Photocatalytic water splitting to form hydrogen can effectively alleviate energy and environmental problems attracting wide attention. However, the current photocatalysts have low photocatalytic efficiencies due to the narrow absorption spectrum, which is far from the actual application requirements. Herein, we use the as-prepared zinc porphyrin self-assemblies to visible-light-drive photocatalytic hydrogen evolution with Pt as the cocatalyst and ascorbic acid (AA) as the sacrificial agent. The results exhibit morphology-dependent performance and hexagonal stacks achieved optimal H2 evolution rate (47.1 mmol/h/g), then followed by nanodiscs, nanorod and tetragonal stacks, meanwhile the nanorods with different aspect ratios show size-dependent properties. The UV-vis absorption and photoluminescence spectra and the shortening of decay time of the corresponding ZnTPyP aggregates reveal that the well-defined self-assembled porphyrin networks are J-aggregation and boost efficient energy transfer with respect to monomer. Such porphyrin self-assemblies are standing for one of the most promising photosensitizers in photocatalysis field and provide an important reference for designing the next generation of hydrogen production.

Porphyrins are vital pigments involved in biological energy transduction processes. Their abilities to absorb light, then convert it to energy, have raised the interest of using porphyrin nanoparticles as photosensitizers in photodynamic therapy. A recent study showed that self- assembled porphyrin-silica composite nanoparticles can selectively destroy tumor cells, but detection of the cellular uptake of porphyrin-silica composite nanoparticles was limited to imaging microscopy. Here we developed a novel method to rapidly identify porphyrin-silica composite nanoparticles using Atmospheric Solids Analysis Probe-Mass Spectrometry (ASAP-MS). ASAP-MS can directly analyze complex mixtures without the need for sample preparation. Porphyrin-silica composite nanoparticles were vaporized using heated nitrogen desolvation gas, and their thermo-profiles were examined to identify distinct mass- to-charge (M/Z) signatures. HeLa cells were incubated in growth media containing the nanoparticles, and after sufficient washing to remove residual nanoparticles, the cell suspension was loaded onto the end of ASAP glass capillary probe. Upon heating, HeLa cells were degraded and porphyrin-silica composite nanoparticles were released. Vaporized nanoparticles were ionized and detected by MS. The cellular uptake of porphyrin-silica composite nanoparticles was identified using this ASAP-MS method.

Uniform silver chlorobromide nanocubes have been used to regulate the availability of an extremely low concentration of Ag+ that react with different thiol molecules to form silver thiolate nanoplates with high controllability. The sacrificial silver chlorobromide nanocubes also serve as templates to provide surface nucleation sites for forming the silver thiolate nanoplates, which grow against the surfaces of the nanocubes to organize into nanocages upon the consumption of the entire nanocubes. The precise regulation of the extremely low concentration of Ag+ prevents the uncontrolled fast reaction with thiol molecules and the formation of irregular silver thiolate particles. This method represents a versatile strategy to control the reaction rate of fast reactions involving in the synthesis of colloidal nanoparticles, thus enabling the synthesis of uniform nanoparticles with desirable parameters.

Semiconductor nanomaterials like zinc sulphide have interesting potential applications, consequent to their size-dependent optical properties. These nanostructures can be used on optoelectronic, photocatalysis, solar cells, and fluorescence microscopy, among others. Due to the great use of these nanoparticles in society, there is great concern in the scientific community about the potential negative interaction of these nanomaterials in aquatic environments. The present research was conducted on generation of nanostructures of ZnS with modified surface. This work had three goals: 1) morphological, compositional, and optical characterization of ZnS nanoparticles; 2) surface chemical modification of ZnS nanoparticles with biocompatible molecules; and 3) interaction studies of ZnS nanoparticle. A main absorption peak at ∼365-375nm range and a trap emission peak at ∼425nm were observed in the emission spectrum of ZnS nanoparticles synthesized at 160°C and 180°C and 30 minutes of reaction. The morphology and the size of ZnS were carried out by High Resolution Transmission Electron Microscopy (HR-TEM). In this way, nanoparticles were spherical and with a size less than 10nm. Energy Dispersive X-Ray Spectroscopy evidenced the chemical composition of produced nanostructures. The chemical modification of ZnS nanostructures was corroborated by Infrared Spectroscopy Analysis. The interaction studies of ZnS nanoparticles were studied in aquatic systems in presence of marine organisms. The concentrations of nanoparticles for these studies ranged from 0ppm to 300ppm and the contacting time with the living organisms was 24 and 48 hours. Also, Zn2+ (as Zinc nitrate and Zinc sulphate) was used as comparison purposes. Zinc sulphide nanoparticles covered with thioglycolic acid and L-cysteine evidenced a negative interaction at concentrations higher than 10ppm.

