Transmission Electron Microscopy Measurements Research Articles

Effects of Cr doping and size reduction on the structural and magnetic properties of α–CoV2O6

We report the effect of Cr-doping on the structural and magnetic properties of powder α–CoV2O6 samples. Samples were synthesized using a wet chemical synthesis method and calcined at temperatures between 350 ℃ and 500 ℃ to promote phase formation. For α–CoV2O6 and Cr-doped α–CoV2O6 samples, a single phase only occurs when the samples are calcined at 450 ℃ and 500 ℃, respectively, as confirmed using powder x-ray diffraction (XRD). Cr-doping results in a compression distortion of the lattice along the c-axis. Transmission electron microscopy (TEM) measurements indicate that Cr-doping causes a reduction in particle size and particle agglomeration. Metamagnetism was observed in field dependence of magnetization, M(μ0H) for α–Co(V1−xCrx)2O6 samples with 0 ≤ x ≤ 0.05. The hysteresis in M(μ0H) curves for μ0H < 5T at 2K indicate that the magnetization is metastable and suggests magnetic irreversibility. Zero-field-cooled (ZFC) and field-cooled (FC) temperature dependence of magnetization, M(T), show antiferromagnetic (AFM) ordering of the α–Co(V1−xCrx)2O6 samples at fields, μ0H ≤ 1T. Increasing field strength to 2.5T causes a transition from the AFM state to a ferrimagnetic (FI) state, and an introduction of spin-glass (SG)-like behavior. At 5T, a transition from the FI state to a ferromagnetic (FM) state and a suppression of SG-like behavior is observed.

Evidence for multiferroicity in single-layer CuCrSe2

Multiferroic materials, which simultaneously exhibit ferroelectricity and magnetism, have attracted substantial attention due to their fascinating physical properties and potential technological applications. With the trends towards device miniaturization, there is an increasing demand for the persistence of multiferroicity in single-layer materials at elevated temperatures. Here, we report high-temperature multiferroicity in single-layer CuCrSe2, which hosts room-temperature ferroelectricity and 120 K ferromagnetism. Notably, the ferromagnetic coupling in single-layer CuCrSe2 is enhanced by the ferroelectricity-induced orbital shift of Cr atoms, which is distinct from both types I and II multiferroicity. These findings are supported by a combination of second-harmonic generation, piezo-response force microscopy, scanning transmission electron microscopy, magnetic, and Hall measurements. Our research provides not only an exemplary platform for delving into intrinsic magnetoelectric interactions at the single-layer limit but also sheds light on potential development of electronic and spintronic devices utilizing two-dimensional multiferroics.

Simultaneous Li-Doping and Formation of SnO2-Based Composites with TiO2: Applications for Perovskite Solar Cells.

Tin oxide (SnO2) has been recognized as one of the beneficial components in the electron transport layer (ETL) of lead-halide perovskite solar cells (PSCs) due to its high electron mobility. The SnO2-based thin film serves for electron extraction and transport in the device, induced by light absorption at the perovskite layer. The focus of this paper is on the heat treatment of a nanoaggregate layer of single-nanometer-scale SnO2 particles in combination with another metal-dopant precursor to develop a new process for ETL in PSCs. The combined precursor solution of Li chloride and titanium(IV) isopropoxide (TTIP) was deposited onto the SnO2 layer. We varied the heat treatment conditions of the spin-coated films comprising double layers, i.e., an Li/TTIP precursor layer and SnO2 nanoparticle layer, to understand the effects of nanoparticle interconnection via sintering and the mixing ratio of the Li-dopant on the photovoltaic performance. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) measurements of the sintered nanoparticles suggested that an Li-doped solid solution of SnO2 with a small amount of TiO2 nanoparticles formed via heating. Interestingly, the bandgap of the Li-doped ETL samples was estimated to be 3.45 eV, indicating a narrower bandgap as compared to that of pure SnO2. This observation also supported the formation of an SnO2/TiO2 solid solution in the ETL. The utilization of such a nanoparticulate SnO2 film in combination with an Li/TTIP precursor could offer a new approach as an alternative to conventional SnO2 electron transport layers for optimizing the performance of lead-halide perovskite solar cells.

Chiral Stacking Identification of Two-Dimensional Triclinic Crystals Enabled by Machine Learning.

