Siti Halimah Sarijo

Synthesis of (cinnamate-zinc layered hydroxide) intercalation compound for sunscreen application

BackgroundZinc layered hydroxide (ZLH) intercalated with cinnamate, an anionic form of cinnamic acid (CA), an efficient UVA and UVB absorber, have been synthesized by direct method using zinc oxide (ZnO) and cinnamic acid as the precursor.ResultsThe resulting obtained intercalation compound, ZCA, showed a basal spacing of 23.9 Å as a result of cinnamate intercalated in a bilayer arrangement between the interlayer spaces of ZLH with estimated percentage loading of cinnamate of about 40.4 % w/w. The UV–vis absorption spectrum of the intercalation compound showed excellent UVA and UVB absorption ability. Retention of cinnamate in ZLH interlayers was tested against media usually came across with sunscreen usage to show low release over an extended period of time. MTT assay of the intercalation compound on human dermal fibroblast (HDF) cells showed cytotoxicity of ZCA to be concentration dependent and is overall less toxic than its precursor, ZnO.Conclusions(Cinnamate-zinc layered hydroxide) intercalation compound is suitable to be used as a safe and effective sunscreen with long UV protection effect.

Herbicide-Intercalated Zinc Layered Hydroxide Nanohybrid for a Dual-Guest Controlled Release Formulation

Herbicides, namely 4-(2,4-dichlorophenoxy) butyrate (DPBA) and 2-(3-chlorophenoxy) propionate (CPPA), were intercalated simultaneously into the interlayers of zinc layered hydroxide (ZLH) by direct reaction of zinc oxide with both anions under aqueous environment to form a new nanohybrid containing both herbicides labeled as ZCDX. Successful intercalation of both anions simultaneously into the interlayer gallery space of ZLH was studied by PXRD, with basal spacing of 28.7 Å and supported by FTIR, TGA/DTG and UV-visible studies. Simultaneous release of both CPPA and DPBA anions into the release media was found to be governed by a pseudo second-order equation. The loading and percentage release of the DPBA is higher than the CPPA anion, which indicates that the DPBA anion was preferentially intercalated into and released from the ZLH interlayer galleries. This work shows that layered single metal hydroxide, particularly ZLH, is a suitable host for the controlled release formulation of two herbicides simultaneously.

Effect of incoming and outgoing exchangeable anions on the release kinetics of phenoxyherbicides nanohybrids

The release of chlorophenoxyherbicides agrochemicals, namely 2-chloro- (2CPA), 4-chloro and 2,4,5-trichloro (TCPA) phenoxyacetates from their nanohybrids into various aqueous solutions; carbonate, sulfate and chloride was found to be controlled by pseudo-second order rate expression. The percentage saturated released was found to be anionic-dependent, in the order of carbonate>sulfate>chloride for the release media and 2CPA>4CPA>TCPA for the anionic guests. This study demonstrates that the release of the phenoxyherbicides agrochemicals from the nanohybrid compounds can be tuned by choosing the right combination of exchangeable anions both the incoming and the outgoing anions.

Raman spectroscopic study of carbon nanotubes prepared using Fe/ZnO-palm olein-chemical vapour deposition

Multiwalled carbon nanotubes (MWCNTs) were synthesized using Fe/ZnO catalyst by a dual-furnace thermal chemical vapor deposition (CVD) method at 800-1000°C using nitrogen gas with a constant flow rate of 150 sccm/min as a gas carrier. Palm olein (PO), ferrocene in the presence of 0.05M zinc nitrate, and a p-type silicon wafer were used as carbon source, catalyst precursor, and sample target, respectively. D, G, and G′ bands were observed at 1336-1364, 1559-1680, and 2667-2682 cm-1, respectively. Carbon nanotubes (CNTs) with the highest degree of crystallinity were obtained at around 8000?C, and the smallest diameter of about 2nm was deposited on the silicon substrate at 1000°C.

Synthesis of Phenoxyherbicides-Intercalated Layered Double Hydroxide Nanohybrids and Their Controlled Release Property

Synthesis of new generation of agrochemicals of phenoxyherbicides-type, namely 2-chloro- (2CPA) and 2,4,5- trichlorophenoxy acetates (TCPA) were accomplished by hybridization of the phenoxyherbicides into zinc-aluminium-layered double hydroxide interlamellae for the formation of new nanohybrids of 2CPA and TCPA, labeled as N2CPA and NTCPA, respectively. Basal spacing expansion from 8.9 A in the layered double hydroxide (LDH) to 18.5 and 26.2 A in the resulting N2CPA and NTCPA nanohybrid, respectively, together with FTIR, CHNS and TGA/DTG data support that the phenoxyherbicides were successfully intercalated into the layered double hydroxide inorganic interlayers. The release of the phenoxyherbicides from their nanohybrids at various pHs can be expressed by parabolic diffusion at the beginning of the process, but the release data for the whole process followed the pseudo-second order equation. The release process was found to be pH-dependent, in the order of pH 12 > 3 > 6.25. In addition, the release time for TCPA is longer than 2CPA, suggesting a stronger interaction of TCPA than 2CPA with the layered double hydroxide inorganic interlayer. This study indicates the potential application of zinc-aluminium-layered double hydroxide as the matrix of the controlled release formulation of agrochemicals such as 2-chlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid.

