Next-generation nanomaterials for environmental applications through the advanced green chemistry approach

I nanomateriali di nuova generazione (NM) ad alte prestazioni sono molto desiderati; tuttavia, le procedure di sintesi esistenti sono costose, complicate e insostenibili. Il forte consumo di risorse naturali, l'uso di reagenti sintetici pericolosi e i metodi di sintesi dannosi per l'ambiente sono le principali preoccupazioni che richiedono metodi di progettazione più sicuri. Soprattutto, seguendo gli Obiettivi per lo Sviluppo Sostenibile (SDG) delle Nazioni Unite, vale la pena implementare un approccio di nanosintesi sostenibile (SNS). Un passo avanti, un modo molto efficiente potrebbe essere il concetto "dal rifiuto - al trattare il rifiuto", che è stato seguito attivamente nella presente tesi di laurea. I NM di nuova generazione ad alte prestazioni sono stati ottenuti attraverso la valorizzazione di rifiuti eterogenei e comprendono a)- grafene mutato come NM b)- TiO2-NM anatasio puro c)- TiO2-NM policristallino d)- TiO2-NM anatasio termostabile non drogato con metalli e)- nanocellulosa f)- nanocompositi (NC) combinando nanocellulosa e TiO2-NM o ossido di grafene ridotto (rGO). Il monitoraggio operando di un sensore di metanolo a temperatura ambiente in nanocomposito (TiO2@rGO-NC) ha dimostrato che il meccanismo di rilevamento del nanocomposito si basa sull'effetto combinato dell' assorbimento fisico reversibile del metanolo e del chemi-assorbimento irreversibile, sulla modifica del sensore nel tempo, e sulla deplezione/ripristino di elettroni/O2 a causa di una reazione elettrochimica superficiale che forma CO2 e H2O. Inoltre, i TiO2-NMs di sintesi green (GS) hanno dimostrato una rapida rimozione degli inquinanti organici (Crystal Violet, Methyl Violet) dalle acque reflue attraverso l'adsorbimento superficiale e la fotocatalisi, nonché la degradazione fotocatalitica (NO)x sotto luce UV e visibile, rispettivamente, superiore del 70% rispetto a quella di due TiO2-NMs di grado commerciale. Inoltre, i TiO2-NM non drogati con metalli, aggiunti a vernici a base d'acqua, sono stati in grado di ottenere una rimozione del 99% degli inquinanti adsorbiti in superficie sotto i raggi UV e la luce naturale del sole, insieme a un'eccellente stabilità nella formulazione di una vernice.High performance next-generation nanomaterials (NMs) are much desired; however, the existing synthesis procedures are costly, complicated, and unsustainable. Robust consumption of natural resources, use of hazardous synthetic reagents and environmentally harmful synthesis methods are the main concerns which demand safer-by-design methods. Most importantly, following UN Sustainable Development Goals – SDGs, it is worthwhile to implement sustainable nanosynthesis (SNS) approach. A step forward, a much efficient way could be the concept of from waste – to treat waste which was actively followed in the current dissertation. High performance next-generation NMs were obtained through heterogenous waste valorization and include a)- mutated graphene like NMs b)- pure anatase TiO2-NMs c)- polycrystalline TiO2-NMs d)- non-metal-doped thermostable anatase TiO2-NMs e)- nanocellulose f)- nanocomposites (NC) by combining nanocellulose and TiO2-NMs or reduce graphene oxide (rGO). Operando monitoring of a room temperature nanocomposite (TiO2@rGO-NC) methanol sensor demonstrated that the sensing mechanism of the nanocomposite relies on the combined effect of methanol reversible physisorption and irreversible chemisorption, sensor modification over time, and electron/O2 depletion-restoration due to a surface electrochemical reaction forming CO2 and H2O. Moreover, green synthesized (GS) TiO2-NMs have demonstrated rapid removal of organic pollutants (Crystal Violet, Methyl Violet) from wastewater through surface adsorption and photocatalysis as well as photocatalytic (NO)x degradation under UV and visible-light respectively, 70% higher than that of two commercial grade TiO2-NMs. Additionally, non-metal-doped TiO2-NMs, when added to water-based paint, were able to achieve 99% removal of surface adsorbed pollutants under UV and natural sunlight, paralleled by excellent stability in a paint formulation

GREEN SYNTHESIS OF PLANT-MEDIATED METAL NANOPARTICLES: THE ROLE OF POLYPHENOLS

The use of metal nanoparticles (MNPs) in various fields is increasing day-by-day leading to a genuine concern about the issues related to their environmental and biological safety. The major approaches for the synthesis of NPs include physical and chemical methods which are expensive and hazardous to health in addition to being toxic to the environment. This review highlights the potential of plant extracts to carry out the synthesis of MNPs with a special emphasis on the role of flavonoids in nanosynthesis. This green and clean approach have been actively utilized in recent years as an alternative to conventional hazardous approaches. It has proved as cost-effective, non-toxic, less time and labor consuming, efficient, and eco-friendly method for the synthesis of MNPs with specific biological actions. This review also focuses on the role of polyphenols, including the flavonoids as bioreductants of metal salts for the synthesis of NPs along with their biomedical applications. Various examples of the MNPs, along with their biological actions, have also been summarized

Plant-mediated synthesis of nanoparticles: A newer and safer tool against mosquito-borne diseases?

