Different Concentrations Of Precursors Research Articles

NATURE OF ZINC OXIDE COLLOIDAL NANOCRYSTALS PHOTOLUMINESCENCE

The purpose of the study is to determine the nature of the radiative transitions responsible for the visible radiation of zinc oxide nanocrystals. Show that the size of nanocrystallites does not affect the spectral composition and location of long-wave luminescence. ZnO nanocrystals obtained by the method of colloidal synthesis with or without gelatin stabilization were investigated in the paper. The size of the nanocrystallites was determined in the approximation of the effective masses by the magnitude of the fundamental absorption edge shift. The results of calculating the size of nanocrystallites agree well with the results of SEM studies. It is shown that the main factor affecting the size of nanocrystallites is the concentration of precursors. Photoluminescence spectra of colloidal ZnO nanocrystals were studied in two spectral regions – ultraviolet and visible. Photoluminescence spectra in the ultraviolet region are characterized by three emission lines, the location of which depends on the concentration of precursors, that is, on the width of the band gap. Analysis of the energy states of intrinsic defects in nanostructured zinc oxide showed that the first two emission lines are associated with radiative transitions of excitons bound on neutral interstitial zinc atoms and on neutral zinc vacancies. The third line of ultraviolet radiation is caused by radiative transitions with the participation of deep donors, which are interstitial zinc atoms in the +2 charge state. The visible radiation spectra of colloidal ZnO nanocrystals are characterized by broad non-elemental emission bands in the blue-green and yellow-red regions of the spectrum. A detailed analysis of the spectra at different concentrations of precursors showed that the change in concentrations of precursors does not affect the spectral location of elementary emission lines. The absence of impurity absorption lines indicates that the centers responsible for visible radiation are donor-acceptor pairs. The analysis of the ratio of the emission lines intensities with increasing concentrations of the precursors shows that interstitial zinc and oxygen atoms dominate in the studied nanocrystals at high concentrations. As a result, in samples with a high concentration of precursors, blue radiation dominates over yellow and green. Thus, the study shows that by changing the concentrations of precursors, it is possible to influence both the spectral location of the edge ultraviolet luminescence and the intensity of individual long-wave luminescence components. The resulting colloidal ZnO nanocrystals can be used as luminescent sensors.

The beneficial effect of reducing agent on the synthesis of manganese oxide nanowires as electrode materials for supercapacitors

We examine the effects of precursor concentration and changes in the volume of reducing agent on the physico-chemical properties and electrochemical performance of the manganese oxide materials. Despite the fact that studies have been published on the usage of ethylene glycol as a reducing agent in the preparation of manganese oxide, there is no report on the investigation of the change in concentration of the precursor and volume of the reducing agent and how it impacts the physical, chemical, and electrochemical properties of the end products. Hence, the present work attempts to attain knowledge of the found research gap. Three different concentrations of precursor, viz. 0.1, 0.25, and 0.5 M, and four different volumes of reducing agent, viz. 0.5, 1, 3, and 5 ml, are studied. Crystallinity, morphology, chemical state, and surface area characteristics of the prepared samples are thoroughly studied using a variety of techniques. There is an increment in crystallinity and a significant change in morphology observed from nanowires to agglomerated nanostructures when the volume of reducing agent linearly increases. Interestingly, the results indicate that a lower volume of reducing agent can facilitate the development of an end product with optimum electrochemical properties for supercapacitor applications. The samples prepared with a minimum volume of reducing agent achieve a high specific surface area of 241 m2/g with a noteworthy specific capacitance of 179 F/g and also show an acceptable capacitance retention of 74.2% even after 5000 consecutive cycles. These findings might develop a favorable impact and understanding on the ratio of reactants that can be utilized in various material preparations.

The Effect of the Feeding System on Fat Deposition in Yak Subcutaneous Fat.

