Facile Synthesis of Fe-Doped, Algae Residue-Derived Carbon Aerogels for Electrochemical Dopamine Biosensors.

An abnormal level of dopamine (DA), a kind of neurotransmitter, correlates with a series of diseases, including Parkinson's disease, Willis-Ekbom disease, attention deficit hyperactivity disorder, and schizophrenia. Hence, it is imperative to achieve a precise, rapid detection method in clinical medicine. In this study, we synthesized nanocomposite carbon aerogels (CAs) doped with iron and iron carbide, based on algae residue-derived biomass materials, using Fe(NO3)3 as the iron source. The modified glassy carbon electrode (GCE) for DA detection, denoted as CAs-Fe/GCE, was prepared through surface modification with this composite material. X-ray photoelectron spectroscopy and X-ray diffraction characterization confirmed the successful doping of iron into the as-prepared CAs. Additionally, the electrochemical behavior of DA on the modified electrode surface was investigated and the results demonstrate that the addition of the CAs-Fe promoted the electron transfer rate, thereby enhancing their sensing performance. The fabricated electrochemical DA biosensor exhibits an accurate detection of DA in the concentration within the range of 0.01~200 µM, with a detection limit of 0.0033 µM. Furthermore, the proposed biosensor is validated in real samples, showing its high applicability for the detection of DA in beverages.

Polymer System Based on Polyethylene Glycol and TFE Telomers for Producing Films with Switchable Wettability.

Today a lot of attention is paid to the formation of thermosensitive systems for biomedical and industrial applications. The development of new methods for synthesis of such systems is a dynamically developing direction in chemistry and materials science. In this regard, this paper presents results of the studies of a new synthesized supramolecular polymer system based on polyethylene glycol and tetrafluoroethylene telomers. The films formed from the polymer substance have the property of switching wettability depending on temperature after heating activation. It has been established that the wettability changes at 60 °C. The contact angle of activated hydrophobic polymer film reaches 143°. Additionally, the system exhibits its properties regardless of the pH of the environment. Based on data obtained by the methods of infrared and x-ray photoelectron spectroscopy, differential thermal analysis and thermal analysis in conjunction with wettability and morphology, a model of the behavior of molecules in a polymer system was built that ensures switching of the hydrophilic/hydrophobic surface state. The resulting polymer system, as well as films based on it, can be used in targeted drug delivery, implantation surgery, as sensors, etc.

Zwitterion modified chitosan as a high-performance corrosion inhibitor for mild steel in hydrochloric acid solution.

Herein, a novel chitosan Schiff base (CS-FGA) as a sustainable corrosion inhibitor has been successfully synthesized via a simple amidation reaction by using an imidazolium zwitterion and chitosan (CS). The corrosion inhibition property of CS-FGA for mild steel (MS) in a 1.0 M HCl solution was studied by various electrochemical tests and physical characterization methods. The findings indicate that the maximum inhibition efficiency of CS-FGA as a mixed-type inhibitor for MS in 1.0 M HCl solution with 400 mg L-1 reaches 97.6 %, much much higher than the CS and the recently reported chitosan-based inhibitors. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle (WCA) results reveal that the CS-FGA molecules firmly adsorb on the MS surface to form a protective layer. The adsorption of CS-FGA on the MS surface belongs to the Langmuir adsorption isotherm containing both the physisorption and chemisorption. According to the X-ray photoelectron spectroscopy (XPS) and UV-vis spectrum, FeN bonds presented on the MS surface further prove the chemisorption between CS-FGA and Fe to generate the stable protective layer. Additionally, theoretical calculations from quantum chemical calculation (DFT) and molecular simulations (MD) were performed to reveal the inhibition mechanism of CS-FGA.

Facile synthesis of Gd/Ru-doped fluorescent carbon dots for fluorescent/MR bimodal imaging and tumor therapy.

