Abstract:
Green nanotechnology is an innovative research field with emphasis on the development
of methods that minimize the use of health hazardous substances for environmental
remediation. This study reports on the biosynthesis of nanostructured multilayer graphene
(MLG) and zinc oxide (ZnO) from natural extracts for environmental applications. ZnO
nanoparticles are fabricated for the first-time using Ageratum Houstonianum leaf extract
as an effective chelating agent. Besides this, a green chemistry route involving the
utilization of waste biomass was used for fabrication of multilayer graphene. This route
was chosen because it offers good control of size, morphology and does not involve use of
toxic reducing agents or surfactants thus contributing towards green nanotechnology. MLG
was synthesized from corn husk via alkali-acid treatment. This entails extraction of
cellulose followed by carbonization of the nanomaterial and activation of the carbon
material. The separately synthesized nanostructures were used to synthesize MLG/ZnO
nanocomposites of different ratios of MLG/ZnO (1:1, 1:2, 1:3) through ex-situ casting of the
two materials (MLG/ZnO_1, MLG/ZnO_2, MLG/ZnO_3). The X-ray diffraction (XRD) profiles
and Raman spectra exhibited predominant features of MLG and confirmed a hexagonal
wurtzite phase of ZnO in the composite verifying the formation of MLG/ZnO
nanocomposite. The UV-Vis absorbance spectra analysis revealed that incorporation of
MLG to ZnO narrowed the band gap of ZnO nanoparticles, and consequently improved the
light absorption of the semiconductor in the visible range. From Scanning electron
microscopy (SEM) and High-Resolution TEM (HRTEM) analysis, short hexagonal nanorods
were observed for ZnO while sheet-like structures with ripples and crinkles were observed
for MLG. Energy dispersive spectroscopy (EDS) confirmed the purity of the samples and
successful incorporation of MLG and ZnO with presence of only C, O and Zn in the
composites. Brunauer-Emmett-Teller (BET) analysis revealed less surface area of 0.42 m2
/g
for bare ZnO and increased surface area of 148.74 m2
/g in the composite (MLG/ZnO_3).
Brilliant black (BB), congo red (CR) and rhodamine B (RhB) were chosen as model pollutants
in this study, because they are among the many water pollutants from textiles and
industries which are found to be stable with complex structures hence making them
environmentally problematic. The nanocomposites were initially applied for
xv
photodegradation of BB under direct sunlight irradiation to determine the best performing
nanocomposite. It is worth to note that MLG/ZnO_3 nanocomposite showed the best
photocatalytic performance of 93% degradation compared to pristine ZnO, MLG/ZnO_1
and MLG/ZnO_2, which showed lower photocatalytic activity. The best performing
nanocomposite was further used to degrade CR and RhB and gave degradation efficiencies
of 86 and 100%, respectively while pure ZnO showed degradations of 71% and 85% for CR
and RhB, respectively. The obtained results showed high photocatalytic activity for the
optimized MLG/ZnO nanocomposite in RhB and CR under natural sunlight irradiation. The
nanocomposite further demonstrated 95% degradation for doxycycline (DOX) under UV
light. The photodegradation mechanism was proposed and discussed in light of scavenging
experiments using the optimum composite for all the four pollutants. It was revealed that
holes play a major role in photodegradation of BB while the main reactive species in the
photodecomposition of CR, RhB and DOX were found to be superoxide radicals. This work
provides an insight for cheap, sustainable and eco-friendly methods for the fabrication of
nanomaterials for environmental remediation and better ways of recycling waste biomass
to fabricate valuable materials to solve society problems.
Pono, S (2024). Green synthesis of multilayer graphene/zno nanocomposite for photocatalytic application. Afribary. Retrieved from https://afribary.com/works/green-synthesis-of-multilayer-graphene-zno-nanocomposite-for-photocatalytic-application
Pono, Sebuso "Green synthesis of multilayer graphene/zno nanocomposite for photocatalytic application" Afribary. Afribary, 30 Mar. 2024, https://afribary.com/works/green-synthesis-of-multilayer-graphene-zno-nanocomposite-for-photocatalytic-application. Accessed 08 Sep. 2024.
Pono, Sebuso . "Green synthesis of multilayer graphene/zno nanocomposite for photocatalytic application". Afribary, Afribary, 30 Mar. 2024. Web. 08 Sep. 2024. < https://afribary.com/works/green-synthesis-of-multilayer-graphene-zno-nanocomposite-for-photocatalytic-application >.
Pono, Sebuso . "Green synthesis of multilayer graphene/zno nanocomposite for photocatalytic application" Afribary (2024). Accessed September 08, 2024. https://afribary.com/works/green-synthesis-of-multilayer-graphene-zno-nanocomposite-for-photocatalytic-application