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Nanometer-sized particles that are nanoscale in three dimensions. They include nanocrystaline materials; NANOCAPSULES; METAL NANOPARTICLES; DENDRIMERS, and QUANTUM DOTS. The uses of nanoparticles include DRUG DELIVERY SYSTEMS and cancer targeting and imaging.
Of course yes. Depends on several factors including process of synthesis. Can refer my recent paper on zinc ferrite.
Interaction study at interface?
Dec 13, 2012
I wanted to know if you could study the effects of two different software, suppose one is for nanoparticles and the other is for protein simulation, in the same simulation box, especially the interactions at the interface? Is it possible? If so, how?
I am trying to transform S.aureus/E.coli bacterial cells with naked Iron Oxide nanoparticles (200-250nm) with the aim of generating bacteria with magnetic properties. I am bombarding cells in 1ml suspension made of PBS and 0.75M Sorbitol. However, I am unable to confirm transformation after bombardment. There are a lot of particles in the suspension after the bombardment that respond to magnets but how can I confirm whether these particles are inside the cells, outside the cells or attached to the bacteria from outside? I am using 500ug of nanoparticles per bombardment and cells in PBS (not in media) because bombarding them in nutrient medium may cause them to grow and eventually lose the particles.
I had never worked with such biological systems and it is quite far from my work area. One suggestion I have is that if you are sure that your magnetic NP are between 200-250 nm big why not try a filtration? You can separe the NP from the bacteria that way...
If you have a noble metal@oxide (core@shell) system where the noble metal exhibits surface plasmon ressonance UV-vis absorption band (Au, Ag or Cu) is it possible by UV-vis to know the formation of a core@shell NP.
Please give us more details of yous system so that we can give tips about it.
Layer-by-layer (LbL) assembly of multilayer polymer films onto colloidal particles or templates followed by selective template removal has attracted extensive attention as a drug delivery system due to its advantages of precise control over the size, shape, composition, wall thickness and functions of the obtained capsules.
The nanoparticles that I have prepared are in the form of a red powder which have precipitated in the solution. The lamda max is around 568nm. Does the powder consist of copper or cuprous oxide nanoparticles?
Hi Akhini, generally freshly prepared copper oxide particles do not show any peak in the visible regime in UV-Vis spectra and your 568 nm peak indicates copper particles (generally copper particles show peaks within 560 - 600nm). Here is a reference you can look up: Materials Letters, Volume 63, Issues 3–4, 15 February 2009, Pages 441–443. However, for confirmation, as Matteo and Anjali suggested, you should get XRD pattern. Hope this helps,
I want to synthesize Pt nanoparticles from H2PtCl6.6H2O precursor and i checked it by uv-visible spectrophotometer. Instead of having a peak at 215nm I have two peaks one at 196 nm and the other at 251 nm! What does it mean? Are the nanoparticles synthesized?
I have a serious cleaning problem. I put silver nanoparticles on gold electrodes by drop coating. After running some experiments and polishing with emery paper and alumina, I observed that the silver signal still remains. Does anyone know how to solve this problem?
If there is silver on your emery paper or other polishing media, you rub it deeply into the soft gold. Do you use several fresh pieces of emery paper after each other?
I second the proposal to use chemical etching. I'd not use grinding to remove contamination on soft metals. By the way, can gold be electropolished? That would probably work better!
Just an idea: You may also regenerate your expensive gold electrodes not (only) by removing a thin layer from the surface, but (also) by adding a fresh gold layer on top with electroplating, sputtering or evaporation.
Did you confirm that your gold electrode is free of silver in the first place? Silver is a common contaminant and alloying element for gold. Vendor specifications of purity are sometimes not reliable...
I am involved in one pot synthesis of silver and ZnO nanoparticles. I found that a protein (33 kDa) of fungal origin can perform "dual" function of synthesis and stability of nanoparticles. I have successfully characterized the protein and it's complete nucleotide, amino acid and structure is available in our laboratory.
Presently, I am focused to develop a deep understanding of “how this protein is performing dual function” and to elucidate the plausible interactions between the protein corona and a nanoparticle. In our laboratory, we are implementing both "in silico" and "experimental" approaches to understand the concept.
Being a biotechnologist, I am looking for support and guidance from experts of various other fields. I will feel immense pleasure to discuss and disclose more information in this regard., if someone is interested.
Dear L'Hocine, As Navin stated, there are various levels to explain toxicity of nanoparticles. Keep in mind that these may also include apoptosis, necrosis, or a combination of both. I would also add that there may be effects on cell morphology, which we have characterized for example using the parameters of nuclear area factor and cell area factor. let me know if you are interested and I can link you to some of our publications.
For some metals (e.g. Ag, Au) you can sputter thin layers (< 20 nm), followed by an annealing process of the substrate (try 1h@200°C). You get NP with a various sizes and shapes (depending on the layer thickness, annealing time + temperature, substrate type, etc.)
Hello,everyone,recently I have been using EDC/NHS coupling strategy to prepare amide complexes between L-arginine and amino-terminated nanomaterials. However, I have failed many times.
In my experiment, the L-arginine's amino group was derivatived by admantane firstly.Using anhydrous DMSO as a solvent, I just want to activate L-arginine with EDC/NHS to form the NHS ester,and then add the NHS ester (disolved in DMSO) into the aqeuous solution containing amino group surface-capped nanoparticles.Strangely,LCMS didn't find any peak attibuted into L-argine-NHS .
