AFM Studies Research Articles

Hierarchical Arrangement of P(VDF-TrFE) Copolymer Crystals: A SAXS and AFM Study

P(VDF-TrFE) copolymers are materials with high relevance in printed organic electronics. These copolymers easily crystallize into the ferroelectric phase without resorting to post-deposition treatments (thermal annealing, poling, or mechanical stretching). The detection of a morphotropic phase boundary further increased the interest in this copolymer system by demonstrating relaxor behavior for higher TrFE content. This prompted an in-depth analysis of the P(VDF-TrFE) chiral chain structure responsible for the relaxor properties. Nevertheless, the efficient application of these materials also depends heavily on the quality and morphology of the crystalline domains. In this work, we combine SAXS and AFM imaging to analyze the structure of the crystalline domains as a function of the TrFE content. The detection of different structural distributions revealed the presence of hierarchical arrangements within the crystalline domains. Furthermore, these hierarchical arrangements were observed to change with the TrFE monomer content, presenting distinct morphologies for low and high TrFE contents, in line with previous works on the morphotropic phase boundary in these systems.

SPECTROSCOPIC INVESTIGATIONS ON SELF-CLEANING FILMS FOR PHOTOVOLTAIC GLASSES

Titanium dioxide thin coatings are widely used in different fields for the manufacture of various products:electrochromic displays, photocatalytic systems, photosensitized solar cells and many others. At the same time, the possibilities for obtaining protective coatings based on TiO2 are of interest. The chemical and physical characteristics of the TiO2 coatings depend on a large extent of the applied technological method and the temperature values of the heat treatment used. Coatings are prepared by sol gel method applying dip coating technique. The present study characterizes self-cleaning TiO2 thin films for the photovoltaic application. The studies were carried out at different ratios of the components involved, rate of application of the solution on the glass substrate and different curing and holding temperatures. The coatings are dense and nanocrystal line according to AFM studies and optically transparent according to UV-Vis-NIR spectra.

Investigation of the Effects of Different Phases of TiO2 Nanoparticles on PVA Membranes

Introduction: PVA/TiO2 nanocomposite membranes are prepared by solution casting technique where different phases of TiO2 nanoparticles like brookite, brookiterutile and rutile are dispersed in PVA matrix. Sol-gel method was employed to prepare TiO2 nanoparticles, while different phases of TiO2 have been obtained by controlling the calcination temperature. Methods: PVA/TiO2 nanocomposite membranes were characterized by XRD, FTIR, AFM, TEM, UV-visible and PL techniques. XRD results confirmed the presence of different phases of TiO2, exhibiting 3.3 nm, 8.4 nm, and 35.7 nm mean crystalline size. The XRD studies also confirmed that TiO2 nanoparticles became properly dispersed to the PVA matrix, leading to increased PVA crystallinity after doping of different phases of TiO2 nanoparticles. UV-visible analysis revealed an increase in absorption intensity and peak position shifts slightly towards longer wavelengths, which indicates that nanofillers tuned the band gap of PVA. The doping of the TiO2 (brookite) phase in the PVA matrix results in a decreased in PL intensity. Results: This suggests that the PVA/TiO2 (brookite) membrane exhibits a greater degree of photocatalytic activity in comparison to the other two composites. According to the FTIR investigation, the hydroxyl (OH) groups present in PVA interact with the dopants Ti+ ions via intra- and intermolecular hydrogen bonds to produce charge transfer complexes (CTC). The AFM study shows surface roughness details for PVA and PVA/TiO2 composite membranes. The average grain size of TiO2 nanoparticles calculated from TEM images is in good agreement with the grain size calculated by XRD. Conclusion: By adjusting the phase of TiO2 nanoparticles into PVA matrix, composites can be developed that are optimized for a variety of applications such as water purification, UV protection, self-cleaning surfaces, lithium-ion batteries, and optoelectronic devices.

Flavones Suppress Aggregation and Amyloid Fibril Formation of Human Lysozyme under Macromolecular Crowding Conditions.