In situ synthesis of Ag nanoparticles in polyvinylidene fluoride (PVDF) was investigated using different stabilizers such as 3-aminopropyltrimethoxysilane (APS) and 1-dodecanethiol (thiol). Although PVDF is a matrix, it also functions as a stabilizer. Results of UV-vis spectroscopy showed that when APS or PVDF was used, Ag nanoparticles were formed. Yet no formation occurred when thiol was used due to the complexation of Ag+ ions by thiol. Polar groups on stabilizers has an important effect on complexation process. APS, a nitrogen-based ligand, has hard base character inhibiting the complexation between Ag+ and APS. Consequently, Ag+ ions are reduced to Ag nanoparticles in N,N dimethyl formamide (DMF), which acts as a solvent and reducing agent. Transition Electron Microscopy (TEM) image showed a uniform distribution of spherical Ag nanoparticles in PVDF matrix in the presence of APS. The electrical properties of flexible nano-metal polymer were tested and the highest improvements in breakdown strength and energy density of 33 and 58 %, respectively were measured with 0.05 wt.% Ag content and APS as a stabilizer.

The generation of AuNPs was realized in presence of gold chloride (Au3+), and citrate solution as reducing agent. The production of AuNPs was proved by the color change in the solution; from yellow to red wine. Purified nanostructures synthesized at citrate/Au3+ molar ratio of 1.0/10.0 evidenced an absorption peak at 526 nm attributed to the localized surface Plasmon Resonance (LSPR) which suggested the formation of small gold nanoparticles (NPs). The decrease of citrate/Au3+ molar ratio at 1.0/3.0 provoked a growing of gold nanostructures, which was evidenced by a red shift in the SPR at 546nm. High Resolution Transmission Electron Microscopy technique evidenced the spherical form and sizes for both nanoparticles at the range 10-15 nm (small NPs) and 20-25 nm (big NPs), respectively. Electron Diffraction (ED) patterns for both sizes evidenced the (111), (200), (220), (311), and (222) reflections of face centered cubic (FCC) gold nanostructures. Studies of energy-dispersive X-ray Spectroscopy indicated peaks at 1.65, 2.12, 9.71, 11.58 and 13.38 keV for both nanostructures, which suggests the presence of gold into the crystalline structure of the nanoparticles. Interaction tests were carried out in presence of marine crustaceans and different concentrations of gold nanoparticles; including a control test. Both sizes evidenced to be toxic when the concentration and exposure time were increased.

Graphene oxide serves as a precursor to various technologies, which include batteries, biosensors, solar cells, and supercapacitors. Gold nanoparticles exhibit excellent electrochemical and photophysical properties, allowing for electronic absorption and the ability to absorb light energy at the plasmonic wavelength. Palladium nanoparticles are highly sensitive and functional in room temperature, making it an ideal metal for catalytic applications. We report the synthesis of functional graphene oxide from graphite flakes followed by the insertion of gold and palladium nanoparticles through an oleylamine ligand. In this report, the fermi level of graphene oxide (GOx), gold-graphene oxide (Au-GOx), and palladium-graphene oxide (Pd-GOx) was shown to be effectively controlled. Additionally, each system showed complete solubility in ethanol and in the case of Au-GOx, enhanced solubility was seen in tetrahydrofuran as well.

