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Stable monodisperse nanomagnetic colloidal suspensions: An overview

Ramimoghadam D, Bagheri S, Abd Hamid SB

Colloids Surf B Biointerfaces, 2015 Sep 1;133:388-411.
PMID: 26073507 DOI: 10.1016/j.colsurfb.2015.02.003

Magnetic iron oxide nanoparticles (MNPs) have emerged as highly desirable nanomaterials in the context of many research works, due to their extensive industrial applications. However, they are prone to agglomerate on account of the anisotropic dipolar attraction, and therefore misled the particular properties related to single-domain magnetic nanostructures. The surface modification of MNPs is quite challenging for many applications, as it involves surfactant-coating for steric stability, or surface modifications that results in repulsive electrostatic force. Hereby, we focus on the dispersion of MNPs and colloidal stability.

Matched MeSH terms: Colloids*
Fulltext Formation of silver microbelt structures by laser irradiation of silver nanoparticles in ethanol

Zamiri R, Zakaria A, Husin MS, Wahab ZA, Nazarpour FK

Int J Nanomedicine, 2011;6:2221-4.
PMID: 22114485 DOI: 10.2147/IJN.S23830

In the present work, we prepared silver nanoparticles by laser ablation of pure silver plate in ethanol and then irradiated the silver nanoparticles using a 532 nm Q-switched Nd:YAG pulsed laser. Transmission electron microscopic images of the sample after irradiation clearly showed formation of big structures, such as microrods and microbelts in ethanol. The obtained microbelts had a width of about 0.166 μm and a length of 1.472 μm. The reason for the formation of such a big structure is the tendency of the nanoparticles to aggregate in ethanol before irradiation, which causes fusion of the nanoparticles.

Matched MeSH terms: Colloids/chemistry
Fluid management in children with severe dengue: a narrative review

Loi MV, Wang QY, Lee JH

Minerva Pediatr (Torino), 2023 Feb;75(1):49-61.
PMID: 36282485 DOI: 10.23736/S2724-5276.22.06935-X

Dengue is a mosquito-borne arboviral infection of increasing public health importance. Globally, children account for a significant proportion of infections. No pathogen-specific treatment currently exists, and the current approach to reducing disease burden is focused on preventative strategies such as vector control, epidemiological interventions, and vaccination in selected populations. Once infected, the mainstay of treatment is supportive, of which appropriate fluid management is a cornerstone. The timely provision of fluid boluses has historically been central to the management of septic shock. However, in patients with dengue shock, particular emphasis is placed on judicious fluid administration. Certain colloids such as hydroxyethyl starches and dextran, despite no longer being used routinely in intensive care units due to concerns of acute kidney injury and impairment of coagulation, are still commonly used in dengue shock syndrome. Current guidelines recommend initial crystalloid therapy, with consideration of colloids for severe or recalcitrant shock in patients with dengue. In this review, we discuss the pathophysiology of septic shock, and consider whether any differences in dengue exist that may warrant a separate approach to fluid therapy. We critically review the available evidence for fluid management in dengue, including the role of colloids. In dengue, there is increasing recognition of the importance of tailoring fluid therapy to phases of disease, with attention to the need for fluid "deresuscitation" once the critical phase of vascular leak passes.

Matched MeSH terms: Colloids/therapeutic use
Early fluid resuscitation in the management of major burns: ten years experience in Tabuk, Saudi Arabia

Rahoma AH

JUMMEC, 2002;7:127-131.

During the period from January 1992 up to the end of July 2001, the Burns Unit in King Khalid C Hospital treated 1735 cases of burns. The burns cases were of varying causes, age groups, degree, depth and extent. The formula used in lTeating these burns patients was a modification of Parkland fonnula. The fluid used was Ringer lactate solution. This fluid was administered for the first 3 days post burn until the general condilion of the palient was sfabilized. Early oral intake was encouraged in aU patients and was started as early as the second or the third day. Colloids were given by the end of the third or even the fourth day and according to the individual patients' needs. The results of this treatment regime significantly avoided renal complications and ensured patient rehydration. KEYWORDS; Major burns, fluids resuscitation

Matched MeSH terms: Colloids
Silica colloids as non-carriers facilitate Pb2+ transport in saturated porous media under a weak adsorption condition: effects of Pb2+ concentrations

Dai C, Zhou H, You X, Duan Y, Tu Y, Liu S, et al.

