Scanning Atomic Force Microscopy Research Articles

TeO2–ZnO (tellurium oxide – Zinc oxide) thin film deposition by the thermionic vacuum arc plasma

In this study, 75TeO2–25ZnO and 70TeO2–30ZnO (mol %) (TZ) glasses were synthesized by using a traditional melt-quenching method. The synthesized TZ glasses were deposited as a thin film using the thermionic vacuum arc (TVA) system. The structure of the deposited TZ thin films and the synthesized TZ bulk glass samples were compared. The structural properties of the TZ thin films and bulk glass samples were determined by using X-ray diffraction (XRD) analysis, Raman spectroscopy, and Fourier Transform Infrared Spectroscopy (FT-IR). The morphological properties of the TZ thin films were obtained by using field emission scanning electron microscopy (FE-SEM) images and atomic force microscopy (AFM). The optical properties of bulk glass samples are obtained with ultraviolet–visible spectrophotometry in the range of 350–1000 nm. Lastly, the electrical properties were obtained by using dielectric spectroscopy. XRD and Raman analysis showed that the TZ thin films had an amorphous structure similar to the synthesized bulk glasses with limited crystallization. The results show homogenous and amorphous thin film structures with few polycrystalline formations.

Role of oxygen vacancies in the structural phase transformations of granular TiO2 thin films

Tailoring the structural phases of titanium dioxide (TiO2) is nowadays highly attracting for diverse applications, ranging from optical coatings, where rutile outperforms anatase, to photocatalysis, where a mix of the two is preferred. In this framework, the very high temperature transformation of anatase to rutile constitutes a big drawback. Here, we investigate the structural transformations of granular TiO2 thin films subjected to thermal treatments in different gaseous environments, such as air, oxygen, and vacuum, with the latter expected to enhance the formation of oxygen vacancies. To this aim, we used a combined approach of X-ray diffraction (XRD), Raman Spectroscopy (RS), Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM), and we demonstrate that the achievement of a crystallization temperature as low as 150 °C for the anatase and 250 °C for the rutile is possible. By using a Gibbs free energy minimization approach, the combination of granular morphology and oxygen vacancies is proposed to tune both the amorphous to anatase transition and the anatase to rutile transformation. Finally, we explore the possibility of a low-dimensional growth of anatase-TiO2 by studying phonon confinement-like effect and crystallization kinetics thanks to time-dependent RS experiments.

The ATPase cycle of the AAA-ATPase protein transporter Bcs1 is highly concerted.

Bcs1, a homo-heptameric transmembrane AAA-ATPase that belongs to the superfamily of AAA proteins, acts as translocation machinery for the folded Rieske iron-sulfur protein (ISP, a key subunit of the mitochondrial complex-III) across the inner mitochondrial membrane. Cryo-EM structures depicted a ring-shaped transporter with two cavities, a cylindrical one formed by the ATPase domains on the matrix surface and a conical one formed by the transmembrane helices. Structures in different nucleotide states (ATPγS, ADP, APO) provided intuitive snapshots of the functional cycle, but the kinetics and structural transitions of the ATPase cycle remain entirely unknown. Here, using high-speed atomic force microscopy (HS-AFM) and HS-AFM line scanning (HS-AFM-LS), we characterized the ATPase cycle of Bcs1 at the single molecule level with sub-millisecond temporal resolution. We determined, in conditions where the molecules are in a continuous ATPase cycle turnover, that the ATP-bound conformational has a lifetime of ∼3700 ms while the lifetime of ADP/APO conformation is much shorter, ∼400 ms. By monitoring the conformational state of the two Bcs1 protomers on the two opposite sides of the ring at microsecond temporal resolution, we found that ATP-binding and -hydrolysis coupled conformational changes are highly concerted. We propose that the opening of the cone cavity to the intermembrane surface through the straightening of the transmembrane helices in the membrane is energetically costly and membrane elasticity drives the resealing of the gate. Overall, our results establish a working mechanism for the ATPase cycle of Bcs1 at the single molecule level and propose a mechanism for how Bcs1 can translocate a folded protein.