The crowded milieu of a biological cell significantly impacts protein aggregation and interactions. Understanding the effects of macromolecular crowding on the aggregation and fibrillation of amyloidogenic proteins is crucial for the treatment of many amyloid-related disorders. Most in vitro studies of protein amyloid formation and its inhibition by small molecules are conducted in dilute buffers, which do not mimic the complexity of the cellular environment. In this study, we used PEGs to simulate macromolecular crowding and examined the inhibitory effects of flavones DHF, baicalein, and luteolin on human lysozyme (HuL) aggregation at pH 2. Naturally occurring flavones have been effective inhibitors of amyloid formation in some proteins. Our findings indicate that while flavones inhibit HuL aggregation and fibrillation in dilute buffer solutions, complete inhibition is observed with a combination of flavones and PEGs, as shown by ThT fluorescence, light scattering, TEM, and AFM studies. The species formed in the presence of PEG 8000 and flavones were less hydrophobic, less toxic, and α-helix-rich compared to control samples, which were hydrophobic and β-sheet-rich, as demonstrated by ANS hydrophobicity, MTT assay, and CD spectroscopy. Fluorescence titration studies of flavones with HuL showed a significant increase in binding constant values under crowding conditions. These findings highlight the importance of macromolecular crowding in modulating protein aggregation and amyloid inhibition. Further studies using disease-causing mutants of HuL and other amyloidogenic proteins are needed to explore the role of macromolecular crowding in small-molecule-mediated modulation and inhibition of protein aggregation and amyloid formation.

Advanced AIE Materials for Environmental Monitoring: Selective Sensing of Thorium(IV) in Aquatic Systems.

Thorium (Th) is commonly used in various applications, but its long-term exposure poses health risks, necessitating its detection in aqueous environments. Traditional methods such as inductively coupled plasma mass spectrometry are sensitive but require complex instrumentation. Optical sensors, particularly fluorometry-based methods, are simpler, cost-effective, and selective. However, developing effective aggregation-induced emission (AIE) turn-on sensors for Th(IV) requires water-soluble fluorophores with a low background fluorescence. In the present work, we report a turn-on detection method for Th(IV) based on the AIE of the fluorophore tetra(4-sulfophenyl) ethylene (SuTPE). Th(IV)-induced aggregation of SuTPE and the simultaneous drastic enhancement of the emission property of SuTPE have been utilized for the selective sensing of Th(IV) in 100% aqueous media. The sensing mechanism was explored using ground-state absorption, steady-state and time-resolved emission, FTIR, DLS, SEM, AFM and quantum chemical studies of the SuTPE-Th(IV) complex. The selectivity of the present probe toward Th(IV) ions has been established by studying the interference of several metal ions, including lanthanides and uranyl ions. The LOD for Th(IV) was estimated to be 240 nM (56 ppb). The performance of the probe was demonstrated in tap water and diluted seawater matrixes. This work provides a significant advance for Th(IV) detection in aqueous environments, with implications for environmental monitoring and health safety.

Fluorescent Ionic Liquid Aggregates: A Self-Assembled Approach for Pesticide Detection and Catalysis.

The unregulated use of pesticides, industrial discharge of heavy metals, waste, and agricultural runoff may contaminate surface water and groundwater, consequently threatening ecosystems and human health. Thus, the sensitive detection and degradation of pesticides are essential for safety. In this context, herein, we have developed benzimidazolium-based fluorescent surfactant assemblies TA-1/SDS and TA-2/SDBS, which exhibit aggregation-induced emission enhancement in an aqueous medium. The aggregates (TA-1/SDS and TA-2/SDBS) displayed a turn-on emission response upon interaction with carbendazim and azamethiphos with limits of detection 7.5 and 7.8 nM, respectively. The FE-SEM and AFM studies revealed that TA-1/SDS and TA-2/SDBS undergo self-assembly with the addition of AZA and CBZ, resulting in the formation of dendritic structures. In addition to the quantification of AZA and CBZ, TA-1/SDS and TA-2/SDBS have also been evaluated to degrade both pesticides and validated using 31P NMR spectroscopy and LC-MS spectrometry.