I have no idea how to form this amide group.Can anyone give me some advice?
When you want to prove the existence an active ester - not to mention quantification - you have to be careful because it might not survive the LC conditions and/or the MS ionisation! Try to prove its existence by adding a nucleophile in excess (eg an alkyl amine) to your active ester (if there at all) priore the measurement and try to find the amide mass peak in the LCMS thereafter. You might even be able to quantify your active ester this way...
The protonation/deprotonation rate of the surface oxygen atoms (surface charge) will depend on both the pH and ionic strength of the medium. The point of zero charge (PZC), i.e. the pH at which the net surface charge is zero, of magnetite/maghemite nanoparticles in aqueous media is usually located around pH=6-8, but this depends on the electrolytes present in the system. On the other hand, silica PZC is found at pH=2 (again, depending on electrolytes in solution). Said that, you can produce magnetite/maghemite nanoparticles without the necessity of ethanol or similar to keep them apart; this involves precipitation at low pH in the presence of certain electrolytes that produce a proper PZC shift. Here is a reference about the method, where the surface stabilisation is ensured by perchlorate anions:
E. Tronc et al, Journal of Magnetism and Magnetic Materials 221 (2000) 63-79.
Silica coating can be carried out by suspending the nanoparticles in a mixture of water/ethanol/ammonia/TEOS (or just water/ethanol/TEOS), where the final thickness of the silica coating can be tuned by varying this proportion. Here is an example on how you can make it using the Stöber method:
Sonia L. C. Pinho et al, ACS Nano, 2010, 4 (9), pp 5339–5349.
For the sake of simplicity, if you don't know where to start, try a 80/20 water/ethanol mixture with a low concentration of TEOS (that will keep you within the miscibility area of the mixture) and make any amendments on the proportion depending on the results.
Does anyone have experience regenerating the ascorbic acid used as reducer? The composition of the solution is DHAA, PVP, DHAA and nitrate (from copper nitrate). How can I treat this solution to have it ready for another reduction (i.e. reuse of the solution)?
You would have to add a reducing agent that is stronger than the DHAA such as sodium borohydride, however you would then have borate salts remaining the solution, which could potential effect the production of nanoparticles.
Does anyone have a protocol for conjugating FITC and/or Rhodamine-B and cylco-(RGDKfk)-(PEG)-(PEG)-NH2 on to the surface of 50nm Gold NPs?
Dec 12, 2012
I would like to use NHS/EDC chemistry for the conjugation of both dye(s) and the peptide. I would like to possibly use 6-mercaptohexanoic acid to first coat the 50nm Gold NPs (which are made via the Citrate method) via thiols with a alkyl chain spacer and a terminal COOH group for the EDC/NHS conjugation of the dye and peptide. Should the conjugation of the dye and peptide be done simultaneously or step-wise? Does anyone have any suggestions or perhaps a protocol?
Hi. A one step conjugation will probably be messy because the citrate will react with the NHS/EDC.
I haven't done this particular conjugation, but I would look into putting NH2 groups on the gold (e.g wth aminoethanethiol or cysteine) instead of COOH, because you can buy amine reactive fluorescein and rhodamine. You could make the cyclic peptide amine reactive with NHS/EDC seperately.
I want to label cells with fluorescent particles, and study the influence of various coatings/surface properties on extent of uptake.
I need a commercially available polyethylene glycol (PEG)-coated magnetic particle. Ideally, the particles should be non-toxic and have stable retention of their fluorophores. I typically use magnetite-based particles, but other magnetic elements could be used.
I am considering ChemiCell's nano-screenMAG-PEG/P particles (4416-1). Has anyone used these?
We use Peg-coated liposomes for gene delivery which we synthesize.Theoretically, pegylation reduces opsonization of nanoparticles which alters its cellular biodistribution. There does exist a relationship between surface characteristics of your delivery vehicle and how its interacts with a cell or endocytic uptake. These relationships are heavily influence by cell type and in vitro situations (cytotoxicity, transfection) does not necessarily translate into in vivo success.
It depends on the structure of the peptide sequence. More precisely, the side chains in the aminoacids of the peptide. If they are nonpolar then there could be vander waals interaction; if the side chain is polar then you would see stronger interaction due to dipole-dipole forces of attraction in addition to vander waals. The degree of interaction may differ. You should be able to do calculations and study the models using chembiodraw ultra.
To get effective results of these food nanoparticles, how can we match the nano structure with the body's cells?
Dec 12, 2012
Just went through the paper via the link Judith Camacho submitted. It is true that the 50-nanometer polystyrene carboxylated particles affected the absorption of iron into the cell. But this happened AT LARGE DOSES. What was going on is "competitive absorption of iron and the 50-nanometer polystyrene carboxylated particles at the cell/medium interface.
The paper pointed out that at LOW DOSES of the nanoparticles, the iron absorption increased. So, in actual fact, the nanoparticles itself is not the problem but the concentration/dose. Generally, excess of all things are bad!
Hence, we can say that the nature, composition and concentration/dose of the nanoparticle in question is important.
How to remove the capping agent PAA (sodium salt of poly acrylate) from the cubic shaped Platinum nanoparticle in order to increase the electrocatalytic property of the synthesized platinum nanoparticles?
You can remove long chain surfactants from platinum or palladium catalysts electrochemically. One very easy method is to selectively replace the capping agents with carbon monoxide in a process very similar to carbon monoxide stripping. This works for PVP and can be combined with UV-ozone for very strongly adsorbed surfactants like octadecylamine.