Fat deposition is very important to the growth and reproduction of yaks. In this study, the effect of the feeding system on fat deposition in yaks was explored by transcriptomics and lipidomics. The thickness of the subcutaneous fat in yaks under stall (SF) and graze feeding (GF) was evaluated. The transcriptomes and lipidomes of the subcutaneous fat in yaks under different feeding systems were detected by RNA-sequencing (RNA-Seq) and non-targeted lipidomics based on ultrahigh-phase liquid chromatography tandem mass spectrometry (UHPLC-MS), respectively. The differences in lipid metabolism were explored, and the function of differentially expressed genes (DEGs) was evaluated by gene ontology (GO) and Kyoto encyclopedia of genes and genome (KEGG) analysis. Compared with GF yaks, SF yaks possessed stronger fat deposition capacity. The abundance of 12 triglycerides (TGs), 3 phosphatidylethanolamines (PEs), 3 diglycerides (DGs), 2 sphingomyelins (SMs) and 1 phosphatidylcholine (PC) in the subcutaneous fat of SF and GF yaks was significantly different. Under the mediation of the cGMP-PKG signaling pathway, the blood volume of SF and GF yaks may be different, which resulted in the different concentrations of precursors for fat deposition, including non-esterified fatty acid (NEFA), glucose (GLU), TG and cholesterol (CH). The metabolism of C16:0, C16:1, C17:0, C18:0, C18:1, C18:2 and C18:3 in yak subcutaneous fat was mainly realized under the regulation of the INSIG1, ACACA, FASN, ELOVL6 and SCD genes, and TG synthesis was regulated by the AGPAT2 and DGAT2 genes. This study will provide a theoretical basis for yak genetic breeding and healthy feeding.

Phenylpropanoid biosynthetic gene expression and nutrient uptake kinetics for enhanced rosmarinic acid production in suspension cultured cells of Halodule pinifolia

This study investigated the effect of precursors (phenylalanine and tyrosine) and elicitors (methyl jasmonate and yeast) on enhanced rosmarinic acid (RA) biosynthesis, their transcript levels (HpPAL, HpC4H, Hp4CL, HpTAT and HpHPPR) and nutrient uptake kinetics from cell cultures of Halodule pinifolia (Miki) Hartog under in-vitro conditions. Different concentrations of precursors and elicitors were used, among which methyl jasmonate (20 μM) induced higher accumulation of RA (123.16 ± 3.30 mg g−1 DW) followed by phenylalanine (57.086 ± 1.01 mg g−1 DW), tyrosine (28.723 ± 1.55 mg g−1 DW) and yeast elicitor (1.95 mg g−1 DW). Further, the transcript levels of phenylpropanoid biosynthetic genes HpPAL, HpC4H and Hp4CL from MeJA treated cells were found to increase transiently, while TAT and HPPR did not express. It clearly conveyed that H. pinifola culture has undergone phenylpropanoid pathway for RA biosynthesis as compared to the control. Nutrient uptake kinetics determined the consumption of major nutrients such as phosphate, nitrate, sucrose and variations in pH during RA biosynthesis and the optimum pH was found to be pH -7.4, where the concentration of RA accumulated higher during the aforementioned pH. Therefore, the study concludes that methyl jasmonate acts as a potent elicitor for RA accumulation and the enhanced RA biosynthesis in the treated cells might be due to the activation of phenylproponoid genes HpPAL, HpC4H and Hp4CL. Furthermore, the work should be made to influence and optimize the H. pinifolia culture system for better productivity of rosmarinic acid for the food, cosmetic, pharmacy and neutraceutical applications.

Antioxidant Potential and Enhancement of Bioactive Metabolite Production in In Vitro Cultures of Scutellaria lateriflora L. by Biotechnological Methods.

