for developing auto electronic advanced tools, because of their specific power density, fast charging capacity, and long-life time. On the other hand, nanostructured materials for supercapacitor electrodes have demonstrated great potential for constructing a reliable as well as efficient gateway for betterment. Nanostructured form of metal oxides, especially nickel oxide (NiO), is one of the most excel material to design high performance supercapacitors. This review deals with a detailed discussion on some fundamental aspects of supercapacitors incusing variety, performance evaluation criteria, and influencing factors for designing high density supercapacitors. Along with these, recent effective strategical approaches for generating high energy density supercapacitors utilizing NiO and their composites are particularly described the inherent performance influencing factors like their physical, chemical, and compositional variations. Finally, upgrading the next generation devices, the commercial application, challenges, and future prospects of the recently developed NiO-based supercapacitor materials are pointed out.

Sustainable Modification of Naturally Available Resources for Metal-Ion Storage Applications

The adoption of naturally abundant resources for energy storage applications represents a pivotal strategy in advancing large-scale sustainable green energy solutions across diverse sectors. This presentation provides an overview of E2MC's approaches to the green modification of naturally occurring materials at a low cost, focusing on their metal-ion energy storage capabilities. Key natural materials discussed include molybdenum disulfides (MoS2), ilmenite and natural graphite minerals, as well as corn waste. (a) The thermal oxidation of MoS2 is explored as a straightforward and effective method to produce layer-structured molybdenum trioxide (α-MoO3) with crystalline defects, showing enhanced Li-ion storage kinetics. The molten salt treatment of MoS2 produces sodium dimolybdate with improved Li-ion and Na-ion storage performances. Additionally, a hybrid nanostructure comprising metastable monoclinic molybdenum trioxide (β-MoO3), hexagonal MoS2 secondary crystals and graphene nanosheets is produced through mechanochemical-molten salt treatment. This hybrid structure exhibits an interesting Li-ion storage performance. (b) Carbonization of largely available corn lignocellulosic waste in the presence of molten salt is discussed as a facile approach for the preparation of biocarbons with appropriate specific surface area, pore volume, and elemental carbon purity. The partial dissolution of biomass impurities into the molten salt enhances the Li-ion and Na-ion storage performance of the biocarbon. Additionally, the treatment of corn-derived silica with Fe2O3 and graphite-derived graphene nanosheets, leads to the preparation of a nanostructure in which ferric oxide particles are coated with iron silicate, and these hybrid nanostructures are integrated with graphene nanosheets, showcasing an interesting Li-ion storage performance. (c) Efficient exfoliation of naturally available graphite minerals in molten salt is introduced leading to the formation of carbon nanostructures with promising applications in both Li-ion and Na-ion storage. The economic and strategic advantages associated with utilizing such naturally available resources for energy storage applications are also discussed. References W. Zhu, A.R. Kamali*, J. Alloy Compd. 932 (2023) 167724W. Zhu, A.R. Kamali*, J Alloy Compd. 968 (2023) 171823A.R. Kamali*, H. Zhao, J. Alloy Compd. 949 (2023) 169819W. Zhu, A.R. Kamali*, J. Alloy Compd. 831(2020) 154781H. Zhao, A. Rezaei, A.R. Kamali*, J. Electrochem. Soc. 169 (2022) 054512A.R. Kamali*, J. Ye, Miner. Eng. 172 (2021) 107175S. Li, A.R. Kamali*, Chem. Eng. Sci. 265 (2023) 118222S. Li, A.R. Kamali*, Gels 9 (2023) 701S. Li, A.R. Kamali*, Colloids Surf. A 656 (2023) 130275H. Fu, A.R. Kamali* et al, Chem. Eng. J. (2023) 146936W. Zhu, A.R. Kamali*, J. Electrochem. Soc. 168 (2021) 046517

Evolution of 2D Nanostructures on Charged Surfaces through the Precipitation of Hydrolyzable Ions