Chiral materials possess broken inversion and mirror symmetry and show great potential in the application of next-generation optic, electronic, and spintronic devices. Two-dimensional (2D) chiral crystals have planar chirality, which is nonsuperimposable on their 2D enantiomers by any rotation about the axis perpendicular to the substrate. The degree of freedom to construct vertical stacking of 2D monolayer enantiomers offers the possibility of chiral manipulation for designed properties by creating multilayers with either a racemic or enantiomerically pure stacking order. However, the rapid recognition of the relative proportion of two enantiomers becomes demanding due to the complexity of stacking orders of 2D chiral crystals. Here, we report the unambiguous identification of racemic and enantiomerically pure stackings for layered ReSe2 and ReS2 using circular polarized Raman spectroscopy. The chiral Raman response is successfully manipulated by the enantiomer proportion, and the stacking orders of multilayer ReSe2 and ReS2 can be completely clarified with the help of second harmonic generation and scanning transmission electron microscopy measurements. Finally, we trained an artificial intelligent Spectra Classification Assistant to predict the chirality and the complete crystallographic structures of multilayer ReSe2 from a single circular polarized Raman spectrum with the accuracy reaching 0.9417 ± 0.0059.

Giant polarization in tetragonal-like BiFeO3 film via (Ba,Ca)TiO3 doping

BiFeO3 is a multiferroic material, its tetragonality (T) phase usually exhibits large tetragonality (c/a ratio) and strong ferroelectricity. Unlike the commonly used method of strain engineering via substrate, here we present a general and practical approach for obtaining T-like phase BiFeO3 films through (Ba,Ca)TiO3 doping (BF-BCT). The BF-BCT film coherently grows on the La0.7Sr0.3MnO3/(La0.18Sr0.82)(Al0.59Ta0.41)O3 (001) substrate even at 180 nm thick, implying a very large critical thickness, and shows a large tetragonality of 1.12. Impressively, the films exhibit a giant remanent polarization (2Pr) of 320 μC/cm2, which is higher than the corresponding values of any other lead-free ferroelectric films reported to date. Cross-sectional scanning transmission electron microscopy measurements confirm the presence of the T-like phase in BF-BCT films, where the giant polarization might be attributed to the off-center B-site atom. The BF-BCT films are structurally homogeneous without any precipitation of the second phase. The giant polarization observed in the BF-BCT films indicate their great potential for application in next-generation storage and information devices.

Catalytic Reduction of 4-Nitrophenol and Methylene Blue with Silver Nanoparticles Decorated with Drymoglossum piloselloides Extract

Drymoglossum piloselloides is one of the epiphytic plants that is commonly found in Southeast Asia region. In this study, the ethanol extract of D. piloselloides plant has been used in the green synthesis of silver nanoparticles. The synthesized silver nanoparticles were characterized by ultraviolet-visible (UV-Vis) spectrophotometry, X-ray diffraction (XRD),Fourier-transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM) measurements. The UV-Vis spectrum of silver nanoparticles showed a maximum wavelength at 453 nm. The XRD measurement showed the silver nanoparticles peaks at 38.38°, 44.60°, 64.76°, and 77.62°. The FTIR spectra provided evidence of the interaction between silver and chemicals in the plant extract as a weak signal at 682 cm-1. Meanwhile, TEM revealed an average size of 12.63nm. The synthesised silver nanoparticles were utilised for the reduction of 4-nitrophenol with a conversion percentage of up to 100% with a reduction reaction rate constant of 7.104 s-1. In addition, methylene blue was also successfully reduced with the synthesised silver nanoparticles as the catalyst with a reduction reaction rate constant (k) of 21.150 s-1. This study highlights the superior advantage of utilizing ethanolic extract of D. piloselloides to prepare silver nanoparticles with promising catalytic reduction purposes.

Optical tunability with superlattice hyperbolic metamaterial coatings

Optical tunability is demonstrated with multi-metal hyperbolic metamaterial (HMM) structures on varying substrate surfaces. A systematic uniaxial modeling methodology is adapted from classical approaches to extract the anisotropic permittivity of the films to identify epsilon-near-zero (ENZ) behavior over a wide range of metal volume fractions (φ). The anisotropic model accuracy is quantified by a mean squared error (MSE) with the presented modeling routine resulting in a MSE < 35 for all samples. The optical model thicknesses were verified with transmission electron microscopy (TEM) imaging and measurements. This study also demonstrates the ability to tune the optical responses in the visible-to-infrared frequencies with surface microtexturing and applied strain with HMM coatings on flexible Kapton substrates. Furthermore, the structured films and modeling procedure lay the groundwork for future studies on coupling the anisotropic optical and thermal properties for control over advanced multifunctional thin-film coatings.