High content cellulomics by correlative microscopy

The exponential increase in anthropogenic chemicals in our environment necessitates methods to assess impact prior to their release to predict potential environmental and health impacts. Atomic force microscopy (AFM) and laser scanning confocal microscopy (LSCM) each provide abundant information on cell behaviour. In addition to determining cell morphology and surface ultrastructure, AFM in quantitative imaging (QI) mode probes cellular mechanics and surface biochemistry with minimal applied force, and LSCM offers a window into the cell for imaging fluorescently tagged macromolecules. Data from correlative AFM-LSCM is thus complimentary, providing a comprehensive picture of cellular physiology. I will present a correlative AFM-QI-LSCM assay for the simultaneous real-time imaging of living cells in situ that generates real-time multiplexed data, including cell morphology and mechanics, surface adhesion and ultrastructure, along with the localization of intracellular macromolecules. The broad applicability of the assay is demonstrated using disparate cell types, showing altered surface properties, internal molecular arrangement and oxidative stress in model bacterial, fungal and human cells exposed to 2,4-dichlorophenoxyacetic acid. This correlative microscopy assay is broadly applicable to a variety of cell types and can be used to assess the impact of any multitude of contaminants, alone or in combination.

Loading and co-solvent-triggered release of okanin, a C4 plant key enzyme inhibitor, into/from functional microgels

The constantly growing world population leads to increasing demands for food, which challenges modern agriculture manifold. Pests, such as weeds, require the application of agrochemicals to increase crop yield. Due to the environmental impact of these potentially hazardous chemicals, the demand for more efficient formulations is increasing. Promising formulations consist of easily adaptable carriers from which controllable stimuli release the agrochemicals. Here, we investigated poly(N–vinylcaprolactam) (pVCL)-based microgels as a potential carrier for okanin, an inhibitor of the C4 plant key enzyme phosphoenolpyruvate carboxylase, by combining experiments, molecular simulations, and free energy computations. Dynamic light scattering, scanning transmission electron and atomic force microscopy revealed that pVCL microgels collapse and rigidify upon the loading of okanin. The simulations identified loosely adsorbed okanin and tightly bound okanin mediating inter-chain crosslinks. With increasing okanin concentration, stacking interactions of okanin occur with adsorbed and bound okanin. These findings can explain the experimentally observed collapse and the rigidification of the microgels. Based on the atomistic insights, two poly(N–vinylcaprolactam–co–glycidyl methacrylate) microgels were synthesized, for which a doubled loading capacity of okanin was found. Finally, we investigated the triggered release of okanin using the addition of green solvents as a stimulus both in vitro and in planta. This work establishes a basis for the further optimization of pVCL-based microgels as a carrier for the delivery of polyphenolic agrochemicals.

Indium arsenide single quantum dash morphology and composition for wavelength tuning in quantum dash lasers

InAs quantum dot and dash gain media demonstrate performance benefits, such as lower threshold current densities and reduced temperature sensitivity over quantum wells for lasers operating in the C-band telecommunications window. Quantum dashes are of much interest for their higher gain over quantum dots due to an increased density of states. We combine experimental results and simulations to understand how quantum dash morphology and composition can be used to tune the emission wavelengths of these nanoparticles. Atomic force microscopy (AFM) analysis is performed to determine the effect of growth temperature and sublayer type on InAs/InGaAsP/InP nanoparticle morphology and homogeneity. Uncapped InAs nanoparticles grown by CBE on a GaAs sublayer will have dash-like geometries with heights up to 2.36 nm for growth temperatures of 500–540 °C. GaP sublayers will induce taller quantum dots except for a growth temperature of 530 °C, where quantum dashes form. The dimensions extracted from AFM scans are used in conjunction with photoluminescence data to guide parabolic band simulations of an InAs quantum dash with a GaP or GaAs sublayer and InP cap buried within InGaAsP. The calculated emission energy of a buried 30 × 300 nm quantum dash decreases by ∼100 meV for increasing heights from 1.5 to 2.5 nm, or increases by ∼100 meV by addition of 20% phosphorus in the dash and wetting layers. Modifying the quantum dash height and leveraging the As/P intermixing that occurs between the InAs and InP layers are, thus, most effective for wavelength tuning.