Molybdenum disulphide (MoS2) is one of the transition metal dichalcogenide (TMD) materials which has attracted attention due to its various interesting properties. MoS2 is very promising for electronic and optoelectronic devices due to its indirect band gap (∼1.2 eV) for few layer and direct band gap (∼1.8 eV) for monolayer MoS2. In MoS2 based Schottky devices, Schottky barrier height depends on the thickness of MoS2 because of its tunable electronic properties. Here, we have used DC sputtering technique to fabricate metal-semiconductor junction of MoS2 with platinum (Pt) metal contacts. In this work, MoS2 thin film (∼10 nm) was deposited on p-Silicon (111) using DC sputtering technique at optimized parameters. Schottky metallization of Pt metal (contact area ∼ 0.785x10-2 cm2) was also done using DC sputtering. Current-voltage (I-V) characteristics of the Pt/MoS2 Schottky junction have been investigated in the temperature range 80-350K. Forward I-V characteristics of Pt/MoS2 junction are analysed to calculate different Schottky parameters. Schottky barrier height increases and ideality factor decreases on increasing the temperature from 80-350K. The I-V-T measurements suggest the presence of local inhomogeneities at the Pt/MoS2 junction. Schottky barrier inhomogeneities occur in case of rough interface. In such cases, the Schottky barrier height does not remain constant and vary locally. Current transport through the Schottky junction is a thermally activated process. As temperature increases, more and more electrons overcome the spatially inhomogeneous barrier height. As a result, the ideality factor becomes close to unity and apparent barrier height increases due to increase in temperature.

In this work, a poly-Si0.35Ge0.65 microelectromechanical systems (MEMS)- based actuator was designed and fabricated using a CMOS compatible standard process to specifically strain a bi-layered (2L) MoS2 flake and measure its electrical properties. Experimental results of the MEMS-TMDC device show an increase of conductivity up to three orders of magnitude by means of vertical actuation using the substrate as the body terminal. A force balance model of the MEMS-TMDC was used to determine the amount of strain induced in the MoS2 flake. Strains as high as 3.3% is reported using the model fitted to the experimental data.

One of the most promising methods to produce graphene in large scale is the use of chemical exfoliation together with chemical reduction to achieve reduced graphene oxide. Replacing conventional reducing agents, such as NaBH4 and hydrazine, with cheap, widely available, safe, environmentally friendly, and easy-to-prepare reducing agents is a key to large-scale commercial production of reduced graphene oxide. In this work, we investigate the effectiveness of utilizing fruit extracts derived from banana peel and juice to reduce graphene oxide. After the reduction, the oxygen-containing functional groups in graphene oxide are effectively removed, and the sp2 hybridized carbon-carbon bonding networks are restored, as evidenced by the characterization using x-ray photoelectron spectroscopy and Raman spectroscopy. Our banana extracts would offer a promising pathway for realizing cheap, safe, and environmentally friendly reducing agents for the upscale production of reduced graphene oxide.

Spin coating and drop casting are viable methods for rapid and low-cost additive manufacturing of components for flexible devices and sensors. We investigated the cumulative effects of layering a conductive polymer composite 2 wt% MWCNT filler in PEDOT:PSS on a Mylar substrate for application to electromagnetic interference (EMI) shielding. The optical transmittace of spin coated composite layers is 90%, 45%, and 20% with a thickness of 0.05 µm, 0.15 µm, and 0.45 µm respectively. Drop cast composite layers have 0% transmittance due to their much greater starting thickness of 4.4 µm. The addition of isopropyl alcohol (IPA) to the solution mixture and substrate heating to 40 °C improves the conductivity, and drying time of the cured composite layers to 10 min. This study shows that the cumulative effects of composite layering are additive, but the electrical properties do not scale the same way. A significant increase in the EMI SE is mainly attributed to the enhanced electrical conductivity of the composite. The insertion of a 50 µm gap in between two 15 µm composite layers accentuates the EMI shielding effectiveness (SE) significantly to a peak of 21 dB within a narrow frequency range in the Ku-band tested.