Advancing Catalysts by Stacking Fault Defects for Enhanced Hydrogen Production: A Review.

Green hydrogen, derived from water splitting powered by renewable energy such as solar and wind energy, provides a zero-emission solution crucial for revolutionizing hydrogen production and decarbonizing industries. Catalysts, particularly those utilizing defect engineering involving the strategical introduction of atomic-level imperfections, play a vital role in reducing energy requirements and enabling a more sustainable transition toward a hydrogen-based economy. Stacking fault (SF) defects play an important role in enhancing the electrocatalytic processes by reshaping surface reactivity, increasing active sites, improving reactants/product diffusion, and regulating electronic structure due to their dense generation ability and profound impact on catalyst properties. This review explores SF in metal-based materials, covering synthetic methods for the intentional introduction of SF and their applications in hydrogen production, including oxygen evolution reaction, photo- and electrocatalytic hydrogen evolution reaction, overall water splitting, and various other electrocatalytic processes such as oxygen reduction reaction, nitrate reduction reaction, and carbon dioxide reduction reaction. Finally, this review addresses the challenges associated with SF-based catalysts, emphasizing the importance of a detailed understanding of the properties of SF-based catalysts to optimize their electrocatalytic performance. It provides a comprehensive overview of their various applications in electrocatalytic processes, providing valuable insights for advancing sustainable energy technologies.

Transforming Spirulina maxima Biomass into Ultrathin Bioactive Coatings Using an Atmospheric Plasma Jet: A New Approach to Healing of Infected Wounds.

The challenge of wound healing, particularly in patients with comorbidities such as diabetes, is intensified by wound infection and the accelerating problem of bacterial resistance to current remedies such as antibiotics and silver. One promising approach harnesses the bioactive and antibacterial compound C-phycocyanin from the microalga Spirulina maxima. However, the current processes of extracting this compound and developing coatings are unsustainable and difficult to achieve. To circumvent these obstacles, a novel, sustainable argon atmospheric plasma jet (Ar-APJ) technology that transforms S. maxima biomass into bioactive coatings is presented. This Ar-APJ can selectively disrupt the cell walls of S. maxima, converting them into bioactive ultrathin coatings, which are found to be durable under aqueous conditions. The findings demonstrate that Ar-APJ-transformed bioactive coatings show better antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Moreover, these coatings exhibit compatibility with macrophages, induce an anti-inflammatory response by reducing interleukin 6 production, and promote cell migration in keratinocytes. This study offers an innovative, single-step, sustainable technology for transforming microalgae into bioactive coatings. The approach reported here has immense potential for the generation of bioactive coatings for combating wound infections and may offer a significant advance in wound care research and application.

Gas sensors based on the oxide skin of liquid indium.

Various non-stratified two-dimensional (2D) materials can be obtained from liquid metal surfaces that are not naturally accessible. Homogenous nucleation on atomically flat interfaces of liquid metals with air produces unprecedented high-quality oxide layers that can be transferred onto desired substrates. The atomically flat and large areas provide large surface-to-volume ratios ideal for sensing applications. Versatile crucial applications of the liquid metal-derived 2D oxides have been realized; however, their gas-sensing properties remain largely underexplored. The cubic In2O3 structure, which is nonlayered, can be formed as an ultrathin layer on the surface of liquid indium during the self-limiting Cabrera-Mott oxidation process in the air. The morphology, crystal structure, and band structure of the harvested 2D In2O3 nanosheets from liquid indium are characterized. Sensing capability toward several gases, both inorganic and organic, entailing NO2, O2, NH3, H2, H2S, CO, and Methyl ethyl ketone (MEK) are explored. A high ohmic resistance change of 1974% at 10 ppm, fast response, and recovery times are observed for NO2 at an optimum temperature of 200 °C. The sensing fundamentals are investigated for NO2, and its performances and cross-selectivity to different gases are analyzed. The NO2 sensing response from room temperature to 300 °C has been measured and discussed, and stability after 24 hours of continuous operation is presented. The results demonstrate liquid metal-derived 2D oxides as promising materials for gas sensing applications.

