Progress in Color Colorants Coating 19 (2026), 47-65

Overview

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Key numbers

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of ZnO in sunscreen formulations up to a critical threshold of 15 wt. % enhances
UV protection; however, further increases to 21 wt. % result in a decline in
In recent years, there has been a notable increase in UV-A (315-400 nm), UV-B (280-315 nm), and UV-C
frequently included in formulations of reputable cosmetic allowable concentration of ZnO in sunscreens at 25 %.
the dissipation of absorbed UV energy as heat. This a solution containing 0.01 wt. %. ZnO was prepared
dispersive spectroscopy (EDS). X-ray diffraction (XRD) creams, a suspension was prepared with a 10 wt. %
Table 1: Formulation of sunscreen cream.
or other non-stoichiometric phases, X-ray diffraction equations 1 and 2 and presented in Table 2.
Table 2: Lattice parameters (a, b and c) calculated from characteristic diffraction peaks of samples.
Table 3 presents the results of the EDS analysis. provided in Table 3, it can be inferred that the observed
characterized by blades that are interwoven, there exists correlates with a decrease in the energy gap (27). Table
cosmetic products at 1 ppm and that of arsenic at 3 sunscreen samples within the incubator, while Figure
ppm. The Analysis of the samples using ICP analysis 7b shows the sample after one month at 45 °C. This
Therefore, the presence of heavy metals is deemed Furthermore, Table 6 shows the pH values of the
analyzed. Table 5 shows the concentrations of mercury following thermal stability tests. Based on the observed
Table 5: Concentrations of heavy metals in sunscreen samples.
As (ppm) 3.01 2.48 1.47 0.83 1.79 3.03
Hg (ppm) <0.10 <0.12 <0.10 <0.10 <0.10 <0.10
Table 6: pH changes of sunscreen samples prior to and following thermal stability tests.
rate increases as the particle size increases within the 25 %. However, increasing the ZnO concentration
reflection and scattering of UV radiation. wt. % was investigated. Figure 11 illustrates the
predominantly rod-like morphology with an average tration of ZnO is further increased to 15 wt. %, the
dimension of 66 nm, has a larger contact area than the absorption approaches nearly 85 %. However, upon
Z5 sample, the latter (exhibiting a hedgehog increasing the ZnO concentration to 18 wt. %, a decline
12 wt. % enhances the inter-particle contact, leading to As depicted in Figure 12, an increase in ZnO
the formation of clusters. As the ZnO concentration is concentration from 15 to 18 wt. % correlates with a
further elevated to 15 wt. %, the particles achieve decrease in protective efficacy. Furthermore, as the
increasing the concentration to 18 wt. %, the system subsequent decline in protective efficacy.
attributable to the aggregation of particles and their commercial samples. Figure 13 shows the comparison
two commercial samples with SPF of 30 and 60. DRS analysis. The Table 7 presents the amount of the
efficacy of sunscreen products. In this study, the SPF identified to fall within the range of 10 to 11.
Table 7: Investigation the correction coefficient of commercial samples and determining the SPF of Z1 sample.
potential for formulating a highly effective sunscreen approximately 15 weight percent (wt. %). Beyond this
activated by means microwaves. In: Frazao O, editor. Coat. 2020; 13(3):167-75. https://doi.org/10.30509/

Methods (brief)

thereby increasing the level of protection. Notably, the Z1 sample, exhibiting the
protective efficacy. The sun protection factor (SPF) for the Z1 sample, which
for field emission scanning electron microscopy the sunscreen creams were applied to the sample holder
composition of ZnO samples to record Electron To assess the acidity and alkalinity of the produced
patterns were recorded on a Rigaku D/max Ultima III X- concentration of water, and the pH of the samples
rheometric mechanical spectrometer (RMS). The rate of placing 5 grams of each sample in a Falcon tube and
UV absorption of the samples was analyzed using a centrifuging at 5000 rpm for 30 minutes. Additionally,
stability of the samples was tested using the Pole Ideal stability was evaluated using an incubator in
Inductively Coupled Plasma Mass Spectrometry (ICP-
1. Results and Discussion of sample Z3, predominantly rod-shaped, possess an
samples Z4, Z5, and Z6 are classified as plate-like,
Figure 2 a-f shows several FE-SEM images of the ZnO sample has an average width of 42 nm and an average
samples. All six ZnO samples displayed distinct length of 164 nm. For the Z5 sample, which contains
samples Z1, Z2, and Z3 are characterized as plate-like, the hedgehog structures is 840 nm, with an average
spherical, and irregular, respectively. The Z1 sample blade length of 162 nm and an average diameter of 52
demonstrates an average plate width of 71 nm and an nm. Finally, the Z6 sample exhibits an average width
average length of 214 nm. The Z2 sample exhibits an of 40 nm and an average length of 148 nm.
ensure that all the samples in this work are pure ZnO diffraction peaks of each sample using Bragg’s law and

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Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised