Types Of Colloids Research Articles

Transport and deposition of microplastic particles in saturated porous media: Co-effects of clay particles and natural organic matter

Natural colloids such as clays and natural organic matter (NOM) are universally present in environments, which could interact with microplastics (MPs) and thus alter the fate and transport of MPs in porous media. The co-effects of clays and NOM on MPs transport in saturated porous media were systematically explored at both low and high ionic strength (IS) conditions. Specifically, bentonite and humic acid (HA) were employed as representative clays and NOM. 5 mM NaCl and 1 mM CaCl2 solutions were used as low IS conditions, while 25 mM NaCl and 5 mM CaCl2 solutions were employed as high IS conditions. We found that formation of MPs-bentonite heteroaggregates had great effects on MPs transport under different conditions. Without HA, the small MPs-bentonite heteroaggregates formed under low IS increased MPs transport via serving as mobile carriers, while larger MPs-bentonite heteroaggregates formed at high IS led to the decreased MPs mobility. When both HA and bentonite were copresent in MPs suspension, we found that HA could inhibit the formation of larger sized MPs-bentonite heteroaggregates. Particularly, when the two types of natural colloids copresent in MPs suspensions, MPs transport behaviors were similar to those with only bentonite present in MPs suspensions at low IS, while MPs transport was greatly increased at high IS comparing with those only with bentonite in suspensions. Clearly, without HA in suspensions, bentonite played the dominant role on MPs transport under all examined conditions concerned in this study. Instead, when both HA and bentonite copresent in MPs suspensions, MPs transport was mainly controlled by bentonite at low IS, while both bentonite and HA had major contributions at high IS. The results showed that under solution conditions concerned in present study, MPs mobility in porous media would be greatly affected (either enhanced or inhibited) by the two types of natural colloids.

The inhibitory mechanism of natural soil colloids on the biodegradation of polychlorinated biphenyls by a degrading bacterium

In spite of extensive studies of soil model components, the role of natural soil colloids in the biodegradation of organic pollutants remain poorly understood. Accordingly, the present study selected Mollisol colloids (MCs) and Ultisol colloids (UCs) to investigate their effects on the biodegradation of 3, 3′, 4, 4′-tetrachlorobiphenyl (PCB77) by Bradyrhizobium diazoefficiens USDA 110. Results demonstrated that both natural soil colloids significantly decreased the biodegradation of PCB77, which partly resulted from the significant decrease in the bioaccessibility of PCB77. Furthermore, the activity of Bradyrhizobium diazoefficiens USDA 110 was remarkably inhibited under the exposure to the two types of soil colloids, which was mainly ascribed to the inhibition of cell reproduction but not the lethal effect of reactive oxygen species. The calculated results from Ex-DLVO theory further indicated that the repulsion between UCs and biodegrading bacteria retarded the effective contact of cells with adsorbed PCB77 from UCs, resulting in the decline of the rate of cell reproduction. In general, the inhibition of MCs was limited to PCB77 bioaccessibility, whereas the negative effect of UCs was controlled by PCB77 bioaccessibility and the effective contact of cells with colloids. This study could provide implication for the enhancement of microbial remediation in contaminated soil.

Release of colloids in saturated porous media under transient hydro-chemical conditions: A pore-scale study

