Process of preparing 3d array of particles and exemplary application thereof in sensor fabrication

Abstract

The present invention provides a novel and efficient process of preparing a highly organized 3D array of particles by stacking multiple 2D arrays of the particles. The 3D array of particles so prepared is used in fabrication of sensors, such as molecular imprinted photonic (MIP) crystal sensor. The sensor has a 3D array of voids each having a void internal wall. The void internal walls have cavities each having a cavity internal wall made from a material containing the non-metallic element. A binding of the analytes to the cavities induces a detectable variation of the optical property of the 3D array of voids. The invention exhibits numerous technical merits such as high sensitivity, high specificity, fast detection, ease of operation, low power consumption, zero chemical release, and low operation cost, among others.

1 . A process of preparing a 3D array of particles by stacking multiple 2D arrays of the particles, comprising:
 (a) providing a container with a substrate inside the container;   (b) introducing a first liquid into the container to immerse the substrate, and optionally introducing a second liquid to float on top surface of the first liquid and form a two-phase system;   (c) assembling the particles on top surface of the first liquid to form a monolayer (2D array) of the particles thereon, or optionally assembling the particles to form a monolayer at an interface between the first liquid and the second liquid;   (d) moving the monolayer and/or the substrate to reduce a distance therebetween until the monolayer is deposited on the substrate;   (e) subjecting the substrate with the monolayer deposited thereon to steps (a)-(d) to stack/deposit another monolayer on top of the monolayer previously deposited;   (f) optionally repeating step (e) until a desired number of monolayers are stacked on the substrate.   
     
     
         2 . The process according to  claim 1 , wherein a flat surface of the substrate for depositing the monolayer(s) is not vertical to the top surface of the first liquid; for example, the angle between the two surfaces may range from −89° to 89°, from −70° to 70°, from −50° to 50°, from −35° to 35°, from −20° to 20°, from −10° to 10°, from −5° to 5° such as substantially 0°. 
     
     
         3 . The process according to  claim 1 , comprising:
 (i) providing a container with a substrate on a bottom of the container;   (ii) filling a first liquid into the container until the substrate is immersed in the first liquid;   (iii) adding a preparation of the particles into the container, and assembling the particles on top surface of the first liquid to form a monolayer (2D array) of the particles thereon;   (iv) removing or discharging the first liquid from the container so that said monolayer of the particles falls down onto the substrate, and is deposited thereon;   (v) refilling the first liquid into the container until the substrate and the particles previously deposited thereon is immersed in the first liquid;   (vi) repeating steps (iii) and (iv) so that another monolayer of the particles is deposited on the substrate by stacking over an immediate monolayer that has previously deposited thereon; and   (vii) optionally repeating steps (v) and (vi) until a desired number of monolayers of the particles are deposited on the substrate.   
     
     
         4 . The process according to  claim 3 , comprising
 (i) providing the container with the substrate on the bottom of the container;   (ii) filling the first liquid into the container until the substrate is immersed in the first liquid;   (ii.5) adding a second liquid into the container, so that the second liquid is floating on top of the first liquid, wherein an interface is formed between the two liquids;   (iii) adding the preparation of the particles into the container, and assembling the particles between the first liquid and the second liquid (or at their interface) to form the monolayer (2D array) of the particles;   (iv) removing or discharging both the first liquid and the second liquid from the container so that said monolayer of the particles falls down onto the substrate, and is deposited thereon;   (v) refilling the first liquid into the container until the substrate and the particles previously deposited thereon is immersed in the first liquid;   (vi) repeating steps (ii.5), (iii) and (iv) so that another monolayer of the particles is deposited on the substrate by stacking over the immediate monolayer that has previously deposited thereon; and   (vii) optionally repeating steps (v) and (vi) until a desired number of monolayers of the particles are deposited or stacked on the substrate.   
     
     
         5 . The process according to  claim 4 , wherein step (iii) further comprises compressing the monolayer of the particles with a pair of barriers to reduce the area of the monolayer and to pack the particles in the monolayer more densely or more intimately. 
     
     
         6 . The process according to  claim 4 , wherein said adding the preparation of the particles into the container in step (iii) is accomplished with a pipette, a syringe pump, or any combination thereof. 
     
     
         7 . The process according to  claim 4 , further comprising step (viii) annealing the deposited particles at an elevated temperature such as 50-100° C. e.g. 70° C. for a period of time such as 5-20 minutes e.g. 10 minutes, to evaporate a residue of the first liquid, the second liquid, and a liquid in the preparation of the particles, optionally wherein the annealing is accomplished by oven drying, IR lamp heating, or any combination thereof. 
     