Functionalized Concave Cube Gold Nanoparticles as Potent Antimicrobial Agents against Pathogenic Bacteria.

Gold (Au) is an inert metal in a bulk state; however, it can be used for the preparation of Au nanoparticles (i.e., AuNPs) for multidimensional applications in the field of nanomedicine and nanobiotechnology. Herein, monodisperse concave cube AuNPs (CCAuNPs) were synthesized and functionalized with a natural antioxidant lipoic acid (LA) and a tripeptide glutathione (GSH) because different crystal facets of AuNPs provide binding sites for distinct ligands. There was an ∼10 nm bathochromic shift of the UV-vis spectrum when CCAuNPs were functionalized with LA, and the size of the as-synthesized monodisperse CCAu nanoparticles was 76 nm. The LA-functionalized CCAu nanoparticles (i.e., CCAuLA) showed the highest antibacterial activity against Bacillus subtilis. Both fluorescence images and scanning electron microscopy images confirm the damage of the bacterial cell wall as the mode of antibacterial activity of CCAuNPs. CCAuNPs also cause the oxidation of bacterial cell membrane fatty acids to produce reactive oxygen species, which pave the way for the death of bacteria. Both CCAu nanoparticles and their functionalized derivatives showed excellent hemocompatibility (i.e., percentage of hemolysis is <5% at 80 µg of AuNPs) to human red blood cells and very high biocompatibility to HeLa, L929, and Chinese hamster ovary-green fluorescent protein (CHO-GFP) cells. Taken together, LA and GSH enhance the antibacterial activity and biocompatibility, respectively, of CCAu nanoparticles that interact with the bacteria through Coulomb as well as hydrophobic interactions before demonstrating antibacterial propensity.

Liquid Crystal-Mediated 3D Printing Process to Fabricate Nano-Ordered Layered Structures.

The emergence of three-dimensional (3D) printing promises a disruption in the design and on-demand fabrication of smart structures in applications ranging from functional devices to human organs. However, the scale at which 3D printing excels is within macro- and microlevels and principally lacks the spatial ordering of building blocks at nanolevels, which is vital for most multifunctional devices. Herein, we employ liquid crystal (LC) inks to bridge the gap between the nano- and microscales in a single-step 3D printing. The LC ink is prepared from mixtures of LCs of nanocellulose whiskers and large sheets of graphene oxide, which offers a highly ordered laminar organization not inherently present in the source materials. LC-mediated 3D printing imparts the fine-tuning required for the design freedom of architecturally layered systems at the nanoscale with intricate patterns within the 3D-printed constructs. This approach empowered the development of a high-performance humidity sensor composed of self-assembled lamellar organization of NC whiskers. We observed that the NC whiskers that are flat and parallel to each other in the laminar organization allow facile mass transport through the structure, demonstrating a significant improvement in the sensor performance. This work exemplifies how LC ink, implemented in a 3D printing process, can unlock the potential of individual constituents to allow macroscopic printing architectures with nanoscopic arrangements.

Low-Temperature Hydrogen Sensor: Enhanced Performance Enabled through Photoactive Pd-Decorated TiO2 Colloidal Crystals.

The high demand for H2 gas sensors is not just limited to industrial process control and leak detection applications but also extends to the food and medical industry to determine the presence of various types of bacteria or underlying medical conditions. For instance, sensing of H2 at low concentrations (<10 ppm) is essential for developing breath analyzers for the noninvasive diagnosis of some gastrointestinal diseases. However, there are major challenges to overcome in order to achieve high sensitivity and hence low limit of detection (LoD) toward H2. In this study, it is demonstrated that light-assisted amperometric gas sensors employing sensitive layers based on Pd-decorated TiO2 long-range ordered crystals can achieve excellent H2 sensing performance. This unique combination of materials and novel layered structure enables the detection of H2 gas down to 50 ppm with highly promising LoD capabilities. The sensor response profiles revealed that the sensor's signal-to-noise ratio was higher in the presence of light when operated with a 9 V bias (relative to other conditions used), producing a LoD of only 3.5 ppm at an operating temperature of 33 °C. The high performance of the sensor makes it attractive for applications that require low-level (ppm as opposed to conventional % levels) H2 gas detection. Most importantly, the developed sensor exhibited high selectivity (>93%) toward H2 over other gas species such as CO2, C4H8O, C3H6O, CH3CHO, and NO, which are commonly found to coexist in the environment.

