Evaluation of metal nano-particles as growth promoters and fungi inhibitors for cereal crops

Background Nano-particles of metals can be routinely synthesized. The cereal seeds treatment with the particles can improve early growth and crop production. Moreover, the treatment is robust and economical. Methods Metal (Fe0, Cu0, Co0), zinc oxide (ZnO) and chitosan-stabilized silver nano-particles were synthesized and applied to cereal seeds. The germination rate, early plant development and inhibition effects on pathogenic fungi were quantified. Results It was found that all nano-particles had a positive effect on the development of healthy cereal seedlings. In particular, the length of the above-ground part of the seedlings was increased by 8–22%. The highest inhibition effect was observed on Helminthosporium teres with the application of Co0 and chitosan-Ag. Pre-sowing treatment with metal nano-particles reduced the number of infected grains by two times for wheat and 3.6 times for barley. The application also increases the chlorophylls and carotenoids in both uninfected and infected seedlings. Conclusions The results demonstrated a robust application of nano-particles in improving cereal production. Graphical Abstract

Modulation of Conductivity and Contact Resistance of RuO2 Nanosheets via Metal Nano-Particles Surface Decoration

We studied the variation in electrical conductivity of exfoliated RuO2 nanosheets and the modulation in the contact resistance of individual nanosheet devices using charge transfer doping effects based on surface metal nanoparticle decorations. The electrical conductivity in the monolayer and bilayer RuO2 nanosheets gradually increased due to the surface decoration of Cu, and subsequently Ag, nanoparticles. We obtained contact resistances between the nanosheet and electrodes using the four-point and two-point probe techniques. Moreover, the contact resistances decreased during the surface decoration processes. We established that the surface decoration of metal nanoparticles is a suitable method for external contact engineering and the modulation of the internal properties of nanomaterials.

On the role of N-methylmorpholine-N-oxide (NMMO) in the generation of elemental transition metal precipitates in cellulosic materials

Several literature reports describe the role of aqueous solutions of N-methylmorpholine-N-oxide monohydrate (NMMO) as a suitable medium for the generation of transition metal (nano)particles in or on cellulosic materials and further elaborate its role as a co-reactant of the transition metal salts that are reduced to the elemental metal. However, this would assign NMMO the role of a reductant, which is in contradiction of its obvious oxidative nature. In the present study, the exemplary cases of silver, gold, and platinum salts as the precursors of the respective metal (nano)particles in aqueous NMMO/cellulose mixtures were investigated. Naturally, NMMO did not act as a reducing agent in any case—this role was taken over by the frequently used NMMO stabilizer propyl gallate, or by cellulose itself, into which carbonyl and carboxyl groups were introduced. Also, hypochlorite—produced intermediately from chloride ions and subsequently undergoing disproportionation into chloride and chlorate—or transient N-methylene(morpholinium) ions generated from NMMO, which are in turn oxidized to formyl morpholide, can act as the corresponding reductants while the metal ions are reduced, depending on the reaction conditions. Apart from providing interesting mechanistic insights, the study points to the importance of a precise description of the composition of the chemical systems used, as well as the importance of seemingly inert auxiliaries, which turned out to be essential co-reactants in the metal (nano)particle generation. Graphic abstract

Recent Advancements in Green Synthesis of Nanoparticles for improvement of bioactivities: a Review

: Natural products have widely been used in applications ranging from antibacterial, antiviral, antifungal and various other medicinal applications. Use of these natural products was recognized way before the establishment of basic chemistry behind the disease and the chemistry of plant metabolites. After the establishment of plant chemistry various new horizons evolved, and application of the natural products breached the orthodox limitations. In one such interdisciplinary area, use of plant materials in the synthesis of nano particles (NPs) has exponentially emerged. This advancement has offered various environment friendly methods where hazardous chemicals are completely replaced by natural products in the sophisticated and hectic synthesis processes. This review is an attempt to understand the mechanism of metal nano particles synthesis using plant materials. It includes details on the role of plant’s secondary metabolites in the synthesis of nano particles including the mechanism of action. In addition, use of these nano materials has widely been discussed along with the possible mechanism behind their antimicrobial and catalytic action.

Dimethylglyoxime Clathrate as Ligand Derived Nitrogen-Doped Carbon-Supported Nano-Metal Particles as Catalysts for Oxygen Reduction Reaction

Nitrogen-doped carbon-supported metal nano-particles show great promise as high-performance catalysts for novel energies, organic synthesis, environmental protection, and other fields. The synergistic effect between nitrogen-doped carbon and metal nano-particles enhances the catalytic properties. Thus, how to effectively combine nitrogen-doped carbon with metal nano-particles is a crucial factor for the synthesis of novel catalysts. In this paper, we report on a facile method to prepare nitrogen-doped carbon-supported metal nano-particles by using dimethylgly-oxime as ligand. The nano-particles of Pd, Ni, Cu, and Fe were successfully prepared by the pyrolysis of the corresponding clathrate of ions and dimethylglyoxime. The ligand of dimethylglyoxime is adopted as the source for the nitrogen-doped carbon. The nano-structure of the prepared Pd, Ni, Cu, and Fe particles are confirmed by X-ray diffraction, scanning electron microscopy, and trans-mission electron microscopy tests. The catalytic performances of the obtained metal nano-particles for oxygen reduction reaction (ORR) are investigated by cyclic voltammetry, Tafel, linear sweeping voltammetry, rotating disc electrode, rotating ring disc electrode, and other technologies. Results show that the nitrogen-doped carbon-supported metal nano-particles can be highly efficient catalysts for ORR. The results of the paper exhibit a facile methodology to prepare nitrogen-doped carbon-supported metal nano-particles.

Preparation and Application of Metal Nanoparticals Elaborated Fiber Sensors

In recent years, surface plasmon resonance devices (SPR, or named plamonics) have attracted much more attention because of their great prospects in breaking through the optical diffraction limit and developing new photons and sensing devices. At the same time, the combination of SPR and optical fiber promotes the development of the compact micro-probes with high-performance and the integration of fiber and planar waveguide. Different from the long-range SPR of planar metal nano-films, the local-SPR (LSPR) effect can be excited by incident light on the surface of nano-scaled metal particles, resulting in local enhanced light field, i.e., optical hot spot. Metal nano-particles-modified optical fiber LSPR sensor has high sensitivity and compact structure, which can realize the real-time monitoring of physical parameters, environmental parameters (temperature, humidity), and biochemical molecules (pH value, gas-liquid concentration, protein molecules, viruses). In this paper, both fabrication and application of the metal nano-particles modified optical fiber LSPR sensor probe are reviewed, and its future development is predicted.