Environ Sci Pollut Res Int, 2020 May;27(13):15188-15197.
PMID: 32072419 DOI: 10.1007/s11356-020-08064-0

Transport of environmental pollutants in groundwater systems can be greatly influenced by colloids. In this study, the cotransport of Pb2+ and silica (SiO2) colloids at different Pb2+ concentrations was systematically investigated by batch adsorption and saturated sand column experiments. Results showed that SiO2 colloids had low adsorption capacity for Pb2+ (less than 1% of the input) compared with sands. In saturated porous media, SiO2 colloids showed a high mobility; however, with the increase of Pb2+ concentration in the sand column, the mobility of SiO2 colloids gradually decreased. Notably, SiO2 colloids could facilitate Pb2+ transport, although they did not serve as effective carriers of Pb2+. Under the condition of low Pb2+ concentration, SiO2 colloids promoted the Pb2+ transport mainly through the way of "transport channel," while changing the porosity of the medium and masking medium adsorption sites were the main mechanisms of SiO2 colloid-facilitated Pb2+ transport under the condition of high Pb2+ concentration. The discovery of this non-adsorption effect of colloids would improve our understanding of colloid-facilitated Pb2+ transport in saturated porous media, which provided new insights into the role of colloids, especially colloids with weak Pb2+ adsorption capacity, in Pb2+ occurrence and transport in soil-groundwater systems.

Matched MeSH terms: Colloids
Fulltext Formulation and characterisation of alginate hydrocolloid film dressing loaded with gallic acid for potential chronic wound healing

Gan JE, Chin CY

F1000Res, 2021;10:451.
PMID: 34249341 DOI: 10.12688/f1000research.52528.1

Background: A dramatic growth in the prevalence of chronic wounds due to diabetes has represented serious global health care and economic issues. Hence, there is an imperative need to develop an effective and affordable wound dressing for chronic wounds. Recent research has featured the potential of bioactive compound gallic acid (GA) in the context of wound recovery due to their safety and comparatively low cost. However, there is a scarcity of research that focuses on formulating GA into a stable and functional hydrocolloid film dressing. Thus, this present study aimed to formulate and characterise GA-loaded alginate-based hydrocolloid film dressing which is potentially used as low to medium suppurating chronic wound treatment. Methods: The hydrocolloid composite films were pre-formulated by blending sodium alginate (SA) with different combinations of polymers. The hydrocolloid films were developed using solvent-casting method and the most satisfactory film formulation was further incorporated with various GA concentrations (0.1%, 0.5% and 1%). The drug-loaded films were then characterised for their physicochemical properties to assess their potential use as drug delivery systems for chronic wound treatment. Results: In the pre-formulation studies, sodium alginate-pectin (SA-PC) based hydrocolloid film was found to be the most satisfactory, for being homogenous and retaining smoothness on surface along with satisfactory film flexibility. The SA-PC film was chosen for further loading with GA in 0.1%, 0.5% and 1%. The characterisation studies revealed that all GA-loaded films possess superior wound dressing properties of acidic pH range (3.97-4.04), moderate viscosity (1600 mPa-s-3198 mPa-s), optimal moisture vapor transmission rate (1195 g/m 2/day, 1237g/m 2/day and 1112 g/m 2/day), slower moisture absorption and film expansion rate and no chemical interaction between the GA and polymers under FTIR analysis. Conclusion: An SA-PC hydrocolloid film incorporated with gallic acid as a potentially applicable wound dressing for low to medium suppurating chronic wounds was successfully developed.