Polyvinyl Alcohols are very reactive towards Metals and form a complex. just dissolve polyvinyl alcohol in water add silver nano particles and warm. An insoluble gelatinous material form. This gelatinous material is Silver complex of polyvinyl alcohol. It becomes solid on drying.
I have nanoparticle mixture with size ranging from 50nm to 90 nm, how can i separate them. I was thinking of using a centrifugation system which will give different bands corresponding to different particle size. Is their any better way to do the separation?
You can't just use the Scherrer equation for the crystallite size calculation with these data. You have to substact the instrumental line broadening using a diffractogram from a well crystalline sample of Si or BaF2 for example.
Another point is that Scherrer not always gives you a real crystallite size value, this because the FWHM is affected not only by the particle size as by the structural strain. It must be pointed out also that the shape constant (k = 0.89 ~0.9) is used for spherical particles, so that you need to be sure that your crystallits are spherical.
again another question on RG that has little significance. How do you think people can give some meaningful answer without knowing what kind of material you are talking about? It could be TiO2 as you try doing methylene blue degradation experiments, but 3.6 eV is a kinda large bandgap, more close to that of chalcogenides. Seeing some degradation in the visible is quite common and as Dieter pointed out this can be due to defects. Again expect no further meaningful help on those defects if we don't know what material you are talking about or how you determined the bandgap (if you did measure it).
From the answer you gave I also seriously doubt you understand what people are talking about here or what powder XRD can do for you. And seeing you are playing with semiconductors, this is quite frightening. If you talk about impurities in a semiconductor, don't expect to see anything significant in your diffraction pattern (e.g. extra peaks). We talk about substitutional or interstitial atoms, not about extra phases. You will just see some peak shift when the impurity level is sufficiently high and without a reference I doubt you'll be able to quantify it!
What are all the parameters to be considered or known when building a model of a metal nanoparticle and which software will be best suited (one for free)?
Dec 6, 2012
I want to build and optimize nanoparticles and by using that I want to study its interaction with proteins
Try to use tweens as surfactant unless you could modify the surface turning to more hydrophilicity
How to calculate Bohr exciton radius of ZnS quantum dots?
Jan 28, 2013
Is there any relation between Bohr exciton radius and energy bandgap?
Feb 15, 2013
Ms. J Dora, the exciton Bohr radius of the ZnO is about 2.34 nm.
(Synthesis and photoluminescence properties of vertically aligned ZnO nanorod–nanowall junction arrays on a ZnO-coated silicon substrate)
Equation for the Bohr exciton radius:
I have been successfully depositing home-made, 30nm citrate-capped gold nanoparticles onto amine-functionalized glass surfaces. Recently, I noticed that a couple other batches of particles (one is citrate-capped, one is tannic-acid capped) will not appreciably self-assemble. I'm positive the surface functionalization is not the problem, as I can put the same surface back into the original particle batch and monitor self-assembly.
I realize that the capping agent in one of the batches may be an issue; however, am perplexed as to why the other citrate-capped batch does not self-assemble. I noticed that adjusting the PH seems to help a bit, and wondered if anyone know of optimal ph (and/or other relevant conditions) for self-assembly in this system.
If you have cleaned your particle via dialysis or centrifuge cleaning, the pH value and the ionic strength of the solution must have changed and might cause the problems. The main parameters that affect the assembly are 1. the pH value which affects the electrostatic repulsion between gold nanoparticles and the electrostatic attraction between the gold and the substrate surfaces; and 2. the ionic strength ( salt concentration) that screens the Debye length of the interactions. Since citrate is always largely excessive in the synthetic solution, I don't think the covering of the surfactant on the gold surface is a big problem.
Your question is ambiguous. First you will have to state which energy scale you are talking about. Generally, you would express band positions in relation to either vacuum level or Fermi level. However in both cases this is very much a function of deposition parameters of your material and can not be expressed for ITO in general.
In either case, the question would be more suitably expressed in a different way. In case of conduction band position in relation to Fermi level, you would rather be asking where the Fermi level is in relation to the band gap. In the case of vacuum level the question really is how big your surface potential (more specifically the electron affinity) is.
A way to answer both of these questions is to use XPS/UPS measurements, preferably under in situ conditions.
Does anybody know the possibility of coagulating alkane thiol passivated gold nanoparticles in chlorinated solvents like chloroform, dichloroethane etc? Also let me know if there are any references for this.
Every time I add gold nanoparticles (13 nm) to gelatin with stirring at 37 C followed by addind 6 mercaptohexanol for another hour, followed by centrifugation to take pellet ,the gold nanoparticles aggregate.
answer of deepa bhatt is almost correct but in ablation process several parameters is important such as ,cw or Q-switch laser,plasma shielding,pulse width(nanosecond or femtosecond),...if your laser is q-switch,best wavelength for ablation is lower wvelength for example uv pulse because plasma shielding is low
It is a multistep process, when H2PtCl6 has to be reduced into tetrachloroplatinate(II), then prep. Magnus salt ([Pt(NH3)4][PtCl4] with ammonia, sepn. it form the soln. then converting into Pt(NH3)4Cl2 with excess of ammonia. I am sending you the details from the Brauer: Handbuch der Preparativen Anorganischen Chemie
When we use the sol gel method to synthesize nano particles which stage of synthesis determines whether the final product is nano or not? Also how does the pH value become an important factor for the crystallite size?
