Abstract

     Wastewater from pharmaceutical industries contains different antibiotics and other effluents that directly affect the environment. For the degradation of antibiotics, nanotechnology is an emerging field in research that majorly focuses on molecules and atoms. Nanoparticles are fine micro-particles with more than one dimension from a size of 1–100 nm. The synthesized nanoparticles can directly be used for the process of degradation of antibiotics in wastewater. Titanium dioxide nanoparticles are majorly used among nanoparticles due to their small surface area and particle size. There are various physical, chemical and conventional (biological) methods for synthesizing titanium dioxide nanoparticles. Green synthesis is an environmentally friendly, less expensive and harmless approach, and these methods are much more efficient than any other physical-chemical means. Titanium dioxide nanoparticles are used for different purposes. In food products, these nanoparticles act as photocatalysts and are also used as a coating material in food packaging. Electrochemical biosensors are combined with titanium dioxide nanoparticles for developing nano sheet matrices. Furthermore, this review describes the usage of biological components (plants, microorganisms like fungi and bacteria) to synthesize titanium dioxide nanoparticles. The present review also focuses on applying synthesized titanium dioxide nanoparticles in various drug delivery systems and other bioactivities.

Introduction

     Water is one of the important components of life used in the domestic, industrial, and agricultural sectors. The increase in consumption leads to an increase in the toxicity of pollutants inside water. The concentrations of emerging pollutants like pharmaceutical compounds have increased [1]. Various types of pharmaceutical compounds are observed in the aqueous environment, including antibiotics. These compounds reach the aquatic habitat through hospital effluents, the pharmaceutical industry and human livestock. The consumption of antibiotics has increased, and the concentration increases inside the aquatic environment, leading to the development of antibiotic-resistant bacteria [2,3].

     To remove antibiotics from wastewater, the traditional sewage treatment method is not appropriate and is not much effective in removing the residuals of antibiotics. Nanoparticles can be used as a photocatalyst for the degradation of antibiotics and other organic pollutants [4]. Nanotechnology is defined as synthesizing and developing various nanomaterials by manipulating the matter at the nanoscale [5]. Nanomaterials are a bridge between molecular material and bulk material. They have a size range of 1–100 nm due to their different shapes, sizes, large surface area, and possess high reactivity [6]. This has become an emerging field in science in the last few years due to its wide range of applications [7]. Because of its small size, the effect can be seen in the physical, optical, chemical properties, melting point, and dielectric constant of various nanoparticles [8].

Conclusion

     The interest in green synthesis is due to its advantages of being innocuous to the environment. Different parts of plants are used for synthesis purposes, and their characterization using various techniques helps form TiO2 NPs of varied shapes and sizes. The green synthesis of TiO2 NPs can be used in biomedical, and the delivery of drugs and antibiotics in wastewater of pharmaceutical industries can be degraded using nanoparticles. Because of the less use of precursors, TiO2 is widely used to remove microbes from water surfaces. The nanoparticles inhibit the growth of microbes and are used in wound dressing. Moreover, nanoparticles synthesized using the green routes are more effective than chemical or physical means.

1- Introduction

2- Experimental section

3- Results and discussion

4- Conclusions

References

Abstract

In this paper, a targeting hyaluronic acid (HA)/mesoporous silica nanoparticle (MSN) based drug delivery system (DDS) with dual-responsiveness was prepared for cancer therapy. To avoid the side reaction between the anti-cancer drug doxorubicin hydrochloride (DOX) and HA, host-guest interaction was applied to fabricate the DDS named DOX@MSN-SS-N=C-HA. The “nanocontainer” MSN was modified with benzene ring via both pH-sensitive benzoic imine bond and redox-sensitive disulfide linkage. When DOX was loaded in the pores of MSN, the channels were then capped by the “gatekeeper” β-CD grafted HA (HA-g-CD) through host-guest interaction between β-CD and benzene. HA endowed the drug carriers with the targeting capability in CD44 over-expressed cancer cells. After cellular uptake, the carriers could rapidly release DOX for cell apoptosis due to both the hydrolysis of benzoic imine bond at low pH and the cleavage of disulfide bond at a high concentration of glutathione (GSH) intracellular. In vitro drug release studies and in vitro cytotoxicity studies were taken to investigate the dual-responsiveness of the carriers. And the CD44-receptor mediated cancer cell targeting capability was investigated as well. In conclusion, the targeted dual-responsive complex DDS fabricated through host-guest interaction has promising potential in cancer therapy.