Matched MeSH terms: Colloids
Electrosteric stabilization and its role in cooperative magnetophoresis of colloidal magnetic nanoparticles

Yeap SP, Ahmad AL, Ooi BS, Lim J

Langmuir, 2012 Oct 23;28(42):14878-91.
PMID: 23025323 DOI: 10.1021/la303169g

A detailed study on the conflicting role that colloid stability plays in magnetophoresis is presented. Magnetic iron oxide particles (MIOPs) that were sterically stabilized via surface modification with poly(sodium 4-styrene sulfonate) of different molecular weights (i.e., 70 and 1000 kDa) were employed as our model system. Both sedimentation kinetics and quartz crystal microbalance with dissipation (QCM-D) measurements suggested that PSS 70 kDa is a better stabilizer as compared to PSS 1000 kDa. This observation is mostly attributed to the bridging flocculation of PSS 1000 kDa decorated MIOPs originated from the extended polymeric conformation layer. Later, a lab-scale high gradient magnetic separation (HGMS) device was designed to study the magnetophoretic collection of MIOPs. Our experimental results revealed that the more colloidally stable the MIOP suspension is, the harder it is to be magnetically isolated by HGMS. At 50 mg/L, naked MIOPs without coating can be easily captured by HGMS at separation efficiency up to 96.9 ± 2.6%. However, the degree of separation dropped quite drastically to 83.1 ± 1.2% and 67.7 ± 4.6%, for MIOPs with PSS 1000k and PSS 70k coating, respectively. This observation clearly implies that polyelectrolyte coating that was usually employed to electrosterically stabilize a colloidal system in turn compromises the magnetic isolation efficiency. By artificially destroying the colloidal stability of the MIOPs with ionic strength increment, the ability for HGMS to recover the most stable suspension (i.e., PSS 70k-coated MIOPs) increased to >86% at 100 mM monovalent ion (Na(+)) or at 10 mM divalent ion (Ca(2+)). This observation has verified the conflicting role of colloidal stability in magnetophoretic separation.

Matched MeSH terms: Colloids/chemistry
Physicochemical properties of tamarillo (Solanum betaceum Cav.) hydrocolloid fractions

Gannasin SP, Adzahan NM, Hamzah MY, Mustafa S, Muhammad K

Food Chem, 2015 Sep 1;182:292-301.
PMID: 25842340 DOI: 10.1016/j.foodchem.2015.03.010

Tamarillo (Solanum betaceum Cav.) is an underutilised fruit in Malaysia. The fruit, however, contains good proportions of soluble fibre, protein, starch, anthocyanins and carotenoids. Amongst the fruits, only tamarillo mesocarp contains both polar (anthocyanins) and non-polar (carotenoids) pigments. The ability to retain both polar and non-polar pigments in the mesocarp could be related to the unique properties of its hydrocolloids. To understand the pigment-hydrocolloid interaction in the fruit, information on the physicochemical characteristics of the hydrocolloids is required. Therefore, hydrocolloids from the anthocyanin-rich seed mucilage fraction of the tamarillo and its carotenoid-rich pulp fraction were extracted and characterised. Water and 1% citric acid were used to extract the seed mucilage hydrocolloid while 72% ethanol and 20mM HEPES buffer were used for pulp hydrocolloid extraction. Seed mucilage hydrocolloid was primarily composed of arabinogalactan protein-associated pectin whereas pulp hydrocolloid was composed of hemicellulosic polysaccharides with some naturally interacting proteins and neutral polysaccharides.