Mercury-bearing wastes: Sources, policies and treatment technologies for mercury recovery and safe disposal.

Due to the lenient environmental policies in developing economies, mercury-containing wastes are partly produced as a result of the employment of mercury in manufacturing and consumer products. Worldwide, the presence of mercury as an impurity in several industrial processes leads to significant amounts of contaminated waste. The Minamata Convention on Mercury dictates that mercury-containing wastes should be handled in an environmentally sound way according to the Basel Convention Technical Guidelines. Nevertheless, the management policies differ a great deal from one country to another because only a few deploy or can afford to deploy the required technology and facilities. In general, elemental mercury and mercury-bearing wastes should be stabilized and solidified before they are disposed of or permanently stored in specially engineered landfills and facilities, respectively. Prior to physicochemical treatment and depending on mercury's concentration, the contaminated waste may be thermally or chemically processed to reduce mercury's content to an acceptable level. The suitability of the treated waste for final disposal is then assessed by the application of standard leaching tests whose capacity to evaluate its long-term behavior is rather questionable. This review critically discusses the main methods employed for the recovery of mercury and the treatment of contaminated waste by analyzing representative examples from the industry. Furthermore, it gives a complete overview of all relevant issues by presenting the sources of mercury-bearing wastes, explaining the problems associated with the operation of conventional discharging facilities and providing an insight of the disposal policies adopted in selected geographical regions.

Leveraging Cu/CuFe2O4-Catalyzed Biomass-Derived Furfural Hydrodeoxygenation: A Nanoscale Metal-Organic-Framework Template Is the Prime Key.

Enormous efforts have been initiated in the production of biobased fuels and value-added chemicals via biorefinery owing to the scarcity of fossil resources and huge environmental synchronization. Herein, non-noble metal-based metal/mixed metal oxide supported on carbon employing a metal-organic framework as a sacrificial template is demonstrated for the first time in the selective hydrodeoxygenation (HDO) of biomass-derived furfural (FFR) to 2-methyl furan (MF). The aforementioned catalyst (referred to as Cu/CuFe2O4@C-A) exhibited extraordinary catalytic proficiency (100% selectivity toward MF) compared with the conventional Cu/CuFe2O4@C-B catalyst which was prepared by the wet impregnation method. High-resolution transmission electron microscopy and synchrotron X-ray diffraction studies evidenced the existence of both metal (Cu) and mixed metal oxide (CuFe2O4) phases, in which the metal could help in hydrogenation to alcohol and metal oxide could assist in the hydroxyl group removal step during HDO reaction. The stabilization of encapsulated metal/metal oxide nanoparticles in the carbon matrix, modulation of the electronic structure, and regulation of geometric effects in the Cu/CuFe2O4@C-A are thought to play an important role in its excellent catalytic performance, confirmed by X-ray photoelectron spectroscopy and X-ray absorption spectroscopy investigations. Furthermore, the structure and activity interconnection was confirmed by in situ attenuated total reflection-IR studies, which manifested the strong interfacial interaction between FFR and the Cu/CuFe2O4@C-A catalyst. This finding was further supported by NH3 temperature-programmed desorption analysis, which suggested that the presence of more Lewis/weak acidic sites in this catalyst was beneficial for the hydrogenolysis step in HDO reaction. Additionally, H2 temperature-programmed reduction studies revealed that the adsorption of H2 was stronger on the Cu/CuFe2O4@C-A than that over the conventional Cu/CuFe2O4@C-B catalyst; thus, the former catalyst promoted activation of H2. A detailed kinetic analysis which demonstrated the lower activation energy barrier along with dual active sites attributed for the activation of the two separate reactions in the HDO process on the Cu/CuFe2O4@C-A catalyst. This work has great implication in developing a highly stable catalyst for the selective upgradation of biomass without deactivation of metal sites in extended catalytic cycles and opens the door of opportunity for developing a sustainably viable catalyst in biomass refinery industries.