Hepatoprotective Activity of Gingko biloba‐Mediated TiO2 NPs Against Acetaminophen‐Induced Albino Rats‐ In Vitro Studies

AbstractNumerous effects of “titanium dioxide nanoparticles (TiO2 NPs)” have been described and significantly utilized in complementary drugs for many decades. This study is conducted to analyze the therapeutic efficiency of TiO2 NPs against the acetaminophen‐(AMP) induced toxicity. TiO2 NPs were initially prepared using Ginkgo biloba leaf extract as reducing and stabilizing agent. The prepared TiO2 NPs were studied using various spectroscopic and microscopic techniques. AFM, TEM, XRD, and DLS studies have confirmed the formation of TiO2 NPs with size between 20 to 60 nm with negative surface charge of about −12 mV. Later, hepatoprotective studies were performed by administering AMP to albino mice only once at a dosage of 2 g/kg p.o. Post 24 h of AMP intoxication, the animals were treated orally with three different doses of TiO2 NPs (150, 100, and 50 mg/kg) or silymarin at an amount of 50 mg/kg p.o., administered only once. Post 24 h of last treatment, all the animals were surrendered to death. The group of mice administered with AMP displayed a substantial raise in the serum alkaline phosphatase (560 ± 31.90), lactate dehydrogenase (167 ± 10.17), aspartate amino transferase (251 ± 14.82), alanine amino transferase (326 + 18.96), bilirubin (2.2 ± 1.066), cholesterol (96.7 ± 6.2), and albumin (6.0 ± 1.27) in serum, which signified the liver damage. A considerably depleted level of glutathione (5.4 + 1.24) was detected in the mice intoxicated with AMP. The activities of catalase (33.2 ± 2.66) and superoxide dismutase (36 ± 2.93) declined after exposure to acetaminophen, resulting in oxidative stress in liver. The performance of adenosine triphosphatase (901 ± 50.7) and glucose‐6‐phosphatase (3.9 + 1.15) were considerably inhibited after administrating with AMP. On treating with TiO2 NPs, all the variables reversed significantly towards regular levels and were noticed to be nontoxic. The groups treated with TiO2 NPs exhibited less activity of ALT, AST, LDH, and SALP in serum, indicating the protective effect of TiO2 NPs to prevent liver damage. Exposure with TiO2 NPs inverted the cholesterol, albumin, and bilirubin levels towards normal, which is similar to silymarin treatment. TiO2 NPs exhibited a substantial change in tissue and blood biochemical parameters with that of control groups. These results indicate that TiO2 NPs possesses hepatoprotective properties that mitigate the hepatotoxicity induced by acetaminophen in rats. Hence, TiO2 NPs can be further utilized in the preparation of medicine against hepatic and renal diseases, post further clinical and preclinical studies.

Corrosion inhibition assessment of a sustainable inhibitor from the weed plant (Pouzolzia zeylanica L.) on SS-410 surface in 0.5 M HCl acidic medium

BackgroundThe research has looked into the potential of plant extracts as natural corrosion inhibitors as an alternative to synthetic ones. The study aims to investigate the ability of the weed plant Pouzolzia zeylanica L. extract (PZE) to prevent corrosion of stainless steel-410 in a 0.5 M HCl acidic medium. MethodIn this work, the leaf extract of PZE is prepared in water, and the functional activity of the prepared PZ water extract (PZE)is evaluated using various techniques. Both electrochemical and gravimetric techniques are employed in this study. The inhibitor from PZ inhibits the anodic region on the SS-410 surface active sites through straightforward adsorption. Experimental techniques such as UV–visible spectroscopy, FTIR, LC-MS, SEM, AFM, EDX, EIS, and computational studies demonstrate the formation of protective layers under inhibiting conditions. The gravimetric data confirms monolayer adsorption, following the Langmuir adsorption isotherm. Significant findingsThe data obtained demonstrate that when SS-410 is immersed directly in a corrosive solution containing dissolved inhibitor molecules, it effectively prevents corrosion. Therefore, increasing the concentration of this chemical improves its inhibitory efficiency. Indeed, the PZ inhibitor achieved a favourable experimental outcome with an efficacy of 95 % at 400 mg/L in 0.5 M HCl. Based on polarization analysis, the corrosion inhibitor exhibits anodic nature for SS-410 in 0.5 M HCl.