The deposition and consequent release of colloids pose a significant challenge to the environment, groundwater quality and human health. Subsurface soil contains numerous types of colloids that exhibit a diverse range of interaction favorability with the soil grains and their impact on release behavior remains unclear. The objective of this study was to investigate, at the pore-scale, the impact of colloid interaction favorability on colloid deposition and subsequent release in response to perturbations of flow rate and solution chemistry in saturated porous media. Pore-scale experiments were conducted using a micromodel that is geometrically representative of a real sand-stone rock. Favorable, medium-favorable and unfavorable colloids (i.e., repulsion absent, repulsion at long-range of separation distances and attraction absent with the micromodel surface, respectively) were deposited in the micromodel and then a series of colloid release experiments were conducted at different conditions including increasing the flow rate, decreasing the ionic strength and increasing the solution pH. Favorable colloids exhibited extensive deposition on the collector center where the flow streamlines are parallel to the collector surface, as adhesion forces overcome hydrodynamic forces. However, at medium and high ionic strength, deposition in Forward Flow Stagnation Zone (FFSZ) was dominant for unfavorable colloids as the hydrodynamic forces are negligible. Pore-scale images showed that, upon perturbations in flow rate and solution chemistry, colloids that were initially deposited on collector centers were more susceptible to release as compared to colloids that were initially deposited in FFSZs. The negligible hydrodynamic drag forces in FFSZ and deep primary minimum interaction at short separation distances were the major factors that hindered the release of colloids in FFSZ under transient hydro-chemical conditions. The intensity of colloid deposition and release decreases as the favorability of colloids decreases and as the ionic strength decrease for unfavorable colloids. This study provides a clear insight to the pore-scale colloid deposition and release mechanisms during transient hydro-chemical conditions that help in the modeling of environmental and engineering applications including managed aquifer recharge, groundwater contamination and wastewater treatment processes.

Tailoring the Morphology of Supraparticles by Primary Colloids with Different Shapes, Sizes and Dispersities

Surface-templated evaporation driven (STED) method is a promising method to fabricate supraparticles with various sizes, porosities, and shapes by drying colloidal dispersion drops on liquid repellent surfaces. Until now, for the method, only spherical shaped colloidal particles have been used as primary colloids. Here, we introduce six different shapes of nano-colloidal dispersions for the STED method: nanocubics, nanoplates, nanosheets, coffin-shaped nanoparticles (NPs), spherical NPs, and aggregates of NPs. It is confirmed that the shape and size of the primary colloids have little effect for drying the dispersion drop when a single component colloidal dispersion is dried. For heterogeneous supraparticles with composite material assembly, still the shape of the colloids has no influences, while the size and dispersity play roles for tuning the morphology of the supraparticles. From the results, we propose a way to fabricate homogeneous mixture, core/shell, and Janus core/shell structures of the supraparticles depending on the size and dispersity of the mixture colloidal dispersion. Indeed, knowledge on the effects of types of colloids would be of great importance for tailoring supraparticles.

Shock: Pathophysiology, Stage, Classification, and Treatment

Shock is a state of resulting from an indented state of multiple important body works owing to decreased tissue perfusion. It is a circumstance that could menace life. Progressive stage of shock means failing compensatory mechanisms and the body’s compensatory mechanisms weaken to vindicate tissue perfusion. Hypovolemic shock is a circumstance of insufficient organ perfusion caused by destruction of intravascular volume, ordinarily acute. Distributive shock is a state of comparative hypovolemia sequencing from affiliated to pathology spread to other areas of the perfect intravascular volume and is more common form of shock. Dextran has considerable merits over distinctive types of colloids for the initial shock treatment owing to its antithrombotic properties whereby cell satisfactory is obviated and the occurrence of systematic circulations is decisively de-escalated. Drugs that de-escalate the hearts workload and pain such as morphine or fentanyl relieve anxiety or regulate heart rhythm. Vasopressor medications such as dopamine, norepinephrine, which are medications that constrict blood vessels and assists, escalate blood pressure. High amount of IV fluids very quickly and bestowing medications that will escalate the blood pressure to escalate blood flow to the rest of the body and organs.

THE INFLUENCE OF SURFACTANT AND PROTECTIVE COLLOID ON POLYVINYL ACETATE EMULSION SYNTHESIZED BY EMULSION POLYMERIZATION TECHNIQUE