Introduction

Chemotherapy remains one of the major therapeutic approaches applied to treat cancer in clinic. However, the disadvantages of traditional chemotherapeutic drugs such as unfavorable pharmacokinetics, poor biodistribution and lack of selectivity for target tissues reduce the utilization of the drugs and cause serious side effects [1]. To tackle these problems, anti-cancer drug delivery systems (DDSs) based on nanotechnology have been introduced and developed rapidly in recent decades [1–4]. DDSs such as liposomal daunorubicin (DaunoXome), pegylated liposomal doxorubicin (Doxil), albumin nanoparticle based Nan-paclitaxel (Abraxane) and polymeric micelle paclitaxel (GenexolPM) have already been approved for clinical treatment of cancer [3,4]. These nanosized DDSs can be accumulated in tumor tissues more easily via enhanced permeability and retention (EPR) effect to improve the pharmacokinetics and biodistribution of the drugs, as well as to reduce their side effects [5]. Though the commercial DDSs represented by the liposomal doxorubicin can overcome part of the shortcomings of traditional anticancer drugs, they cannot or only modestly improve patients’ overall survival [3,6–9]. Therefore, more efforts are needed to develop novel advanced DDSs. The properties including controlled drug release based on stimuli- sensitivity [10,11] and ligand-mediated active cancer targeting [12–15] introduced make the newly reported DDSs with better therapeutic effects [1–4]. During the past decade, mesoporous silica nanoparticle (MSN) based DDSs have attracted considerable attention from scientists worldwide [16,17]. MSNs can be simply synthesized with tunable size, shape, pore size and volume [17,18], and are easy surface functionalization [16]. These advantages, as well as the high drug loading capacity and good biocompatibility, ensure that MSNs are excellent choices for designing safe and efficient drug carriers [16–18].

1- Introduction

2- Material and methods

3- Results and discussion

4- Conclusions

References

Abstract

Mesoporous silica nanoparticles with folic acid (MSN−COOH-Tet-HBP-FA) are able to mediate targeting and have a pH stimulation response character, and therefore have been successfully synthesized as vectors for antitumor drug delivery. The model drug is tetrandrine (Tet). The chemical structure and properties of these NPs were characterized through systematic characterization analyses. Their drug loading capacity was significantly improved through carboxy modification (26.86 % in max), and they exhibited pH-dependent drug release profiles(“zero pre-release” within 20 h in a normal physiological environment). In vitro cytotoxicity and cell uptake of the as-synthesized NPs in Hela and A549 cells were also evaluated, and exhibited high cytotoxicity and cell-targeted uptake capacity. It was concluded that MSN−COOH-Tet-HBP-FA could be used as a promising drug delivery system for cancer therapy.

Introduction

Cancer is currently considered to be a leading factor that threatens human lives, and chemotherapy remains one of the most common methods used for cancer treatment. However, traditional drugs are nonspecific and cannot discriminate cancer cells and normal cells, which not only limits the accumulation of drugs in tumor cells, but also leads to systemic toxicity and adverse side effects. In order to improve the efficacy of chemotherapy, many studies have been devoted to the development of tumor-targeted nanocarriers, which can be used to control the delivery of antitumor drugs. Using the enhanced permeation and retention (EPR) effects, researchers have developed multiple nanocarrier platforms, including liposomes, polymer nanoparticles, nano-micelles, and dendrimers, which are used to delivery anticancer drugs into tumor tissues. However, the EPR effect is not efficient enough to eradicate the side effects of cytotoxic drugs and to exert the anticancer therapy selectively in cancer cells. In order to enhance the targeting and tumoral uptake ability, the external surface of nanocarrier is often modified with various ligands, which can significantly enhance the interaction between the cancer cells and the nanocarriers[. Targeted agents typically include antibodies (such as monoclonal antibodies), peptides (such as Arg-Gly-Asp (RGD)), and small molecule compounds (such as folic acid).

