Gold Nanoparticles - Science topic

Hello, yes you can make Tannic acid stabilised AuNPs and its dispersity will be affected by pH, I recommend to use alkaline pH. Most probably that the attachment of AuNPs to the 3-mercaptopropyltrimethoxysilane layer on glass did not take place due to RSH groups got oxidised during the synthesis then you can try to reduce it using DDT Dithiothreitol. Regarding the attachment to the surface everything depends on the following application, you can contact me in person. Some information regarding synthesis of AgNPs "Antimicrobial and antioxidant activity of AgNPs stabilized with Calendula officinalis flower extract" Article reference RSURFI_100109 Journal Results in Surfaces and Interfaces 2023 March

Binay PRIYADARSAN Nayak

The quantitative amount of a substance (mol) is a measure of how many elementary elements of a given substance (atom, molecule, electron ....) are contained in an object or sample. A nanoparticle is not an elementary element. It is impossible to calculate the mole of nanoparticles. So it is impossible to calculate the concentration of mol / l.

The light is scattered in inhomogeneous media (gold NP in the solution/any media), and the spectrum depends on the size of the particles, concentration, optical constants of the particles, etc. The original study was published in 1904 by J. C. Maxwell Garnett in Phil. Trans. Royal Soc. London. Several effects are not accounted for in MG theory, such as size, shape, and clustering variation. These effects were added to the model in the publication by B.N.J.Persson in Solid State Comm (1982). You may check these papers and find the answer to your question as several factors are important to quantify the absorption shift.

As Dr. Sobisch mentioned above, you need two points of connection. In other words, you have to use directional Ostwald ripening process to produce Au nanowires.

To the best of my knowledge, 1-naphtol assisted synthesis fo Au nanowires is the most facile and rapid method. It works as a coordination, reducing and structure-directing agent at the same time. The reaction yield is very high. Read this paper for your reference 10.1039/C8TA06676K

However, if you need to control aspect ratio precisely, try seed-mediated growth method.

Add Brij-35 in gold before coupling

Sunil V D

The word millimolar indicates the concentration of gold nanoparticles in units of mmol/L. This is a low concentration of nanoparticles. Look or think carefully about what problem you need to solve.

Assuming there were no other protein, you can do BCA on the nps and on the reaction volume to ensure that the antibody is present at a known concentration on the beads.

Sorry, cannot send books or articles due o copyright issues

Dear all, even if you have nanoparticles with MW (I prefer molecular mass, weight has a force unit) such as TiO2 or CaCO3, you don't need it, rather size and its distribution, shape, and more importantly specific surface area, are the pivot factors for NPs loading and distribution in the matrix. My Regards

If the sensing depends upon the surface area then chose such morphology which has more surface area.

Best wishes

Adamu Mamman

In addition to dialysis and centrifugation, you can purify nanoparticles by long-term settling, extraction of impurities with various solvents, electrophoresis, electrodialysis, washing with solvents on membrane filters. You can combine these methods together.

Make a very dilute dispersion of your nanoparticles in methanol/ethanol. Take a micropipette and drop cast on the TEM grid (Cu grid) or FESEM stub (already coated with carbon/aluminium tape). Let the solvent evaporate and then your sample is ready for analysis.

Thank you, unfortunatelly I dont have any experience with this technique, but it seems plausable that you can trap them in the subtrate as they seems to be from SEM images. I just look for some papers about this technique, and it seems temperature plays a role in the agglomeration - maybe this may be your case.

To conclude, beside SEM, I would perform any chemical analysis (EDX, XPS) to be sure it is gold. Optical spectroscopy may also help, those AuNPs on quartz should have the distinguish absorbance somewhere about 600nm (blue/purple-ish look).

There are several ways to coat the optical fibers. Our research group tried a block copolymer templating method. If you are interested, please refer to our work (DOI:

Use normal dilution and measure absorbance, if it is 0.45 AU, then the system followed a linear relation.

