A free browser tool that checks dynamic light scattering (DLS) data and, if you add TEM images, compares the two. It looks for problems in four stages (interpretation, measurement setup, sample preparation, synthesis or flow) and tells you what each finding means and what to fix.
Researchers and students who measure particle size with DLS and TEM: polymer, lipid, metal and inorganic nanoparticles, and coated particles.
Yes, it is free during the public beta. Before any paid plans start, we will announce them; nothing is charged without your explicit purchase.
Wali Inam, Turku, Finland. PhD in Drug Development, with expertise in nanomaterial synthesis and microfluidics. Skilled in advanced analytical characterization (DLS, TEM, FTIR, HPLC, ITC, NanoDSF) for nanocarrier development, with experience in surface interaction studies, method validation and industrial R&D collaboration.
No. Your measurement files and TEM images are analysed only in your browser and are never uploaded. Only what you choose to send in the review or bug-report forms is sent to us.
Your email address if you sign up, and anonymous usage counts (for example how many analyses were run). See the privacy policy for details.
Yes, from the account menu ("Delete my account"). It removes your account and email address.
DLS: Malvern Zetasizer .dts files and CSV exports. TEM: image files (TIFF, PNG or JPG).
At minimum: a column of delay times in microseconds (µs), followed by one column of g2 − 1 correlation values for each run. Use numbers only, with at least 20 rows. Commas, semicolons or tabs can separate the columns, and a decimal comma is accepted. A text header row is optional and is ignored. Every column after the first is read as one repeat run.
Strongly recommended: one extra row that starts with the word countrate, then the count rate in kcps for each run in the same order as the columns, for example countrate,310,305,298. Without it, count-rate stability between runs cannot be checked.
A CSV holds no instrument details. The date, attenuator, intercept, the instrument’s own Z-average and PDI, and the dispersant are therefore left empty, and anything that depends on them cannot be checked or sorted. You still answer the quick questions (particle type, solvent and so on). For the most complete check, use the Zetasizer .dts file.
Visitors without an account can run 10 full checks per month. Signed-in users have no limit during the beta.
It is free, there is no password (we email you a sign-in link), and signed-in users are not limited.
An optional test in the report that checks whether the size drifts from batch to batch. It uses the Mann–Kendall trend test and the Theil–Sen slope on the Z-average of each batch, ordered by measurement date. It sits under "Batch trend" in the report, before the TEM comparison.
When 5 or more batches pass the quality test. Batches that fail are taken out and the test runs on the rest; if fewer than 5 pass, the button stays grey and cannot be clicked. The batches that pass must also have been measured in the same dispersant, with a similar attenuator setting (within one step) and on different dates, so that their order is known. Tick "Batch" in step 1 only for batches of the same recipe.
A batch is taken out if it has 2 or fewer repeats (at least 3 are needed to judge the scatter within a batch), if fewer than 90% of its runs are clean (dust, an unsettled first run or any other flagged run counts as not clean), if its PDI is 0.3 or higher, if the correlation curve oscillates, if the count rate falls (sedimentation) or the size grows during the measurement (aggregation), or if the signal is too weak or too strong. The report shows a card for each such batch with the reason. If the taken-out batches are the newest or the oldest ones, the card says so, because this can hide a trend. The limits (90%, PDI 0.3, 3 repeats, 5 batches) are rules of this tool, not published standards.
The Mann–Kendall p-value must be below 0.05 (the usual convention; the exact test is used for up to 8 batches) and the total change estimated by the Theil–Sen slope must be larger than 3 times the repeat scatter (a rule of this tool). A drift that is detectable but smaller than that is reported as within measurement scatter. With few batches the test can miss a small drift. References: Mann 1945, DOI 10.2307/1907187; Sen 1968, DOI 10.1080/01621459.1968.10480934.
The accepted difference between DLS and TEM sizes: polymer ±15%, uncoated metal or inorganic ±5%, coated particles ±10% (plus the expected coating), other or unknown ±10%.
Pick "Coated particle", then the core and the coating. DLS measures the hydrodynamic size, so it should read about the TEM size plus two coating thicknesses. The tool compares your data with the thickness range for that coating and shows the core and shell. If your coating is not listed, write its name and enter the thickness if you know it.
The tool flattens the image background, finds the size of the particles from the image itself, and fits a circle to each particle's visible outline using gradient Hough circle detection (Duda & Hart 1972, DOI 10.1145/361237.361242). Particles that overlap keep their own visible arc, so partly hidden particles are still measured. Irregular particles are reported as an equivalent-circle diameter and marked with a red dot instead of being thrown away. The pixel size comes from the file or from the scale bar.
Each particle is labelled by the group it belongs to: isolated (a single particle, or a small group of 2 or 3 touching particles) or aggregate (a group of 4 or more). You see the counts, the percentage of particles and the share of the image area in each class. The DLS-versus-TEM comparison uses the isolated particles. These limits are this tool’s own rules, not published standards. Dense clumps in which no single particle can be seen are counted as aggregate area only.
The number-weighted DLS size is compared with the TEM mean and coloured: agreement, minor, medium, major or smaller. A medium or major gap points first to sample preparation, and if that is clean, to the synthesis.
DLS weights large particles very strongly. From your TEM sizes, the tool calculates the Z-average a perfectly dispersed sample would give and compares it with the one you measured. A much higher measured value points to larger species, such as aggregates, in suspension.
Dust and aggregates are the most common and cheapest causes, so they are ruled out before the synthesis is blamed.
It applies checks and thresholds taken from the published literature. Every finding lists its source; thresholds labelled "standard practice" are guidance, not standards.
They are estimates, not certified measurements. They do not replace expert judgement, validated methods or regulatory testing. See the disclaimer.
No.
When a result suggests mixing problems, the report shows a Flow & mixing card with a button to contact us about a fluid flow analysis. The button only opens a contact page; no data is sent.
Use the "Report a bug" tab at the top of the tool page: say what happened and add a screenshot if it helps.
Yes, after you have generated a report, at the bottom of the report page. Reviews are shown publicly only if you tick the box and after we have checked them.