Green synthesis of pectin-functionalized silver nanocomposites using Carpesium nepalense and evaluation its bactericidal kinetics and hepatoprotective mechanisms

The present study reports the green synthesis of pectin-fabricated silver nanocomposites (Pectin-AgNPs) using Carpesium nepalense leaves extract, evaluating their bactericidal kinetics, in vivo hepatoprotective, and cytotoxic potentials along with possible mechanisms. GC/MS and LC/MS analyses revealed novel phytochemicals in the plant extract. The Pectin-AgNPs were characterized using UV/Vis, AFM, SEM, TEM, DLS, FTIR, and EDX techniques, showing a spherical morphology with a uniform size range of 50–110 nm. Significant antibacterial activity (P < 0.005) was found against four bacterial strains with ZIs of 4.1 ± 0.15 to 27.2 ± 3.84 mm. AFM studies revealed significant bacterial cell membrane damage post-treatment. At 0.05 mg/kg, the nanocomposites showed significant (P < 0.005) hepatoprotective activity in biochemical and histopathology analyses compared to the CCl4 control group. Pectin-AgNPs significantly reduced (P < 0.005) LDH, AST, ALT, ALP, and DB levels. qPCR analysis showed ameliorative effects on PPARs and Nrf2 gene expression, restoring gene alterations caused by CCl4 intoxication. In vivo acute toxicity studies confirmed low toxicity of Pectin-AgNPs in major organs. Pectin-AgNPs exhibited cytotoxic activity against HeLa cell lines at higher doses with an LC50 of 223.7 μg/mL. These findings demonstrate the potential of Pectin-AgNPs as promising antibacterial, hepatoprotective, and cytotoxic agents.

Characterization of Dislocations in GaN Wafers Using Correlative Microscopy: A Raman-SEM-EDS and AFM Study

Characterization of Dislocations in GaN Wafers Using Correlative Microscopy: A Raman-SEM-EDS and AFM Study

Exploring Heterointerface Characteristics and Charge-Storage Dynamics in ALD-Developed Ultra-Thin TiO2-In2O3/Au Heterojunctions

Directional ionic migration in ultra-thin metal-oxide semiconductors under applied electric fields is a key mechanism for developing various electronic nanodevices. However, understanding charge transfer dynamics is challenging due to rapid ionic migration and uncontrolled charge transfer, which can reduce the functionality of microelectronic devices. This research investigates the supercapacitive-coupled memristive characteristics of ultra-thin heterostructured metal-oxide semiconductor films at TiO2-In2O3/Au Schottky junctions. Using atomic layer deposition (ALD), we nano-engineered In2O3/Au-based metal/semiconductor heterointerfaces. TEM studies followed by XPS elemental analysis revealed the chemical and structural characteristics of the heterointerfaces. Subsequent AFM studies of the hybrid heterointerfaces demonstrated supercapacitor-like behavior in nanometer-thick TiO2-In2O3/Au junctions, resembling ultra-thin supercapacitors, pseudocapacitors, and nanobatteries. The highest specific capacitance of 2.6 × 104 F.g−1 was measured in the TiO2-In2O3/Au junctions with an amorphous In2O3 electron gate. Additionally, we examined the impact of crystallization, finding that thermal annealing led to the formation of crystalline In2O3 films with higher oxygen vacancy content at TiO2-In2O3 heterointerfaces. This crystallization process resulted in the evolution of non-zero I-V hysteresis loops into zero I-V hysteresis loops with supercapacitive-coupled memristive characteristics. This research provides a platform for understanding and designing adjustable ultra-thin Schottky junctions with versatile electronic properties.

Bioenergy feedstock production in Chlamydomonas reinhardtii (microalgae) cultivated under mixotrophic growth with cellulose hydrolysate from agricultural waste.