1- Introduction

2- Materials and methods

3- Results and discussion

4- Conclusions

References

Abstract

Nowadays, a combinatorial drug delivery system that simultaneously transports two or more drugs to the targeted site in a human body, also recognized as a dual-drugs delivery system, represents a promising strategy to overcome drug resistance. Solid lipid nanoparticles loaded with clotrimazole (CLZ) and alphalipolic acid (ALA), considered as an effective agent in the reduction of reactive oxygen species, can enhance anti-infective immunity being proposed as a non-toxic and mainly non-allergic dual-drugs delivery system. In this study, uncoated and cationic CLZ-ALA-loaded SLN were prepared and compared. Suspensions with a narrow size distribution of particles of mean size below 150 nm were obtained, having slight negative or highly positive zeta potential values, due to the presence of the cationic lipid, which also increased nanoparticles stability, as confirmed by Turbiscan® results. Calorimetric studies confirmed the rationale of separately delivering the two drugs in a dual-delivery system. Furthermore, they confirmed the formation of SLN, without significant variation in presence of the cationic lipid. In vitro release studies showed a prolonged drug release without the occurrence of any burst effect. In vitro studies performed on 25 strains of Candida albicans showed the antimicrobial drug activity was not altered when it was loaded into lipid nanoparticles. The study has proved the successfully encapsulation of CLZ and ALA in solid lipid nanoparticles that may represent a promising strategy to combine ALA protective effect in the treatment with CLZ.

Introduction

Fungal infections, most of all candidiasis, represent an increasing challenge affecting global health, that in many cases produces morbidity and mortality in immunocompromised and intensive care unit patients [1,2]. Among different types of fungi, Candida albicans represents the main cause of fungal diseases, responsible of both orally and vaginally yeast infections, overall when a decrease in Lactobacillus concentration appears [3]. Usually, polyenes, echinocandins and azoles are the most used drugs for the treatment of fungal infections [4], even if the requirement of early treatment and the occurrence of side effects still limit the efficiency of the therapy. Among azoles, Clotrimazole (CLZ) is one of the most broad-spectrum antimycotic drug used for the treatment of vulvovaginal and oropharyngeal candidiasis [5]. Moreover, CLZ has been claimed to show a selective antibacterial activity [6,7] and ability to inhibit in vitro Streptococcus mutans biofilm and virulence [8]. CLZ antifungal activity is related to its capability to interfere with the biosynthesis of ergosterol, the major component of the fungal cytoplasmic membrane, with the consequent depletion of ergosterol and its replacement with the aberrant sterol species, 14-amethylsterol, thus disturbing the membrane permeability and fluidity [9]. However, the increasing antifungal resistance to azoles, mainly among immunocompromised patients, strongly limits the effective treatment of mycoses [10]. Combinatorial drug delivery is a promising strategy to prevent potential drug resistance [11]. We have recently demonstrated the possibility to improve CLZ effectiveness exploiting its nanoencapsulation in lipid nanoparticles prepared by additionally using of essential oils from Mediterranean area, highlighting their synergistic effect [12].

1- Introduction

2- Experimental section

3- Results and discussion

4- Conclusion

References

Abstract

A series of hemiphasmidic luminescent liquid crystalline polymers, in which the hemiphasmidic mesogen containing cyanostilbene were linked to the polymethacrylate main-chains via flexible spacers with different lengths, named poly {(Z)-m-(4-(1-cyano-2-(3,4,5-tris(octyloxy)phenyl)vinyl)phenoxy)alkyl methacrylate} (donated as Pr-m, m = 2, 4, 6, 8, 10) were synthesized via free radical polymerization. The phase structures and photophysical properties of Pr-m were investigated in detail by a combination of techniques including differential scanning calorimetry (DSC), polarizing optical microscopy (POM), small-angle X-ray scattering (SAXS), UV–Vis absorption spectra (UV–Vis spectra), photoluminescence spectra (PL spectra) and particle size analyzer. The results revealed that the phase structures of Pr-m transformed from hexagonal columnar phase (m = 2, 4) to smectic A phase (m = 6, 8, 10) with the increasing of flexible spacer length. All of the polymers featured similar AIEE properties, however, the solid state quantum yields of Pr-m decreased with the increasing flexible spacer length, and the solid quantum yields of Pr-m decreased from 8.55 (Pr-2) to 3.71 (Pr-10) with the increasing flexible spacer length.