Many, many thanks Nick Gee! Could you please give me a paper that discusses the aforementioned mechanism.

In order to do that, typically organic solvents are pretty good, such as dehydrated DMSO or dehydrated DMF. You can run your reaction in these solvents until the coordination is complete between Au-SH.

In the coming period, use heat and non-ionized water

Dear Hassan Arkaban, Usually the higher the concentration of HAuCl4 during the synthesis the larger average particle size. I would suggest to use higher concentration of stabilizing agent. I did previously prepared AuNPs suspension up to 4 mM/L 787 mg/L

Though I haven't combined all the materials you mention, the graphene oxide's hydrophobicity could cause this problem. Even if there isn't a lot of GO in your formula, you likely need some binder to hold the electrode together.

Khalil Ur Rehman

HAuCl4 3H2O solution (10 mL, 10 mM) was added to 10 mL (containing 0.025 g 3-mercaptopropyl)dimethoxysilane , 5 mL water and 5 mL ethanol) and stirred at room temperature for 8 h. Then, for the system, a considerable amount of newly prepared NaBH4 solution was added and stirred for 2 h. Samples were collected by centrifugation and dried in a vacuum oven at 60 °C for 3 h for further use.

Thank you very much for your help!

Too complicated, buy it from sigma or jenkem.

Measurement of binding kinetics

Spectrophotometry

Székely István, it may be possible, though it is difficult to tell from your question where you might be running into issues.

No, it's not possible and even if you could do it, you would probably get very poor performance. For lateral flow detection, you will have a particle that is between 40 and 80nm and you will have potentially over 100 Abs on the surface. Fc coupling is not simple, and I doubt you actually need it, but Dmitriy Berillo has suggested one possible approach.

Hi, you can use any of this . OPLS-AA, AMBER03, CHARMM FFs, as well as united-atom GROMOS G53A6 FF

I am not sure if this could really help you out.

Measure the solvent-accessible surface area (SASA) of the system (i) keeping gold nanoparticles in it (V_Total) and (ii) after removing the gold nanoparticles (V_w/o_gold).

Then subtract (V_w/o_gold) from V_Total, this will give you the surface area of gold nanoparticles.

Hi Motagare,

This website provides conjugation procedure, https://nanocomposix.com/pages/covalent-conjugation-of-antibody-to-gold-nanoparticles-for-lateral-flow-assays, by taking a brief look, the temperature is in RT and pH might comes to neutral as it mentioned, https://tools.thermofisher.com/content/sfs/manuals/MAN0011309_NHS_SulfoNHS_UG.pdf, these two reagent works in pH4.5~7.2, thereby the suggestion.

Or a SPR might help?

That is a good question.

The high sensitivities of the detectors on UV/Vis spectrophotometers result in minimun desviation between the experimental measurements of the same sample. Thus, the "error bars" would be very small.

Dear all, nothing is said on the preparation conditions and the medium where Au-NPs are. This crucial and the key to understand the surface chemistry/charge of NPs. Please have a look at the following document. My Regards

The problem has been solved.

Utilizing the x, y and z components of the Polarization and surface normal vector, the surface charge density can be calculated. (See "López-Ortega et al. Light: Science & Applications (2020) 9:49")

Noe Arjona Your suggestion is a good one, but it would need an intermediate conductive layer to connect to. One can buy ITO coated mylar and I've used this in the past to attempt to make plastic LCD's. I suspect that the end result would be a discontinuous film of Au and not the 'nanoparticles' as the questioner is requiring or requesting.

You don't need to go that far. SDS-PAGE will be enough. The stability of the nanoparticles (once you contact them with protein) depends on the presence of enough protein on the surface. When you surpass certain threshold, the protein is on the surface.

Note that the dithiol molecule is a linker between two Au nanoparticles with calixarene.