Functional metal doping endows fluorescent carbon dots with richer physical and chemical properties, greatly expanding their potential in the biomedical field. Nonetheless, fabricating carbon dots with integrated functionality for diagnostic and therapeutic modalities remains challenging. Herein, we develop a simple strategy to prepare Gd/Ru bimetallic doped fluorescent carbon dots (Gd/Ru-CDs) via a one-step microwave-assisted method with Ru(dcbpy)3Cl2, citric acid, polyethyleneimine, and GdCl3 as precursors. Multiple techniques were employed to characterize the morphology and properties of the obtained carbon dots. The Gd/Ru-CDs are high mono-dispersity, uniform spherical nanoparticles with an average diameter of 4.2 nm. Moreover, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) confirmed the composition and surface properties of the carbon dots. In particular, the successful doping of Gd/Ru enables the carbon dots not only show considerable magnetic resonance imaging (MRI) performance but also obtain better fluorescence (FL) properties, especially in the red emission area. More impressively, it has low cytotoxicity, excellent biocompatibility, and efficient reactive oxygen species (ROS) generation ability, making it an effective imaging-guided tumor treatment reagent. In vivo experiments have revealed that Gd/Ru-CDs can achieve light-induced tumor suppression and non-invasive fluorescence/magnetic resonance bimodal imaging reagents to monitor the treatment process of mouse tumor models. Thus, this simple and efficient carbon dot manufacturing strategy by doping functional metals has expanded avenues for the development and application of multifunctional all-in-one theranostics.

Characterization and In Vitro Behavior of PEO Coated Mg Modified with Antibacterial Ag(I) and Cu(II) Complexes.

The use of Mg-based biomaterials with a number of their advantageous properties are overshadowed by uncontrollable metal corrosion. Moreover, the use of implants goes alongside with the threat of pathogens-associated complications. In this study, PEO coated Mg biomaterial loaded with antibacterial Ag(I) and Cu(II) complexes is produced and tested to meet both appropriate protective characteristics as well as sufficient level of antibacterial activity. To achieve a suitable level of anticorrosion protection phosphate and fluoride-phosphate electrolytes are used in the PEO process. Investigation of the surface thickness and morphology done by means of cross-section analysis and scanning electron microscopy (SEM), as well as electrochemical impedance spectroscopy (EIS) assay show precedence of the fluoride containing PEO coating and make it the material of choice for further modification with Ag(I) and Cu(II) complexes. The presence of the complexes on the PEO surface is confirmed by energy dispersive X-ray spectroscopy (EDX). X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and glow discharge optical emission spectroscopy (GDOES) are used to estimate the complexes' chemical state and depth of penetration in the coating surface. Based on the results of antibacterial assay, the modified coatings are found to be active against both Gram-positive and Gram-negative bacteria.

Automated, real-time material detection during ultrashort pulsed laser machining using laser-induced breakdown spectroscopy, for process tuning, end-pointing, and segmentation.

The rapid, high-resolution material processing offered by ultrashort pulsed lasers enables a wide range of micro and nanomachining applications in a variety of disciplines. Complex laser processing jobs conducted on composite samples, require an awareness of the material type that is interacting with laser both for adjustment of the lasering process and for endpointing. This calls for real-time detection of the materials. Several methods such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-Ray spectroscopy (EDS) can be used for material characterization. However, these methods often need interruption of the machining process to transfer the sample to another instrument for inspection. Such interruption significantly increases the required time and effort for the machining task, acting as a prohibitive factor for many laser machining applications. Laser induced breakdown spectroscopy (LIBS) is a powerful technique that can be used for material characterization, by analyzing a signal that is generated upon the interaction of laser with matter, and thus, it can be considered as a strong candidate for developing an in-situ characterization method. In this work, we propose a method that uses LIBS in a feedback loop system for real time detection and decision making for adjustment of the lasering process on-the-fly. Further, use of LIBS for automated material segmentation, in the 3D image resulting from consecutive lasering and imaging steps, is showcased.

Nickel-doped vanadium pentoxide (Ni@V2O5) nanocomposite induces apoptosis targeting PI3K/AKT/mTOR signaling pathway in skin cancer: An in vitro and in vivo study.

In the present study, the vanadium pentoxide (V2O5) nickel-doped vanadium pentoxide (Ni@V2O5) was prepared and determined for in vitro anticancer activity. The structural characterization of the prepared V2O5 and Ni@V2O5 was determined using diverse morphological and spectroscopic analyses. The DRS-UV analysis displayed the absorbance at 215 nm for V2O5 and 331 nm for Ni@V2O5 as the primary validation of the synthesis of V2O5 and Ni@V2O5. The EDS spectra exhibited the presence of 30% of O, 69% of V, and 1% of Ni and the EDS mapping showed the constant dispersion. The FE-SEM and FE-TEM analysis showed the V2O5 nanoparticles are rectangle-shaped and nanocomposites have excellent interfaces between nickel and V2O5. The X-ray photoelectron spectroscopy (XPS) investigation of Ni@V2O5 nanocomposite endorses the occurrence of elements V, O, and Ni. The in vitro MTT assay clearly showed that the V2O5 and Ni@V2O5 have significantly inhibited the proliferation of B16F10 skin cancer cells. In addition, the nanocomposite produces the endogenous reactive oxygen species in the mitochondria, causes the mitochondrial membrane and nuclear damage, and consequently induces apoptosis by caspase 9/3 enzymatic activity in skin cancer cells. Also, the western blot analysis showed that the nanocomposite suppresses the oncogenic marker proteins such as PI3K, Akt, and mTOR in the skin cancer cells. Together, the results showed that Ni@V2O5 can be used as an auspicious anticancer agent against skin cancer.