Studies carried out using three different in vitro assays and a biological setting (Escherichia coil) demonstrated the antioxidant activity of Scutellaria lateriflora microshoot extract. Moreover, the extract exhibited no toxicity in a brine shrimp lethality bioassay. These results indicated that microshoots are a rich, safe source of antioxidants, which encouraged us to enhance their production in vitro. In agar and agitated cultures, two biotechnological strategies were applied: feeding the cultures with the biogenetic precursors of the phenolics—phenylalanine and tyrosine, and eliciting them with methyl jasmonate. Specific Scutellaria flavonoids and verbascoside were analysed by HPLC. Feeding with precursors (1 g/L) in agar cultures decreased the production of the metabolites. In agitated cultures, different concentrations of precursors (1.0–2.5 g/L) and the elicitor (10; 50; 100 µM) were tested. Additionally, parallel feeding with the precursor and elicitor in a concentration of 50 µM were applied. The best strategy for total flavonoid and verbascoside production was phenylalanine feeding (1.5 g/L), max. 3765 and 475 mg/100 g DW, respectively, after 7 days. This is the first report documenting the high antioxidant production in S. lateriflora microshoots after feeding with phenylalanine. Moreover, for the first time, bioreactor cultures were successfully maintained, obtaining attractive results (max. total flavonoid content 2348 and verbascoside 485 mg/100 g DW).

Synthesis different sizes of cerium oxide CeO2 nanoparticles by using different concentrations of precursor via sol–gel method

The aim of this research is to synthesize different nano sizes of cerium oxide by using different concentrations of precursors. The sol–gel method was used to synthesis CeO2 nanoparticles calcined at 400° C. The products obtained by used different concentrations of precursor (Ce(NO3)3·6H2O placed in deionized water) are range from 13.5 to 14.6 nm in diameter. With band gap from 3.2 to 3.4 e.V, nanoparticles were characterized by using .XRD, UV–vis, SEM, TEM and FTIR, this method has good Characteristic such as, It easy to use and low cost material.

Isolation and optimization of plumbagin production in root callus of Plumbago zeylanica L. augmented with chitosan and yeast extract

Chitrak (Plumbago zeylanica L.), a renowned traditional medicinal plant, is being exploited extensively for its roots which are employed in the preparations of many important herbal products (e.g. Dashmularisht, Chitrakadivati) possessing anticancer, anti-atherogenic, cardiotonic, hepatoprotective and neuroprotective properties. P. zeylanica roots, being the major source of plumbagin, were used for its isolation. Plumbagin isolation from in vivo roots was done employing column chromatography and thin layer chromatography (TLC) using a hexane: ethyl acetate (70:30) mobile phase. A total of 65 fractions were obtained which pooled down to 8 (F1–F8) based on their similar Rf values. Of the 8 fractions, F2 gave a single spot corresponding to that of the standard plumbagin which subsequently was validated and confirmed through 1H-NMR and FT-IR. For elicitation to increase plumbagin, in vitro root callus initially raised on Murashige and Skoog medium +5 μM TDZ was augmented with different concentrations of precursors (sodium acetate, l-tyrosine), biotic (chitosan, proline, lysine, salicylic acid, yeast extract) and abiotic [Pb(NO3)2, CdCl2] elicitors either alone or in combinations. The optimum increase of up to 2.07 and 2.64–folds in plumbagin was seen when callus cultures were fed individually with sodium acetate (1 mg/L) and l-tyrosine (25 mg/L), respectively. Similarly, chitosan and yeast extract when used alone, the plumbagin content was enhanced 4.58–fold at 50 mg/L and 6.50–fold at 100 mg/L, respectively. However, an enormous increase of 12.08–fold plumbagin content occurred when a combination of 50 mg/L chitosan + 100 mg/L yeast extract was used. A combination of salicylic acid (25 μM) and yeast extract (100 mg/L) also enhanced plumbagin content up to 8.23–fold. Thus, this is our first report of scaling up to 12.08–fold plumbagin content using simple and cost effective elicitors.

