A method for synthesising mesoporous silica microparticles comprising the steps of: producing mesoporous particles of silica with an average diameter of up to 50 μm by preparing a sol from an ammonium catalysed hydrolysis and condensation reaction of a pre-sol solution comprising a silica precursor and a structure directing agent which is a surfactant dissolved in a mixed solvent system comprising water and an alcohol which is one or more of ethanol, methanol, 1-propanol, 2-propanol, and 1-butanol; hydrothermally treating the particles in an amine-water emulsion to increase the pore size; heating the particles to a temperature of 400 °C to 800 °C or treating the particles with microwave irradiation to remove residual structure directing agent; and further increasing the pore size of the particles using an etching process utilising a base catalyst which is one or more of ammonium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide and calcium hydroxide; wherein the silica precursor is one or more selected from the group consisting of: tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), tetrapropoxysilane (TPOS), tetrabutoxysilane (TBOS), tetra-acetoxysilane and tetrachlorosilane or an organic derivative thereof; wherein the organic derivative has the formula: R n SiX (4-n) wherein: R is an organic radical; X is a hydrolysable group selected from one or more of the group consisting of: halide, acetoxy, and alkoxy; and n is an integer from 1 to 4, or the silica precursor is a hybrid silica precursor selected from the group consisting of: dimethyldimethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isobutyltriethoxysilane, isobutyltrimethoxysilane, phenyltrimethoxysilane, n-octyltriethoxysilane, iso-octyltrimethoxysilane, or a bridged hybrid silica precursor having the general formula: R n X( 3-n)Si-R'-Si-R n X (3-n) wherein: R is an organic radical; X is halide, acetoxy, or alkoxy; R' is methyl, ethyl, propyl or butyl; and n is 1 or 2; the surfactant has the structure (CH 3) 3 N + C x H y, wherein x is an integer between 12 and 20, and y is an integer between 23 and 41. producing mesoporous particles of silica with an average diameter of up to 50 μm by preparing a sol from an ammonium catalysed hydrolysis and condensation reaction of a pre-sol solution comprising a silica precursor and a structure directing agent which is a surfactant dissolved in a mixed solvent system comprising water and an alcohol which is one or more of ethanol, methanol, 1-propanol, 2-propanol, and 1-butanol; hydrothermally treating the particles in an amine-water emulsion to increase the pore size; heating the particles to a temperature of 400 °C to 800 °C or treating the particles with microwave irradiation to remove residual structure directing agent; and further increasing the pore size of the particles using an etching process utilising a base catalyst which is one or more of ammonium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide and calcium hydroxide; wherein the silica precursor is one or more selected from the group consisting of: tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), tetrapropoxysilane (TPOS), tetrabutoxysilane (TBOS), tetra-acetoxysilane and tetrachlorosilane or an organic derivative thereof; wherein the organic derivative has the formula: R n SiX (4-n) wherein: R is an organic radical; X is a hydrolysable group selected from one or more of the group consisting of: halide, acetoxy, and alkoxy; and n is an integer from 1 to 4, R is an organic radical; X is a hydrolysable group selected from one or more of the group consisting of: halide, acetoxy, and alkoxy; and n is an integer from 1 to 4, or the silica precursor is a hybrid silica precursor selected from the group consisting of: dimethyldimethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isobutyltriethoxysilane, isobutyltrimethoxysilane, phenyltrimethoxysilane, n-octyltriethoxysilane, iso-octyltrimethoxysilane, or a bridged hybrid silica precursor having the general formula: R n X( 3-n)Si-R'-Si-R n X (3-n) wherein: R is an organic radical; X is halide, acetoxy, or alkoxy; R' is methyl, ethyl, propyl or butyl; and n is 1 or 2; R is an organic radical; X is halide, acetoxy, or alkoxy; R' is methyl, ethyl, propyl or butyl; and n is 1 or 2; the surfactant has the structure (CH 3) 3 N + C x H y, wherein x is an integer between 12 and 20, and y is an integer between 23 and 41.