A series of experiments have been carried out and reported. This report describes the stages of the polymerization reaction during emulsion Polyvinyl Acetate (PVAc) synthesis. PVAc was synthesized from the Vinyl Acetate Monomer (VAM) with Ammonium Peroxydisulphate (APS) as an inorganic thermal initiator in the aqueous media under reaction temperature was keep at 65 until 75oCs by agitation speed was 300 rpm respectively during 4 hours of reaction time. The protective colloid agents and several types of surfactants were added to improve the obtained emulsion PVAc performance. The polymerization reaction was carried out without the addition of a protective colloid agent. The surfactants were produced the emulsion PVAc with the properties of solid content 0.89%, density 1.02 g/ml, viscosity 0.0033 Poise, pH 2.8, conductivity 12 ms, respectively. While the polymerization reaction involved protective colloid agents by using Polyvinyl Alcohol (PVOH) was obtained properties of emulsion PVAc with Solid Content 4.36%, density 1.17 g/ml, viscosity 0.0216 Poise, pH 2.8, and conductivity 10 ms respectively. The same thing was shown when the surfactant was present in the polymerization reaction. The emulsion PVAc was synthesized with nonionic surfactant has solid content 8.20%, density 1.17 g/ml, viscosity 0.0099 Poise, pH 2.8, and conductivity 7 ms, the result is better rather than synthesized with anionic surfactant has solid content 2.65%, density 1.13 g/ml, viscosity 0.0068 Poise, pH 2.8, and conductivity 11 ms. According to the preliminary observations obtained, emulsion PVAc’s appearance is better when the protective colloid agents and the surfactant is present rather than without additional those substances. The physical properties of emulsion were depended on the addition of protective colloid agents and surfactants. In addition, the complete reaction indicated by solid content value was obtained from emulsion when the additional substances were present. All the testing parameters were observed using Viscometer Ostwald, Pycnometer, pH Meter, FTIR Spectrophotometer, Conductometer, and another supporting testing to explain the polymerization reaction stage of synthesis emulsion PVAc.

Fabrication of floating colloidal crystal monolayers by convective deposition

HypothesisWell-defined two-dimensional colloidal crystal monolayers (CCM) have numerous applications, such as photonic crystal, sensors, and masks for colloidal lithography. Therefore, significant effort was devoted to the preparation of preparing CCM. However, the fabrication of CCM that can float in the continuous phase and readily transfer to other substrate remains an elusive challenge. ExperimentsIn this article a facile approach to prepare floating CCM from polymeric colloids as building blocks is reported. The key to obtain floating CCM is the selection of an appropriate solvent to release the formed CCM from the substrate. There are two steps involved in the preparation of floating CCM: formation and peeling off. FindingsFirst, colloids are dispersed in a solvent. Evaporation of this solvent results in the formation of a meniscus structure of the air–liquid interface between the colloids that are on the substrate. The deformation of the meniscus gives rise to capillary attraction, driving the colloids together in a dense monolayer. Once a crystallization nucleus is formed, a convective flow containing additional colloids sets in, resulting in the formation of CCM on the substrate. Second, the remaining bulk dispersion is replaced by an extracting solvent that wets the substrate and peels the formed CCM off. The influence of the several solvents, the substrate materials, and the types of colloids on the CCM formation are investigated systematically. The robustness of the approach facilitates the preparation of CCM. Furthermore, the floating feature of the CCM in principle makes transfer of the CCM to other substrates possible, which broadens its applications.

Bronchiolar Adenoma/Pulmonary Ciliated Muconodular Papillary Tumor.

To describe the histologic features that are helpful in the diagnosis of the rare bronchiolar adenomas/ciliated muconodular papillary tumors (BAs/CMPTs) during intraoperative consultation. Multi-institutional retrospective review of frozen sections of 18 BAs/CMPTs. In 14 of 18 cases, BA/CMPT was the primary reason for sublobar lung resection, and in 4 cases, BA/CMPT was an incidental finding intraoperatively for resections performed for carcinoma in other lobes. There were 11 proximal-type/classic BAs/CMPTs and 7 distal-type/nonclassic BAs/CMPTs. Only 3 (16.7%) of 18 were correctly diagnosed at the time of frozen section, all of which were proximal type/classic. The remainder were diagnosed as adenocarcinoma (n = 7); invasive mucinous adenocarcinoma (n = 1); non-small cell lung carcinoma (n = 1); cystic mucinous neoplasm, favor adenocarcinoma (either mucinous or colloid type) (n = 1); favor adenocarcinoma, cannot exclude CMPT (n = 1); atypical proliferation (n = 2); mucinous epithelial proliferation (n = 1); and mucous gland adenoma (n = 1). BA/CMPT can potentially be misdiagnosed as carcinoma during intraoperative consultation. On retrospective review of the frozen sections, the presence of the following may help to avoid misdiagnosis: a mixture of bland ciliated columnar cells, mucinous cells, and, most important, a basal cell layer, as well as a lack of necrosis, significant atypia, and mitoses.