Sol-gel based coatings for the protection of cultural heritage textiles

In this paper, the procedure for the development of sol-gel silica coatings for the protection of cultural heritage textiles, using a multistep approach, is described. With this aim, Tetraethoxysilane precursor was used at two different concentrations to realize coatings onto textile samples, using Dibutyltindiacetate as polycondensation catalyst for sol-gel reactions. The relationship between the presence of the catalyst, the number of coating layers deposited on cotton fabrics, and the influence of such architecture on several properties of treated textiles, were investigated. In particular, the chemical structure of thin films and their morphology were studied by infrared spectroscopy and scanning electron microscopy, respectively. The thermo-oxidative properties and the abrasion resistance of sol-gel treated cotton fabrics were studied, as well as the durability of the coatings after different washing cycles. Both silica coatings provided high adhesion onto cotton textiles, while the higher silica concentration resulted in higher thermal stability and washing fastness of treated fabrics. An enhancement in the washing fastness and abrasion resistance for the two different concentrations of precursor in the presence of the catalyst was also observed. All experimental findings demonstrated the efficiency of sol-gel based materials specifically tailored to the protection and preservation of cultural heritage textiles.

Bacillus spp.: potent microfactories of bacterial IAA.

BackgroundAuxin production by bacteria is one of the most important direct mechanisms utilized by plant growth-promoting bacteria (PGPB) for the betterment of plants naturally because auxin is a plant friendly secondary metabolite synthesized naturally by bacteria, and hence improves the growth of associated plants. So, the current study focuses on bacterial synthesis of Indole-3-acetic acid (IAA) for plant growth improvement.MethodsIn the current study, the PGPB were selected on the basis of their auxin production potential and their growth promoting attributes were evaluated. Indole-3-acetic acid producing potential of two selected bacterial isolates was observed by varying different growth conditions i.e., media composition, carbon sources (glucose, sucrose and lactose) and different concentrations of precursor. Influence of various physiological factors (temperature and incubation time period) on IAA production potential was also evaluated.ResultsBoth the bacterial strains Bacillus cereus (So3II) and B. subtilis (Mt3b) showed variable potential for the production of bacterial IAA under different set of growth and environmental conditions. Hence, the IAA production potential of the bacterial isolates can be enhanced by affecting optimum growth conditions for bacterial isolates and can be used for the optimal production of bacterial IAA and its utilization for plant growth improvement can lead to better yield in an eco-friendly manner.

One-step hydrothermal synthesis of marigold flower-like nanostructured MoS2 as a counter electrode for dye-sensitized solar cells

MoS2 thin films with marigold flower-like nanostructures were grown on conductive fluorine-doped tin oxide (FTO) substrates through a one-step hydrothermal synthesis for their application as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). Different MoS2 thin film samples (A–D) were grown on FTO slides using different concentrations of precursors (sodium molybdate and thioacetamide), while keeping the Mo/S molar ratio constant (1:4.6), in all samples. The effect of varying precursor concentrations (3.2–12.6 mM on MoS2 basis) on the structure of the nanostructured thin films and their performance as DSSC-CEs was investigated. Scanning electron microscopy revealed a material with an infolded petal-like morphology. With increasing precursor concentration, the petal-like structures tended to form bunched nanostructures (100–300 nm) resembling marigold flowers. X-ray diffraction analysis, X-ray photoelectron, and Raman spectroscopy studies showed that the thin films were composed of hexagonal MoS2 with good crystallinity. Hall effect measurements revealed MoS2 to be a p-type semiconductor with a carrier mobility of 219.80 cm2 V−1 s−1 at room temperature. The electrochemical properties of the thin films were examined using cyclic voltammetry and electrochemical impedance spectroscopy. The marigold flower-like MoS2 thin films showed excellent electrocatalytic activity towards the I¯/I3¯ reaction and low charge transfer resistance (Rct) values of 14.77 Ω cm−1, which was close to that of Pt electrode (12.30 Ω cm−1). The maximum power conversion efficiency obtained with MoS2 CE-based DSSCs was 6.32%, which was comparable to a Pt CE-based DSSC (6.38%) under one sun illumination. Similarly, the maximum incident photon-to-charge carrier efficiency exhibited by MoS2 CE-based DSSCs was 65.84%, which was also comparable to a Pt CE-based DSSC (68.38%). The study demonstrated that the marigold flower-like nanostructured MoS2 films are a promising alternative to the conventional Pt-based CEs in DSSCs.