Controlled growth of 3R phase niobium diselenide and its properties

Inversion symmetry broken 3R phase transition metal dichalcogenides (TMDs) show fascinating prospects in spintronics, valleytronics, and nonlinear optics. However, the controlled synthesis of 3R phase TMDs is still a great challenge. In this work, two-dimensional 3R-NbSe2 single crystals up to 0.2 mm were synthesized for the first time through chemical vapor deposition method by designing a space-confined system. The crystal size and morphology can be controlled by the location of the stacked substrates and the amount of the Nb2O5 precursor. Scanning transmission electron microscopy and Raman measurements reveal the NbSe2 exhibits a pure 3R stacking mode with relatively weak interlayer van der Waals interactions. Importantly, 3R-NbSe2 shows obvious second harmonic generation signal which intensity intensified as thickness increases. Density functional theory calculations and optical absorption demonstrate the coexistence of metallic and semiconducting optical properties of 3R-NbSe2. We designed a NbSe2/WS2/NbSe2 photodetector utilizing the metallicity of 3R-NbSe2, which shows good performance especially an ultrafast response (6–7 μs, 0.5 ms–7.9 s for Au electrodes in literature). The proposed strategy and findings are of great significance for the growth of many other 3R-TMDs and applications of nonlinear optical and ultrafast devices.

Fast fabrication of High-Yield WS2 nanoscrolls via ultrasound sonication

Transforming the bulk of tungsten disulfide (WS2) into one-dimensional (1D) nanoscrolls has potential applications in a variety of fields. The current methods for fabricating (1D) WS2nanoscrolls suffer from low yields, high temperatures, a complicated fabrication process, and the use of surfactants. We have reported a facile and cost-effective approach for fabricating WS2 nanoscrolls in high yield using ultrasound probe sonication (20 KHz) from bulk WS2 in dimethylformamide (DMF) in two hours. Importantly, this simple method achieves a 90 % WS2 nanoscroll yield.This depends on critical experimental parameters such as the choice of solvent, the initial concentration of WS2, and the sonication time. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements confirm that the nanoscrolls have a closely uniform shape, with an interlayer spacing of ∼ 0.62 nm between adjacent layers of WS2 nanoscrolls. Atomic force microscopy (AFM) reveals that the nanoscrolls have a length of approximately 650 nm and a height profile of 5–10 nm, indicating their formation from multiple layers of WS2. We further investigate the fabricated nanoscrolls using other techniques such as X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy.

THE DESIGN AND CHARACTERIZATION OF MODIFIED POLYTHIOPHENE SUPPORTED PLANT MEDIATED CO-NI BIMETALLIC NANOCOMPOSITES

Ficus mucuso leaf extract was employed as reducing agent in the synthesis of Co-Ni bimetallic nanoparticles (BMNPs) with two precursors namely; Cobalt (ii) nitrate hexahydrate; [CO(NO3)2.6H2O] and nickel (ii) nitrate hexahydrate; [Ni (NO3)2.6H2O]. Afterwards, acid modified polythiophene was synthesized through the in-situ and ex-situ coupling approach. The nanocomposite obtained from the in-situ method was labelled ‘A’ and that of the ex-situ, ‘B’. The in-situ approach was considered to be more appropriate for synthesizing the BMNPs as confirmed by characterization using Fourier Transform Infrared Spectroscopy (FTIR), X-Ray diffraction analysis (XRD), Energy dispersive X-ray (EDX) analysis, Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) and Scanning electron microscopy (SEM) techniques. The hexagonal cobalt and the cubic nickel were investigated using XRD to determine the particle sizes taking Debye-Scherrer’s equation to be around 14.495nm for sample A and 15.689nm for sample B. This was reported to be responsible for the corresponding intense peak at A over B. The SEM and TEM measurements portray good correlation indicating the presence of agglomerates in sample B. The EDS analysis taken reported a higher weight of the cobalt and nickel compositions in A than in B. TGA explained the higher decomposition rate of B than A. Also, a more pronounced intense peak was observed in A than in B using FTIR technique. This comparison of both samples makes in-situ synthesis unquestionably the best because of its outstanding performance over ex-situ approach. This is the first report of Ficus Mucuso plant extract being used in nanosynthesis.