I would like to synthesize 20 to 30 nm of Fe3O4.. My material is not reaching that size. I am following acetate route sol gel method. As I am very new to sol gel method I have no idea how the parameters you mentioned are affecting the synthesis. If i control only one parameter like hydrolysis rate ,then can I achieve the size what I am expecting or I should control many parameters together to achieve the goal? In general I would like to know what each parameter does so that I can understand how to control the parameters.
One of my work on hydrolysis using plant extract for zirconia NPs synthesis is recently published in Mat.Letts. I believe this is the first of its kind. Have anyone aware of hydrolysis rxn using plant ext to synthesize NPs?
From general point of view, it should be a difference, as carboxylic groups absorb IR . To test this I would measure temperature coefficient of resistance ( TCR) for MWNT and functionalized MWNT thin films
I want to decorate carbon nanotubes with Pt nanoparticles. The procedure is two pot. At first I synthesized pt nanoparticles (I have a solution) and then I mixed it with functionalized CNTs. How should I make the CNTs solution (the ratio of the amount)? I need the amount and the procedure to have a uniform loading of Pt on CNT? Which parameters can determine the amount of loading?
It is almost impossible to get real nano particles by common wet or dry ball milling. Vibratory milling in steel containers using steel balls does give some 200 nm sized particles but the iron contamination is a problem. Attrition ball milling would help but then drying and de-agglomeration will pose a problem. Cryogenic planetary ball mill would be the best choice
You can try by electrodeposition. You'll need to control the localization by ajusting the metallic ion concentration in your solution. You can have a look at the paper: Journal of Porous Materials 7, 77–80 (2000) / DOI 10.1023/A:1009611225946
I'm looking for a commercial supplier where I can purchase magnetic nanoparticles with an affinity for thiol bonds. So either a core-shell structure or an alloy are both fine. Does anyone have any good suggestions?
There are several chemical methods to synthesize nanoparticles of gold, silver, and iron oxide, as co-precipitation or thermal decomposition. But physical methods either are not widely known or publicized. There is the laser ablation in a liquid medium, which can obtain any type of nanoparticles, but lasers for this technique are expensive. Does anyone know a way to make it cheaper or other physical process to obtain nanoparticles?
There are in fact a large variety of physical techniques, many of which have been already described in earlier answers. The typical 'top-down' approach is high energy ball milling, which can yield sub-10nm particles. But the major drawbacks are surface contamination and introduction of structural defects.
The 'bottom-up' variety of physical techniques can be classsified into the following two categories:
(1) Spray techniques such as spray dry, freeze dry, plasma spray and hot spray.
(2) PVD-based techniques are particularly suitable for obtaining nanocrystalline thin films. They include Evaporation-Condensation, CVD and PE-CVD, Laser Ablation and Magnetron Sputtering. Of these, the last is by far the most versatile. One can obtain nanocrystalline films of most metals (dc sputter), oxides, nitrides, sulphides etc. (rf sputter) either using reactive sputtering or from targets having the same composition. Low substrate temperatures, high sputter-gas pressure and low energy conditions generally favour smaller particles. But if you are looking for a cheaper technique without sophisticated instruments, chemical techniques are better and provide larger yield.
Several reviews are available on this topic. Some representative references are added below (I have chosen older references that give more details).
1. SPUTTERING: (i) Hahn & Averback, JAP 67 (1990) 1113, (ii) Ayyub et al., Appl Phys A 73 (2001) 67; Scr. Mat, 44 (2001) 1915
2. LASER ABLATION: (i) Koshizaki et al. J Phys Chem B 107 (2003) 9220; Appl Phys A 76 (2003) 641
I have modified nanoparticles then calculated the surface coverage by CC, but I got the value of Qads (adsorption reaction at electrode surface) as the negative charge. What is the effect of the negative intercept of Qads?
Maybe you used the experimental setting (working electrode, same electrolyte et al.) repeatedly, that will induce something collected on the working electrode. So it is better for you to try it again and using all the fresh setting.
I think the confusion is growing here. There is NO standard definition for the word "crystallite". In different communities has different meaning and within some communities it is misused and abused (i.e. most people don't know the meaning of their "cruystallite size").
I will stick to powder diffraction as I spent the last 15 years working on the measurement of size and defects in nanostructured materials using this technique. By powder diffraction you can easily measure interatomic distances that are in the Angstrom range and the number of digits of acuracy you can get is impressive (check NIST SRMs) so there is in principle no limit to the measurement of sizes in the same range.
The whole diffraction pattern bears also information on the size of the coherently scattering domains. Those are called by some people "crystallites". If you use TEM to measure the size of the objects you see, you intrinsically measure a slightly different size. And again the measured objects are called "crystallites". people doing the synthesis of amorphous nanoclusters call them "crystallites" as well (after all we all call "crystal glass" something that is not crystalline at all!).
So I keep insisting that "crystallite" should NOT be used unless you give a definition of what you mean by it. And I also keep insisting on the fact that the size and shape of an object have noting to do with the internal (atomic) structure.
As to Graphene, the IDEAL Graphene is a 2D object. In 2D a crystal is an object that has 2D translational periodicity so again if by "crystallite" you mean a crystal of small size, this is a "crystallite". And again you can measure the coherent domain size by XRD (it will just be the in-plane one).