Thanks for the reply. The XRD was carried out from 2theta of 10-80 deg with a step size of 0.001. The XRD scan was done on 3 samples attached below. Where I see only sample-C with appropriate FCC peaks whereas for sample B/C, there was no sign of (111) peak, and other peaks were shifted. I think there was no proper development of the diffraction planes in B/C. What's your view on this?

You can try up to 200ppm of Ag nanoparticle for conjugation studies with Antibodies.

I drop casted the nanoparticles suspension on my thin film instead of electrochemical deposition. Because lectrochemical deposition was not working. Hope it will help you

There are numerous reasons but probably one of the most simple answers is:

they are efficient and easy to make (Turkevich and reverse Turkevich synthesis);

comfortable measurements of Abs. at 520-535 nm and high absorption coefficient (good relation between size and e);

higher stability (capping dependant) in buffered solutions of bioconjugation.

some reading:

best regards

The organosilane is require, silica has -OH group while gold has thiol. You need a linkage agent, MPTMS for example.

Electron microscopic results would confirm this.

Dear all, it would be better if the nanoparticles under investigation are given. Please have a look at the following documents. My Regards

Dear Preety Rohilla

I think the following link will be useful for you

Best regards

You can see the following links:

1.

2. https://www.researchgate.net/publication/47820413_Titanium_nitride_as_a_plasmonic_material_for_visible_wavelengths/figures?lo=1

3.

4. https://www.hindawi.com/journals/jnm/2012/154736/

Dear Mohamad Sofi Abu Hassan this is an important technical question which is of significant general interest to everyone working with green synthesized nanoparticles. There are a number of relevant discussions and research papers available in which this problem is discussed. Please have a look e.g. at the following potentially useful links:

(34 answers)

This paper has been published Open Access so that the full text is freely available on the internet (please see attached pdf file).

(also attached)

I hope this helps. Good luck with your work and please stay safe and healthy!

Dear Navoda,

The characteristics of magnification, voltage, etc. will depend on the microscope. Each microscope responds differently. An SEM is not the same as a Field Emission SEM. The results are very different; the quality and the possible magnification also. My recommendation is to carry out different tests until the desired quality and magnification are achieved, although this will depend on the microscope.

I think there is some problem with the activity of the photocatalyst. Try some alternative catalyst synthesis methodology...

Yes its affect

The nanoparticles are most likely dispersed in water and have adsorbed citrate ions on their surface. I do not use oligonucleotides, but have some questions. Are the particles stable in phosphate buffer? If the olinucleotide is negatively charged and so are the phosphate molecules, are not they going to compete for the same adsorption sites?

The toxicity can be mainly to what is in the surface of either nanoparticle. Hence, gold nanorods are way more toxic.

Citrate is negatively charged and provides the nanoparticles with a repulsive charge. Generally it is best not to do too much handling of the particles as they can aggregate easily. You can try to centrifuge and wash but some aggregation is almost inevitable. If it is extreme aggregation, the solution will turn blue/grey and there is no recovery from this position. More subtle aggregation can be seen on absorbance scans, especially an uplift in absorbance around 600-650 nm wavelength (there is little signal in this region normally, at least compared with the main peak at ~520nm). The ratio 650/520 is a useful indicator of aggregation if you want to monitor what is happening when you try to remove the citrate.

If it is possible, I would use the particles as provided, as the citrate is there for a reason. It is usually at a very low concentration.

Dear Alfonso Gomez , as pointed above, Raman is the appropriate technique for characterization of Au NP´s. By the way, "characterization" of anything, -Au NPs in this case- can be a very broad term. There are multiple parameters or/and properties you could determine from your sample. Let us guess that you want to describe the Au NPs size distribution (polydispersity) and shape, if they have a shell or not,... just to mention some common NPs aspects. In this case you can find lots of analytical techniques for measuring these parameters.