The significance of surface charge at solid-liquid interfaces extends to crucial roles in diverse chemical processes, including crystallization, self-assembly, fuel cell reactions, and heterogeneous catalysis. Building upon the classical mean field description derived from the Gouy–Chapman model, the electrostatic attraction between a charged interface and counterions in solutions prompts oppositely charged ions from the solution to accumulate at the interface, forming an electric double layer (EDL), with distinct properties from those observed in bulk solutions. While the model accounts for the distribution of ions based on their spatial average perpendicular to the surface, the discussion regarding the lateral structure at the interface, particularly the local molecular-level details, is relatively limited.In this study, we explored the interfacial structure of mica, a mineral with an atomically flat surface and intrinsic negative charge, in electrolytes containing different multi-valent cations, utilizing in-situ liquid phase atomic force microscopy (LP-AFM). We find that, as the solution pH is gradually raised, cations precipitate and form a monolayer hydroxide film on mica surface. Divalent ions such as Mg2+, Ni2+, and Co2+, form large continuous monolayers in a manner that aligns with expectations based on classical nucleation theory. For trivalent ions like Al3+, Fe3+, and Cr3+, hydrolyzed species adsorb in increasing amounts as pH is increased. Instead of exhibiting a random distribution, these ions reveal intricate lateral ordering and eventually evolve into an ordered ion network. Upon further pH increase, the ion network undergoes a transition to a discontinuous film with a persistent network of gaps. The links between the surface nanostructure and local surface charge were investigated using three-dimensional fast force mapping (3D FFM) and complementary streaming potential apparatus (SPA) measurements. As films form, an inversion from negative to positive zeta potential on mica is observed through SPA and is accompanied by the appearance of a long-range tip-sample forces through 3D FFM. These findings suggest that electrostatic interactions between positively charged ions/films and a negatively charged substrate stabilize the surface nanostructure. Furthermore, films created by trivalent ions are more strongly charged compared to those formed by divalent ions.The lateral structure at mica-electrolyte interfaces was simulated using a charge-frustrated lattice gas model, where the ions experience competing interactions between short-range chemical bonding and long-range electrostatic forces. For weak charge effects, the film undergoes a first-order transition from sparse adsorbates to large continuous sheets, aligning with the behavior observed with divalent ions. When the charge effect is sufficiently strong, the surface forms various states, including ordered patterns of ions, ion clusters, and microphase-separated partial films, corresponding to the behavior observed with trivalent ions. This study provides molecular-level understanding of how electric fields control the spontaneous formation of interfacial nanostructures, and offers valuable insights into using electric fields to control crystallization processes for the development of functional materials.

Low-Temperature Anodization: An Electrochemical Route to Tailored Nanostructures in Heavily Doped p-Type Silicon for Forming Quantum Dots

This study presents a pioneering electrochemical approach to tailor the anodization outcomes of heavily doped p-type silicon, a subset of low-resistivity semiconductor materials, via low-temperature anodization. Conventionally, anodizing such silicon in hydrofluoric acid at room temperature leads to the formation of coarse porous silicon with negligible photoluminescence (PL) upon exposure to ultraviolet (UV) radiation.In this investigation, we embark on an unconventional path by conducting the anodization process at an exceptionally low temperature of -20°C. This seemingly subtle adjustment, however, triggers a remarkable transformation in the optical characteristics of the silicon substrate. Strikingly, the anodized surface, when illuminated with UV radiation, emits a vibrant and distinct red PL signal (Figure 1), signifying the emergence of quantum confinement effects attributable to nanocrystals, i.e., quantum dots.To substantiate the existence of these nanostructures, we employ advanced characterization techniques, with a focus on transmission electron microscopy (TEM). These rigorous analyses confirm the presence of well-defined silicon nanocrystals, typically measuring within the 3~4 nm range (Figure 2), meeting the prerequisites for quantum confinement effects. Notably, it is worth mentioning that the formation of such nanostructures is unattainable on heavily boron-doped silicon due to its high etching rate.In conclusion, our findings underscore the potential of low-temperature anodization as a versatile tool to tailor the luminescent properties of porous silicon at the nanoscale. This breakthrough not only advances our fundamental comprehension of semiconductor electrochemistry but also holds the promise of driving progress in electrochemical fabricating semiconductor quantum dots and optoelectronics. Figure 1

Binaphthalene-Assisted Axial Chirality in Porphyrins: Toward Solid-State Circularly Polarized Luminescence from Self-Assembled Nanostructures.

Circularly polarized luminescence (CPL) is emerging as an effective tool to study the excited-state optical activity in molecules and their self-assembled nanostructures. Chiral porphyrins are a class of optically active molecules wherein the ground-state chirality has been extensively studied in recent times using circular dichroism (CD) spectroscopy. However, obtaining CPL from porphyrin nanostructures, which would have vast implications in biological applications, has remained an uphill task. In this work, we design and synthesize a pair of chiral porphyrin enantiomers functionalized by axially chiral binaphthalene units at the four meso-positions. The molecule undergoes self-assembly following an isodesmic polymerization model, leading to the formation of a spherical nanostructure possessing opposite chirality. Favorable thermodynamic parameters achieved through the controlled experimental conditions helped drive the self-assembly in the forward direction. The limitations imposed by a large nonradiative decay constant arising due to the aggregation-induced quenching could be overcome by fabricating self-standing polymeric films of the nanostructures. The films exhibited relatively high radiative decay and, more interestingly, good CPL activity with clear mirror image spectra for the nanostructures with opposite chirality. The work on CPL-active solid-state materials opens avenue for the design and synthesis of a variety of porphyrin-based chromophoric systems and their nanoaggregates that can find potential application in the field of chiral biosensing and bioimaging, security tags, and display devices.