But beware as the size of a single object has in most cases no meaning (you are going to use several of those) so you should rather ask for a size distribution. And if you are given a "mean crystallite" size, double check (again) what is the meaning of it. Most people that will read this answer probably use Scherrer formula for estimating the "average crystallite size" for a crystalline material and probably none of them realise e.g. that the values they obtain are NOT the mean of the domain size distribution.
I am doing nanoparticles of Ag with biomass in a liquid media. I obtained my results of size dispersion and the results shows big and small distribution. At this time I don't know if the big sizes are aggregates, but does anybody know how to obtain or induce a major distribution in size?
dear ari, this question is what keeps most scientists in the field of particle technology (especially for smaller particles down to nanoparticles) at work. It is not very trivial to answer your question. First you have to ask: what is it that keeps your particles together. If you are faced with aggregation, very strong covalent bonds exist which are hard to "break". Mechanical procedures include stirred media milling and even ultrasonication (which is very limited to about larger 100 nm). If you're faced with agglomeration instead you most of all and universially need to overcome van der Waals attrraction. This can be achieved by mechanical input as well. The next question is how to introduce a repulsive interaction to prevent agglomeration of the particles. This is achieved in a variety of ways. You can increase the electric double layer repulsion by increasing the charge of the particles (expecially in water) and in addition prevent compression of the double layer by high ionic strength. Another repulsive interaction is based on "decorating" the surface of the particles with polymers or macromolecules. This is often referred to as steric repulsion and it is based on a combined entropic and anthalpic effect. In combination such molecules can also cary a net charge and so called electro-steric stabiliztaion can be achieved.
Purging of the argon gas was done in order to prevent the further oxidation of platinum complex due to air and it also helps to prevent the agglomeration of platinum complex by increasing the surface area at the interface...
Deagglomeration of aqueous nanoparticle agglomerates by adsorption of amphiphiles at the liquid-liquid interface!
Oct 17, 2012
What do you think about my Thoughts (Gedankenexperiment)? See the attached "comic". This is based on a publication of mine to be found in Journal of Nanoparticle Research 2012 14(7), Nr. 990
How did you measure number of separate particles with respect to total particles in the solution?
1. Definition of hydrophobosity can be use only for aqueous surrounding media and cannot be applied to other media. It is incorrect to claim that your particles are hydrophobic in non-aqueous solution because you need presence of water to support such claim.
2. Double layer is not a typical way to stabilize suspension because presence of other ions in most cases will rander it useless. More popular approach is using steric stabilization that keeps particles far enough causing week VDW interaction.
3. Amphiphilates cannot exist as separate entities in aqueous solution or its interface (they will create a layer with hydrophilic part facing aqueous solution and hydrophobic submerged in the "friendly solvent"), but can in some organic solvents.
Yes, please send the publication while I have my doubts I want to make sure that we do not have a simple case of misunderstanding.)
I agree with Shahnaz Qadri on the question of the X-ray tube target, Mo or Cu. More often it is Cu K alpha radiation. If Akkini Devi wishes, i can help her to resolve the question. She may send the details on the experimental conditions and the preparation method.
Dear Ravi, this represents a scale to measure the d spacing corresponding to the radius of a particularr ring in the electron diffraction pattern. The scale of this type already takes account of camera length and wavelength used in the experiment and pixel conversion of them. If you have Gatan software and .dm3 format of your data then you just need to measure the radius and take the reciprocal of it to calculate the corresponding d spacing and subsequently the orientation of crytals plane. I hope this would be satisfactory answer to your question.
Do we need an extended DLVO theory?
Oct 11, 2012
For particles with electric double layers, DLVO theory explains well colloidal stability; however, many systems involve other non-DLVO interactions such as hydrophobic, hydophilic or steric interactions and may lack of EDL ... is there a need for an extended DLVO theory?
Many interesting comments. Originally, DLVO theory meant the superposition between electric double layer repulsion and van der Waals attraction. Superposition of other contributing forces has been a common approach (e.g. steric, hydrophobic). I know that in the cases for both electric double layer and steric repulsion, theories vary from quite simple to very complex. As Titus Sobish points out, direct measurements may be preferable over a complex theory. Rheology may prove extremely useful in that regard as it allows one to measure colloid interaction forces for concentrated systems.
Because the electrons are confined to a much smaller space than in a (practically infinite) crystal (or other macroscopic solid state object). Intuitively, we can see from quantum mechanics that this confinement leads to a shift in the energy levels, which therefore can affect the band gap. - Think of the particle in a box usual example from quantum mechanics: when you squeeze the box and make its length smaller, the energy levels of solutions to the Schrödinger equation will shift.
When you come from a potential which is period in all three dimensions, and then take away the periodicity in one (nanowire e.g.), two (graphene e.g.), or even three dimensions (quantum dot e.g.), you can see that this will have an effect on the energy levels (band structure more precisely) and therefore the difference between the highest occupied level and the lowest unoccupied level (or band of levels) may shift, thus changing the band gap when we make the transition from "infinite" solid to nano-scale material.
I am investigating the catalytic effects of copper nanoparticles. I would like to know of some reactions which can be used to show the catalytic effects, also methods for quantification of the produced product would be great. I would be highly interested in reactions which show colour change.