Matched MeSH terms: Colloids/chemistry*
Fulltext An experimental study on pile spacing effects under lateral loading in sand

Khari M, Kassim KA, Adnan A

ScientificWorldJournal, 2013;2013:734292.
PMID: 24453900 DOI: 10.1155/2013/734292

Grouped and single pile behavior differs owing to the impacts of the pile-to-pile interaction. Ultimate lateral resistance and lateral subgrade modulus within a pile group are known as the key parameters in the soil-pile interaction phenomenon. In this study, a series of experimental investigation was carried out on single and group pile subjected to monotonic lateral loadings. Experimental investigations were conducted on twelve model pile groups of configurations 1 × 2, 1 × 3, 2 × 2, 3 × 3, and 3 × 2 for embedded length-to-diameter ratio l/d = 32 into loose and dense sand, spacing from 3 to 6 pile diameter, in parallel and series arrangement. The tests were performed in dry sand from Johor Bahru, Malaysia. To reconstruct the sand samples, the new designed apparatus, Mobile Pluviator, was adopted. The ultimate lateral load is increased 53% in increasing of s/d from 3 to 6 owing to effects of sand relative density. An increasing of the number of piles in-group decreases the group efficiency owing to the increasing of overlapped stress zones and active wedges. A ratio of s/d more than 6d is large enough to eliminate the pile-to-pile interaction and the group effects. It may be more in the loose sand.

Matched MeSH terms: Colloids/chemistry*
Fulltext The influence of fluid resuscitation strategy on outcomes from dengue shock syndrome: a review of the management of 691 children in 7 Southeast Asian hospitals

Trieu HT, Vuong NL, Hung NT, Nguyen Minh T, Nguyen Van VC, Phan TQ, et al.

BMJ Glob Health, 2025 Mar 11;10(3).
PMID: 40068930 DOI: 10.1136/bmjgh-2024-017538

INTRODUCTION: The pathognomonic feature of dengue shock syndrome (DSS) is a transient capillary leak syndrome resulting in profound intravascular volume depletion. WHO management guidelines recommend particular parenteral fluid regimens during the critical leakage phase, including synthetic colloid solutions in certain circumstances. We set out to describe the actual fluid management strategies employed in different settings and to investigate relationships with clinical outcomes.
METHODS: We performed a retrospective review of paediatric DSS cases managed at seven hospitals across Malaysia, Myanmar and Vietnam. We explored the effects of both initial resuscitation (crystalloid alone or mixed crystalloid/colloid in the first 2 hours) and general management: group 1 (conservative-colloid, crystalloid only), group 2 (intermediate-colloid, colloid for 1-4 hours) or group 3 (liberal-colloid, continuous colloid for more than 4 hours) categorised according to the fluid given over the first 6 hours in clinically stable patients. We incorporated an inverse probability weighting score to adjust for potential differences in baseline severity.
RESULTS: Among all 691 patients, respiratory compromise (HR 2.08, p=0.022), requirement for nasal continuous positive airway pressure (NCPAP)/ventilation (OR 2.34, p<0.045) and days in hospital after DSS onset (risk ratio, RR 1.33, p=0.032) were significantly worse for mixed crystalloid/colloid versus crystalloid-only initial resuscitation regimens, after adjusting for baseline severity. Among the 547/691 children who stabilised within 2 hours, although a liberal-colloid general management strategy (group 3) was associated with a reduction in recurrent shock episodes (RR 0.13, p=0.043) when compared with a conservative-colloid strategy (group 1), the risks for respiratory compromise (OR 8.84, p<0.001) and requirement for NCPAP/ventilation (OR 8.16, p<0.001) were markedly increased. Additionally, the respective costs for group 3 vs group 1 were significantly higher.
CONCLUSIONS: The study highlights the potential benefits and risks of using colloid solutions in children with DSS. Formal randomised trials could help determine the most effective and safe parenteral fluid regimens for paediatric DSS. In the meantime, prolonged use of colloid solutions may be inappropriate, especially in settings without access to respiratory support.