Microscopic studies of binder blending on laboratory recycled asphalt mix

ABSTRACT During blending between the binders in hot mix recycling, two physical processes occur, namely blending due to diffusion and blending due to mechanical agitation. In the present study, an experimental approach is developed to observe these processes directly on the laboratory recycled asphalt mix samples. Atomic Force Microscopy (AFM) and Confocal Laser Scanning Microscopy (CLSM) are used as the probing tools. The binder concentration profile is estimated at different locations around the reclaimed asphalt pavement material (RAPM) aggregate. Diffusion is observed to be predominant in some of these locations, while, in some other locations, mechanical mixing is observed to be predominant. Assuming that pure Fickian diffusion is happening at those diffusion-spots, the coefficient of diffusion is estimated from the concentration profile at those locations. It is envisaged that the proposed approach would provide a microscopic perspective of the extent of blending during the recycling process.

Sr2+ vs. Ca2+ as post-processing ionic crosslinkers: implications for 3D bioprinting of polysaccharide hydrogels in tissue engineering

Among the possible ionic crosslinkers Ca2+ is the most widely used. However, due to its numerous physiological functions, other cations such as Sr2+ may be more suitable depending on the application. Because a systematic comparison is currently lacking, this work aims to compare solutions of CaCl2 and SrCl2 as ionic crosslinkers of alginate- and cellulose-based materials and to investigate their effects on the structural and biological properties of 3D bioprinted scaffolds. In particular, swelling and degradation under cell culture conditions, mechanical properties (with quasi-static compression tests), surface topology (with scanning electron microscopy and atomic force microscopy) and elemental composition were investigated. In addition, cytotoxicity on pancreatic islet cells was assessed by measuring viability, metabolic activity and morphology. The obtained results show that Sr2+-crosslinked scaffolds have higher compressive strength, swell faster and degrade more slowly under cell culture conditions and have a rougher surface. Both crosslinking agents were gentle on the cells, either when directly embedded into scaffolds or in contact with scaffold extracts, and allowed stable culture for 30 days. However, Sr2+-crosslinked scaffolds elicited higher metabolic activity. Overall, Sr2+ are a viable crosslinking alternative to Ca2+ and allow expanding the range of scaffold properties by adjusting the concentration or ratio in a mixed solution.

Investigating CO2 storage properties of Pd(II) and Co(II) chelates of a Schiff's base ligand

A new metal complexes are made from the ligands derived from amoxicillin based Schiff's base coordinated with Pd(II) and Co(II) have been synthesized and characterized via different spectroscopic methods. FT-IR spectroscopy have shown a formation of tetrahedral and square planar geometry for Co(II) and Pd(II) complexes, respectively. Surface morphology was inspected via field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The Brunauer–Emmett–Teller surface area of the metal complexes samples is about 6.63 to 8.71 m2/g, with pore diameters and volume of 0.030–0.0501 cm3/g and 18.39–22.98 nm, respectively. The quadrupole moment of CO2 has a great effect on the adsorption capacity as it is highly diffusible of 21.38, 26.16 cm3.g−1 for Co(II) and Pd(II) complex.

Sphalerite oxidation simulating acidic, circumneutral and alkaline conditions to account for weathering behavior and Zn release