Oct 25, 2012
It seems to be possible to transform carbon dioxide,
Depending who you ask that can mean a variety of things. First stability can relate to the materials themselves, are they stable or chemically break down. It could relate to their orientation, the materials may not chemically degrade, but physically alter their arrangement/confirmation over time or under different conditions (temperature, light, humidity, aq, pH, etc.,). If the nanoparticles are serving as drug carriers it could relate to the stability of the drug within or attached or associated with carrier, or its ability to remain with the carrier under different conditions, eg., laboratory in water vs buffer vs serum, or in vivo, i.e., systemic circulation (blood). There can be also overall stability or performance where you are evaluating ability of product to not degrade, retain drug/imaging agent, distribute to desired region and perform as designed (intracellular uptake) or maybe undergo some change to release drug. One of the challenges in nanomedicine is engineering match the drug/diagnostics physicochemical proprieties with nanoparticles to achieve sufficient stability to protect drug/agent (or prevent toxicity) yet allow it to "function" ie., release drug or be taken up, at target sites.
What I have seen is that it is possible to increase the sharpness of the image, reducing the size of the nanoparticle. A shape anisotropy may increase the magnetic moment, but it can also block access to certain regions.
I'm using dynamic light scattering to measure size of TiO2 nano-particle, and I need the absorption of TiO2. I looked up many literature, but I only found a spectrum of the absorption, no accurate numbers. I only know it's really small.
Is there any handbook or publication I can look up for the number?
There is an online resource for several materials at http://luxpop.com/ and TiO2 (rutile) is listed there. For 20C and 633nm the values n=2.42 and k-0.0006 are provided with a reference. So that should provide a decent first guess for the values.
For dynamic light scattering keep in mind that the z-average (=average size based on cumulants fit), polydispersity index (=indication of the relative width of an assumed Gaussian distribution), and intensity based particle size distribution are all independent of the refractive index of the material. It is only when you want to convert to volume/mass or number distributions that the refractive properties of the scattering objects come into effect. In practical applications, as long as your particles are 100nm or less, the influence of the refractive index and the absorption will be very small. You can test this yourself by reanalyzing data with changed refractive index values to observe the effect.
If your TiO2 nanoparticles are less than 100nm there should be no problem using the rutile values.
TiO2 or Ti or TiO nanoparticles
Oct 8, 2012
what precursors are used for the synthesis of TiO2 or Ti or TiO nanoparticles?
There are plenty of precursor solutions available, but the process may differ while using each of these precursor to get TiO2 or Ti(OH)2.. etc., For example, you have titanium isopropoxide, titanium butoxide, titianium tetra chloride, titanyl nitrate, etc. Just try to search a suitable method to obtain your required product.
Indeed! Nanoparticles’ chemistry is based on the tuning of precipitation. You need to choose the system accordingly. However, organometallic chemistry is more useful to decorate the nanoparticles for certain purposes. For instance, thiol based donors attached to gold nanoparticles can be linked to the organometallic moieties at other end to alter their functional characteristics.
Try silane coupling chemistry with either (3-amino propyl)-triethoxy-silane (APTES) or (3-mercaptopropyl)-trimethoxy-silane (MPTMS). Mptms can couple the sulfur specific region of the isothiocyanate to SiO2 surface while Aptes can couple the amino region of the isothiocyanate to SiO2.
Fan did you noticed your TGA result still showing weight loss below 1000 C, so that we have to go down lower than which showed 20 % of the compound is still un degradable. Form your datas 20 % residual indicates not only Platinum metal, but also some carbonized materials of your dendrimers and if any halogen may presences. Upto 300 C trace out the moisture lost of your G4 material, which reflects in derivative curves indicates both physic and chemisorped water loss. Can you able to see the sharp melting peak region near 600 C, it has established that starting stage of degrade your polymer of amido group trace till 900 C. if you want to conform it you know the quantity of dendrimers weight kept in the sample holder compared to major weight loss in your TGA contributes from 50 to 20 % weight loss = 30 %. That 30 % multiplied in to molecular weight of your G4 dendrimer. The results suppose to be match we assign it loss due to denderimenrs. Fine your TGA trace till 1000 C and I felt your nano incorporate in ppm level it dosent show any structural changes in platinum residual in TGA. The stable structure of platinum I guess FCC up to 1700 C, but I am not sure. May 800 C before possible to form platinum oxide, but their identification through the weight loss is tedious.
If you lyophilize without any cryoprotectant aggregation is bound to occur and the aggregates will take longer time to get dispersed in water. So add 5% mannitol to aqueous dispersion of nanoparticle and lyophilize.You will get the desired particles.
Please refer our paper entitled "Diclofenac-loaded Eudragit S100 nanosuspension for ophthalmic delivery , Journal of microencapsulation. 01/2011; 28(1):37-45."
We have discussed the same.
How can we prevent agglomeration of particles while preparing nanoproducts /nanoformulation / nanopesticides?