Mercury in natural gas streams: A review of materials and processes for abatement and remediation.

The role of natural gas in mitigating greenhouse gas emissions and advancing renewable energy resource integration is undoubtedly critical. With the progress of hydrocarbons exploration and production, the target zones become deeper and the possibility of mercury contamination increases. This impacts on the industry from health and safety risks, due to corrosion and contamination of equipment, to catalyst poisoning and toxicity through emissions to the environment. Especially mercury embrittlement, being a significant problem in LNG plants using aluminum cryogenic heat exchangers, has led to catastrophic plant incidents worldwide. The aim of this review is to critically discuss the conventional and alternative materials as well as the processes employed for mercury removal during gas processing. Moreover, comments on studies examining the geological occurrence of mercury species are included, the latest developments regarding the detection, sampling and measurement are presented and updated information with respect to mercury speciation and solubility is displayed. Clean up and passivation techniques as well as disposal methods for mercury-containing waste are also explained. Most importantly, the environmental as well as the health and safety implications are addressed, and areas that require further research are pinpointed.

Facile conversion of zinc hydroxide carbonate to CaO-ZnO for selective CO2 gas detection.

Tailored synthesis of heterostructures for low temperature (sub 200 °C) CO2 sensing continues to be a challenging task. The present study demonstrates CO2 sensing characteristics of CaO-ZnO heterostructures achieved by zinc hydroxide carbonate (Zn5(CO3)2(OH)6) conversion to ZnO using Ca(OH)2 at 50 °C. Control samples namely, Zn5(CO3)2(OH)6, Ca(OH)2, ZnO, and CaO integrated microsensors exhibited low sensitivity towards CO2 gas. However, CaO-ZnO heterostructures demonstrated significant sensitivity (26 to 91%) at 150 °C for gas concentration ranging from 100 to 10000 ppm, respectively. In this study, zinc hydroxide carbonate sensitized with 25 wt% Ca(OH)2 to form CaO-ZnO heterostructures (25CaZMS) displayed a promising sensitivity (77%) and selectivity (98%) towards 500 ppm CO2 gas. Moreover, the selectivity studies were conducted in the presence of 10 commonly found gases and their sensing performance was compared against CO2 gas in dry and humid conditions. The developed CaO-ZnO sensor exhibited faster kinetics in comparison to the control samples. Improved sensing performance observed here is attributed to the low-temperature synthesis route which resulted in a large number of active pores and high surface area morphology. Additionally, the high CO2 adsorption capacity of CaO combined with compatible n-type semiconductors in forming highly dynamic nano-interfaced heterostructure is a promising step towards developing a precise CO2 gas microsensor.

Fabrication of a novel ZnIn2S4/g-C3N4/graphene ternary nanocomposite with enhanced charge separation for efficient photocatalytic H2 evolution under solar light illumination.

Design and synthesis of efficient photocatalyst systems for a large volume of hydrogen (H2) evolution under solar light is still a great challenge. To obtain high photocatalytic activity, graphene-based semiconductor photocatalysts are gaining heightened attention in the field of green and sustainable fuel production due to their good electronic properties, high surface area and chemical stability. Herein, we demonstrate an efficient, novel and smart architecture of a graphene-based ZnIn2S4/g-C3N4 nanojunction by a simple hydrothermal process for H2 generation. In the present study, graphene (G) is chosen as the electron mediator and ZnIn2S4 (ZIS) and g-C3N4 (CN) are chosen as two different semiconductor photocatalysts to construct a smart architecture for the ternary photocatalytic system. Different characterization techniques such as XRD, TGA, FT-IR, SEM, TEM, HR-TEM, XPS, BET, and UV-vis DRS were employed to ensure the successful integration of graphene, ZnIn2S4, and g-C3N4 in the nanocomposite. As a result, high and efficient H2 evolution (477 µmol h-1 g-1) is attained for the graphene-based ZnIn2S4/g-C3N4 nanocomposite. Transient photocurrent experiments, ESR, PL, and time-resolved PL studies suggested that the intimate ternary nanojunction effectively promotes fast charge transfer and thereby enhances photocatalytic H2 evolution.