There is little evidence of sphalerite oxidation accounting for interfacial behavior, evolution of its oxidation capacity and kinetics processes under simulated weathering conditions. Accordingly, the present study combines surface analyses of pristine and leached low Fe-bearing and Pb-bearing sphalerite samples (PbS-ZnS) including X-ray Photoelectron Spectroscopy (XPS), Glow Discharge Optical Emission Spectroscopy (GDOES), Raman spectroscopy, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), along with the chemical evolution of leachates obtained after 24 h of mineral contact with 0.1 M NaOH, 0.1 M NaNO3, 0.1 M H2SO4 or 0.1 M HClO4 solution. An electrochemical study using Cyclic voltammetry (CV), Chronopotentiometry (CP), Chronoamperometry (CA), Linear sweep voltammetry (LSV) and Tafel plots (TP) of PbS-ZnS and marmatite-like sphalerite ((Fe, Zn)S) samples were also conducted to evaluate the oxidation capacity of the mineral interfaces in the solutions. Results reveal slow sphalerite oxidation linked to formation and heterogeneous polysulfides distribution, thus defining bare modifications of surface as indicated by SEM, AFM, GDOES, XPS and Raman studies. The highest oxidation was obtained in NaOH solution (NaOH > NaNO3 > HClO4 > H2SO4). While the corresponding Kf·CRb parameters were 1.07 × 10−7 and 3.14 × 10−8 mol·s−1 for PbS-ZnS and (Fe, Zn)S samples, respectively. A clear oxidation trend involving the progressive passivation of (Fe, Zn)S sample was revealed during evolution of sphalerite oxidation, whereas an alternative passive to transpassive oxidation was observed for the PbS-ZnS sample. We suggest weathering mechanisms for sphalerite, and their environmental implications are discussed.

Crystal Plane-Related Oxygen-Evolution Activity of Single Hexagonal Co3 O4 Spinel Particles.

The electrocatalytic activity for the oxygen evolution reaction in alkaline electrolyte of hexagonal spinel Co3 O4 nanoparticles derived using scanning electrochemical cell microscopy (SECCM) is correlated with scanning electron microscopy and atomic force microscopy images of the droplet landing sites. A unique way to deconvolute the intrinsic catalytic activity of individual crystal facets of the hexagonal Co3 O4 spinel particle is demonstrated in terms of the turnover frequency (TOF) of surface Co atoms. The top surface exposing 111 crystal planes displayed a thickness-dependent TOF with a TOF of about 100 s-1 at a potential of 1.8 V vs. RHE and a particle thickness of 100 nm. The edge of the particle exposing (110) planes, however, showed an average TOF of 270±68 s-1 at 1.8 V vs. RHE and no correlation with particle thickness. The higher atomic density of Co atoms on the edge surface (2.5 times of the top) renders the overall catalytic activity of the edge planes significantly higher than that of the top planes. The use of a free-diffusing Os complex in the alkaline electrolyte revealed the low electrical conductivity through individual particles, which explains the thickness-dependent TOF of the top planes and could be a reason for the low activity of the top (111) planes.

A novel electrochemical hybrid platform for sensitive determination of the aminoglycoside antibiotic Kasugamycin residues in vegetables

Kasugamycin residues (KASU), a pest control antibiotic, was reported as an ecosystem threat owing to its over-application in plant protection to meet the growing global need for agronomic products. Therefore, we report herein the first electrochemical sensor for fast and sensitive analysis of KASU in vegetables based on the synergetic hybridization between conducting polyserine film (poly (SER)), and carbon nanomaterials including functionalized multiwalled carbon nanotubes (fMWCNTs) and reduced graphene oxide (rGO). The sensor was characterized morphologically using Scanning electron (SEM) and atomic force Microscopy (AFM), while cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for electrochemical characterization. Under the optimized conditions using differential pulse voltammetry (DPV), the sensor exhibited an outstanding sensitivity and selectivity, with a good linear response of 3–106 µg/mL and an assessed limit of detection and quantification of 0.40 and 1.33 µg/mL, respectively. Furthermore, the electrochemical sensor was effectively applied to quantify KASU in cucumber, zucchini, and carrots with a recovery range 95.5–100.1%, and RSD lower than 4.1% (n = 3), showing its applicability and efficiency for selective analysis of KASU in foodstuffs.

Methods of dislocation structure characterization in AIIIBV semiconductor single crystals