Matched MeSH terms: Colloids/therapeutic use
Fulltext Effects of xanthan gum and HPMC on physicochemical and microstructure properties of sponge cakes during storage

Noorlaila A, Hasanah HN, Yusoff A, Sarijo SH, Asmeda R

J Food Sci Technol, 2017 Oct;54(11):3532-3542.
PMID: 29051648 DOI: 10.1007/s13197-017-2810-6

The effects of xanthan gum (XG) and hydroxypropyl methylcellulose (HPMC) in sponge cakes were studied. Hydrocolloids enhanced the thickening effect in batter that affected the textural attributes of sponge cakes. During storage, the structural changes in XG-cake resulted in higher hardness compared to HPMC-cake. Similar to XG, HPMC also contributed moistness to cake. The moisture loss of cake containing XG was slower than HPMC-cake. FTIR study showed absorption of OH at region of 3600-2900 cm-1 that explained the strong interaction of water in cake containing XG compared to other cake formulations.

Matched MeSH terms: Colloids
Fulltext Supramolecular Nested Microbeads as Building Blocks for Macroscopic Self-Healing Scaffolds

Yu Z, Liu J, Tan CSY, Scherman OA, Abell C

Angew Chem Int Ed Engl, 2018 03 12;57(12):3079-3083.
PMID: 29377541 DOI: 10.1002/anie.201711522

The ability to construct self-healing scaffolds that are injectable and capable of forming a designed morphology offers the possibility to engineer sustainable materials. Herein, we introduce supramolecular nested microbeads that can be used as building blocks to construct macroscopic self-healing scaffolds. The core-shell microbeads remain in an "inert" state owing to the isolation of a pair of complementary polymers in a form that can be stored as an aqueous suspension. An annealing process after injection effectively induces the re-construction of the microbead units, leading to supramolecular gelation in a preconfigured shape. The resulting macroscopic scaffold is dynamically stable, displaying self-recovery in a self-healing electronic conductor. This strategy of using the supramolecular assembled nested microbeads as building blocks represents an alternative to injectable hydrogel systems, and shows promise in the field of structural biomaterials and flexible electronics.

Matched MeSH terms: Colloids
Unified View of Magnetic Nanoparticle Separation under Magnetophoresis

Leong SS, Ahmad Z, Low SC, Camacho J, Faraudo J, Lim J

Langmuir, 2020 07 21;36(28):8033-8055.
PMID: 32551702 DOI: 10.1021/acs.langmuir.0c00839

The migration process of magnetic nanoparticles and colloids in solution under the influence of magnetic field gradients, which is also known as magnetophoresis, is an essential step in the separation technology used in various biomedical and engineering applications. Many works have demonstrated that in specific situations, separation can be performed easily with the weak magnetic field gradients created by permanent magnets, a process known as low-gradient magnetic separation (LGMS). Due to the level of complexity involved, it is not possible to understand the observed kinetics of LGMS within the classical view of magnetophoresis. Our experimental and theoretical investigations in the last years unravelled the existence of two novel physical effects that speed up the magnetophoresis kinetics and explain the observed feasibility of LGMS. Those two effects are (i) cooperative magnetophoresis (due to the cooperative motion of strongly interacting particles) and (ii) magnetophoresis-induced convection (fluid dynamics instability originating from inhomogeneous magnetic gradients). In this feature article, we present a unified view of magnetophoresis based on the extensive research done on these effects. We present the physical basis of each effect and also propose a classification of magnetophoresis into four distinct regimes. This classification is based on the range of values of two dimensionless quantities, namely, aggregation parameter N* and magnetic Grashof number Grm, which include all of the dependency of LGMS on various physical parameters (such as particle properties, thermodynamic parameters, fluid properties, and magnetic field properties). This analysis provides a holistic view of the classification of transport mechanisms in LGMS, which could be particularly useful in the design of magnetic separators for engineering applications.

Matched MeSH terms: Colloids
Continuous separation of colloidal particles using dielectrophoresis

Yunus NA, Nili H, Green NG

Electrophoresis, 2013 Apr;34(7):969-78.
PMID: 23436439 DOI: 10.1002/elps.201200466

Dielectrophoresis is the movement of particles in nonuniform electric fields and has been of interest for application to manipulation and separation at and below the microscale. This technique has the advantages of being noninvasive, nondestructive, and noncontact, with the movement of particle achieved by means of electric fields generated by miniaturized electrodes and microfluidic systems. Although the majority of applications have been above the microscale, there is increasing interest in application to colloidal particles around a micron and smaller. This paper begins with a review of colloidal and nanoscale dielectrophoresis with specific attention paid to separation applications. An innovative design of integrated microelectrode array and its application to flow-through, continuous separation of colloidal particles is then presented. The details of the angled chevron microelectrode array and the test microfluidic system are then discussed. The variation in device operation with applied signal voltage is presented and discussed in terms of separation efficiency, demonstrating 99.9% separation of a mixture of colloidal latex spheres.