In the present study, cellulose purified from finger millet agricultural waste is subjected to enzymatic hydrolysis, and the hydrolysate (predominantly glucose) is used as a carbon source supplement in the media for the mixotrophic growth of Chlamydomonas reinhardtii. Interestingly, a switch between excess starch production and excess lipid (triacylglycerols, TAG) production occurs by a small change in hydrolysate concentration in the media. Starch production increased 4.5-fold with respect to the photoautotrophic control, with a glucose concentration of 3mg/mL in the media after hydrolysate addition. This culture had TAG production enhancement by 1.5-fold. However, mixotrophic cultivation with 4mg/mL glucose concentration in the media with hydrolysate addition resulted in TAG productivity enhancement by 4.2-fold compared to control and starch amount increase of 1.3-fold. The organic carbon source (glucose) and the inorganic carbon source (citrate ions) in the hydrolysate together played a role in this delicate switching between starch and lipid pathways. Proteins, starch, and TAG molecules are analyzed in the microalgal cells grown under different conditions with FTIR spectroscopy, a rapid, high-throughput method of biomolecular estimation. High-resolution single-cell AFM studies of the cell wall structure reveal enhanced corrugations in surface morphology during mixotrophic growth with cellulose hydrolysate, illustrating an adaptive mechanism with improved mechanical stress management. Lipid droplet morphology at the single-cell level points to two distinct mechanisms of lipid accumulation: one in which the lipids are segregated as droplets, and the other in which lipid molecules are uniformly dispersed in the cytosol as unresolved, ultra-small droplets. The present study therefore analyzes both the bulk and the single-cell level changes when cellulose hydrolysate is used as a carbon source for Chlamydomonas reinhardtii mixotrophic cultivation, which serves a four-fold purpose: value from waste, fixation of atmospheric CO2, production of lipids for biodiesel, and starch for bioethanol.

Comparison of the effect of oxygen and nitrogen plasma treatments on the surface activation of PLA/rGO composites

Cold plasma is known as a method to enhance the adsorption of proteins on the surface of biomaterials. In this experimental study, the efficacy of oxygen and nitrogen plasma treatment on the activation of Poly l-lactic acid/reduced graphene oxide composite (PLAG) was investigated. For this purpose, the chemical, physicochemical, and morphological characteristics, ability to adsorb amino acid l-tyrosine, and biological behavior of the oxygen and nitrogen plasma-treated composites (PLAG-O and PLAG-N) were studied. Following the exposure to oxygen and nitrogen plasma, (PLAG-O) composites presented more enhancement in Raman CC and CH bonds. The evaluation of l-tyrosine adsorption revealed the higher intensity of FTIR CN, CC and NH and Raman CH chemical bonds and also lower intensity of l-tyrosine UV absorbance in solution medium for l-tyrosine-adsorbed oxygen plasma-treated (PLAG-Ot) compared to l-tyrosine-adsorbed nitrogen plasma-treated (PLAG-Nt) composites. More apparent l-tyrosine island-shaped zones were appeared all over the surface of PLAG-Ot composites through FE-SEM experiment. Moreover, conducting detailed AFM study revealed a higher difference in surface roughness (Ra) of the PLAG-O and PLAG-Ot (140 nm) compared to the PLAG-N and PLAG-Nt composites (25 nm). From the biological point of view, the oxygen plasma-treated composites presented better HDF cell behavior in terms of viability and attachment, as well. According to the results of this study, the oxygen plasma treatment exhibits a higher potential to activate Poly l-lactic acid–reduced graphene oxide composite surface compared to the surface treatment in nitrogen plasma.

Thin Film Formation of HSA in the Presence of CTAB-Capped Gold Nanorods through Phase Separation.

Phase behavior in protein-nanoparticle systems in light of protein corona formation has been investigated. We report the formation of HSA thin films following the addition of a solid protein to a solution of CTAB-capped gold nanorods (AuNRs) via phase separation. The phase separation behavior was observed through UV-vis spectroscopy, turbidity assays, and DLS studies. UV-vis spectra for the protein-AuNR solution indicated a possible self-assembly formation by CTAB-HSA complexes and AuNR-HSA conjugates. The turbidity was found to increase linearly up to 30-50% v/v for each component. The growth phase slope is proportional to the concentration of the components, AuNRs, and HSA, with no lag phase. Dynamic light scattering (DLS) shows the formation of larger aggregates with time, implying a segregated phase of AuNR-HSA and a CTAB-HSA-AuNR network. ζ-potential values confirm surface modification, implying protein corona formation on nanorods. The thin films were also characterized using SEM, AFM, SAXS, XPS, FTIR, and TGA studies. SEM images show a smooth surface with a reduced number of pores, indicating the compactness of the deposited structure. AFM shows two different structural pattern formations with the deposition, indicating possible self-assembly of the protein-conjugated nanoparticles. FTIR studies indicate a change in the hydrogen bonding network and confirm the CTAB-HSA-AuNR complex network formation. The XPS studies indicate Au-S bond formation, along with Au-S-S-Au interactions. SAXS studies indicate the formation of aggregates (oligomers), as well as the presence of dominant attractive intermolecular interactions in the thin films.