You could rely on microscopy techniques for size identification. Because they are nanoparticles, you would need a SEM or TEM (Scanning or Transmision electron microscopes) or an AFM (Atomic Force Microscope). It would be also useful a SNOM (Scanning Near field Optical Microscope) which will take advantage of the the same principle that allows SERS, the excitation of Localized Surface Plasmon Resonances (LSPRs) by means of a very localized source of light on the tip of an AFM like tip. Because your Au NPs could be coated with a protective shell, it could be labelled with some fluorescent label or if the shel would be autofluorescent, you could use that property to study your particles by fluorescence microscopies.

If you want to study the size distribution of your Au NP´s you could rely on light scatered by the particles by means of a Zetasizer.

Another way to do estimate the size distribution would be the use of a representative number of particles in a microscopic image, normally SEM or TEM, and using some selection and statistics software to obtain the corresponding hystogram and then the polydispersity.

Conventional UV-Vis spectroscopy can be also very useful when you have your particles in solution, because the spectrum will be dependent upon the particle´s size /or distribution /or shape. Once more, light from the spectrometer source will excite plasmons at different wavelengths depending on the size and shape of the Au NPs.

Hope this helps. Good luck with your research project and my best wishes.

use can use hydrothermal synthesis technique.

Dear all, generally speaking, all factors altering the interparticles distance/interaction and surface chemistry, may break colloïdal stability. These are : temperature, pressure, ionic strength, concentration, and additives. My Regards

Kang Rui Garrick Lim

Ulf has provides excellent comments above. I've just had a chance to look at the .dts file you provided above. Have a look at the phase plots (Configure-Report pages-Phase Plot). You'll see that they're pretty good - look at the standard, in particular, as this shows what you'd be seeing without issues. It also confirms instrument performance is fine.

Lower dilutions or no dilution are likely to be the best way of acquiring good signal. You'll see that the particles are negatively charged if you look at the first deflection in the phase plot (toward negative). See attached for the transfer standard (your record #104).

Compare your phase plots to those you've got in the initial reports you posted and you'll see the difference in quality.

Dear Zenande,

this is a very interesting technical question. Indeed, when gold nanoparticles are intended to be used in for in vivo biomedical applications they must be sterile. In this context please have a look at the following very useful article in which different sterilization methods are reviewed

Fortunately this paper has been posted by the authors as public full text on RG. Thus you can freely access it and download it as pdf file. I hope it helps answering your question.

Good luck with your research and best wishes, Frank Edelmann

@Santosh @Asghar Thank you very much..😊

Hello Ibrahim,

as a synthetic inorganic chemist I must admit that I'm not a specialist in this field enough to provide a qualified answer to your very interesting question. From reading some relevant papers I got the impression that Francisco Manuel Marquez is rigth in that both situations (hydrophobic and hydrophilic) are possible depending on the environment. In this context I recommend that you read the following very interesting review article:

Luckily this very useful paper has been posted by the authors as public full text on RG. Thus you can freely download it as pdf file. I hope it helps claryfying your question.

Good luck with your research and best wishes, Frank Edelmann

Dear Ibrahim,

Dear Aseel Alnaimi, the above FTIR spectrum is not appropriate given the fact that the corresponding transmission percentages of all peaks are higher than 90% signifying that the sample content in your KBr pellete has been rather too low. In such a condition, on account of low signal to noise ratio, some characteristic peaks are embedded in the noise level and cannot be detected at all. So, I suggest you either repeate the FTIR analysis once more with a well-prepared KBr pellete or use ATR-FTIR technique which can provide you with a higher S/N ratio for the surface functional groups. However, FTIR spectrum might not solely justify what you are dealing with but if it is accompanied with other surface characterizations especially XPS, it will most likely lead to a more rational conclusion. Please note, the characteristic peaks of the carbon materials are usually of low intensity, that is why it is mostly preferred to use XPS as a more reliable technique for inspecting their chemical structure.

Best,

Dear Ainin

Gold NPs solution should give an absorption band at about 500nm, however, the spectrum depends on many factors such as pH, size of NPs and etc. Please check the following paper for more information.

