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  • Open access
  • 36 Reads
The impact of the core material on the absorption of a quantum dot – metal nanoshell hybrid system

We study the linear optical response in a hybrid nanostructure composed of a semiconductor quantum dot and a metal shell nanoparticle. We analyze the case that the nanostructure interacts with an incident electromagnetic field with polarization parallel to the symmetry axis of the nanosystem. We derive the nonlinear density matrix equations, in the rotating wave approximation, under quasistatic response of the system and use a series expansion method to obtain analytical functions of the linear susceptibility of both components of the hybrid nanostructure. The derived susceptibilities particularly depend on the average radius and the thickness of the metal nanoshell, on the material of the dielectric core and on the distance between the semiconductor quantum dot and metal nanoshell. We can identify two distinct types of hybrid exciton states, each one emerging under different circumstances. The regime in which the first type of the hybrid exciton state arises requires low values of the dielectric constant and the radius of the dielectric core. This state is characterized by a significantly amplified gain without population inversion resulting from non-radiative energy transfer between the two nanoparticles, as well as to a quenched absorption resonance associated with a suppressed exciton lifetime. The second type of the hybrid exciton state appears when the exciton-plasmon coupling is quite weak, either due to the reduction of the thickness of the metal nanoshell, or the use of a core dielectric material with a high dielectric permittivity. These conditions favor the suppression of the gain arising on the absorption spectrum of the metal nanoshell and the creation of an amplified absorption resonance that corresponds to an enhanced exciton lifetime.

  • Open access
  • 31 Reads
Preparation and characterization of poly(lactic acid) nanoparticles for the encapsulation of cytostatic compounds
Published: 02 December 2022 by MDPI in 3rd International Electronic Conference on Applied Sciences session Student Session

Due to growing environmental concerns, biopolymeric nanoparticles (NPs) have gained importance in several areas as an alternative to synthetic polymeric NPs. One of the most promising biopolymers is poly(lactic acid) (PLA) due to its biocompatibility and biodegradability, allowing its use in the biomedical field for the development of drug delivery systems.

In this work, PLA NPs were synthesized by combining a single-emulsion method with nanoprecipitation. The influence of several experimental parameters, namely, stirring method, PLA and poly(vinyl alcohol) (PVA) concentrations, and type of PLA in the size and aggregation of the particles, was evaluated. The use of a tip sonicator, a PLA concentration of 10 mg/mL, a PVA concentration of 2.5 mg/mL, and a low molecular weight PLA (Mw=5,000) were established as the best experimental conditions to obtain monodisperse PLA NPs.

After the optimization step, flutamide was used as a model drug to evaluate the encapsulation capability of the PLA NPs. The obtained results showed that this cytostatic compound, used in cancer treatment, could be encapsulated in these NPs, with an efficiency of 44%. Furthermore, preliminary cell viability tests using the HCT-116 cell line showed that PLA-flutamide NPs allowed cells viabilities above 70% up to a concentration of 20 mg/L.

The overall results demonstrate that PLA NPs prepared by this simple approach can be used to encapsulate flutamide, representing an alternative for future cancer therapies.

  • Open access
  • 43 Reads
A Novel DEA Based on Construction Productivity Calculation Method

Construction is a labor-intensive industry. Each construction project involves aspects of execution complexity, construction records, management objectives, evaluation benchmarks, and construction productivity. In order to complete a construction project on time, on budget, and with high quality, construction productivity is a key factor. Construction productivity involves various working groups (reinforcement, template, concrete, plastering, water, electricity, furnishing, and heavy machinery). All working groups must execute their daily tasks, including corresponding work items and schedules. To calculate the productivities of all working groups, many input and output factors must be considered, which is related to multi-attribute decision making (MADM). The traditional productivity calculation method is use single outputs / single inputs, but such method cannot solve the problems of multiple outputs / multiple inputs of construction productivity. In order to solve the above-mentioned problem, this paper integrates technique for order preference by similarity to the ideal solution (TOPSIS) and data envelopment analysis (DEA) method to handle the issue of construction productivity. The paper further uses the data of three cases in a construction project, namely the installations of windows and blinds, concrete slabs, and sheet metal pipes, to verify the effectiveness and feasibility of the proposed novel construction productivity calculation method. The test results show that the proposed novel construction productivity calculation method could be widely used to evaluate the problems related to construction productivity, as well as to rank and to compare the daily labor productivity regardless of efficiency values. The findings can provide a direction for construction managers to improve labor productivity.