     
         8 . The process according to  claim 4 , wherein the particles comprise silica nanoparticles, polystyrene nanoparticles, polymer beads, oxide ceramic nanoparticles, oxides, nitrides, carbides, quantum dots, macromolecules, carbon nanostructures, or any mixture thereof; wherein some particles assembled in a monolayer may be the same as, or different from, other particles assembled in the same monolayers; and wherein the particles assembled in one of the monolayers may be the same as, or different from, the particles assembled in another one of the monolayers. 
     
     
         9 . The process according to  claim 4 , wherein the preparation of the particles comprises a suspension of the particles in an organic solvent such as ethanol, for example nanoparticle colloid mono-dispersed in ethanol. 
     
     
         10 . The process according to  claim 4 , wherein the substrate comprises a material made of glass or oxide ceramic; wherein the first liquid comprises a hydrophilic liquid such as water; and wherein the second liquid comprises a hydrophobic liquid or oil such as hydrocarbon liquid such as hexane, heptane, or any mixture thereof. 
     
     
         11 . The process according to  claim 4 , wherein the particles have an average size in the range of 10-1000 nm, 50-1000 nm, 50-500 nm, 150-300 nm, or 180-400 nm; and wherein each monolayer of the particles has a thickness that is substantially the same as the particles' average size. 
     
     
         12 . The process according to  claim 4 , wherein the stack of the monolayers comprises 1-00, 5-50, 5-20, or 10-20 (e.g. 10) monolayers of the particles, and the stack has a height of approximately 2-10 μm. 
     
     
         13 . A process for preparing a sensing body of a working sensor for a sensing device useful for detecting an analyte containing a non-metallic element, comprising
 (1) fabricating a 3D array of particles according to  claim 1 ;   (2) infiltrating the 3D array of particles with a mixture of a solidifiable material and the analyte, wherein the solidifiable material comprises said non-metallic element too;   (3) solidifying the solidifiable material with the analyte; and   (4) washing away the 3D array of particles and the analyte, forming a sensing body including a 3D array of voids each having a void internal wall;   wherein at least a part of the voids are interconnected to each other and are configured to expose to said analyte in a future sample, and admit said analyte into said at least a part of the voids;   wherein void internal walls of said at least a part of the voids have cavities each having a cavity internal wall;   wherein each of the cavities has a shape that is complementary to a shape of the analyte; and   wherein the cavity internal wall is made from a material containing said non-metallic element.   
     
     
         14 . The process according to  claim 13 , wherein the non-metallic element is selected from F, Cl, Br, I, O, S, Se, Te, N, P, As, Sb, B, C, H, or any combination thereof; and wherein the sensing body, the void internal walls, and the cavity internal walls are all made from a same material containing said non-metallic element. 
     
     
         15 . The process according to  claim 14 , wherein said same material comprises a polymer prepared from photo polymerization and/or thermal polymerization using monomers containing said non-metallic element. 
     
     
         16 . The process according to  claim 15 , wherein said same material is prepared from a pre-polymerization composition comprising said monomers containing said non-metallic element, the analyte containing said non-metallic element, and an optional cross-linking agent. 
     
     
         17 . The process according to  claim 16 , wherein the pre-polymerization composition comprises template/analyte molecule PFOA; functional monomers including 2-(trifluoromethyl) acrylic acid (TFMAA), 2-(difluoromethyl) acrylic acid (DFMAA), and/or 2-(monofluoromethyl) acrylic acid (MFMAA); and cross-linking agent EGDMA that utilizes an interaction between the non-metallic elements such as fluorine-fluorine interactions, electrostatic attraction, and associated weak interactions; and optionally wherein the pre-polymerization composition further comprises monomers that do not contain said non-metallic element such as acrylic acid (AA), methyl acrylic acid (MAA), and any mixture thereof. 
     
     
         18 . The process according to  claim 13 , wherein the analyte is selected from fluorinated chemicals such as perfluorinated chemicals (PFCs), e.g. perfluoroalkyl substance, for example, perfluorooctane sulphonate (PFOS) and perfluorooctanoic acid (PFOA); an herbicide such as atrazine, and PFAS (EPA 537). 
     
     
         19 . The process according to  claim 13 , wherein a binding of the analytes to the cavities induces or triggers a detectable variation of the optical property of the 3D array of voids, including the spectrum of light that is transmitted through, reflected from, and/or diffracted from the 3D array of voids; and a degree of the detectable variation is correlated with the amount of the analytes bound to the cavities. 
     
     
         20 . The process according to  claim 13 , further comprising preparing a reference sensor that is the same as the working sensor except that the reference sensor does not include the cavities as those in the working sensor, and the voids' size of the reference sensor is different from (bigger than or smaller than) that of the working sensor.