Enhanced Macroanion Recognition of Superchaotropic Keggin Clusters Achieved by Synergy of Anion-π and Anion-Cation Interactions.

Keggin clusters are the most widely used polyoxometalate building blocks for the construction advanced materials, but effective methods for precisely recognizing the isostructural analogues of Keggins are still limited. In this study we employed the zwitterionic molecule 4,4'-dipyridyl N,N'-dioxide as a recognition receptor to specifically bind to the three Keggin analogues PW12 O40 3- , PMo12 O40 3- , and SiW12 O40 4- , which separately co-assembled into three different types of spherical charged colloids of different sizes. The recognition phenomena were confirmed by electrochemical methods and their crystallization behavior. Compared with solely anion-cation interaction-driven systems, the synergism with the anion-π interactions between the superchaotropic Keggins and the electron-deficient pyridine rings is believed to enhance the recognition. This observation is intriguing as the long-range solution assembly of Keggins is mainly driven by short-range anion-π interactions. Our results show that the little-noticed hydration shell of Keggins is significantly influenced by the superchaotropic effect, leading to differentiated binding affinity to the receptors and more obvious recognition phenomena between tungsten/molybdenum Keggin analogues.

Atto-Molar Raman detection on patterned superhydrophilic-superhydrophobic platform via localizable evaporation enrichment

The detection of molecules in ultra-low concentration solution is essential in numerous fields including pollutant monitoring, explosive detection and disease early diagnosis. Recently, studies indicated that surface-enhanced Raman scattering (SERS) combining with superhydrophobic surfaces were capable of breaking diffusion limit, realizing detection in femto/atto-molar range. However, the complicated and costly fabrication methods limited larger-scale practical application. In this regard, patterned superhydrophilic-superhydrophobic platform fabricated by ultrafast laser, which could simplify the preparation process and fix the droplet, attracted attention. Nevertheless, the related works reported cannot realize atto-molar detection. Therefore, the SERS platform with abilities of simplified fabrication processes, on-demand locating analyte and ultra-high sensitivity (1 aM) is needed. In this paper, we processed a new patterned SERS platform via femtosecond laser, achieving atto-molar detection with an enhancement factor of 1.09 × 1014. After evaporation enrichment, the target molecules were deposited on the superhydrophilic area of ∼0.01 mm2. We further optimized the SERS substrates by comparing three types of colloids: Ag nano-particles, Au nano-particles and Au nano-stars, finding Au nano-stars exhibited the best. Meanwhile, this platform showed good uniformity: the relative standard deviation (RSD) was 11.7 % at 10−14mol/L. The results offer valuable information and potentials on the ultra-low concentration molecular detection in biosensors.

Different surface charged plastic particles have different cotransport behaviors with kaolinite ☆particles in porous media

The wide utilization of plastic related products leads to the ubiquitous presence of plastic particles in natural environments. Plastic particles could interact with kaolinite (one type of typical clay particles abundant in environments) and form plastic-kaolinite heteroaggregates. The fate and transport of both plastic particles and kaolinite particles thus might be altered. The cotransport and deposition behaviors of micron-sized plastic particles (MPs) with different surface charge (both negative and positive surface charge) with kaolinite in porous media in both 5 and 25 mM NaCl solutions were investigated in present study. Both types of MPs (negatively charged carboxylate-modified MPs (CMPs) and positively charged amine-modified MPs (AMPs)) formed heteroaggregates with kaolinite particles under both solution conditions examined, however, CMPs and AMPs exhibited different cotransport behaviors with kaolinite. Specifically, the transport of both CMPs and kaolinite was increased under both ionic strength conditions when kaolinite and CMPs were copresent in suspensions. While, when kaolinite and positively charged AMPs were copresent in suspensions, negligible transport of both kaolinite and AMPs were observed under examined salt solution conditions. The competition deposition sites by kaolinite (the portion suspending in solution) with CMPs-kaolinite heteroaggregates led to the increased transport both CMPs and kaolinite when both types of colloids were copresent. In contrast, the formation of larger sized AMPs-kaolinite heteroaggregates with surface charge heterogeneity led to the negligible transport of both kaolinite and AMPs when they were copresent in suspensions. The results of this study show that when plastic particles and kaolinite particles are copresent in natural environments, their interaction with each other will affect their transport behaviors in porous media. The alteration in the transport of MPs or kaolinite (either increased or decreased transport) is highly correlated with the surface charge of MPs.