Zinc Titanate Nanoarrays with Superior Optoelectrochemical Properties for Chemical Sensing.

In this report, the gas sensing performance of zinc titanate (ZnTiO3) nanoarrays (NAs) synthesized by coating hydrothermally formed zinc oxide (ZnO) NAs with TiO2 using low-temperature chemical vapor deposition is presented. By controlling the annealing temperature, diffusion of ZnO into TiO2 forms a mixed oxide of ZnTiO3 NAs. The uniformity and the electrical properties of ZnTiO3 NAs made them ideal for light-activated acetone gas sensing applications for which such materials are not well studied. The acetone sensing performance of the ZnTiO3 NAs is tested by biasing the sensor with voltages from 0.1 to 9 V dc in an amperometric mode. An increase in the applied bias was found to increase the sensitivity of the device toward acetone under photoinduced and nonphotoinduced (dark) conditions. When illuminated with 365 nm UV light, the sensitivity was observed to increase by 3.4 times toward 12.5 ppm acetone at 350 °C with an applied bias of 9 V, as compared to dark conditions. The sensor was also observed to have significantly reduced the adsorption time, desorption time, and limit of detection (LoD) when excited by the light source. For example, LoD of the sensor in the dark and under UV light at 350 °C with a 9 V bias is found to be 80 and 10 ppb, respectively. The described approach also enabled acetone sensing at an operating temperature down to 45 °C with a repeatability of >99% and a LoD of 90 ppb when operated under light, thus indicating that the ZnTiO3 NAs are a promising material for low concentration acetone gas sensing applications.

Co3O4 needles on Au honeycomb as a non-invasive electrochemical biosensor for glucose in saliva.

While glucose monitoring technology is widely available, the continued prevalence of diabetes around the world coupled with its debilitating effects continues to grow. The significant limitations which exist in the current technology, instils the need for materials capable of non-invasive glucose detection. In this study a unique non-enzymatic electrochemical glucose sensor was developed, utilising a gold honeycomb-like framework upon which sharp Co3O4 needles are anchored. This composite nanomaterial demonstrates excellent sensing performance in glucose concentrations ranging between 20 µM and 4 mM, exceeding the range required for non-invasive glucose sensing. In conjunction with this high sensitivity (2.014 mA mM-1·cm-2), the material possesses excellent selectivity towards glucose for commonly interfering physiological species such as uric acid and ascorbic acid. Glucose detection in synthetic saliva was then performed showing excellent capability in the low concentration range (20 µM-1 mM) for non-invasive sensing performance. Further tests showed good selectivity of the sensor in physiological contaminants commonly found in saliva such as cortisol and dopamine. This development provides excellent scope to create next-generation non-invasive diabetes monitoring platforms, with excellent performance when detecting low glucose concentrations in complex solutions such as saliva.

CeO2-Decorated ?-MnO2 Nanotubes: A Highly Efficient and Regenerable Sorbent for Elemental Mercury Removal from Natural Gas.

CeO2 nanoparticle-decorated ?-MnO2 nanotubes (NTs) were prepared and tested for elemental mercury (Hg0) vapor removal in simulated natural gas mixtures at ambient conditions. The composition which had the largest surface area and a relative Ce/Mn atomic weight ratio of around 35% exhibited a maximum Hg0 uptake capacity exceeding 20 mg?g?1 (2 wt %), as determined from measurements of mercury breakthrough which corresponded to 99.5% Hg0 removal efficiency over 96 h of exposure. This represents a significant improvement in the activity of pure metal oxides. Most importantly, the composite nanosorbent was repeatedly regenerated at 350 ?C and retained the 0.5% Hg0 breakthrough threshold. It was projected to be able to sustain 20 regeneration cycles, with the presence of acid gases, CO2, and H2S, not affecting its performance. This result is particularly important, considering that pure CeO2 manifests rather poor activity for Hg0 removal at ambient conditions, and hence, a synergistic effect in the composite nanomaterial was observed. This possibly results from the addition of facile oxygen vacancy formation at ?-MnO2 NTs and the increased amount of surface-adsorbed oxygen species.