Matched MeSH terms: Colloids/isolation & purification*; Colloids/chemistry
Fulltext Room temperature radiolytic synthesized Cu@CuAlO(2)-Al(2)O(3) nanoparticles

Abedini A, Saion E, Larki F, Zakaria A, Noroozi M, Soltani N

Int J Mol Sci, 2012;13(9):11941-53.
PMID: 23109893 DOI: 10.3390/ijms130911941

Colloidal Cu@CuAlO(2)-Al(2)O(3) bimetallic nanoparticles were prepared by a gamma irradiation method in an aqueous system in the presence of polyvinyl pyrrolidone (PVP) and isopropanol respectively as a colloidal stabilizer and scavenger of hydrogen and hydroxyl radicals. The gamma irradiation was carried out in a (60)Co gamma source chamber with different doses up to 120 kGy. The formation of Cu@CuAlO(2)-Al(2)O(3) nanoparticles was observed initially by the change in color of the colloidal samples from colorless to brown. Fourier transform infrared spectroscopy (FTIR) confirmed the presence of bonds between polymer chains and the metal surface at all radiation doses. Results of transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDX), and X-ray diffraction (XRD) showed that Cu@CuAlO(2)-Al(2)O(3) nanoparticles are in a core-shell structure. By controlling the absorbed dose and precursor concentration, nanoclusters with different particle sizes were obtained. The average particle diameter increased with increased precursor concentration and decreased with increased dose. This is due to the competition between nucleation, growth, and aggregation processes in the formation of nanoclusters during irradiation.

Matched MeSH terms: Colloids/chemical synthesis; Colloids/chemistry
Do colloids in comparison to crystalloids for fluid resuscitation improve mortality?

Naing CM, Win DK

Trans R Soc Trop Med Hyg, 2010 May;104(5):311-2.
PMID: 20206954 DOI: 10.1016/j.trstmh.2010.02.001

Permanent neurological impairment or death arising from hospital-acquired hyponatremia in both children and adults is well documented. The choice of intravenous fluids for fluid resuscitation in critically ill patients is a top priority in evidence-based medicine. The question of whether colloids in comparison to crystalloids can improve mortality in such cases remains to be answered. Well powered, randomized clinical trials addressing the comparative efficacy of different types of intravenous fluids is a high priority as is the ethical justification for such trials. The understanding of the pathophysiological process serves important information on clinical practice.

Matched MeSH terms: Colloids/adverse effects; Colloids/therapeutic use*
Fulltext Rheological properties of native and modified corn starches in the presence of hydrocolloids

Shaari, N.A., Sulaiman, R., Cheok, C.Y.

International Food Research Journal, 2017;24(5):2082-2089.
MyJurnal

Starch and hydrocolloids were often used together in food industry to modify the rheological properties with the aim to enhance the starch tolerance to processing conditions. As such, the rheological properties of xanthan gum (XG), carrageenan, high (HMP) and low methoxyl pectin (LMP), with native corn starch (NCS) and modified corn starch (MCS) at different temperature were evaluated in this study. The flow behavior index (n) of corn starch-hydrocolloid mixtures were observed in the range from 0.160 to 0.604 where indicated the shear thinning behavior. The addition of hydrocolloids increased the apparent viscosity of the starch system. NCS mixtures showed consistency index (K) and apparent viscosities (na,100) decreased with increase in the temperature. The addition of XG and carrageenan increased the storage (G’) and loss (G”) moduli. Among the hydrocolloids, the XG addition to the NCS exhibited superior viscoelastic properties as evidenced by the highest G’ and lowest tan δ values. XG was observed capable to increase while pectin reduced the solid-like starch system. This result provides pragmatic data for food engineer in process design and food product development by minimizing the cost of trial and error.