You want to achieve a zeta potential of +/-30 as a rule of thumb to truly help prevent agglomeration. So, depending on your particles and application, deciding on a good capping agent or surfactant can take a bit of investigation and consideration. For a biological application, this becomes a bit more tricky as you have to consider the effects of pH, osmolarity, and the toxicity of any capping agents or surfactnants, and furthmore, as you are developing a pesticide you are going to want to find something inert or biocomaptible with the host your are protecting and may or may not be toxic to the 'pest' you are trying to kill. Also, consider the 'solvent' you are going to use for dispersion of your NP suspension as a pesticide; if water is going to be used, again major considerations are pH and osmolarity of the final suspension. Considering the final end product when engineering a NP-based product is a must, and this is where most fail because under lab conditions everything worked well, but when used in the actual environment the products perform very poorly. Amine or carboxylic acid group surface functionlization are very common methods for capping particles, as well as various PEG ligands. You can adsorb or covalently modify the surface depending upon the chemistry you use and your application and also the material you are using. Pluronics series surfactants are interesting as they are non-ionic, and provide a nice range of different MWs and HBLs (hydrophilic-lipophilic balance; a very important, often over-looked characteristic of a surfactant), as well as some being non-toxic and even FDA approved for medical use (i.e. Pluronic F68) and others being rather toxic (i.e. P65); looking for one that has differential toxicity based on HBL, that is being toxic to the 'pest' and non-toxic to the host, might be something worth investigating. That way you are adding an additional level of efficacy to your NPs as well as stablizing them at the same time. There are many other lines of surfactants out there such as Brij, PEGs, PVPs, etc.. some of the more common ones that come to mind though, such as Tx-100 would probably not be a good idea as they are highly toxic. There are also anionics (e.g. sulfates and sterates, common in soaps and detergents) and cationic surfactants (e.g. CTAB, which is an effective antimicrobial agent).
In nanoparticle preparation does the molarity have any effect on the the grain size of the particle?
Sep 15, 2012
If we increase the molarity of the solution does the particle size increases or decreases?
Molarity is a very important factor concerning metal ions as well as surfactant high concentration of metal ions inhibits the regular forward formation of metal nanoparticle as well as it increase the rate of agglomeration and sizes of metal nanoparticles . There is a critical concentrations for both metal ions and surfactant above which you may not get what you want
PVP selectivily bind to Ag(100) plane which promotes the growth of silver nanocubes. On the other hand, citrate ions bind to Ag(111) plane which allows the growth of silver triangular and discal nanoplate. I suggest you the next paper about silver nanoplates
I have noticed a range of values used in the literature are used, most notably 284.5 eV and 285 eV. However, am I right in thinking that 284.8 eV is the most accurate value to use? I'm trying to distinguish between AgO and Ag species in my spectra for powdered samples of Ag nanoparticles capped with N-(2-Mercaptopropionyl)glycine http://www.sigmaaldrich.com/catalog/product/FLUKA/33986?lang=en®ion=GB. Ag is present in the form of metallic Ag and Ag(I).
Why not consider using a reference sample? Just take a clean Ag substrate (e.g.silver foil after Ar ion etching or an in-situ prepared Ag film by e-beam evaporation), and look at the energy position of the Fermi edge and the Ag-3d doublet. After storing the sample ex-situ you can look at the binding energy for C1s. For hydrocarbons from adsorbates, we usually take 284.5 eV (for resolution in the FWHM=1.0-1.5 eV range).
However, energy calibration via C-1s for nanoparticles covered with complex carbon compounds seems to be not without problems unless you know
exactly the chemical shift for these carbon species. In case you observe a four peak structure in the Ag-3d doublet, the lower binding energy part is metallic Ag, while the higher energy part is due to oxide formation, irrespective of an exact calibration of the energy axis (especially when also charging may be a problem).
LAMMPS is a good choice, but I know this program only by reputation; I never used it myself. You are correct that you need to do minimization. An important question is which force field parameters to use. I don't have an answer to that. You'll need to take a look in the literature to see what others have done for Cu - C interction.
You can try add to your suspension penthanoic, hexanoic acid or larger organic hydrophobic alkyl acids. ZnO caped nanoparticles would be floating from water media and could be separated by organic apolar solvents.
Hi Colleague- Cu nanoparticles, although SPR response is weak compare to Ag or Au nanoparticles, are useful in the visible region. SPR absorption peak for Cu nanoparticles in glass appears around 560 nm (2.21 eV). [Kreibig & Vollmer: Optical properties of metal clusters, Springer, 1995].
Although I am aware that Fujifilm Dimatix provides one of the best solutions for inkjet printing hydrophobic nanoparticles (NPs), I am interested in using commercial inkjet printer+refillable cartridge for this purpose. If you have used/are using some configuration like this, can you recommend which instruments work well, especially to achieve the highest resolution possible (finer feature) using the most current inkjet printer ? Any suggestions on the concentration of the ink ?
Hm, this is interesting. Regarding gel content I presume you refer to soluble polymer content and residue - considered to be "gel". It is well known in rubber chemistry that carbon black and silica aerogels (sometimes denotes ad "white soot") adsorb polymer molecules so strongly that this strongly bound layer cannot be removed even by good solvents of the polymer. This is probably what you call "gel". To a certain point probably this insoluble part increases with the filler content. It has been shown by sevaral authors that nanoparticles influence the polymer structure (including mobility) at far distances even at low concentration.
The second part of the statement (lower water absorption) is somewhat puzzling for me. So far in all of my earlier studies (which were normal micro-filler in various polymers) the addition of the filler increased rather than decreased the water absorption and this was well detectable by dielecric spectroscopy. This water adsorption at the filler/polymer interface proved to be fairly reversible.