Introduction

Over the past few decades, liquid crystals (LCs) have been widely studied as a type of functional material [1-9]. A substantial number of LCs have been synthesized, and their physical and chemistry properties have been investigated because the LCs show excellent anisotropic physical properties that can be used in many classical fields, such as stimuli-responsive [10-12], information storage [3, 4], and photomechanical materials [13, 14] etc. Among various applications of LCs, display materials is always the most important application direction of LCs. However, the conventional liquid crystal materials are non-self-luminescent, so that a backlight needs to be added in the liquid crystal display device, which violates the development trend of energy saving and thinning of liquid crystal display device [15]. Therefore, new strategy toward more efficient liquid crystal display device is highly desirable. Luminescent liquid crystals (LLCs), which combines optoelectronic characteristics of luminescent materials with the unique properties of anisotropic fluids, is expected to be an effective way to solve those problems mentioned above. LLCs can overcome the shortcomings of traditional liquid crystals as display materials and enjoy tremendous advantages for the construction of linear or circular polarized light emitting materials [16, 17]. In view of the traditional luminogens, researchers have tried to construct fluorescent liquid crystal materials [18-20]. However, due to the aggregation caused quenching (ACQ) effect, these fluorescent liquid crystal materials usually emit strong fluorescence only in dilute solution while hardly emit light in aggregate state, which makes the preparation of LLCs with excellent performance intractable [21-24].

1- Introduction

2- Experimental

3- Results and discussion

4- Conclusions

References

Abstract

Multiple wall carbon nanotubes (MWCNT) present advantages for optoelectronic applications such as the large effective photo-collector surface as well as the possibility to tune their band gap and absorbance through the growth parameters. We demonstrate a hybrid MWCNT/Si3N4/n-Si photodetector based on ordered MWCNTs and evaluate its performance in the UV, visual and near IR spectrum (200–1000 nm). The basic device and some meaningful variations including additional layers are electrically and optically tested and compared. The overall results suggest that all devices had a satisfactory performance in the visual part of the spectrum and that the basic structure had the better performance as a UV detector (EQE 90% @ 275 nm@ 7 V). The aim of this work is to demonstrate that the growth of dense ordered MWCNTs can be successfully combined with other semiconductor clean room processes in order to fabricate photodetectors, provided that the side effects are taken into account and the process flow is selected appropriately.

Introduction

Carbon nanotubes (CNT) along with other carbon allotropes like fullerenes, quantum dots and graphene have attracted great interest because of their unique optoelectronic properties that may lead to novel photosensitive devices. The advantages of these materials are their tunable bandgap, high absorption coefficients and high charge carrier mobility [1],[2]. Several photodevices have appeared, based either on single wall (SWCNT)[3],[4], [5], multiple wall carbon nanotubes (MWCNT)[6],[7] or combinations with graphene[8] using diverse geometries such as planar metal-semiconductor-metal (MSM) or vertical metal-insulator-semiconductor (MIS) structures. The use of CNTs in detector devices for infrared has attracted particular attention[4], [7], [9]. The combination of CNTs with conventional semiconductors and metals to form a device presents technological challenges because of the high temperatures required for the production of CNTs and the catalysts used (e.g. Fe). These conditions may result in structural modifications of the substrate specially when the CNT formation temperature approaches the formation temperatures of other layers or even cause metal migration. One way to circumvent these problems is the separate preparation of CNTs in solution[10], [11]. The drawback of using CNTs from solution is that the effective area of the sensor is limited and this effects the responsivity of the device. On the other hand the use of ordered free-standing MWCNTs for photodevices[12] presents advantages, since they have a tunable absorbance depending on their height while their ordering results in a large effective area sensor. Additionally the bandgap depends on their thickness, thus it is tunable by changing the formation conditions. In this work we fabricated and evaluated a hybrid MWCNT/Si3N4/n-Si photodetector based on ordered dense MWCNTs. The intermediate silicon nitride layer is conductive because of the contamination from the Fe catalyst (Ferrocene, present in MWCNT growth process) and the Au electrode and its conductance is regulated by its thickness. The basic device shows adequate responsivity in the UV and visible part of the spectrum. Along with this device we also fabricated two variations, one with an additional Si3N4 layer on the backside (device NC) and one with an Indium Tin Oxide (ITO) film which overlaps the MWCNT film and the Au electrode (device CI). We investigated the effect of the inclusion of these layers in the basic device (C) by studying the electrical and optical properties.

1- Introduction

2- Experimental

3- Results and discussion

4- Conclusions

References

Abstract

The chiral separation of baclofen (Bac) was obtained by nano-liquid chromatography tandem mass spectrometry (nano-LC–MS/MS) using a 100 μm I.D. fused silica capillary column packed with silica particles chemically modified with vancomycin. Various experimental parameters, such as composition (buffer concentration, water content, organic modifier) and pH of the mobile phase and sample solvent were investigated for method optimization. In order to increase the sensitivity an on-column focusing procedure was applied. Acceptable separation of Bac enantiomers was obtained in less than 11 min eluting in isocratic mode, with 90:10 MeOH/water (v/v) containing 10 mM ammonium acetate at pH 4.5. These optimized experimental conditions were applied to the analysis of human plasma samples spiked with racemic mixture of Bac. The use of a Buckypaper disc as sorbent membrane allows one to recover both enantiomers with yields ≥ 65%. The method was fully validated, following the identification criteria of the European Commission Decision 2002/657/EC.