Using colloidal lithography to control the formation of gas sorption sites through galvanic replacement reaction.

Using colloidal lithography, a series of inverted long-range ordered crystals (i-LROCs) of Pd honeycombs were fabricated on quartz crystal microbalance (QCM) sensors. The structures formed provided the required platform for the proceeding galvanic replacement reaction (GR) process to generate seamless Au nanoparticle deposits throughout the i-LROC. The results showed that controlling the dimensions of the pores in the developed Pd i-LROCs is important in the formation of gold deposition sites on the uniform structures through the GR reaction process. The developed Pd/Au i-LROC deposited sensors showed significant enhancement in the sensitivity toward Hg0 vapor when compared to pure Pd structures, with limit of detection improving from 60.0 to 13.7 µg/m3, respectively. Furthermore, a significant improvement in the modified sensor's selectivity toward Hg0 in the presence of other industrial related gas species was observed which is attributed to the addition of Au to the Pd structures through GR reaction.

Functionalization of Elongated Tetrahexahedral Au Nanoparticles and Their Antimicrobial Activity Assay.

Gold nanoparticles are inert for the human body, and therefore, they have been functionalized to provide them with antibacterial properties. Here, elongated tetrahexahedral (ETHH) Au nanoparticles were synthesized, characterized, and functionalized with lipoic acid (LA), a natural antioxidant with a terminal carboxylic acid and a dithiolane ring, to generate ETHH-LA Au nanoparticles. The antioxidant activity of Au nanoparticles was investigated in vitro, showing that LA enhances the 2,2-diphenyl-1-picrylhydrazyl free-radical scavenging and Fe3+ ion reducing activity of ETHH-LA at higher amounts. The antimicrobial propensities of the nanoparticles were investigated against Gram-positive ( Bacillus subtilis) and Gram-negative ( Escherichia coli) bacteria through propidium iodide assay as well as disk diffusion assay. ETHH-LA Au nanoparticles showed significantly higher antimicrobial activity against B. subtilis compared with E. coli. Furthermore, ETHH-LA Au nanoparticles also showed significantly better antimicrobial activity against both bacterial strains when compared with ETHH. ETHH Au nanoparticles also bring about the oxidation of bacterial cell membrane fatty acids and produce lipid peroxides. ETHH-LA showed higher lipid peroxidation potential than that of ETHH against both bacteria tested. The hemolytic potential of Au nanoparticles was investigated using human red blood cells and ETHH-LA showed reduced hemolytic activity than that of ETHH. The cytotoxicity of Au nanoparticles was investigated using human cervical cancer cells, HeLa, and ETHH-LA Au nanoparticles showed reduced cytotoxicity than that of ETHH. Taken together, LA enhances the antimicrobial activity of ETHH Au nanoparticles and Au nanoparticles interact with the bacteria through electrostatic interactions as well as hydrophobic interactions and damage the bacterial cell wall followed by oxidation of cell membrane fatty acids.

Role of Ceria in the Design of Composite Materials for Elemental Mercury Removal.

The necessity to drastically act against mercury pollution has been emphatically addressed by the United Nations. Coal-fired power plants contribute a great deal to the anthropogenic emissions; therefore, numerous sorbents/catalysts have been developed to remove elemental mercury (Hg0 ) from flue gases. Among them, ceria (CeO2 ) has attracted significant interest, due to its reversible Ce3+ /Ce4+ redox pair, surface-bound defects and acid-base properties. The removal efficiency of Hg0 vapor depends among others, on the flue gas composition and temperature. CeO2 can be incorporated into known materials in such a way that the abatement process can be effective at different operating conditions. Hence, the scope of this account is to discuss the role of CeO2 as a promoter, active phase and support in the design of composite Hg0 sorbents/catalysts. The elucidation of each of these roles would allow the integration of CeO2 advantageous characteristics to such degree, that tailor-made environmental solution to complex issues can be provided within a broader application scope. Besides, it would offer invaluable input to theoretical calculations that could enable the materials screening and engineering at a low cost and with high accuracy.