Hello Jiaying,

this is a very interesting technical question. In the article which you cited in you question the authors state in the Introduction that (citation) "Polyacrylic acid-gold (PAA-Au) Janus nanoparticles (JNPs) are difficult to prepare and characterize due to their specific structures and properties". However, I just came across an relevant literature reference in which a rather simple and straightworward synthetic protocol for making PAA-Au JNPs is described. Please have a look at the following article:

Unfortunately this paper has not been posted as public full text on RG. However, four of the authors have RG profiles. Thus there is a good chance that you can request the full text directly from the corresponding author via RG. The same is true for the following paper which provides a good overview of the field:

I hopw this information is useful. Good luck with your research work and best wishes, Frank Edelmann

Omar Gonzalez-Ortega Gracias Professor. It's very kind of you to answer all the questions. I really appreciate your help. I have some more questions but I should explore by my self first.

Thank you very much for your help, now I get the idea.

THANK YOU EVERY ONE

Ainin Razak

There are good comments above from Leo Vleugels and Omar Z. Sharaf . I would add the following:

Based on the above 2 bullet points, and if you have a transparent (no turbidity or evidence of settling) purple sol then the likely size for your material is in the ~ 5 - 50 nm region and your particles of > 100 nm shown in SEM are a result of agglomeration and aggregation in the SEM preparation stage (drying , coating etc). Take a look at:

Dispersion and nanotechnology

-Increasing the intensity may be represent the increasing the concentration of the formed nanoparticles (the number of Au NPs) this may be assigned to that reaction still working.

- On other hand using weak stabilizing agent, give the chance of aggregation specially if you prepare nanoparticles in the presence of polysaccharides.

Just as an additional idea: you can monitor the size of your colloidal gold with dynamic light scattering, to confirm whether aggregates appear or the sample is unchanged: https://instrumat.ch/wp-content/uploads/2016/08/MRK956-01-Characterisation-of-colloidal-Gold-using-DLS-LRLL.pdf

Hi Dr Aisha Kanwal . I hope the following link could help : https://nanocomposix.com/pages/ultra-uniform-gold-nanospheres

Dear Prateechee Padma Behera thanks for posting this very interesting technical question. Depending on how much money your supervisor has available, it might be worth thinking about buying a pre-fabricated NHS-activated gold nanoparticle conjugation kit. Various researchers seems to work with such kits. Please see e.g. the following freely accessible reference:

For a choice of commercial sources just search the internet for "NHS-activated gold nanoparticle conjugation kit".

Good luck with your research work and best wishes, Frank Edelmann

please check the above link.

Thank you John sir and Omar sir

Frank T. Edelmann Thanks for this answer professor!

I also found the "concentrated 8 times" quite subjective even though it is a critical step in the synthesis so in my experiments I simply varied just how concentrated those seeds were by adjusting the amount of CTAB/DIW I resuspended the AuNRs in.

As for the color, I had originally thought the end product should be of dark gray/green-ish color (from other literature) but I reached out to the authors of this paper and one of them just informed me that their end product is of blue/purple color which is what I obtained however my SPR peak (uv-vis) seems to be different than theirs. So I'll have to investigate why.

I also plan on doing TEM this week to confirm morphology so hopefully my new samples actually show spiky structure albeit of different size than the original.

The "Adjuvant-Loaded Spiky Gold Nanoparticles..." is actually the second method I was already considering after this one.

Thanks for your input!

Hi Prateechee Padma Behera.

Although some literature suggested that the antibody itself can be a capping reagent, I guess using linkers to covalently bond the antibody onto the AuNP surface can provide better stability.

For the EDC/NHS reaction, it converts COOH to NHS ester. So, in principle, whether there is PEG or not will not affect the reaction.

Hope this can help.

Vivian Triana

My thought is that the surface has oxidized and XPS should show this. We only ever found gold in the +3 oxidation state (and one could argue that you need an oxidized form to bond to negative capping agents). The surface is everything - composition, charge, corona etc. And for a system in air or water the the surface cannot be id