Abstract Prevention and control of mosquito-borne diseases is a key challenge of huge public health importance. Plant-mediated synthesis of nanoparticles has recently gained attention as a cheap, rapid and eco-friendly method to control mosquito vector populations, with special reference to young instars. Furthermore, plant-fabricated nanoparticles have been successfully employed as dengue virus growth inhibitors. In this Editorial, parasitologists, entomologists and researchers in drug nanosynthesis are encouraged to deal with a number of crucial challenges of public health importance

Recent advances in multistep solution nanosynthesis of nanostructured three-dimensional complexes of semiconductive materials

AbstractConstructing simply nanostructured zero-, one-, and two-dimensional crystallites into three-dimensional multifunctional assemblies and systems at low-cost is essential and highly challenging in materials science and engineering. Compared to the simply nanostructured components, a three-dimensional (3D) complex made with a precisely controlled spatial organization of all structural nanocomponents can enable us to concert functionalities from all the nanocomponents. Methodologically, so doing in nm-scales via a solution chemistry route may be much easier and less expensive than via other mechanisms. Hence, we discuss herein some recent advances in multistep solution syntheses of nanostructured 3D complexes of semiconductors with a focus mainly on their synthetic strategies and detailed mechanisms

Nanosynthesis Techniques of Silica-Coated Nanostructures

Core-shell nanomaterials are fast-emerging hybrid nanocomposites in area of nanotechnology, materials science and biochemistry, which are fast attracting research attention. Nanostructured nanomaterials are utilized in wide industry fields such as electronics, biopharmaceutical, biomedicine, optics and biocatalysis. Owing to the additional exterior shell-coating material, the primary core material’s functionality, biocompatibility, chemical stability and colloidal dispersibility can be greatly enhanced. Silica, in particular, is found to be an excellent exterior shell-coating material, has been widely researched for the synthesis of core-shell nanocomposite materials. So far, there have been numerous publications devoted to silica-coating techniques using hydrophobic silanes, such as tetraethylorthosilicate (TEOS) or tetramethyl orthosilicate (TMOS), via the classic Stober method. Recently, there has been strong interest in the use of water-soluble silanes such as MPTMS (3-(mercaptopropyl)-trimethoxysilane), MPTES (3-(mercaptopropyl-triethoxysilane), MTMS (3-(methyltrimethoxysilane)) and sodium silicate for water-based silica-coating techniques have gained much attention, due to the fast-growing need to focus on process simplicity, large-scale fabrication and environmental-friendly synthesis techniques of silica-based core-shell nanomaterials. Hence, this chapter focuses on the recent development on silica-coating techniques for colloidal nanoparticles, particularly on water-based techniques and morphologies. In summary, we emphasize the importance of advanced nanomaterials in today’s world and envisage there will be more breakthrough research on aqueous silica-coating techniques for silica-encapsulated core-shell nanomaterials

Molecular mechanics and molecular dynamics analysis of Drexler-Merkle gears and neon pump

Over the past two years at the Materials and Process Simulation Center, we have been developing simulation approaches for studying the molecular nanomachine designs pioneered by Drexler and Merkle. These nanomachine designs, such as planetary gears and neon pump, are described with atomistic details and involve up to 10 000 atoms. With the Dreiding and universal force fields, we have optimized the structures of the two planetary gear designs and the neon pump. At the Fourth Foresight conference, we reported rotational impulse dynamics studies of the first and second generation designs of planetary gears undergoing very high-frequency rotational motions. We will explore stability of these designs in the lower frequency regimes which require long time simulations. We will report the molecular mechanics and molecular dynamics simulations performed on these model systems. We explore the following modes in these studies: (1) impulse mode; (2) constant angular velocity - perpetual rotation; (3) constant torque - acceleration from rest

Electrochemically assembled quasi-periodic quantum dot arrays

doi: 10.1088/0957-4484/7/4/010We describe two electrochemical self- assembly processes for producing highly ordered quasi-periodic arrays of quantum dots on a surface. The advantages of these techniques are: (i) they are `gentle' and do not cause radiation damage to nanostructures unlike beam lithography, (ii) they have high throughput and are amenable to mass production unlike direct-write lithography, (iii) structures can be delineated on non- planar substrates, and (iv) the techniques are potentially orders of magnitude cheaper to implement than conventional nanosynthesis. Samples produced by these techniques have been characterized by microscopy, optical and transport measurements, Auger and x-ray. These measurements reveal intriguing properties of the nanostructures. In this paper, we describe our initial results and show the promise of such techniques for low-cost and high-yield nanosynthesis.This work was supported by the Department of Energy grant DE-FG02-90ER45427 administered by the Midwest Superconductivity Consortium (Nebraska, Notre Dame and Missouri), and by the US Army Research Office under grants DAAH04-95-1-0586 (Nebraska and Notre Dame) and DAAL03-92-G0381 and EPSCoR DAAL03-92- G0367 (Missouri). The work at Argonne was supported by the US Department of Energy under grant BESDMS-W-31-109-ENG-38

Production and characterization of silver nanoparticles in cultures of the cyanobacterium A. platensis (Spirulina)

The increasing application of Silver nanoparticles in biologically-relevant areas (including production of textiles, cosmetics, and biomedical devices), where their presence provides a continuous release of silver ions to provide protection against bacteria and other unwanted microbial contaminants urges adoption of intrinsically biologically safe production processes. Various species of cyanobacteria and algae have been known to absorb and take up heavy metal ions. This capability is shown also by Arthrospira platensis (Spirulina), a cyanobacterium that enjoys the Generally Recognised as Safe (GRAS) status and has been declared by WHO one among the greatest superfood. The present study aims at investigating the coupling between the recognised beneficial effects of Spirulina biomass to the antimicrobial activity of Ag nanoparticles (SNPs). In this work, Spirulina was grown in sequential cultures targeting biomass production and nanoparticle formation. The cultures were conditioned during their lifetime in order to assess the effect of pH and added polysaccharides on the size and on the stability of the obtained SNPs. The synthesized SNPs were characterized as to their size and stability (Nanosizer), composition (XRD) and structural aspect (Scanning Electron Microscope)