Facile Synthesis and Characterization of Ag₃PO₄ Microparticles for Degradation of Organic Dyestuffs under White-Light Light-Emitting-Diode Irradiation.

This study demonstrated facile synthesis of silver phosphate (Ag3PO4) photocatalysts for the degradation of organic contaminants. Ag3PO4 microparticles from different concentrations of precursor, AgNO3, were produced and characterized by scanning electron microscopy, powder X-ray diffraction, and UV–visible diffuse reflectance spectroscopy. Degradation rates of methylene blue (MB) and phenol were measured in the presence of microparticles under low-power white-light light-emitting-diode (LED) irradiation and the reaction rate followed pseudo-first-order kinetics. The prepared Ag3PO4 microparticles displayed considerably high photocatalytic activity (>99.8% degradation within 10 min). This can be attributed to the microparticles’ large surface area, the low recombination rate of electron–hole pairs and the higher charge separation efficiency. The practicality of the Ag3PO4 microparticles was validated by the degradation of MB, methyl red, acid blue 1 and rhodamine B under sunlight in environmental water samples, demonstrating the benefit of the high photocatalytic activity from Ag3PO4 microparticles.

Adsorptive removal of toluene and carbon tetrachloride from gas phase using Zeolitic Imidazolate Framework-8: Effects of synthesis method, particle size, and pretreatment of the adsorbent

Dynamic adsorption of toluene and carbon tetrachloride was studied on Zeolitic Imidazolate Framework-8 (ZIF-8). The ZIF-8 was synthesized using environmentally friendly procedures in an aqueous solution at ambient temperature with different concentrations of precursors. ZIF-8 samples were characterized by XRD, FTIR, SEM, DLS, and BET, and the results indicated that both synthesis methods lead to pure ZIF-8 products. The adsorption of toluene and carbon tetrachloride from gas phase was studied in a fixed bed reactor. The effects of different pretreatment conditions, particle size, and surface area of ZIF-8 on the adsorption performance were studied using a breakthrough curve. Experimental results revealed that ZIF-8 adsorption performance was improved as pretreatment temperatures was increased and particle size was reduced. The results of the experimental dynamic adsorption of toluene and carbon tetrachloride on ZIF-8 were fitted into the Thomas and Yan models. It was observed that toluene adsorption breakthrough curves were fitted in both models better than those of carbon tetrachloride curves.

Down-top nanofabrication of binary (CdO)x (ZnO)1-x nanoparticles and their antibacterial activity.

In the present study, binary oxide (cadmium oxide [CdO])x (zinc oxide [ZnO])1–x nanoparticles (NPs) at different concentrations of precursor in calcination temperature were prepared using thermal treatment technique. Cadmium and zinc nitrates (source of cadmium and zinc) with polyvinylpyrrolidone (capping agent) have been used to prepare (CdO)x (ZnO)1–x NPs samples. The sample was characterized by X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. XRD patterns analysis revealed that NPs were formed after calcination, which showed a cubic and hexagonal crystalline structure of (CdO)x (ZnO)1–x NPs. The phase analysis using EDX spectroscopy and FTIR spectroscopy confirmed the presence of Cd and Zn as the original compounds of prepared (CdO)x (ZnO)1–x NP samples. The average particle size of the samples increased from 14 to 33 nm as the concentration of precursor increased from x=0.20 to x=0.80, as observed by TEM results. The surface composition and valance state of the prepared product NPs were determined by X-ray photoelectron spectroscopy (XPS) analyses. Diffuse UV–visible reflectance spectra were used to determine the optical band gap through the Kubelka–Munk equation; the energy band gap was found to decrease for CdO from 2.92 to 2.82 eV and for ZnO from 3.22 to 3.11 eV with increasing x value. Additionally, photoluminescence (PL) spectra revealed that the intensity in PL increased with an increase in particle size. In addition, the antibacterial activity of binary oxide NP was carried out in vitro against Escherichia coli ATCC 25922 Gram (−ve), Salmonella choleraesuis ATCC 10708, and Bacillus subtilis UPMC 1175 Gram (+ve). This study indicated that the zone of inhibition of 21 mm has good antibacterial activity toward the Gram-positive B. subtilis UPMC 1175.