Direct Determination of Ca, K, and Mg in Soy Leaf Samples Using Laser-Induced Breakdown Spectroscopy.

This study was dedicated to developing analytical methods for determining macronutrients (Ca, K, and Mg) in soy leaf samples with and without petioles. The study's primary purpose was to present Laser-induced breakdown spectroscopy (LIBS) as a viable alternative for directly analyzing leaf samples using chemometric tools to interpret the data obtained. The instrumental condition chosen for LIBS was 70 mJ of laser pulse energy, 1.0 µs of delay time, and 100 µm of spot size, which was applied to 896 samples: 305 of soy without petioles and 591 of soy with petioles. The reference values of the analytes for the proposition of calibration models were obtained using inductively coupled plasma optical emission spectroscopy (ICP-OES) technique. Twelve normalization modes and two calibration strategies were tested to minimize signal variations and sample matrix microheterogeneity. The following were studied: multivariate calibration using partial least squares and univariate calibration using the area and height of several selected emission lines. The notable normalization mode for most models was the Euclidean norm. No analyte showed promising results for univariate calibrations. Micronutrients, P and S, were also tested, and no multivariate models presented satisfactory results. The models obtained for Ca, K, and Mg showed good results. The standard error of calibration ranged from 2.3 g/kg for Ca in soy leaves without petioles with two latent variables to 5.0 g/kg for K in soy leaves with petioles with two latent variables.

Molecular Adhesion of a Pilus-Derived Peptide Involved in Pseudomonas aeruginosa Biofilm Formation on Non-Polar ZnO-Surfaces.

Bacterial colonization and biofilm formation on abiotic surfaces are initiated by the adhesion of peptides and proteins. Understanding the adhesion of such peptides and proteins at a molecular level thus represents an important step toward controlling and suppressing biofilm formation on technological and medical materials. This study investigates the molecular adhesion of a pilus-derived peptide that facilitates biofilm formation of Pseudomonas aeruginosa, a multidrug-resistant opportunistic pathogen frequently encountered in healthcare settings. Single-molecule force spectroscopy (SMFS) was performed on chemically etched ZnO 11 2 ‾ 0 ${\left(11\bar{2}0\right)}$ surfaces to gather insights about peptide adsorption force and its kinetics. Metal-free click chemistry for the fabrication of peptide-terminated SMFS cantilevers was performed on amine-terminated gold cantilevers and verified by X-ray photoelectron spectroscopy (XPS) and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). Atomic force microscopy (AFM) and XPS analyses reveal stable topographies and surface chemistries of the substrates that are not affected by SMFS. Rupture events described by the worm-like chain model (WLC) up to 600 pN were detected for the non-polar ZnO surfaces. The dissociation barrier energy at zero force ΔG(0), the transition state distance xb and bound-unbound dissociation rate at zero force koff (0) for the single crystalline substrate indicate that coordination and hydrogen bonds dominate the peptide/surface interaction.

X-ray photoelectron spectroscopy and tunable photoluminescence study of gold nanoparticles embedded in PVA films.

This article reports the systematic photoluminescence study of the various contents of gold nanocomposites in polyvinyl alcohol (PVA) films. The variations in the gold content in PVA film were 0.2, 0.5, 1.0, and 1.5 wt%. All the samples were excited at two selected wavelengths; those are at 400 nm and 532 nm. On exciting the gold-PVA nanocomposite films at 400 nm the photoluminescence was observed in the region of 430-500 nm in comparison to pure PVA films that show an emission at 400 nm. However, on exciting the gold-PVA nanocomposites at 532 nm, the emission was observed at 560-650 nm with a long tail till 700 nm that is unlike the pure PVA films that do not show any emission peak in this region. This suggests that emission between 430 and 500 nm regions is due to the coordination of PVA with gold nanoparticles because PVA has an emission at 400 nm. However, the emission peak between 560 and 650 nm is entirely due to the gold nanocomposite particle. The peak also shows a smaller red-shift that is usually with the increasing nanoparticles size with the increasing content in the PVA films. The formation of gold nanoparticles was justified by X-ray diffraction (XRD) analysis which is further supported by X-ray photoelectron spectroscopy (XPS) analysis.