Influence of the magnetic nanoparticle coating on the magnetic relaxation time.

Colloidal systems consisting of monodomain superparamagnetic nanoparticles have been used in biomedical applications, such as the hyperthermia treatment for cancer. In this type of colloid, called a nanofluid, the nanoparticles tend to agglomeration. It has been shown experimentally that the nanoparticle coating plays an important role in the nanoparticle dispersion stability and biocompatibility. However, theoretical studies in this field are lacking. In addition, the ways in which the nanoparticle coating influences the magnetic properties of the nanoparticles are not yet understood. In order to fill in this gap, this study presents a numerical simulation model that elucidates how the nanoparticle coating affects the nanoparticle agglomeration tendency as well as the effective magnetic relaxation time of the system. To simulate the self-organization of the colloidal nanoparticles, a stochastic Langevin dynamics method was applied based on the effective Verlet-type algorithm. The Néel magnetic relaxation time was obtained via the Coffey method in an oblique magnetic field, adapted to the local magnetic field on a nanoparticle.

Intravenous Fluid of Choice in Major Abdominal Surgery: A Systematic Review

Background Intravenous fluid therapy plays a role in maintaining the hemodynamic status for tissue perfusion and electrolyte hemostasis during surgery. Recent trials in critically ill patients reported serious side effects of some types of fluids. Since the most suitable type of fluid is debatable, a consensus in perioperative patients has not been reached. Method We performed a systematic review of randomized control trials (RCTs) that compared two or more types of fluids in major abdominal surgery. The outcomes were related to bleeding, hemodynamic status, length of hospital stay, and complications, such as kidney injury, electrolyte abnormality, major cardiac adverse event, nausea, vomiting, and mortality. A literature search was performed using Medline and EMBASE up to December 2019. The data were pooled to investigate the effect of fluid on macrocirculation and intravascular volume effect. Results Forty-three RCTs were included. Eighteen fluids were compared: nine were crystalloids and nine were colloids. The results were categorized into macrocirculation and intravascular volume effect, microcirculation, anti-inflammatory parameters, vascular permeability, renal function (colloids), renal function and electrolytes (crystalloids), coagulation and bleeding, return of bowel function, and postoperative nausea vomiting (PONV). We found that no specific type of fluid led to mortality and every type of colloid was equivalent in volume expansion and did not cause kidney injury. However, hydroxyethyl starch and dextran may lead to increased bleeding. Normal saline can cause kidney injury which can lead to renal replacement therapy, and dextrose fluid can decrease PONV. Conclusion In our opinion, it is safe to give a balanced crystalloid as the maintenance fluid and give a colloid, such as HES130/0.4, 4% gelatin, or human albumin, as a volume expander.

Synthesis and In Vitro Study of the Biodegradation Resistance of Magnetic Nanoparticles Designed for Studying the Viscoelasticity of Cytoplasm

An approach to the analysis of intracellular motion with nanosecond temporal resolution, based on the Mossbauer study of particles incorporated into a cell, has been developed. A possibility of applying magnetic nanoparticles as probes for studying in vitro the cytoplasm properties is analyzed. Two types of aqueous colloids of nanoparticles enriched with the 57Fe isotope are synthesized, and their cytotoxicity and biodegradation resistance under living cell conditions are investigated by an example of breast cancer cell line. It is found that the particles barely undergo any changes characteristic of biodegradation processes during their 120-h incubation in cells, although intracellular oxidation of divalent iron in the particle composition is observed. This result indicates possibility of using these particles for in vitro Mossbauer studies.