Introduction

Still today, chirality is a key topic of research because of the overriding importance of enantiomers in various areas such as environmental, food, pharmaceutical, and above all human health science. In this regard, it is worth mentioning that more than a half of the produced and prescribed drugs have one or more chiral centres [1] and, as a result, they exhibit one or more couples of enantiomers. It is well-known that drug/receptor interaction is greatly stereoselective. Consequently, only one of the two enantiomers can give the wanted pharmacological activity, whereas the other one may display inactivity, lower potency, toxicity, and even undesirable side effects. Moreover, in the pharmaceutical industry, the importance of single enantiomer preparation on drug pharmacodynamics or pharmacokinetics is still not completely understood, butin many countries, the regulatory agencies, engaged in the registration of new drugs,focus their efforts inlegislating for the registrationofthe single enantiomers. In this regards, pharmaceutical industries are asked to provide complete information about the stereochemistry and stereoselectivity of all chiral products as well as the stereoselective analytical techniques for their determination. In this context, US Food and Drug Administration and other health regulatory agencies have issued definite guidelines for both the marketing of chiral drugs and their enantiomeric separation [2].

1- Introduction

2- Experimental

3- Results and discussion

4- Conclusion

References

Abstract

In this work, the bulk and surface composition of Fe3O4 supermagnetic nanoparticles were modified for efficient epoxy curing. The bare, ethylenediaminetetraacetic acid (EDTA) capped, and cobalt (Co)-doped EDTA capped Fe3O4 nanoparticles were synthesized electrochemically. The crystalline structure and phase information, surface capping, morphology and magnetization behavior of nanoparticles were studied by X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometer (VSM), respectively. A low amount of the prepared nanoparticle (0.1 wt.%) was used in preparation of epoxy nanocomposites. Nonisothermal differential scanning calorimetry (DSC) under different heating rates was performed to study the potential of nanoparticles in curing epoxy resin with an aliphatic amine. The heat release data on nanocomposites suggest that EDTA capped Co-doped Fe3O4 considerably improved the curing reaction between epoxy resin and the curing agent. Calculations based on Cure Index approved qualitatively a shift from Poor to Good cure by concurrent lattice and surface modifications of magnetic nanoparticles. It is bielived that the approach used in this work can pave the way to enhance curability of epoxy nanocomposites by the combined modification of bulk and surface of nanoparticles.

Introduction

Addition of nanoparticles and their surface functionalization has been practised over the past three decades in order to enhance the ultimate properties and performance of organic coatings [1–5]. A Nevertheless, there is a need for looking at properties of coatings containing functionalized nanoparticles from a molecular perspective so as to be able to tune properties by controlling the curability of thermoset resins under the influence of surface-functionalized nanoparticles. The difficulty is that no molecular-level gauge is available for quantifying the status quo of cross-link density of thermoset nanocomposite to assess whether or not functionalized nanoparticles added to the system are reactive towards curing moieties [6–8]. The effect of surface modification of a wide variety of nanoparticles with low- and high-molecular weight molecules of amine, carboxylic and hydroxyl on the curability of epoxy resin was addressed in previous works of this group, which are including carbon nanotubes (CNTs) [9–11], graphene oxide (GO) nanoflakes [12–14], halloysite nanotubes (HNTs) [15–17], silica nanoparticles [18,19] and zinc oxide (ZnO) nanoparticles [20]. Reports suggest that surface functionalization of nanoparticles with high-molecular-weight ethylenediaminetetraacetic acid (EDTA) can affect ultimate properties of cross-linkable polymer nanocomposites. For instance, Syuhada et al. showed that EDTA surface-functionalized GO was dispersed well in chitosan matrix due to interaction of EDTA functional groups with chitosan [21]. Well-dispersed GO-EDTA in chitosan matrix led to facilitation of stress transfer resulting in 71% improvement in tensile strength compared to the neat chitosan film.