Multi-directional electrodeposited gold nanospikes for antibacterial surface applications.

The incorporation of high-aspect-ratio nanostructures across surfaces has been widely reported to impart antibacterial characteristics to a substratum. This occurs because the presence of such nanostructures can induce the mechanical rupture of attaching bacteria, causing cell death. As such, the development of high-efficacy antibacterial nano-architectures fabricated on a variety of biologically relevant materials is critical to the wider acceptance of this technology. In this study, we report the antibacterial behavior of a series of substrata containing multi-directional electrodeposited gold (Au) nanospikes, as both a function of deposition time and precursor concentration. Firstly, the bactericidal efficacy of substrata containing Au nanospikes was assessed as a function of deposition time to elucidate the nanopattern that exhibited the greatest degree of biocidal activity. Here, it was established that multi-directional nanospikes with an average height of ∼302 nm ± 57 nm (formed after a deposition time of 540 s) exhibited the greatest level of biocidal activity, with ∼88% ± 8% of the bacterial cells being inactivated. The deposition time was then kept constant, while the concentration of the HAuCl4 and Pb(CH3COO)2 precursor materials (used for the formation of the Au nanospikes) was varied, resulting in differing nanospike architectures. Altering the Pb(CH3COO)2 precursor concentration produced multi-directional nanostructures with a wider distribution of heights, which increased the average antibacterial efficacy against both Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus bacteria. Importantly, the in situ electrochemical fabrication method used in this work is robust and straightforward, and is able to produce highly reproducible antibacterial surfaces. The results of this research will assist in the wider utilization of mechano-responsive nano-architectures for antimicrobial surface technologies.

Silicon as a ubiquitous contaminant in graphene derivatives with significant impact on device performance.

Silicon-based impurities are ubiquitous in natural graphite. However, their role as a contaminant in exfoliated graphene and their influence on devices have been overlooked. Herein atomic resolution microscopy is used to highlight the existence of silicon-based contamination on various solution-processed graphene. We found these impurities are extremely persistent and thus utilising high purity graphite as a precursor is the only route to produce silicon-free graphene. These impurities are found to hamper the effective utilisation of graphene in whereby surface area is of paramount importance. When non-contaminated graphene is used to fabricate supercapacitor microelectrodes, a capacitance value closest to the predicted theoretical capacitance for graphene is obtained. We also demonstrate a versatile humidity sensor made from pure graphene oxide which achieves the highest sensitivity and the lowest limit of detection ever reported. Our findings constitute a vital milestone to achieve commercially viable and high performance graphene-based devices.

Hybrid Surface and Bulk Resonant Acoustics for Concurrent Actuation and Sensing on a Single Microfluidic Device.

While many microfluidic devices have been developed for sensing and others for actuation, few devices can perform both tasks effectively and simultaneously on the same platform. In piezoelectric sensors and actuators, this is due to the opposing operating requirements for sensing and actuation. Sensing ideally requires narrow resonant peaks characterized by high quality factors, such as those found in quartz crystals. However, these materials usually have poor electromechanical coupling coefficients that are not ideal for actuation. In this work, we show that it is possible to achieve both sensing and actuation simultaneously on a shared device by exploiting the distinct advantages of both bulk waves for effective mass sensing and surface waves for highly efficient microfluidic actuation through a unique hybrid surface and bulk acoustic wave platform. In light of the recent resurgence of interest in portable inhaled insulin devices for personalized diabetes management, we demonstrate the use of this technology for efficient aerosolization of insulin for inhalation without denaturing the protein, while being able to concurrently detect the residual mass of the un-nebulized insulin remaining on the device such that the actual dose delivered to the patient can be determined in real time.