Fluorescent ‘turn-on’ porphyrin CQD nanoprobes for selective sensing of heavy metal ions

In this work, a one-step pyrolysis technique is employed to synthesize porphyrin based carbon quantum dots (Porp-CQDs). The as-synthesized Porp-CQDs permit fluorescence “on/off” strategies to detect heavy metal ions. The structural formation of the Porp-CQDs with optical properties is confirmed through characterization techniques like UV–visible, fluorescence spectroscopy, HR-TEM, AFM, X-ray diffraction, and FT-IR studies. Porp-CQDs have an average particle size of 2.4 nm and a spherical shape with a semi-crystalline appearance. The excitation wavelength appears at 434 nm corresponding to the π-π* electronic transition of the soret band between the HOMO and LUMO energy levels with emission at 670 nm. The CV curves of the modified Porp-CQDs/GCE at a scan rate of 10 mV s−1 and Porp-CQDs/GCE exhibits good oxidation and reduction peaks at 1.43 V and − 0.36 V, respectively. The metal ion sensing mechanism is driven through the structure of the porphyrin core which makes it easy to form transition complexes with various metal ions in the central cage of the system. Porphyrins tagged on CQDs have been used as active sensing components in this work. The Porp-CQDs effectively sensed the Zn2+ metal ions with a limit detection of 75 μM in bore well water analysis.

Investigating the effect of nitrogen and chlorine Co–doped carbon quantum dots in phenazine and quinoxaline sensitized solar cells

We investigated five dyes for dye-sensitized solar cells (DSSCs) relying upon derivatives of phenazine and quinoxaline and also studied their optical characteristics and the influence of functional groups such as (-CH3, -NO2, -C = O, -CN, and -OH) on these characteristics. When the prepared dyes are directly used at DSSCs, 9-Nitrobenzo[a]phenazin-5-ol (3b) dye device showed an improved Jsc (0.288 mA cm−2), Voc (0.437 V), FF (0.446), and η (0.056 %) than the sensitized solar cells by other dyes. In the following, nitrogen-doped carbon quantum dot and nitrogen, chlorine co-doped carbon quantum dot are used to improve the performance of DSSCs. The results showed that the device sensitized using the sensitizer (5-hydroxybenzo[α]phenazin-9-yl)(phenyl) methanone (3c)/NCQD has the highest photovoltaic efficiency with Jsc (0.979 mA cm−2), Voc (0.465 V), FF (0.370), and η (0.168 %). The N and Cl co-doped carbon dots were synthesized with a green approach to improve the performance of solar cells by the co-sensitization method. This approach is improving the efficiency of DCSSs with a simple, eco-friendly, and low-cost technique. Among the prepared sensitizers, (5-hydroxybenzo[α]phenazin-9-yl)(phenyl) methanone (3c)/N, Cl-CQD demonstrates the highest photovoltaic efficiency with Jsc (1.31 mA cm−2), Voc (0.495 V), FF (0.466), and η (0.303 %). FT-IR, XRD, 13C NMR, 1H NMR, TEM, EDS-Map, AFM, DLS, and PL studies were used to confirm the structure of the synthesized dyes and quantum dots.

Impact of post deposition treatment on optoelectrical and microstructural properties of tin sulfide thin film for photovoltaic applications

Tin sulfide (SnS) has attracted significant interest due to its advantageous optoelectrical characteristics and abundant presence in nature. Post-deposition treatments (PDTs) are frequently employed to enhance the crystallinity of chalcogenide-based solar cells. This study examined the influence of the post-deposition heat treatment procedure on thermally evaporated SnS thin film. The post-deposition annealing process, as determined by XRD and AFM studies, supplies the necessary thermal energy for re-crystallization, potentially resulting in a modification of crystallite dimensions. The occurrence of Sn-S polytypes was examined using Raman and XPS studies. Annealing causes changes in the optical properties, as observed through optical analysis, which can be attributed to the improvement in crystallinity. Subjecting the material to annealing at temperature of 300 °C greatly improves both mobility and conductivity, while also causing a change in conduction type. The observed variations in conduction type are attributed to the differing ratios between the amounts of Sn2+ and Sn4+. This strategy offers a novel route for the fabrication of thin-film photovoltaic cells by using a p-type buffer layer.