  • Open access
  • 8 Reads
Influence of printing parameters on the dimensional accuracy of concave/convex objects in FDM printing

3D printing belongs to the emerging technologies of our time. An important aspect regarding the potential applications of 3D printed objects is their dimensional accuracy. Especially in case of the most often used fused deposition modeling (FDM) technique, dimensional differences between the digital model and the printed object are common and depend not only on the printer’s accuracy, but also on the printing parameters as well as the chosen material. Here we report on the dimensional accuracy of FDM printed objects with sharp inner or outer corners, dependent on the printing parameters. We show that different adhesion assistants lead to a variation of the dimensional accuracy and can this be used to optimize this parameter.

  • Open access
  • 24 Reads
Reasons for high adsorption efficiencies on lead removal from aquatic solution

Heavy metals are of great concern worldwide in terms of environmental pollution due to their effects such as persistence in the environment, bioaccumulation, and toxicity for organisms. These pollutants in the non-biodegradable inorganic form are released into water, soil, and air from different industrial sectors. Lead ions are also a toxic heavy metal in terms of human health and permanent in terms of the ecosystem, which is included in this pollutant group. Among the many treatment methods, adsorption is an inexpensive, eco-friendly and efficient process for removing Pb(II) ions from water contaminated with lead ions. The most important detail that draws attention both in our research in the literature and in our own studies is that very high removal efficiencies of lead ions can be obtained with many different inorganic and organic adsorbents. Such high removal efficiencies cannot be obtained for other heavy metals and metalloids. Therefore, it was aimed to reveal the difference in the adsorption process of lead in this study. The physicochemical and biological properties of lead ion and the effects of specific properties such as amphoteric structure, free electron, post-transition metal, and the low melting temperature were investigated accordingly.

  • Open access
  • 14 Reads
Heterogeneous photo-Fenton oxidation of methylene blue solution using Fe(II)-montmorillonite calcinated clay catalyst
Published: 02 December 2022 by MDPI in 3rd International Electronic Conference on Applied Sciences session Student Session

The textile dyes such as methylene blue are used with high frequency in the dying and printing of natural, synthetic, man-made and mixed textile materials such as wool, silk, nylon among others. These textile dyes are very dangerous if released into the environment due to the dark colors, and because their recalcitrant nature, which makes them very hard to degrade. Thus, chemical methods such as advanced oxidation processes (AOPs) can be applied. Among the AOPs, Fenton based processes are suitable methods to degrade these contaminants, with the generation of hydroxyl radicals. However, considering the drawbacks associated with homogeneous Fenton processes, the aim of this work was to develop a catalyst using a montmorillonite clay as based material. After the application of an impregnation method, the Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction analysis showed the successful impregnation of iron into the montmorillonite clay. The catalyst Fe(II)-Mt was tested under different AOPs and results showed that under the best operational conditions (pH = 3.0, [Fe(II)-Mt 0.5M] = 1.0 g/L, [H2O2] = 4 mM, [MB] = 0.16 mM, radiation = UV-C (254 nm), time = 25 min) it was achieved 99.7% MB removal. The catalyst showed great stability and was reused for 3 consecutive cycles. It is concluded that the catalyst Fe(II)-Mt is efficient for MB removal from aqueous solution.

  • Open access
  • 50 Reads
Role of land-surface hydrology schemes in simulating the global incident solar radiation of Tropical Africa using the RegCM4

In the present study, two 12-years (1995-2007) simulations were conducted to examine the potential influence of two land-surface hydrology schemes (TOPMODEL; TOP and Variable Infiltration Capacity; VIC) of the community land model version 4.5 (CLM45) on the Surface Solar Irradiance (SSI) of Tropical using a regional climate model (RegCM4). With enabling the Carbon-Nitrogen (CN) module, the two simulations were designated as: CN-TOP and CN-VIC. The two simulations were evaluated with respect to the Solar Radiation Budget (SRB) reanalysis product. Evaluation process was conducted in two aspects: seasonal climatology overall Africa and over three sub-regions. The results showed that the CN-VIC outperforms the CN-TOP in all seasons while compared to the SRB reanalysis dataset particularly during the summer season. For instance, the CN-VIC underestimates the SSI over the Northern Savannah region by up to 15 W.m-2, while the CN-TOP underestimates the SSI by 30-50 W.m-2. Over different sub-regions, the CN-VIC performs better than the CN-TOP over Northern Savanna during the summer season and over the Congo basin during the winter season. The regional coupled RegCM4-CLM45-CN-VIC model can reasonably simulate the SSI with a reasonable bias when the four parameters of the VIC surface dataset are calibrated against in-situ observation, and therefore it can be recommended for future studies of solar energy projects in Tropical Africa.