The development pace of advanced electronics raises the demand for semiconductor single crystals and strengthens the requirements to their structural perfection. Dislocation density and distribution pattern are most important parameters of semiconductor single crystals which determine their performance as integrated circuit components. Therefore studies of the mechanisms of dislocation nucleation, slip and distribution are among the most important tasks which make researchers face the choice of suitable analytical methods. This work is an overview of advanced methods of studying and evaluating dislocation density in single crystals. Brief insight has been given on the main advantages and drawbacks of the methods overviewed and experimental data have been presented. The selective etching method (optical light microscopy) has become the most widely used one and in its conventional setup is quite efficient in the identification of scrap defects and in dislocation density evaluation by number of etch pits per vision area. Since the introduction of digital light microscopy and the related transfer from image analysis to pixel intensity matrices and measurement automation, it has become possible to implement quantitative characterization for the entire cross-section of single crystal wafers and analyze structural imperfection distribution pattern. X-ray diffraction is conventionally used for determination of crystallographic orientation but it also allows evaluating dislocation density by rocking curve broadening in double-crystal setup. Secondary electron scanning electron microscopy and atomic force microscopy allow differentiating etch patterns by origin and studying their geometry in detail. Transmission electron microscopy and induced current method allow obtaining micrographs of discrete dislocations but require labor-consuming preparation of experimental specimens. X-ray topography allows measuring bulky samples and also has high resolution but is hardly suitable for industry-wide application due to the high power consumption of measurements.Digital image processing broadens the applicability range of basic dislocation structure analytical methods in materials science and increases the authenticity of experimental results.

Adsorption and corrosion inhibition capability of Rheum ribes root extract (Işgın) for mild steel protection in acidic medium: A comprehensive electrochemical, surface characterization, synergistic inhibition effect, and stability study

The adsorption and inhibitory effect of Rheum ribes (RR) root extracts on mild steel (MS) corrosion in 1 M HCI solution were examined by electrochemical techniques. The characteristics of the electrode surface after exposure to corrosive solutions were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The chemical composition and the distribution of the surface film was examined with energy dispersive X-ray spectroscopy (EDX). The hydrophilic or hydrophobic properties of the MS surface were investigated using contact angle (CA) measurements. According to the findings, molecules of RR root extract adsorb to the metal surface, which form a protective and uniform film. Increasing the concentration of RR root extract improves the resistance of the alloy's surface to corrosion attacks. The extract acts as a mixed-type corrosion inhibitor with dominantly cathodic action. The molecules of the extract predominate the anodic reaction in the presence of iodide ions. Physical interactions are the most important in the extract molecule adsorption. The synergy between the iodide ions and the molecules of the extract improves the extracts protection ability and the film's stability. The film of extract molecules on the surface of the steel reduces surface deterioration and increases hydrophobicity.

2D porphyrin-based MOFs with highly dispersed Pt nanoparticles via in-situ partial reduction strategy from porphyrin embedded with single-atom Pt for enhancing photocatalytic hydrogen production

An efficient and stable 2D MOF TMF-Pt/Pt NPs photocatalyst was prepared by in-situ partial hydrogenation reduction of TMF-Pt with single-atom Pt embedded in porphyrin center to improve photocatalytic hydrogen production. It is important to note that TMF-Pt/Pt NPs has an extremely high photocatalytic hydrogen generation rate (33185.66 µmol·g−1·h−1) in comparison to the majority of previous MOFs photocatalysts, which could be due to the in-situ uniformly grown Pt NPs are very adjacent to the Ti-oxo clusters within the 2D MOFs so that the gradually accumulated electrons around the Ti-oxo clusters via LMCT pathway could instantaneously transfer to Pt NPs through the Schottky injection field effect. Through a series of experimental characterizations, especially atomic force microscopy (AFM) and transmission scanning electron microscope (TEM), confirmed the highly dispersed Pt NPs within the 2D MOFs. This work provided us with a novel idea to realize the uniform distribution of noble metals nanoparticles in the channel cavity of MOFs through an in-situ synthesis strategy, so as to facilitate the more efficient Schottky injection field effect between noble metals nanoparticles and metal clusters of the MOFs, thereby achieving more excellent charge carrier separation efficiency.