A novel activation method for regulating surface characteristics and flotation performance of smithsonite: XPS, SEM-EDS, AFM, ToF-SIMS and FT-IR studies

Smithsonite is a typical zinc oxide mineral, and the flotation index is not ideal for the recovery of smithsonite via sulfidization–xanthate flotation. In this study, Pb2+ was used as an activator for the stepwise activation of smithsonite in a sulfidization–xanthate flotation system. Micro-flotation tests and various surface analytical assays were employed to investigate the effects of Pb2+ stepwise activation on the flotation behavior and surface properties of smithsonite. The micro-flotation tests revealed that the flotation recovery of smithsonite reached 90.26 % after the stepwise activation of Pb2+ at an appropriate concentration. X-ray photoelectron spectroscopy, scanning electron microscopy-energy-dispersive X-ray spectroscopy, atomic force microscopy, and time-of-flight secondary ion mass spectrometry indicated that abundant active sites of Pb components appeared on the smithsonite surface after Pb2+ stepwise activation, which promoted the adsorption of S ions on the smithsonite surface. The increase in the proportion of the PbS component after sulfidization effectively enhanced the reaction activity of the mineral surface. Fourier-transform infrared spectroscopy and contact angle measurements showed that xanthate could be stably adsorbed on the smithsonite surface after Pb2+ stepwise activation, thereby enhancing the surface hydrophobicity and flotation behavior of smithsonite. Therefore, Pb2+ stepwise activation can promote sulfidization on the smithsonite surface, improve the reactivity and hydrophobicity of the mineral surface, and substantially increase the flotation index of smithsonite.

Realization of CO2 gas sensors and broadband photodetectors using metal/high-k CeO2/p-Si heterojunction

Realization of high-k dielectric oxide material-based devices such as photodetectors (PDs)/gas sensors fabricated on silicon substrate seems to be the utmost promising as a cost-effective approach to use in next generation optoelectronic field. We have explored metal/CeO2/p-Si heterojunction to construct as a broadband (BB) PD and CO2 gas sensor device. The effect of post-annealing procedure on photodetection and CO2 gas sensing characteristics were correlated using AFM, XRD, XPS, Raman and UV–Vis studies. At 0 V bias, the fabricated as-deposited Au/CeO2/p-Si PD device exhibits outstanding performance with enhanced responsivity of 85 AW−1 (at 910 nm), detectivity of 1.36×1015 Jones (at 850 nm), EQE of 1.3×104 % (at 850 nm), faster rise and fall times of 124 ms and 107 ms (at 900 nm). On the other hand, the photodetection characteristic parameters were slightly deteriorated as a function of annealing with respect to the as-deposited device. One of the causes for this fact was attributed to the increase in rms surface roughness (AFM) and decrease in absorbance of CeO2 thin film (UV–Vis). Additionally, Ag/CeO2/p-Si heterojunction was studied as a CO2 gas sensor and evaluated response/recovery times as a function of CO2 gas concentration. Sensing responses of CeO2 as-deposited, CeO2-400, CeO2-500, CeO2-600 and CeO2-700 °C were around 58, 60, 62, 81 and 90 %, respectively, when exposed to 200 ppm of CO2. Thus, we validate that the prospect of integrating enhanced performance in BB PDs and CO2 gas sensors using metal/CeO2/p-Si heterojunction could serve as a basic building block in near future optoelectronic applications. Furthermore, the effect of post-annealing temperature on the morphological, structural, BB photodetection and CO2 gas sensing properties were discussed in detail.

Adsorption of poly(rA) in duplex (A-motif) conformation on graphene oxide: spectroscopy and AFM study

Adsorption of poly(rA) in duplex (A-motif) conformation on graphene oxide: spectroscopy and AFM study