1- Introduction

2- Experimental methods

3- Results and discussion

4- Conclusions

References

Abstract

Cu2O-CuO layers were prepared in situ on copper foam substrates by thermal oxidation at 400 °C in air using different pretreatments with acetone, HCl and NaOH. The effect of the pretreatment in the shape and physicochemical properties of the Cu2O-CuO layers, as well as in the growth or inhibition of the copper oxide nanostructures was studied, and a growth mechanism is proposed. It was found that the pretreatment modulates the nucleation and growth of the copper oxide nanostructures, being the process with NaOH the most suitable to promote the formation of well-defined nanoneedles, while in the case of the samples pretreated with acetone and HCl, copper oxide layers with irregular shape microstructures were obtained. The composition, structural, morphological and optical properties of the copper oxide structures were determined by X-ray diffraction, scanning electron microscopy, UV-vis diffuse reflectance and photoluminescence spectroscopy. The results showed that in all cases, the presence of both copper oxides, Cu2O and CuO was observed, with an optical band gap of 1.0 and 1.3 eV. The copper oxide structures exhibited photoluminescence emission centered at 551 nm, related to the recombination of the electron-hole pairs in the samples. The materials prepared with a NaOH pretreatment showed the lower emission and recombination rate.
Moreover, the 3D Cu-Cu2O-CuO based materials were evaluated as photocathodes in a 0.5 M Na2SO4 solution and under Xe lamp illumination. The photoelectrode where 1D nanostructures were grown, exhibited the lower resistance to the charge transference in the Nyquist plots, the highest current density in the linear voltammetry and the highest photoresponse in the on-off light experiments. The improved electrical and physicochemical properties of the samples pretreated with NaOH was related to the particular 1D nanoneedle morphology, which promoted higher conductivity and photoresponse, lower resistance to the charge transference and lower recombination of free charge carriers, demonstrating the potential use of these electrodes for photoelectrochemical applications. Finally, this work proved that it is possible to grow well-defined and highly crystalline CuO nanoneedles on copper foam porous substrates through a simple, fast and clean method.

Introduction

1D nanostructured copper oxides have attracted attention recently due to their potential use in several applications such as cathodes for lithium-ion batteries [1,2], gas sensors [3] and biosensors [4,5], catalysts [6] and photocatalysts [7], as well as photocathodes for hydrogen generation from water [8,9], since cuprous and cupric oxides are usually p-type semiconductors, with a direct band gap of approximately 2.0–2.5 eV and 1.3–1.7 eV, respectively [10]. Moreover, these nanostructures are obtained from copper, an earth-abundant metal, and can be synthesized through facile and scalable methods such as simple thermal oxidation of the copper substrate [3,7,11]. Typically, copper oxide structures in the form of nanowires or nanoneedles are grown on copper substrates by thermal annealing at temperatures between 400 °C and 600 °C in air or oxygen atmospheres [12]. CuO wires, sheets and flower nanostructures have been grown on copper foam substrates and studied as supercapacitors [13], while in other work, highly porous CuO structures for batteries and fuel cells were sculptured tunning the pore sizes through the variation of the deposition conditions [14]. The scalable and facile anodization-calcination process was used also for the preparation of copper oxide anodes for ion-lithium batteries [15]. Moreover, the copper-based nanostructures prepared by this method have exhibited high selectivity, sensitivity and stability for gas sensing applications [16]. The shape of the nanostructures has been also modified through the use of surfactants, such as Triton X-100, for obtaining cabbage rose CuO structures on copper foam substrates [17], and core-shell CuO-NiO hybrid structures with enhanced supercapacitance performance have been prepared [18].

Introduction

Experimental section

Results and discussion

Conclusions

References

Abstract

Intrinsic activity modifying of electrocatalysts is crucial to realizing the excellent catalytic performance towards hydrogen evolution reaction. Herein, we demonstrate a highly efficient electrocatalyst based on heterogeneous cobalt phosphides nanoparticles. The ultrafine size of the as-prepared catalyst (∼5 nm) ensures the efficient extension of active sites. Furthermore, the incorporation of orthorhombic CoP and Co2P contributes to the improvement of the inherent catalytic property. As a consequence, the as-prepared heterogeneous cobalt phosphides nanoparticles supported on carbon cloth exhibit impressive electrocatalytic activity, which only acquire a small overpotential of 90 mV at a current density of 10 mA cm−2, and present a low Tafel slope (67.9 mV dec−1), a large exchange current density (0.58 mA cm−2) as well as good durability. Therefore, this work provides a favorable guidance for exploring executable strategies to improve catalyst activity.