Potential of Ruthenium as a photosensitizer in radiation-activated Photodynamic Therapy (radioPDT)

In Photodynamic Therapy (PDT), light is used to activate photosensitizers (PS) to generate reactive oxygen species (ROS) as a cell-killing mechanism. However, PDT's application is limited to the surface and small size tumors because of the inefficiency of light in penetrating larger and deep-seated tumors. We have developed novel nanoparticles (NPs) that can be activated by radiation, a process known as the radiation-activated PDT (radioPDT). In our studies we developed a new variant of pegylated poly-lactic-co-glycolic (PEG-PLGA) encapsulated nanoscintillators (NSC) and ruthenium-based photosensitizer (Ru/rPDT) that exhibits minimal cell toxicity while having significant cell killing effect upon radiation activation. Our data suggest that radioPDT with Ru/rPDT can be a more effective strategy than previous protoporphyrin-based iterations in treating many deep-seated tumors.Introduction and Background: Toxicity and normal tissue damage are limiting factors for the application of radiotherapy (RT) where higher doses of radiation is required to cure deep-seated tumor such as prostate cancer. In Photodynamic Therapy (PDT), photosensitizers (PS) are activated by light to generate reactive oxygen species (ROS) to kill tumor cells. However, the main limitation of the current PDT is the limited tissue penetration of PS-activating light. Thus, PDT cannot be effectively used to treat deep-seated and larger size tumors. RT has higher tissue penetration depth, making the radiation-activated PDT (radioPDT) advantageous in treating deep seated tumors.We aim to develop novel radioPDT nanoparticles (NP) with more efficient anti-cancer therapeutic effect in vitro and in vivo to enhance targeted radiotherapy.Methods: LaF3:Ce3+ nanoscintillators (NSCs) were synthesized in a single step wet chemistry technique. The NSCs along with Ruthenium-based PS (Ru) with matching excitation/emission spectra were successfully encapsulated in PEG-PLGA. UV-Vis spectrometry and inductively coupled plasma mass spectrometry (ICP-MS) were used to confirm the presence of NSCs and Ru, and dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to determine the size of NP. Singlet oxygen generation was measured by Singlet Oxygen Sensor Green (SOSG) and direct singlet oxygen fluorescence. RadioPDT therapeutic potential was evaluated in PC3 prostate cancer cell under radiation by Alamar Blue cell viability assay.Results: UV-Vis spectrometry and ICP-MS determined the successful PEG-PLGA encapsulation of NSC and Ru. The TEM imaging confirmed the encapsulation NSC inside the nanocarrier PEG-PLGA. TEM and DLS measurements showed the size of radioNP ranged from 90nm to 150nm with polydispersity index of <0.3. Singlet oxygen generation by Ru/rPDT NPs was greater than PPIX based radioPDT (PPIX/rPDT) NPs. Furthermore, the direct measurement of singlet oxygen generation with fluorescence spectroscopy of Ru/rPDT showed preserved singlet oxygen yield and no evidence of quenching. The Ru/rPDT and PPIX/rPDT showed minimal PC3 cell cytotoxicity in dark conditions. The PC3 cell killing efficiency was comparable between Ru/rPDT and PPIX/rPDT either under light or radiation activation.Conclusion: Our in vitro studies show Ru/rPDT significantly increases anti-cancer therapeutic effect of RT, with minimal toxicity. Future studies will refine in vivo NP biodistribution, dosing, and RT dose/fractionation schemes.

Air/water vapor control with lithium chloride/polyvinyl alcohol/sulfone composite films

With the burgeoning membrane market focusing on moisture control applications, air/water filtered membranes find increasing use in diverse fields from electronics to food preservation. Fabrication and investigations of lithium chloride (LiCl)/Polyvinyl Alcohol (PVA)/sulfone composite films designed to dehumidify the surrounding air have been conducted. These films combine hydrophilic PVA with sulfone, a material known for its water vapor selectivity. Additionally, this research analyzes the impact of LiCl concentration on the film's performance, revealing that an optimal balance between water permeability and air blockage can be achieved by adjusting material compositions. Various material characterizations, including X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), Raman spectroscopy, photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), optical microscopy (OM), and confocal optical surface measurements, shed light on the film's surface morphology, lattice structure, and optical properties. The results demonstrate that the LiCl/PVA/sulfone composite films hold promise as effective dehumidifying components with potential applications in air conditioning and smart wearable garments.