Synthesis of a layered organic-inorganic nanohybrid of 4-chlorophenoxyacetate-zinc-layered hydroxide with sustained release properties

A zinc-layered hydroxide-4-chlorophenoxy acetate (4CPA) organic-inorganic nanohybrid was prepared using a simple direct reaction of 4CPA anions with ZnO under an aqueous environment to be used as a controlled release formulation of the herbicide, 4CPA. The concentration of the active agent, 4CPA, was found to be a controlling factor for the formation of a pure phase well-ordered nanolayered hybrid in which it could be synthesised at 0.2M 4CPA. ZnO shows a well-defined grain structure of variable size in the nanometre range. However, the formation of the 4CPA-ZLH nanohybrid resulted in a flake-like fibrous structure. On heating at 500°C for 5 h under atmospheric conditions, the nanohybrid transformed back to a well-defined grain structure, as previously observed with the starting material, ZnO. The release of 4CPA was found to occur in a controlled manner and was generally governed by pseudo-second-order kinetics.

Evaluation of Controlled-Release Property and Phytotoxicity Effect of Insect Pheromone Zinc-Layered Hydroxide Nanohybrid Intercalated with Hexenoic Acid

A controlled release formulation for the insect pheromone hexenoic acid (HE) was successfully developed using zinc-layered hydroxide (ZLH) as host material through a simple coprecipitation technique, resulting in the formation of inorganic-organic nanolayered material with sustained release properties. The release of HE from its nanohybrid was found to occur in a controlled manner, governed by a pseudo-second order kinetics model. The maximum amount of HE released from the nanocomposite into solutions at pH 4, 6.5, and 8 was found to be 84, 73, and 83% for 1100 min, respectively. The hexenoate zinc-layered hydroxide nanomaterial (HEN) was found to be nontoxic for plants when green beans and wheat seeds were successfully germinated in all HEN concentrations tested in the experiment, with higher percentage of seed germination and higher radical seed growth as compared to its counter anion, HE. ZLH can be a promising carrier for insect pheromone toward a new generation of environmentally safe pesticide nanomaterial for crop protection.

3,4-Dichlorophenoxyacetate interleaved into anionic clay for controlled release formulation of a new environmentally friendly agrochemical

A new layered organic–inorganic nanohybrid material, zinc-aluminum-3,4-dicholorophenoxyacetate (N3,4-D) in which an agrochemical, 3,4-dichlorophenoxyacetic acid (3,4-D), is intercalated into zinc-aluminum-layered double hydroxide (ZAL), was synthesized by coprecipitation method. A well-ordered nanomaterial was formed with a percentage loading of 53.5% (w/w). Due to the inclusion of 3,4-D, basal spacing expanded from 8.9 Å in ZAL to 18.7 Å in N3,4-D. The Fourier transform infrared study shows that the absorption bands of the resulting nanohybrid composed of both the 3,4-D and ZAL further confirmed the intercalation episode. Thermal analysis shows that ZAL host enhances the thermal stability of 3,4-D. Controlled-release experiment shows that the release of 3,4-D in the aqueous media is in the order of phosphate > carbonate > sulfate > chloride. These studies demonstrate the successful intercalation of the 3,4-D and its controlled release property in various aqueous media.

Gelatin-coated zeolite y for controlled release of anticancer drug (zerumbone)

An oral slow release drug delivery system of zerumbone-zeolite Y-gelatin composites were prepared by two coating techniques namely dipping already shaped drug loaded zeolite y beads in gelatin and by blending gelatin with drug loaded zeolite Y powder followed by pelletizing by drop wise addition into sunflower oil. Zeolite Y acted as the support material in the nanocomposite preparation. In both coating techniques, pellets obtained were spherical in shape. Zerumbone (ZER) a natural anticancer drug was extracted from local Zingiber Zerumbet and loaded into zeolite Y via wet impregnation method. The composites were tested via UV-VIS for in- vitro drug delivery study and were characterized using TLC, SEM and XRD methods. From the data obtained, dip coated composite samples showed best sustained release of zerumbone for 24 h compared to blended zerumbone-zeolite Y-gelatin pellet. The inert zeolite Y acted as a carrier and support for drug, and the pores encapsulated, protected and controlled the released of the drug.

Parameter optimisation of carbon nanotubes synthesis via hexane decomposition over minerals generated from Anadara granosa shells as the catalyst support

The synthesis of carbon nanotubes (CNTs) by the chemical vapour deposition (CVD) method using natural calcite from Anadara granosa shells as the metal catalyst support was studied. Hexane and iron (Fe) were used as the carbon precursor and the active component of the catalyst, respectively. Response surface methodology (RSM) based on central composite design (CCD) was used to optimise the effect of total iron loading, the duration of reaction, and reaction temperature. The optimal conditions were total iron loading of 7.5%, a reaction time of 45 min, and a temperature of 850°C with a resulting carbon yield of 131.62%. Raman spectra, field-emission-scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses showed that the CNTs were of the multiwalled type (MWNTs).