Direct screening of enzyme activity using infrared matrix-assisted laser desorption electrospray ionization.

High-throughput screening (HTS) is a critical step in the drug discovery process. However, most mass spectrometry (MS)-based HTS methods require sample cleanup steps prior to analysis. In this work we present the utility of infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) for monitoring an enzymatic reaction directly from a biological buffer system with no sample cleanup and at high throughput. IR-MALDESI was used to directly analyze reaction mixtures from a well plate at different time points after reaction initiation. The percent conversion of precursors to products was used to screen the enzyme activity. The reaction was performed with two different concentrations of precursors and enzyme in order to assess the dynamic range of the assay. Eventually, a pseudo-HTS study was designed to investigate the utility of IR-MALDESI screening enzyme activity in a high-throughput manner. IR-MALDESI was able to readily monitor the activity of IDH1 over time at two different concentrations of precursors and enzyme. The calculated Z-factors of 0.65 and 0.41 confirmed the suitability of the developed method for screening enzyme activity in HTS manner. Finally, in a single-blind pseudo-HTS analysis IR-MALDESI was able to correctly predict the identity of all samples, where 8/10 samples were identified with high confidence and the other two samples with lower confidence. The enzymatic activity of IDH1 was screened by directly analyzing the reaction content from the buffer in well plates with no sample cleanup steps. This proof-of-concept study demonstrates the robustness of IR-MALDESI for direct analysis of enzymatic reactions from biological buffers with no sample cleanup and its immense potential for HTS applications.

Development of α-Fe<sub>2</sub>O<sub>3</sub> as Adsorbent and its Effect on CO<sub>2</sub> Capture

Iron oxide (α-Fe2O3) as adsorbent was no longer new in CO2 adsorption studies. However, its contributions in the industry still in limited wherein lack of convincing results of quantifying of adsorbed CO2. This work presents an analysis for α-Fe2O3 was prepared by simple mixing method with identified the adsorption capacity that applied in CO2 capture. The synthesized α-Fe2O3 from different concentrations of precursor were analyzed using XRD, N2 adsorption-desorption isotherms with BET and BJH method, TEM, FTIR, CO2 adsorption at 298 K, CO2-TPD and TGA-DTG. It was noted that 2M concentration of precursor (s2M) with highest crystallite peaks shows highest surface area among all samples which indicative of well generated pores. The different concentration of precursor was found generated more porosity rather than particle size according to TEM micrograph. The sphere shape crystallite particle with high surface area (50.5 m2/g) and porosity were desirable properties in CO2 adsorption. Consequently, physically adsorbed CO2 with adsorption at 298 K was highest with adsorption capacity of at 17.0 mgCO2/gadsorbent. Finally, chemically adsorbed CO2 was successfully identified from CO2–TPD analysis with adsorption capacity of 0.19 mgCO2/gadsorbent and 1.31 mgCO2/gadsorbent at maximum desorption temperature of 375 °C and 749 °C respectively.

Effect of ZnO Seed Layer with Various Concentrations of Precursor on the Growth of ZnO Nanostructures

In this work, Zinc oxide (ZnO) thin films were deposited on silicon and glass substrates using spin-coating method with different concentrations of precursor (zinc acetate dihydrate) and stabilizer (monoethanolamine). The concentrations of zinc acetate dihydrate and monoethanolamine in isopropanol were varied from 6 mM to 500 mM. Subsequently, the substrate with ZnO thin film as a seed layer was used to grow ZnO nanostructures by hydrothermal process with the same concentration of precursor (zinc nitrate hexahydrate), temperature, and time for each growth. The samples were characterized by field-emission scanning electron microscopy (FESEM), X-rays diffractometer (XRD), and UV-visible spectrophotometer (UV-vis) to study morphology, crystallographic structure, and optical property, respectively. The results showed that particle size, crystallinity, and transmittance of seed layers were changed with increasing concentrations of spin-coated precursor. Furthermore, the nanostructures were found that higher precursor concentration of seed layers affected the formation of ZnO nanorods to be nanosheets.