Helium plasma immersion ion implantation studies of tungsten and tungsten heavy alloys for fusion plasma facing components

Plasma fusion devices will require plasma-facing components (PFCs) which can withstand the extreme environment at the edge of a hot fusion plasma. Despite the excellent properties of tungsten(W) as a hard refractory metal, adverse effects such as embrittlement, melting, and morphological evolution have been observed in W when it is bombarded by a high-fluence of low-energy ions including helium. This study investigates the effect of helium ion bombardment on pure tungsten and a tungsten heavy alloy (W-HA)(NAECOMET 1000). Pure tungsten and NAECOMET 1000 samples were implanted with 3 keV helium ions with fluences ranging from to , using Plasma Immersion Ion Implantation (PIII). After PIII treatment, samples were analysed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), which revealed differences in surface morphology and topography. Although the melting and cracking of the Ni/Cu binder phase in the NAECOMET 1000 samples was seen under all implantation conditions, the Ni/Cu presence did somewhat slow the formation of W fuzz in comparison to pure tungsten. X-ray diffraction (XRD) studies showed peak shifts increasing with helium ion fluence for both the pure W and NAECOMET 1000 samples, as well as increase in mean crystallite size, confirming the distortion of the lattice. XPS compositional analysis showed a strong oxidation (>97) near the metal surface, after helium PIII treatment, for both pure W and NAECOMET 1000 W-HA samples. Some conclusions about the potential suitability of W-HA materials for fusion plasma PFCs are drawn.

Effect of Different Etching Time on Fabrication of an Optoelectronic Device Based on GaN/Psi

Gallium nitride (GaN)/porous silicon (PSi) film was prepared using a pulsed laser deposition method and 1064 nm Nd: YAG laser for optoelectronic applications and a series of Psi substrates were fabricated using a photoelectrochemical etching method assisted by laser at different etching times for 2.5–15 min at 2.5 min intervals. X-ray diffraction, room-temperature photoluminescence, atomic force microscopy and field emission scanning electron microscopy images, and electrical characteristics in the prepared GaN on the Psi film were investigated. The optimum Psi substrate was obtained under the following conditions: 10 min, 10 mA/cm2, and 24% hydrofluoric acid. The substrate exhibited two highly cubic crystalline structures at (200) and (400) orientations and yellow visible band photoluminescence, and homogeneous pores formed over the entire surface. The pores had steep oval shapes and were accompanied by small dark pores that appeared topographically and morphologically. The GaN/Psi film fabricated through PLD exhibited a high and hexagonal crystallographic texture in the (002) plane. Spectroscopic properties results revealed that the photoluminescence emission of the deposited nano-GaN films was in the ultraviolet band (374 nm) related to GaN material and in the near-infrared band (730 nm) related to the Psi substrate. The topographical and morphological results of the GaN films confirmed that the deposited film contained spherical grains with an average diameter of 51.8 nm and surface roughness of 4.8 nm. The GaN/Psi surface showed a cauliflower-like morphology, and the built-in voltage decreased from 3.4 to 2.7 eV after deposition. The fabricated GaN/Psi film exhibited good electrical characteristics.

Controlled degradation of polycaprolactone-based micropillar arrays.

Herein we demonstrate the fabrication of arrays of micropillars, achieved through the combination of direct laser writing and nanoimprint lithography. By combining two diacrylate monomers, polycaprolactone dimethacrylate (PCLDMA) and 1,6-hexanediol diacrylate (HDDA), two copolymer formulations that, owing to the varying ratios of the hydrolysable ester functionalities present in the polycaprolactone moiety, can be degraded in the presence of base in a controllable manner. As such, the degradation of the micropillars can be tuned over several days as a function of PCLDMA concentration within the copolymer formulations, and the topography greatly varied over a short space of time, as visualised using scanning electron microscopy and atomic force microscopy. Crosslinked neat HDDA was used as a control material, demonstrating that the presence of the PCL was responsible for the ability of the microstructures to degrade in the controlled manner. In addition, the mass loss of the crosslinked materials was minimal, demonstrating the degradation of microstructured surfaces without loss of bulk properties was possible. Moreover, the compatibility of these crosslinked materials with mammalian cells was explored. The influence of both indirect and direct contact of the materials with A549 cells was assessed by profiling indices reflective of cytotoxicity such as morphology, adhesion, metabolic activity, oxidative balance, and release of injury markers. No significant changes in the aforementioned profile were observed in the cells cultured under these conditions for up to 72 h, with the cell-material interaction suggesting these materials may have potential in microfabrication contexts towards biomedical application purposes.

Recent advances in nanoflowers: compositional and structural diversification for potential applications.