Pemahaman Konsep Sistem Koloid Hasil Pembelajaran Menggunakan Metode Diskusi Berbantuan LKS Pada Siswa Kelas XI SMA Negeri 1 Manuhing Tahun Ajaran 2017/2018

Diskusi merupakan metode pembelajaran menggunakan percakapan ilmiah oleh beberapa orang yang tergabung dalam satu kelompok untuk saling bertukar pendapat tentang suatu topik masalah, atau sama-sama mencari pemacahan mendapatkan jawaban dan kebenaran suatu masalah. Tujuan penelitian ini adalah mendeskripsikan pemahaman konsep sistem koloid hasil pembelajaran menggunakan metode diskusi berbantuan LKS pada siswa kelas XI-IPA SMA Negeri 1 Manuhing Tahun Ajaran 2017/2018. Penelitian ini merupakan penelitian deskriptif. Subjek penelitian ini adalah siswa kelas XI IPA-2 SMA Negeri 1 Manuhing yang berjumlah 30 orang siswa. Instrumen yang digunakan berupa soal tes pemahaman konsep (pretes dan postes) berbentuk essay sebanyak 3 soal, lembar keterlaksanaan pembelajaran, lembar pengamatan aktivitas siswa dan angket respon siswa. Data pemahaman konsep diperoleh dari hasil tes tertulis berupa essay yang diberikan sebelum dan sesudah pembelajaran menggunakan metode diskusi berbantuan LKS. Hasil penelitian menunjukkan pemahaman konsep siswa pada kelas XI IPA SMA Negeri 1 Manuhing tahun ajaran 2017/2018 tentang sistem koloid setelah pembelajaran menggunakan metode diskusi berbantuan LKS rata-rata sebesar 81,5. Perubahan pemahaman konsep siswa pada setiap konsep sesudah pembelajaran menggunakan metode diskusi berbantuan LKS yaitu: (1) Menjelaskan perbedaan suspensi kasar, larutan sejati dan koloid sebesar 2,96% menjadi sebesar 77,03%; (2) Menjelaskan jenis-jenis koloid berdasarkan fese terdispersi dan fase pendispersi sebesar 4,44% menjadi sebesar 69,62%; (3) Menjelaskan sifat-sifat koloid (effek tyndall, gerak brown) sebesar 25% menjadi sebesar 100%.

The Effect of Lymph Nodes' Histologic Response on Survival Outcomes in Moroccan Patients with Rectal Cancer.

Prognosis for patients with locally advanced rectal cancer remains controversial. The purpose of this study was to elucidate possible association between therapeutic effect on lymph nodes (LNs) and patient prognosis. Overall, 149 patients with rectal cancer received preoperative radiotherapy in concomitance with chemotherapy or exclusive radiotherapy before rectal excision. Microscopic examination of formalin-fixed lymph nodes was assessed for therapeutic effect. The establishment of groups combined reaction tissue types of fibrosis, colloid, and necrosis after neoadjuvant treatment was assigned. The average age was 56.38 years, ranged between 22 and 88 years, 53% were female, and 47% were men, with a sex ratio of 1 : 12. In the present study, we noticed that after a median follow-up time of 40.67 months (0–83; SD: 21.1), overall survival was statistically significant depending on age groups. Kaplan–Meier analysis showed significant differences in the rate of patients with an age under 65 years (70.64%) versus those with an age over 85 years (36.5%) (p < 0.001). Also, the OS was statistically significant depending on therapeutic effect groups composed of 0TE (No Therapeutic effect), C+ (presence of only colloidal effect), F+ (presence of only fibrosis tissue), and ME+ (mixture of 2 or 3 types of therapeutic effect) group. Indeed, we observed a significantly higher OS rate in the ME + group (86%) compared with the OS rate of LNs group with no therapeutic effect (57%) (p=0.028). Additionally, there was a significant association between the presence of fibrosis on LNs and an extended delay of more than 8 weeks to neoadjuvant treatment completion and surgery. Our study indicates that the best patient prognosis could be predicted based on tumor presenting a best pathologic effect on lymph nodes, and that delaying surgery for more than 8 weeks to neoadjuvant treatment completion improves therapeutic response on LNs.

Analysis of Prostate Adenocarcinoma Histopathological Types in Relation to Tumor Grade.