Yellow-emitting carbon dots as fluorescent sensors for the rapid determination of curcumin.

The non-standard use of curcumin could cause some adverse drug reactions, such as diarrhea, nausea and skin allergies. Thus, the curcumin determination was fundamental to disease treatment and prevention. Herein, a facile and efficient fluorescent probe was developed based on carbon dots, which was prepared through hydrothermal method (o-phenylenediamine and N-isopropylacrylamide as the reaction raw materials). Characteristics of the as-fabricated carbon dots (NCDs) were studied through some analysis techniques, such as UV-vis absorption spectroscopy, transmission electron microscopy, Fourier transform infrared instrument, X-ray photoelectron spectroscopy and fluorescence spectrophotometer. Fluorescence quenching phenomenon could be observed after addition of curcumin. This as-prepared fluorescent probe displayed a significant response for the determination of curcumin with a satisfactorily lower detection limit of 0.017 µM and a considerable linear range of 0.5-50 µM compared to reported literatures. Because of the preeminent repeatability and anti-jamming capability, the as-developed CDs suggested mighty potentiality for actual applications of curcumin detection in real samples and temperature sensing.

Optimization of electrochemical regeneration of intercalated MXene for the adsorptive removal of ciprofloxacin: Prospective mechanism.

2D-Ti3C2Tx MXene nanosheets intercalated with sodium ions (SI-Ti3C2Tx) were synthesized and utilized in simultaneous adsorption and electrochemical regeneration with ciprofloxacin (CPX). The primary focus of this study is to investigate the long-term stability of SI-Ti3C2Tx MXene and to propose the underlying regeneration mechanisms. The successful synthesis of Ti3AlC2, Ti3C2Tx MXene, and SI-Ti3C2Tx MXene was confirmed using X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. Electrochemical regeneration parameters such as charge passed, regeneration time, current density, and electrolyte composition were optimized with values of 787.5 C g-1, 7.5 min, 10 mA cm-2, and 2.5w/v% sodium chloride, respectively, enabling the complete regeneration of the SI-Ti3C2Tx MXene. In addition, the electrochemical regeneration significantly enhanced CPX removal from the SI-Ti3C2Tx MXene owing to partial amorphization, disorderliness, increased functional groups, delamination, and defect creation in the structure. Thus, the synthesized nano-adsorbent has proven helpful in practical water treatment with optimized electrochemical regeneration processes.

Exploring Multifunctional Response of Ca10(PO4)6(OH)2-K0.5Na0.5NbO3 Ceramic Composite for Biomedical Applications.

This study focuses on investigating the intriguing properties of Ca10(PO4)6(OH)2 (HAP)-K0.5Na0.5NbO3 (KNN) bioceramic composites, seeking to elucidate the relationship between their structural, electrical, biological, and optical behavior. The article begins with a close inspection of the O 1s spectra of the specimens obtained from X-ray photoelectron spectroscopy (XPS). The spectra reveal the peak related to lattice oxygen, O vacancy and the surface adsorbed O. The formed O vacancy strongly influences the changes in lattice parameters as observed from the X-ray diffraction (XRD) patterns. The frequency variation of the dielectric response for the composites in the radio frequency (RF) regime has electrical polarization effective for biomedical applications. Nyquist plots along with equivalent RC circuits further confirm that those electrical responses are mainly contributed from the grain boundaries. Adsorption dynamics of protein on the ceramic surface are investigated using bovine serum albumin (BSA), which established the major role of electrostatic interaction. Surface charge and O vacancies are modeled to understand the adsorption of protein and a linear correlation is reported. The role of O vacancies in modulating adsorption dynamics adds a new dimension to this study. The conformational change of BSA has also been considered by constructing the secondary structure following the protein-ceramic interaction. Excitingly, the composites are also found to be fluorescent active, a courtesy of the defects and vacancies leading to electron-hole recombination in the forbidden region. These promising properties envision an exciting future for HAP-KNN composites, especially in the domain of bioimaging and bone-tissue engineering.