Nanocrystalline NiO hollow spheres in conjunction with CMC for lithium-ion batteries

Hollow spherical NiO particles were prepared using the spray pyrolysis method with different concentrations of precursor. The electrochemical properties of the NiO electrodes, which contained a new type of binder, carboxymethyl cellulose (CMC), were examined for comparison with NiO electrodes with polyvinylidene fluoride (PVDF) binder. The electrochemical performance of NiO electrodes using CMC binder was significantly improved. For the cell made from 0.3 mol L−1 precursor, the irreversible capacity loss between the first discharge and charge is about 43 and 24% for the electrode with PVDF and CMC binder, respectively. The cell with NiO–CMC electrode has a much higher discharge capacity of 547 mAh g−1 compared to that of the cell with NiO–PVDF electrode, which is 157 mAh g−1 beyond 40 cycles.

Sonochemical Synthesis and Gas Sensing Properties of Well-Aligned ZnO Nanorods

A simple method of using ultrasound radiation is presented here as a means of fabricating the well-aligned one-dimensional nanostructure of zinc oxide nanorods. X-ray diffraction and scanning electron microscopy were used to characterize ZnO nanorods prepared under different concentrations of precursors. The morphologies of the ZnO nanorods can be controlled by varying the concentration of the solution. An investigation of the gas sensing property of the materials confirms that the properties of the sensors are influenced by the morphologies of the nanorods. The results indicate that the ZnO nanorods have great potential as gas sensors.

Structural and luminescent properties of ZnO nanorods prepared from aqueous solution

A simple method to fabricate the one-dimensional nanostructure of zinc oxide nanorods from aqueous solution was presented. ZnO nanorods, prepared under different concentrations of precursors, were characterized by techniques such as XRD and SEM. The results indicated that the ZnO nanorods were single crystalline and grown in the direction of [001] with the hexagonal wurtzite structure. Photoluminescence measurement of the ZnO nanorods was carried out and it showed that a strong near-band-gap emission dominated the PL spectra with several weak emission peaks related to the deep level. We also analyzed the effect of the concentration of precursors on the luminescent properties of ZnO nanorods. In addition, the growth mechanism of ZnO nanorods from aqueous solution was preliminarily discussed.

Fabrication and test of sol–gel based planar oxygen optodes for use in aquatic sediments

We describe the fabrication of organically modified sol–gel (ORMOSIL) planar optodes for mapping the two-dimensional oxygen distribution in sediments. All sensor foils were based on the use of ruthenium(II)-tris-(4,7-diphenyl-1,10-phenantrolin)-perchlorate, which is a fluorescent dye quenched dynamically by oxygen. Sensors made with different sol–gel immobilisation matrices, different concentrations of precursors and indicator dye, as well as different types of scattering particles co-immobilised in the sensor foil were investigated systematically. Optimal sensor performance was obtained with dye concentrations of 2–10 mmol/kg in an immobilisation matrix made of diphenyldiethoxy-silan and phenyltriethoxy-silan precursors with addition of organically coated TiO 2 particles. The sensors exhibited a good mechanical stability and a high sensitivity from 0% to 100% oxygen, which remained constant over at least 36 days. The planar optodes were used with a fluorescent lifetime imaging system for direct mapping of the spatio-temporal variation in oxygen distribution within marine sediment inhabited by the polychaete Hediste diversicolor. The measurements demonstrated the spatio-temporal heterogeneity of the oxygen distribution in bioturbated sediments due to burrow structures and non-constant irrigation activity of the polychaete, which is difficult to resolve with microsensors or with traditional biogeochemical techniques.