A team of researchers from Universitas Mulawarman, Samarinda, has developed a silver–zinc oxide (Ag–ZnO) nanocomposite that significantly improves ultraviolet (UV) protection compared with zinc oxide alone. The study, conducted from February to May 2024 and published in the International Journal of Integrative Research in 2026, found that the optimized Ag–ZnO nanocomposite achieved an in vitro Sun Protection Factor (SPF) of 16.299, nearly twice the SPF value of ZnO. The findings highlight the potential of Ag–ZnO nanocomposites as inorganic UV-protective materials for future sunscreen and topical applications.
Why UV Protection Matters
Ultraviolet radiation is an
important environmental factor that can affect human skin. Excessive exposure
to UV radiation can contribute to skin damage and other adverse effects.
Because of this, inorganic materials such as zinc oxide (ZnO) have attracted
attention as UV-protective ingredients because of their ability to absorb and
interact with UV radiation.
The researchers explored whether
combining ZnO with silver (Ag) could improve its UV-protection performance.
Silver nanoparticles have distinctive optical properties, while ZnO is widely
studied as a semiconductor material with UV absorption characteristics.
Combining the two materials into a nanocomposite could potentially enhance
their optical response and improve UV shielding performance.
Ultrasonic-Assisted Sol–Gel
Synthesis
The research was carried out at
several laboratory facilities. The synthesis and initial experiments were
conducted at the Inorganic Chemistry and Basic Chemistry Laboratories, Faculty
of Mathematics and Natural Sciences, Universitas Mulawarman, Samarinda.
The researchers prepared silver
nanoparticles using a reduction process with ascorbic acid. Zinc oxide was
produced through a sol–gel and precipitation approach. The Ag–ZnO
nanocomposites were then synthesized using an ultrasonic-assisted sol–gel
method.
Three different concentrations of
silver nitrate (AgNO₃) were examined: 0.1 mM, 0.4 mM, and 0.9 mM. These
variations allowed the researchers to evaluate how silver concentration
affected the structural and optical properties of the resulting nanocomposites.
The stability of the materials
was monitored using UV–Vis spectroscopy for four days. The samples were also
characterized using X-ray diffraction (XRD), scanning electron microscopy
(SEM), and particle-size analysis (PSA). Their UV-protection performance was
estimated through an in vitro SPF calculation based on UV–Vis absorbance
measurements across the 290–400 nm wavelength range.
Silver and ZnO Form a Distinct
Nanocomposite Structure
The structural analysis confirmed
the presence of two main crystalline phases in the Ag–ZnO material: hexagonal
wurtzite ZnO and face-centered cubic silver.
Among the three Ag–ZnO
formulations, the sample containing 0.4 mM silver, referred to as Ag–ZnO(B),
showed the highest crystallinity at 71.31%. The Ag–ZnO(A) and Ag–ZnO(C)
samples recorded crystallinity values of 69.94% and 67.74%, respectively.
XRD analysis further supported
the formation of the ZnO and Ag crystalline phases. Meanwhile, SEM observations
showed small silver-containing particles attached to the surface of ZnO
particles, although some agglomeration was also observed.
Particle-size analysis showed
mean values of approximately 75.7 nm for Ag nanoparticles, 325 nm for ZnO,
and 730 nm for Ag–ZnO(B). The larger apparent particle size of the
nanocomposite was associated with aggregation in the dispersed system. The
researchers emphasized that PSA measurements reflect dispersed or aggregated
particle populations and should not be interpreted as the primary crystallite
size of the material.
Ag–ZnO Nearly Doubles the SPF
of ZnO
The most notable finding came
from the in vitro SPF measurements.
The silver nanoparticles alone
produced an SPF value of 7.126, while ZnO recorded an SPF of 8.362.
In contrast, the optimized Ag–ZnO(B) nanocomposite achieved an SPF of 16.299.
This means that the Ag–ZnO(B)
formulation produced an SPF response approximately 94.9% higher than ZnO
alone under the experimental conditions. The result suggests that
incorporating silver into ZnO can substantially enhance the material's
UV-protection response.
Based on the protection
descriptors used in the study, silver nanoparticles were categorized as
providing an “extra” level of protection, ZnO as “maximal,” and Ag–ZnO(B) as
“ultra.” The corresponding BPOM-based interpretation placed Ag and ZnO in the
low category, while Ag–ZnO(B) reached the moderate category.
Stable During Four Days of
Observation
Another important observation was
the spectral stability of the samples. The Ag, ZnO, and Ag–ZnO systems remained
spectrally stable during the four-day monitoring period.
This stability is relevant
because a UV-protective material must maintain its optical properties during
use. However, the four-day laboratory observation does not establish long-term
photostability under real-world sunlight or within a finished cosmetic formulation.
Promising Material, but Not
Yet a Commercial Sunscreen
Despite the promising SPF result,
the researchers emphasized that the Ag–ZnO nanocomposite should not yet be
considered a finished commercial sunscreen.
The SPF value was obtained
through an in vitro UV–Vis screening method using an aqueous dispersion,
rather than through testing of a complete topical sunscreen formulation or an
in vivo skin study. The article also notes that in vitro spectrophotometric
testing is preliminary, while in vivo testing remains the principal standard
for establishing commercial SPF claims.
Further studies are therefore
needed to optimize particle dispersion, evaluate longer-term photostability,
investigate potential cytotoxicity and oxidative effects, assess skin safety,
and develop a complete topical formulation.
The researchers conclude that
silver modification substantially enhances the UV-protection response of ZnO.
With an in vitro SPF of 16.299, Ag–ZnO(B) represents a promising
candidate for further development as an inorganic UV-protective material,
although additional safety and formulation studies are required before any
commercial cosmetic application can be considered.
About the Authors
The study was conducted by Noor
Hindryawati, Angela Bergita, Husna Syaima, Hajar Anuar, Teguh Wirawan, Eva
Marliana, Seorja Koesnapadi, and Irfan Ashari Hiyahara, affiliated with Universitas
Mulawarman, Samarinda, Indonesia. The article does not provide individual
academic degrees or detailed professional fields for each author, so those
details cannot be added without additional sources.
Research Source
Article title: Ultrasonic-Assisted
Sol–Gel Synthesis of Ag–Zno Nanocomposites for Enhanced in Vitro Sun Protection
Factor
Journal: International
Journal of Integrative Research (IJIR)
Volume: 4, No. 8, 2026
Pages: 723–736
Journal: International
Journal of Integrative Research
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