Multicolor Photoluminescent Carbon Dots à La Carte for Biomedical Applications.

Dual-emission fluorescence probes that provide high sensitivity are key for biomedical diagnostic applications. Nontoxic carbon dots (CDs) are an emerging alternative to traditional fluorescent probes; however, robust and reproducible synthetic strategies are still needed to access materials with controlled emission profiles and improved fluorescence quantum yields (FQYs). Herein, we report a practical and general synthetic strategy to access dual-emission CDs with FQYs as high as 0.67 and green/blue, yellow/blue, or red/blue excitation-dependent emission profiles using common starting materials such as citric acid, cysteine, and co-dopants to bias the synthetic pathway. Structural and physicochemical analysis using nuclear magnetic resonance, absorbance and fluorescence spectroscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy in addition to transmission electron and atomic force microscopy (TEM and AFM) is used to elucidate the material's composition which is responsible for the unique observed photoluminescence properties. Moreover, the utility of the probes is demonstrated in the clinical setting by the synthesis of green/blue emitting antibody-CD conjugates which are used for the immunohistochemical staining of human brain tissues of glioblastoma patients, showing detection under two different emission channels.

Adsorption of Ferritin at Nanofaceted Al2O3 Surfaces.

The influence of nanoscale surface topography on protein adsorption is highly important for numerous applications in medicine and technology. Herein, ferritin adsorption at flat and nanofaceted, single-crystalline Al2O3 surfaces is investigated using atomic force microscopy and X-ray photoelectron spectroscopy. The nanofaceted surfaces are generated by the thermal annealing of Al2O3 wafers at temperatures above 1000 °C, which leads to the formation of faceted saw-tooth-like surface topographies with periodicities of about 160 nm and amplitudes of about 15 nm. Ferritin adsorption at these nanofaceted surfaces is notably suppressed compared to the flat surface at a concentration of 10 mg/mL, which is attributed to lower adsorption affinities of the newly formed facets. Consequently, adsorption is restricted mostly to the pattern grooves, where the proteins can maximize their contact area with the surface. However, this effect depends on the protein concentration, with an inverse trend being observed at 30 mg/mL. Furthermore, different ferritin adsorption behavior is observed at topographically similar nanofacet patterns fabricated at different annealing temperatures and attributed to different step and kink densities. These results demonstrate that while protein adsorption at solid surfaces can be notably affected by nanofacet patterns, fine-tuning protein adsorption in this way requires the precise control of facet properties.

Chemical Studies of Multicomponent Kidney Stones Using the Modern Advanced Research Methods.

Defining the kidney stone composition is important for determining a treatment plan, understanding etiology and preventing recurrence of nephrolithiasis, which is considered as a common, civilization disease and a serious worldwide medical problem. The aim of this study was to investigate the morphology and chemical composition of multicomponent kidney stones. The identification methods such as infrared spectroscopy (FTIR), X-ray diffraction (XRD), and electron microscopy with the EDX detector were presented. The studies by the X-ray photoelectron spectroscopy (XPS) were also carried out for better understanding of their chemical structure. The chemical mapping by the FTIR microscopy was performed to show the distribution of individual chemical compounds that constitute the building blocks of kidney stones. The use of modern research methods with a particular emphasis on the spectroscopic methods allowed for a thorough examination of the subject of nephrolithiasis.

ZnO-based Cu metal-organic framework (MOF) nanocomposite for boosting and tuning the photocatalytic degradation performance.

Although metal-organic frameworks (MOFs) are a viable choice for photocatalysts with large surface area and tunable pore structure, the rapid recombination of excited photogenerated charges results in low activity towards photodegradation. Aiming at improving the photocatalytic activities of MOFs, different strategies to incorporate MOF with light-harvesting semiconductors have been developed. In this research, we report an effective photocatalyst designed by incorporating Cu-MOF with ZnO for the photocatalytic degradation of Rose Bengal exhibiting excellent degradation efficiency of 97.4% in 45 min under natural sunlight with catalyst dosage of 320 mg/L. The optical, morphology and surface characteristics of the prepared nanocomposite were studied using scanning electron microscopy (SEM-EDX), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (PXRD), Brunauer-Emmett-Teller (BET) analysis, thermogravimetric (TGA) analysis, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and ultraviolet diffused reflectance spectroscopy (UV-DRS) techniques. Further studies showed that the degradation followed first-order kinetics with a rate constant of 0.077869 min-1. The degradation mechanism was investigated by photoluminescence (PL) study, XPS, zeta potential and quenching experiment in presence of different scavengers. Meanwhile, the fabricated composite displayed good recovery and reuse properties up to 5 cycles as revealed by XRD analysis proving itself a potential MOF-based photocatalyst towards environmental remediation process.