Introduction

The excessive depletion of fossil fuels has led to many terrible issues, such as the global warming and “energy crisis”. Therefore, the urgency of developing eco-friendly and renewable energy sources attracts a large number of researchers to explore in the energy-related fields [1e4]. Hydrogen, due to its high-energy density and pollution-free combustion products, has been considered as an ideal energy carrier to replace exhaustible traditional energy in the future [5e8]. Electrochemical water-splitting is acknowledged to be the simplest method to gathering high-purity hydrogen, while it always requires highly active catalysts to decrease the overpotential and increase the reactive rate towards hydrogen evolution reaction (HER) [9e11]. Considerable studies have manifested that Pt group metals show excellent HER performance in acidic medium, but their large-scale applications are restricted due to their high economic cost and low abundance [12,13].

Accurately evaluating opportunities in new and emerging science and technologies is a growing concern. This study proposes an integrated framework for identifying a range of potential innovation pathways and commercial applications for solid lipid nanoparticles – one particularly promising contender within the field of nanoenabled drug delivery. Several text mining techniques – term clumping, SAO technique, and net effect analysis – as well as technology roadmapping, are combined with expert judgment to identify the main areas of R&D in this field, and to track their evolution over time. Through analysis, data from multiple sources, including research publications, patents, and commercial press, reveal possible future applications and commercialization opportunities for this emerging technology. We find that research is moving away from materials and delivery outcomes toward clinical applications. The most promising markets are pharmaceuticals and cosmetics; however, the “time-to-market” is much shorter for cosmetics than it is for pharmaceuticals. The most significant contributions of this paper have been highlighted as follows. One innovation is extracting the intelligence from three kinds of data sources after in-depth considering their characteristics and matching with the features of different technology development stages to identify innovative research topics. The second one is combining SAO technique with net effect analysis to identify what the evolutionary links between research topics are, and then to use TRM to visualize the evolution of the main areas of R&D over time.

Introduction

New and emerging science and technology has attracted great attention among scholars because of its tremendous potential to improve society and stimulate economic development. However, the threats and opportunities inherent in such technologies can cause developers to proceed with caution. On the one hand, the existing competitive advantages inherent in current technological competencies offer stability, and new technology may threaten these advantages or even eliminate entire markets. On the other hand, early analysis of new technical areas may present opportunities to take the lead before other competitors become entrenched (Guo et al., 2015). Therefore, developing ways to assess the current research focus and future development directions of new and emerging science and technologies is a compelling issue. Technology opportunity analysis (Porter et al., 1994), which applies data mining and text mining tools to ST&I resources to detect technological innovation (Ma et al., 2014 and Ma et al., 2016) offers one possible solution to this problem. The process allows analysts to explore opportunities for transforming new technologies into new products and, thus, provides decision support to researchers, R&D planners and managers, and science policy-makers (Lee et al., 2015). A number of technology opportunity studies that rely on text mining technologies have been conducted to help derive information for competitive technical intelligence analysis, technology development trend analysis (Ma and Porter, 2015), and forecasting (Ailem et al., 2016; Song et al., 2017).

The present study is aimed to reduce the environmental footprints resulted from chromite ore processing residues (COPR); a hazardous waste having Cr(VI). The solidification/stabilization of COPR through geopolymer coupled with green tea synthesized nano zerovalent iron (GT-NZVI) is an effective approach to deal with this challenge. Therefore, the blast furnace slag and metakaolin were used to prepare the composite based geopolymer and GT-NZVI particles were synthesized by oolong tea in current experiment. The GT-NZVI treated and untreated COPR was solidified in composite geopolymer. The efficiency of solidified products was evaluated through compressive strength and leaching analysis. The results depicted that varying sizes of GT-NZVI particles were successively synthesized which could be utilized for reduction of Cr(VI) existed in COPR. The solidified products having GT-NZVI treated COPR (GCM (GTNZVI) and untreated COPR (GCM) had compressive strength of 33Mpa and 47 MPa, respectively up to 50% addition of COPR waste. The immobilization effect of GCM (GT-NZVI) samples were better than GCM samples. The leaching toxicity of Cr(VI) in both GCM (GT-NZVI) and GCM samples was far below than safe limits(<5 mg/L). In addition, the fourier transform infrared spectrometry, X-Ray diffraction, scanning electron microscope equipped with energy dispersive spectrometer analysis had verified that COPR was effectively solidified in composite based geopolymer by physical and chemical means.