It would be interesting to see your results on decreasing water absorption on filler addition. If thsi proves to be true, it would eb inetrestting to study the mobility of water in these sysems by NMR or by dielectric methods.
the key is the different reaction pathways followed by the system depending on the Fe(II)/Fe(III) ratio, which is the usual one that leads to the stabilization of the spinel structure of magnetite. I assume that you use a basic pH for precipitating the magnetite. When it is sensibly higher than 0.5, 2-line ferrihydrite may be quickly formed at the beginning of the precipitation process, although due to its instability it will evolve to either goethite or poorly crystalline magnetite. When it is sensibly lower, formation of iron(III) hydroxide hydrate as intermediate specie becomes possible (the latter is also unstable and evolves to geothite) and, in oxidative conditions, you could end up having maghemite instead of magnetite . Ratios around the optimum one, will probably produce mixtures of magnetite and some oxyhydroxide (mainly goethite), or poor quality magnetite. In any case, the initial complexation/polymerization of the hydrated iron cations plays a crucial role on the reaction pathway, and in this sense Fe(II) and Fe(III) behave quite distinctly. For further information on the mechanisms involved in the formation of iron oxdes from the precursors in aqueous medium, I recommend you the following review focused on the hydrolysis of Fe(III) salts:
Charles M. Flynn Jr., Chem. Rev., 1984, 84 (1), pp 31–41
Note that these comments do not apply for different pH conditions, temperature or addition rate of the precursors, among others.
Hope this helps.
Synthesis of TiO/TiO2 nanoparticles
Oct 28, 2012
Is there any other precursor other than titanium isopropoxide or titanium tetraisopropoxide for the synthesis of TiO/TiO2 nanoparticles?
as Mathias mentioned the type of titanium precursor for obtaining TiO/TiO2 nanoparticles depends on the synthesis route you are using. So, if you are working with an polymerization method you can try titanium oxalate, but if your method is based on solvothermal synthesis you should use TiCl4 as already suggested.
Hi Hadi, when you say Fe2O3 you mean maghemite? We were successful in the preparation of magnetite nanoparticles in carrageenan hydrogel matrices (kapa, iota and lambda) using in situ co-precipitation method. You can find more details in the article:In situ synthesis of magnetite nanoparticles in carrageenan gels.
Ana L Daniel-da-Silva, T Trindade, Brian J Goodfellow, Benilde F O Costa, Rui N Correia, Ana M Gil , Biomacromolecules . 09/2007; 8(8):2350-7. DOI:10.1021/bm070096q
As iron oxide nanoparticles are incorporated into an increasing number of medical products subject to FDA regulation, questions about formulation, pyrogenicity, sterility, and sterilization procedures are emerging.
Have a look at Melissa et al 2014: Challenges facing sterilization and depyrogenation of nanoparticles: Effects on structural stability and biomedical applications.
Filtration will be the best method, however the surface charges of the oxides nanoparticles and the filter should be taken into consideration. If you need further information do not hesitate to contact me.
Full prof is nice for the modelling and much else. I went to the ICDD course in Philadelphia and they recommended it as complimentary to their software. So if the best in the business recommends it, I like it too.
I haven't found a particular need to use it, for much of what full prof offers a lot of the JADE software takes account for what I am asked to find. But I HAVE full prof, and am looking for opportunities to use it.
To use it.. You need some familiarity, it is not straightforward and the GUI is an antique version of DOS. Take your time to familiarize it, and come back here to ask specific questions.
In very general terms: de-localized carriers will produce DC (low frequency) conductivity, while localized carriers will contribute to the polarization only. Of course, there is a whole range of transitions between the two extremes, where the carrirs may diffuse along a certain path only (e.g. Maxwell-Wagner polarization) and electrode polarization may also cause problems but the general picture desribed above remains valid.
Does anyone have experience of using the qNano system from Izon or the Nanosight, to measure nanoparticles in biological samples?
Oct 31, 2012
I would like to demo these systems and would appreciate any information on them.
Yes. FTIR is able to differentiate FeOOH and the H2O adsorbed on the surface of iron oxide nanoparticle. You can see more complete answer in Cornell R.M., Schwertmann U. The iron oxides: Structure, properties, reactions, occurrence and uses - Weinheim: Wiley-VCH, 1996. - 604 p. I think it is one of the best book about iron oxides/oxyhydroxides.
I formulated some nanoparticles using w/o/w methods and am having problems determining the drug content encapsulated. While separating the pellets and free drug solution with PVA, i detected more drug amount than i initially added. Scanned through solution using UV spec at 200-400nm, realised that the baseline seems raised (my concentration curve was generated with drug in DI water, and the free drug solution recovered from centrifugation was drug in DI water and PVA)
Modern instruments usually include the option to display derivatives. On the other hand if you have the option to export the data derivation of the spectra can be done separately.
It is quite a long time ago when I dealt with this for determination of pyrene in soil extracts.
If I remember well with the 4th derivative you can separate all the information contained in the spectra into very sharp maxima and minima. Then you can use the most pronounced maxima and minima for a calibration.
A number of the effects that nanoparticles have on the properties of a composite material (such as the relative permittivity) are attributed to reorganisation of the polymer in the interfacial zone. What technique can we use to "see" what is happening in this interfacial zone?
Generally, the arrangement of the polymer chains, and hence the free volume, change near an interface or a nanoparticle. This leads to a gradient in free volume which can be probed by positron annihilation lifetime spectroscopy (PALS). In a nanocomposite, the interfacial range around the nanoparticles makes up a significant portion of the total volume fraction and should give rise to an additional lifetime in a PALS spectrum which increases as the filling factor becomes larger.
I have a solution of decorated CNTs with nanoparticles and Pt nanoparticles which are not decorated. How can I separate the carbon nanotubes from the undecorated nanoparticles? If filtration is suitable, what kind of filter and with what pore-size should I use? I heard that the centrifuge is not suitable because both of them will sediment.