Development of electronic sum frequency generation spectrophotometer to assess the buried interfaces.

The interfacial region between two bulk media in organic semiconductor based devices, such as organic field-effect transistors (OFETs), organic light-emitting diodes, and organic photovoltaics, refers to the region where two different materials such as an organic material and an electrode come in contact with each other. Although the interfacial region contains a significantly smaller fraction of molecules compared to the bulk, it is the primary site where many photoinduced excited state processes occur, such as charge transfer, charge recombination, separation, energy transfer processes, etc. All such photoinduced processes have a dependence on molecular orientation and density of states at the interfaces, therefore having an understanding of the interfacial region is essential. However, conventional spectroscopic techniques, such as surface-enhanced Raman scattering, x-ray photoelectron spectroscopy, atomic force microscopy, etc., face limitations in probing the orientation and density of states of interfacial molecules. Therefore, there is a need for noninvasive techniques capable of efficiently investigating the interfaces. The electronic sum frequency generation (ESFG) technique offers an interface selectivity based on the principle that the second-order nonlinear susceptibility tensor, within the electric dipole approximation, is zero in the isotropic bulk but nonzero at interfaces. This selectivity makes ESFG a promising spectroscopy tool to probe the molecular orientation and density of states at the buried interface. For beginners interested in employing ESFG to study the density of states at the interface, a detailed description of the experimental setup is provided here.

Smart Copolymer Surface Derived from Geminized Cationic Amphiphilic Polymers for Reversibly Switchable Bactericidal and Self-Cleaning Abilities.

Bacterial adhesion and colonization on material surfaces pose a serious problem for healthcare-associated devices. Cationic amphiphilic polymer brushes are usually used as surface coatings in antibacterial materials to endow an interface with excellent bactericidal efficiency, but they are easily contaminated, which puts a great limitation on their application. Herein, novel antibacterial copolymer brush surfaces containing geminized cationic amphiphilic polymers (pAGC8) and thermoresponsive poly(N-isopropylacrylamide) polymers (pNIPAm) have been synthesized. Surface functionalization of polymer brushes was investigated by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, atomic force microscopy, and water contact angle measurements. A proportion of AGC8 and NIPAm units in copolymer brushes has been adjusted to obtain a high-efficiency bactericidal surface with minimal interference to its self-cleaning property. The killing and releasing efficiency of the optimized surface simultaneously reached up to above 80% for both Staphylococcus aureus and Escherichia coli bacteria, and the bactericidal and self-cleaning abilities are still excellent even after three kill-release cycles. Such a novel copolymer brush system provides innovative guidance for the development of high-efficiency antibacterial materials in biomedical application.

Stable chemical enhancement of passivating nanolayer structures grown by atomic layer deposition on silicon.

Incorporation of carrier-selective passivating contacts is on the critical path for approaching the theoretical power conversion efficiency limit in silicon solar cells. We have used plasma-enhanced atomic layer deposition (ALD) to create ultra-thin films at the single nanometre-scale which can be subsequently chemically enhanced to have properties suitable for high-performance contacts. Negatively charged 1 nm thick HfO2 films exhibit very promising passivation properties - exceeding those of SiO2 and Al2O3 at an equivalent thickness - providing a surface recombination velocity (SRV) of 19 cm s-1 on n-type silicon. Applying an Al2O3 capping layer to form Si/HfO2/Al2O3 stacks gives additional passivation, resulting in an SRV of 3.5 cm s-1. Passivation quality can be further improved via simple immersion in hydrofluoric acid, which results in SRVs < 2 cm s-1 that are stable over time (tested for ∼50 days). Based on corona charging analysis, Kelvin probe measurements and X-ray photoelectron spectroscopy, the chemically induced enhancement is consistent with changes at the dielectric surface and not the Si/dielectric interface, with fluorination of the Al2O3 and underlying HfO2 films occurring after just 5 s HF immersion. Our results show that passivation is enhanced when the oxides are fluorinated. The Al2O3 top layer of the stack can be thinned down by etching, offering a new route for fabrication of ultra-thin highly passivating HfO2-containing nanoscale thin films.