In-situ failure behavior and interfacial bonding of an interpenetrating metal matrix composite reinforced with lattice-like metallic glass (Ni60Nb20Ta20) preform

Metallic glasses (MG) have an amorphous atomic structure and exhibit several exceptional properties such as high strength, hardness associated with high elastic strain limit and elastic energy storage. But MGs are also prone to brittle fracture, making them difficult to use as monolithic structural components and might better be used as a reinforcement phase in hybrid composites such as metal matrix composites (MMC). The failure behavior of composites depends on the structure of the reinforcement phase. In this work, the failure behavior of an interpenetrating MMC reinforced with a MG (Ni60Nb20Ta20) lattice-like preform and AlSi12-matrix was investigated by in-situ compression tests under scanning electron microscopy to get a better understanding of the influence of the lattice-like preform and mechanical interference between both phases. Additionally, microstructure analysis by scanning transmission electron microscopy and energy dispersive X-ray measurements were carried out to gain insight into the chemical composition of the interfaces. The failure behavior in manufacturing direction of the MMC is dominated by shear stress whereas transversely to manufacturing direction by normal stress and exhibits therefore an anisotropic failure behavior. Investigations of the interfaces show more of a mechanical than chemical bonding but in general a good interfacial bonding was confirmed.

4H-SiC/SiO2 Interface Degradation in 1.2 kV 4H-SiC MOSFETs due to Power Cycling Tests

Power cycling tests (PCTs) assess the reliability of power devices by closely simulating their operating conditions. A PCT was performed on commercially available 1.2 kV 4H-SiC power metal–oxide–semiconductor field-effect transistors to observe its impact on the 4H-SiC/SiO2 interface. High-resolution transmission electron microscopy and electron energy loss spectroscopy measurements showed variations in the length of the 4H-SiC/SiO2 transition layer, depending on whether the device was power cycled. Moreover, the total resistance at Vg &gt;&gt; Vt in Rtot − (Vg-Vt)−1 graph increased to 16.5%, while it changed more radically to 47.3% at Vg ≈ Vt. The threshold voltage shifted negatively. These variations cannot be expected solely through the wearout of the package.

Reversible CsPbBr3 ↔ CsPb2Br5 Transformation via Reverse Micellar Aqueous Solution.

Lead halide perovskites suffer from water and moisture instability due to the highly ionic nature of the crystal structures, though a few groups took advantage of it for chemical transformation via water-assisted strategy. However, direct exposure of the perovskite to bulk water leads to uncontrolled chemical transformation. Here, we report a controlled chemical transformation of CsPbBr3 to CsPb2Br5 triggered by nanoconfined water by placing CsPbBr3 in the nonpolar phase within a reverse micelle. The chemical transformation reaction is probed by using steady-state and time-resolved optical spectroscopy. We observe absorption and photoluminescence in the UV region stemming clearly from the CsPb2Br5 phase upon interaction with the reverse micellar aqueous solution. Transmission electron microscopy and X-ray diffraction measurements further provided the structure and morphology. Our results direct the formation of CsPbBr3-CsPb2Br5 nanocomposite under dry conditions while the chemically transformed CsPb2Br5 phase exists only in moist conditions, which we explain via the CsBr-stripping mechanism.

Direct observation and quantification of nanosecond laser induced amorphization inside silicon

The nature of structural changes of nanosecond laser modification inside silicon is investigated. Raman spectroscopy and transmission electron microscopy measurements of cross sections of the modified channels reveal highly localized crystal deformation. Raman spectroscopy measurements prove the existence of amorphous silicon inside nanosecond laser induced modifications, and the percentage of amorphous silicon is calculated based on the Raman spectrum. For the first time, the high-resolution transmission electron microscopy images directly show the appearance of amorphous silicon inside nanosecond laser induced modifications, which corroborates the indirect measurements from Raman spectroscopy. The laser modified channel consists of a small amount of amorphous silicon embedded in a disturbed crystal structure accompanied by strain. This finding may explain the origin of the positive refractive index change associated with the written channels that may serve as optical waveguides.

Influencing the morphological stability of MOVPE-grown β-Ga2O3 films by O2/Ga ratio

The morphology evolution of (100) β-Ga2O3 films grown by metalorganic vapor phase epitaxy (MOVPE) is studied by atomic force microscopy (AFM). In particular, when grown under a high O2/Ga ratio (O2/Ga = 1250) and above a thickness of 350 nm, these films exhibit striking morphological instabilities, including step meandering and bunching, which contribute significantly to surface roughening. Transmission electronic microscopy (TEM) measurements reveal a morphological transition on the growing surface with a coexistence of step-flow and step-bunching growth modes resulting from these instabilities. In contrast, growth conditions with low O2/Ga ratios (O2/Ga = 350) effectively suppress meandering and bunching instabilities, resulting in films with excellent electrical properties. These observations are rationalized through the Burton-Cabrera-Frank (BCF) theory and Bales-Zangwill (BZ) instability (Gibbs-Thompson effect and Mullins-Sekerka instability) , thus bridging theoretical models and the experimental results.