Matched MeSH terms: Colloids
Fulltext Effects of different drying methods and hydrocolloids on quality properties of semi-dried catfish jerky

Ishamri Ismail, Nur Husna Mohd Fauzi, Mastura Zahidi Baki, Ho, Lee Hoon

Malaysian Journal of Applied Sciences, 2018;2(1):11-18.
MyJurnal

This study was carried out to evaluate the effects of different drying methods (sun drying, cabinet
drying and convection oven) and hydrocolloids (carrageenan and alginate) on physicochemical
properties of semi-dried catfish jerky. The concentration of hydrocolloids used was 1% and 2%.
Samples without the addition of hydrocolloid served as the control group. The water activity of semidried catfish jerky decreased with the addition of hydrocolloids. For colour properties, lightness (L*)
value of semi-dried catfish jerky increased with the increased concentration of hydrocolloids. The
addition of 2% alginate (2%A) and 2% carrageenan (2%C) showed higher lightness (L*) than the
controlled group for all drying methods, except for sun drying with carrageenan. Both carrageenan and
alginate added into semi-dried catfish jerky increased the processing yields. The addition of 2%
carrageenan (2%C) and 1% alginate (1%A) improved the product yields for all drying methods. This
paper argues that the application of cabinet dryer gives better shelf stability due to the lower range of
water activity than other drying methods while preserving colour quality and product yields.

Matched MeSH terms: Colloids
Initial stages of GaAs/au eutectic alloy formation for the growth of GaAs nanowires

Rosnita M, Yussof W, Zuhairi I, Zulkafli O, Samsudi S

Sains Malaysiana, 2012;41:1133-1138.

Annealing temperature plays an important role in the formation of an Au-Ga eutectic alloy. The effects of the annealing temperature on gold nanoparticles colloid and substrate surface were studied using AFM, FE-SEM and TEM. At 600oC, the layer of gold colloids particle formed an island in the state of molten eutectic alloy and absorbed evaporated metalorganics to formed nanowire (NW) underneath the alloy. Pit formed on the substrate surface due to the chemical reactions during the annealing process have an impact on the direction of growth of the NW. Without annealing, the NW formed vertically on the GaAs (100) surface. The growth direction depends on the original nucleation facets and surface energy when annealed. When annealed, the wire base is large and curved due to the migration of Ga atoms on the substrate surface towards the tip of the wire and the line tension between the substrate surface and gold particle.

Matched MeSH terms: Colloids
Tio2 nanoparticles coated with porphyrin dye thin film as fluorescence gas sensor

Nurul Huda Yusoff, Muhamad Mat Salleh, Muhammad Yahaya

Sains Malaysiana, 2008;37:233-237.

This research explores the possibility of using fluorescence technique to detect the presence of volatile organic compounds based on a single sensing material. The material used was TiO2 nanoparticles coated with porphyrin dye. The TiO2 nanoparticles colloid is in a sol-gel form synthesized from titanium (IV) ethoxide in ethanol with addition of kalium chloride (KCl) as stabilizer. TiO2 nanoparticles were then coated with porphyrin dye, Manganase (III) 5,10,15,20 tetra (4-pyridyl)-21H, 23H porphine chloride tetrakis (metachloride). The coated nanoparticles were deposited on quartz substrate using self-assembly through dip coating technique. The sensing properties of the thin film toward volatile organic compounds; ethanol, acetone, cyclohexane and 2-propanol were studied using luminescence spectrometer. It was found that the thin film produced different emission spectra peaks for different volatile organic compounds (VOCs). Hence, it eases chemical identification process and potentially be use as fluorescence gas sensor.

Matched MeSH terms: Colloids

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