In recent years, nanoscience and nanotechnology have emerged as promising fields in materials science. Spectroscopic techniques like scanning tunneling microscopy and atomic force microscopy have revolutionized the characterization, manipulation, and size control of nanomaterials, enabling the creation of diverse materials such as fullerenes, graphene, nanotubes, nanofibers, nanorods, nanowires, nanoparticles, nanocones, and nanosheets. Among these nanomaterials, there has been considerable interest in flower-shaped hierarchical 3D nanostructures, known as nanoflowers. These structures offer advantages like a higher surface-to-volume ratio compared to spherical nanoparticles, cost-effectiveness, and environmentally friendly preparation methods. Researchers have explored various applications of 3D nanostructures with unique morphologies derived from different nanoflowers. The nanoflowers are classified as organic, inorganic and hybrid, and the hybrids are a combination thereof, and most research studies of the nanoflowers have been focused on biomedical applications. Intriguingly, among them, inorganic nanoflowers have been studied extensively in various areas, such as electro, photo, and chemical catalysis, sensors, supercapacitors, and batteries, owing to their high catalytic efficiency and optical characteristics, which arise from their composition, crystal structure, and local surface plasmon resonance (LSPR). Despite the significant interest in inorganic nanoflowers, comprehensive reviews on this topic have been scarce until now. This is the first review focusing on inorganic nanoflowers for applications in electro, photo, and chemical catalysts, sensors, supercapacitors, and batteries. Since the early 2000s, more than 350 papers have been published on this topic with many ongoing research projects. This review categorizes the reported inorganic nanoflowers into four groups based on their composition and structure: metal, metal oxide, alloy, and other nanoflowers, including silica, metal-metal oxide, core-shell, doped, coated, nitride, sulfide, phosphide, selenide, and telluride nanoflowers. The review thoroughly discusses the preparation methods, conditions for morphology and size control, mechanisms, characteristics, and potential applications of these nanoflowers, aiming to facilitate future research and promote highly effective and synergistic applications in various fields.

Understanding molecular and electrochemical charge transfer: theory and computations.

Electron, proton, and proton-coupled electron transfer (PCET) are crucial elementary processes in chemistry, electrochemistry, and biology. We provide here a gentle overview of retrospective and currently developing theoretical formalisms of chemical, electrochemical and biological molecular charge transfer processes, with examples of how to bridge electron, proton, and PCET theory with experimental data. We offer first a theoretical minimum of molecular electron, proton, and PCET processes in homogeneous solution and at electrochemical interfaces. We illustrate next the use of the theory both for simple electron transfer processes, and for processes that involve molecular reorganization beyond the simplest harmonic approximation, with dissociative electron transfer and inclusion of all charge transfer parameters. A core example is the electrochemical reduction of the S2O82- anion. This is followed by discussion of core elements of proton and PCET processes and the electrochemical dihydrogen evolution reaction on different metal, semiconductor, and semimetal (say graphene) electrode surfaces. Other further focus is on stochastic chemical rate theory, and how this concept can rationalize highly non-traditional behaviour of charge transfer processes in mixed solvents. As a second major area we address ("long-range") chemical and electrochemical electron transfer through molecular frameworks using notions of superexchange and hopping. Single-molecule and single-entity electrochemistry are based on electrochemical scanning probe microscopies. (In operando) scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) are particularly emphasized, with theoretical notions and new molecular electrochemical phenomena in the confined tunnelling gap. Single-molecule surface structure and electron transfer dynamics are illustrated by self-assembled thiol molecular monolayers and by more complex redox target molecules. This discussion also extends single-molecule electrochemistry to bioelectrochemistry of complex redox metalloproteins and metalloenzymes. Our third major area involves computational overviews of molecular and electronic structure of the electrochemical interface, with new computational challenges. These relate to solvent dynamics in bulk and confined space (say carbon nanostructures), electrocatalysis, metallic and semiconductor nanoparticles, d-band metals, carbon nanostructures, spin catalysis and "spintronics", and "hot" electrons. Further perspectives relate to metal-organic frameworks, chiral surfaces, and spintronics.