Spherical and porous Cu2O nanocages with Cu2O/Cu(OH)2 Surface: Synthesis and their promising selectivity for catalysing CO2 electroreduction to C2H4

In the production of C2H4, a vital raw material in the synthesis of polyethylene and polyvinyl chloride, Cu2O is a highly promising catalyst with excellent Faradaic efficiency and selectivity. We propose a method involving the partial reduction of Cu(OH)2 to Cu2O by sodium L-ascorbate for the synthesis of spherical and porous Cu2O nanocages (SPNCs) with a surface containing both Cu2O and Cu(OH)2. High-resolution transmission electron microscopy and electron diffraction measurements revealed ∼ 3-nm pores and a (13¯2) high-index facet on the SPNC, respectively. As SPNCs have a porous structure, their specific surface area is greater (31.10 m2 g−1) than that (6.35 m2 g−1) of spherical Cu2O nanocrystals (SNCs) with solid interiors. Furthermore, SPNCs, when applied as electrocatalysts for catalysing the CO2 reduction reaction (CO2RR), demonstrated remarkable mass activities (16.92 mA mg−1 at −1.15 V vs. reversible hydrogen electrode) for C2H4 production, with a Faraday efficiency reaching an impressive 55.3 %. Stability test data showed a consistent CO2RR current density over 6 h, owing to the porous structure and the presence of both Cu(OH)2 and Cu2O on the catalyst surface. Our proposed SPNC catalysts can be employed as effective CO2RR catalysts for producing C2H4, which may help in reducing the present reliance on petrochemical processes.

Electron-Transport-Chain-Mediated Selective Growth of Gold Nanocrystals in the Intermembrane Space of Live Microbial Cells.

Hybridization of microbial cells with inorganic nanoparticles that could dramatically improve cellular functions such as electron transfer has been realized by the random attachment or stochastic entry of the nanoparticles. Clearly, the selective growth of inorganic nanoparticles on target functional organelles is ideal for such hybridization. Here, we report the selective growth of gold nanocrystals in the intermembrane space (IMS) of Escherichia coli by exploiting the electron transport chain (ETC). We systematically show that gold ions are permeated through porins in the outer membrane of E. coli and further reduced to gold nanocrystals by the ETC in live E. coli. We directly observe that the resulting gold nanocrystals exist only in the IMS by transmission electron microscopy measurements of cross-sectioned E. coli. Molecular dynamics simulations suggest that once gold ions are reduced to small nuclei by the ETC, the nuclei can be stably physisorbed onto ETC complexes, further supporting the ETC-mediated growth. Finally, we show that the ATP synthesis of E. coli where gold nanocrystals are formed in the IMS is up to 9 times higher than that of E. coli alone. We believe that our work can significantly contribute to not only improving microbial metabolic functions for biological energy conversion but also restoring physiological dysfunctions of microbial cells for biomedicine.

Deciphering the immobilization of lipases on hydrophobic wrinkled silica nanoparticles

In this work, the adsorption of Candida antarctica B (CALB) and Rhizomucor miehei (RML) lipases into hydrophobic wrinkled silica nanoparticles (WSNs) is investigated. WSNs are hydrophobized by chemical vapor deposition. Both proteins are homogeneously distributed inside the pores of the nanoparticles, as confirmed by Transmission Electron Microscopy and Energy Dispersive X-ray measurements. The maximum enzyme load of CALB is twice that obtained for RML. Fourier Transform Infrared Spectroscopy confirms the preservation of the enzyme secondary structure after immobilization for both enzymes. Adsorption isotherms fit to a Langmuir model, resulting in a binding constant (KL) for RML 4.5-fold higher than that for CALB, indicating stronger binding for the former. Kinetic analysis reveals a positive correlation between enzyme load and RML activity unlike CALB where activity decreases along the enzyme load increases. Immobilization allows for enhancing the thermal stability of both lipases. Finally, CALB outperforms RML in the hydrolysis of ethyl-3-hydroxybutyrate. However, immobilized CALB yielded 20 % less 3-HBA than free lipase, while immobilized RML increases 3-fold the 3-HBA yield when compared with the free enzyme. The improved performance of immobilized RML can be explained due to the interfacial hyperactivation undergone by this lipase when immobilized on the superhydrophobic surface of WSNs.