Introduction

In start of 19th century, the chromium salt production has gained popularity in industrial sectors due to its use in leather tanning, stainless steel production, metallurgy, dyestuff, pigment, metal polishing, wood preservative etc. (Lehoux et al., 2017). Basically, the chromium salt is produced by two ways which includes high lime and non-lime process. High lime process is considered as outdated because each ton of Cr produces 2e3 t of hazardous solid waste called chromium ore processing residues (COPR). The COPR is a hazardous waste due to presence of hexavalent chromium/Cr(VI) which is highly mobile and carcinogenic in nature. Therefore, COPR production through high lime process is prohibited in UK and USA. While, Pakistan, China, India and Russia are still using high lime process and facing the problems associated with COPR (Yu et al., 2012). The COPR associated problems are; (a) high utilization of lands during its storage as heaps and (b) increase in leaching concentration results in contamination of ecosystem (Dermatas et al., 2006). Hence, resourceful utilization/remediation of COPR is necessary which can prevent the leaching and contamination of Cr(VI). Generally, Cr(VI) remediation technologies are classified into three broad categories i.e. toxicity reduction, removal and contaminants. More specifically, the researchers had remediated Cr(VI) in COPR waste through wet detoxification, high temperature reduction, electro-kinetic remediation and solidification/stabilization (Asavapisit et al., 2005; Lehoux et al., 2017; Xu et al., 2011; Yoon et al., 2010). Among these technologies, solidification/stabilization is regarded as one of best available remediation technology that had been widely used for treatment of 57 types of hazardous wastes since 1970s (Batchelor, 2006).

Previous studies showed that Mg-Al layered double hydroxides (Mg-Al LDHs) had well anti-ultraviolet (anti-UV) aging properties when used in the asphalt materials, but it cannot contribute to improve the self-healing properties to repair cracks caused by UV aging under the microwave radiation. Fe3O4 has well microwave absorption and based on the layered structure and large surface area of Mg-Al LDHs, the primary objective of this work was to synthesize Fe3O4-decorated Mg-Al layered double hydroxides magnetic nanosheets, to envisage that the added bitumen modifier has both enhanced anti-UV aging properties and microwave absorption properties. Three modifiers were obtained by the adhesion of Fe3O4 magnetic particles on the surface of Mg-Al LDHs nanosheets, and named as L1F1 (the mass ratio of LDHs: Fe3O4 = 1:1), L2F1 (the mass ratio of LDHs: Fe3O4 = 2:1) and L1F2 (the mass ratio of LDHs: Fe3O4 = 1:2). Morphology, phase composition, chemical structure, anti-UV aging properties, static magnetic properties and microwave absorption properties of them were detected by different analytical methods. Results demonstrate that all magnetic nanosheets present the ferromagnetic behavior, L2F1 shows the lowest MS value among three types of magnetic nanosheets, and the value increases from 28.67 emug1 to 56.78 emug1 with augmented Fe3O4-LDHs ratio. Additions of Fe3O4 significantly enhance the anti-UV aging properties and microwave absorption properties of Mg-Al LDHs. The maximum RL value of L1F2 is recorded as more than two times of that of LDHs, and L1F2 shows the best anti-UV aging properties and microwave absorption properties among all magnetic nanosheets.

Introduction

Layered double hydroxides (LDHs) is a type of multifunctional inorganic supramolecular materials, which is formed by the orderly assembly of positively charged metal cation twodimensional laminate and interlayer anions [1–3]. The nanometer two-dimensional laminates of LDHs are arranged in a longitudinal order to form a three-dimensional crystal structure, which mainly composed of Mg2+ and other metal cations [4,5]. The chemical formula of LDHs can be represented by [M2+ 1xM3+ x (OH)2] x+(An)x/n- mH2 O, where M2+ and M3+ represent divalent and trivalent metal cations, respectively [6–9]. Studies have shown that the layered structure of LDHs has well shielding effect on ultraviolet rays, and can effectively improve the anti-ultraviolet (anti-UV) aging properties of the asphalt materials [5,10]. Zeng added 3% of Mg-Al layered double hydroxides (Mg-Al LDHs) into AH-90, AH-90 and SBS modified bitumen as anti-UV aging agent. The comparisons of equivalent brittle point and fatigue parameters showed that LDHs could effectively reduce the photo-oxidative aging rate of bitumen [11]. This is because when ultraviolet light passes through LDHs, the main layer of metal hydroxide can reflect and absorb ultraviolet light for multiple times. To a certain extent, it can also absorb ultraviolet rays, and the physical shielding effect of the layers on ultraviolet rays is dominant.