Prostate adenocarcinomas are some of the most common malignancies diagnosed in men, and the evaluation of tumor growth patterns is the basis for establishing the aggressiveness of the lesions. The study included 283 cases of prostate adenocarcinomas for which histopathological type and tumor grade were analyzed. The results indicated the association of ductal, sarcomatoid and signet ring-like cell types with aggressive growth patterns and high scores, atrophic and pseudohyperplastic types with mild growth patterns and low scores, foamy gland type presented intermediate growth patterns/scores, while conventional and colloid types had variable aspects. The grading systems used may be considered consistent with the histological types of prostate adenocarcinomas.

Entropic Effects in Solvent-Free Bidisperse Polymer Brushes Investigated Using Density Functional Theories.

Solvent-free polymer-functionalized nanoparticles form a special type of colloid composed of inorganic cores self-suspended by their grafted coronas. In the absence of intervening solvent molecules, the fluidity of the system is provided by these tethered polymers as they fill the space. Here, we study the structure and interaction of neighboring polymer-grafted surfaces in the solvent-free condition using mean-field density functional theories. For opposing flat surfaces, the brush configuration and the associated energy landscape are semianalytically investigated given the incompressibility of the tethered entropic chains. The effect of brush polydispersity (including variations in both chain length and surface grafting density) is considered by two bidisperse models corresponding to different physical scenarios: one for opposing brushes uniformly mixed with two species at a fixed grafting density, and the other for opposing brushes with distinct chain lengths and grafting densities. The space-filling capabilities of the neighboring coronas differ not only by their ratio of radii of gyration for the composing polymers but also by their ratio of grafting densities. We show that the system energy depicts a steric repulsion as the brushes are compressed, which is typical for hairy particles in a solvent. However, as the interwall separation increases, the cooperative stretching of the chains leads to an entropic attraction between them, a unique characteristic of solventless systems. The corresponding brush profiles change from a bell-like shape to a more step-function-like feature as the interwall spacing increases significantly. The interwall separation associated with the overall free energy minimum therefore characterizes the favorable interparticle spacing for solvent-free polymer-functionalized particles. The limiting accessible parameter space of polymer sizes and grafting densities subjected to the space-filling constraint is comprehensively explored for representative interparticle spacing characterizing the compressed, relaxed, and stretched regimes for a given polymer species, respectively. Such information would be useful for guiding the design of experimental solvent-free polymer-functionalized nanoparticles.

Parameter control and concentration analysis of graphene colloids prepared by electric spark discharge method

AbstractIn this study, graphene colloids were prepared using the electric spark discharge method (ESDM) with graphite rods (99.9% purity) in deionized water (DW) at a normal temperature and pressure. Five different types of graphene colloids were prepared using an electrical discharge machine (EDM) with five different pulse cycle switching times (Ton:Toff) = 10:10, 30:30, 50:50, 70:70, and 90:90 μs. According to the Ultraviolet-visible spectra (UV-Vis) and Zetasizer analysis, the results showed that the 10:10 μs parameter was the most suitable for the preparation of graphene colloids. UV-Vis was also used to detect the concentration of the graphene colloids; a comparison with a graphene oxide (GO) confirmed that this method could be used to calculate the discharge time needed to produce graphene colloids with different concentrations in the ESDM process.

Combined technique based on light scattering for investigation of the colloid’s parameters

The determination of colloid’s parameters is important issue in different fields of science and industry. The purpose of this work is investigation of the physical and dynamical parameters of colloid’s parameters. This paper offers new experimental setup of combined method based on light scattering techniques (dynamic light scattering and electrophoretic light scattering). Distinctive features of these methods are simplicity, informativeness, non-destructiveness and high accuracy of obtained results. Light scattering techniques are based on the correlation function of fluctuations of the intensity of scattered light calculation. The analysis of correlation function allows one to obtain the size distribution, translational diffusion coefficients and the molecular weight of biomolecules. In addition when an electric field is applied, we can determine electrophoretic mobility, zeta potential and the degree of intermolecular interaction directly in the liquid. In this paper, results of different types of colloid’s parameters are presented. The obtained results can be used, for example, in medical application for investigation of aggregation processes of proteins with nanoparticles (gold, magnetic, carbon and others), which may be useful in the diagnosis and treatment of various diseases.