  • Open access
  • 24 Reads
Mechanical Properties Study of Borosilicate Glass Loaded with Vanadium and Cobalt by Nanoindentation Technique

Nanoindentation test is used to investigate the mechanical properties of borosilicate glass with composition (mol%) 40 Na2B4O7 - 40 SiO2 - (20– x) V2O5 - x Co2O3, with x=0, 1, 3, and 5 mol% were prepared by melt quenching technique at 1373 K. A load-displacement curve was plotted and used to extract some mechanical properties of the glass samples. The creep deformation behavior of the glass composition was studied; the maximum creep rate was observed for the sample that contains the highest vanadium ratio, while the creep rate decreased with decreasing vanadium concentration in glass samples. The hardness and the reduced modulus of elasticity were obtained. The Maxwell-Voigt model was applied to investigate the relaxation kinetics and deformation of the bulk glass.

  • Open access
  • 39 Reads
Salting-Out Induced Recovery of Volatile Organic Acids using Non-Ionic Surfactants
Published: 05 December 2022 by MDPI in 3rd International Electronic Conference on Applied Sciences session Student Session

Non-ionic surfactants are considered as one of the highly utilized surfactants as they are the second largest group by volume at about 35%. Due to their low toxicity, the demand is escalating on extensive use of these amphiphilic materials for efficient, no-energy-requiring recovery of volatile organic acids (VOA). This separation process takes placed due to the cloud point of the surfactants which is referred as the temperature of the system at which two phases are formed. One of the phases is micellar-rich and the other is micellar-poor. In these micelles, the surfactant molecules are oriented in a way that the hydrophilic heads shield the hydrophobic tails from the other water molecules in the system. This assembly partitions the organic compounds through interior of the micelles which acts as the organic pseudo-phase. The goal of this study is to determine how salting-out affects the cloud point of ethoxylated non-ionic surfactants, and consequently, the VOA separation. Based on literatures, cloud point is sensitive to the presence of electrolytes and depends on the parameters hydrophile-lipophile balance (HLB) and on the number of ethylene oxide (EON) units of the surfactant. The mechanism involved upon electrolyte addition is the dehydration of micelles as salt is a water-structure maker. The salt changes the solvent structure by aggregation and formation of larger micelles. This translates into a lipophilic shift which reduces the cloud point and the surfactant HLB. As this HLB decreases, the more hydrophobic is the surfactant and can form better separation. Also, the type of salt influences the interphase mass transfer. Polyvalent cations such as Al3+ and Ca2+ are more effective in decreasing the HLB than the monovalent cations like Na+ and K+, because of their higher surface charge densities. The electrolyte capacity to reduce the cloud point is dependent as well on the hydrophilicity of the surfactant which is dictated by its ethylene oxide component. Non-ionic surfactants with higher EON value can achieve improved separation in the presence of salt. By considering these inferences, the extraction of VOA could be successfully improved.

  • Open access
  • 18 Reads
  • In-situ AFM of electrochemical deposition of Bismuth on GCE

The bismuth film electrode (BiFE), which was first used in stripping analysis, is now widely used in electroanalytical laboratories all over the world. Numerous scientists have been inspired to conduct more research and broaden their understanding of the BiFE's electroanalytical performance, which is comparable to, or in some cases significantly exceeds, that of mercury counterparts for the detection of a variety of heavy metals and certain chosen organic molecules. Numerous variations of bismuth-based paste electrodes as well as in situ and ex-situ manufactured BiFE have all been presented as additional types of bismuth electrodes. Since they must be moved from the preparation/modification solution to the measuring cell device and often need to display greater stability for many measurements, the ex situ produced bismuth films among the various types of bismuth film electrodes require acceptable physical and chemical stability. Therefore, in-situ AFM BiFE is preferred due to its chemical stability.

In this study, we are interested in getting an insight into the formation of BiFe on glassy carbon electrode (GCE). We used our home-constructed AFM cell to fit in commercial GCE(working electrode), platinum wire (counter electrode), and Ag/AgCl (reference electrode) and connected them to a potentiostat. The formation/dissolution of BiFE was In-situ monitored using AFM under different electrochemical conditions.