Table 1.

The main stimuli-response mechanisms of nanocarriers for controlled release of nutrients and pesticide AIs.

Response type	Main response mechanisms	Examples of nanocarriers
pH	(1) Structural change of polymers containing carboxyl or amino groups due to (de)protonation of the groups at different pH values, which influences the hydrogen bonding and electrostatic interaction within the nanocarriers	Alginate-grafted anisotropic silica [45], alginate-g-poly(N-isopropyl acrylamide-co-N,N-diethylacrylamide)/semi-coke [46], alginate-chitosan [47], alginate hydrogel-dopamine-modified attapulgite [48], alginate-g-poly(acrylic acid-co-acrylamide)-clinoptilolite [49], alginate-g-poly(acrylic acid-co-acrylamide)-montmorillonite [50], aminated-cellulose nanofiber/poly(acrylamide-co-2-aminoethyl methacrylate) [51], banana peel cellulose-g-poly(acrylic acid)-polyvinyl alcohol-Mg–Al LDH [52], phosphorylated zein-carboxymethyl cellulose-g-poly(diallyldimethylammonium chloride) [53], carboxymethyl cellulose/3,3′-dithiobis(propionohydrazide) [54], carboxymethyl chitosan@carbon nanoparticle [55], carboxylated porous carbon nanoparticle@chitosan [56], carboxymethyl chitosan-amino-functionalized MSN [57], chitosan [58], chitosan-tripolyphosphate [59], chitosan-lignosulfonate [60], chitosan-diatomite/Fe3O4 [61], chitosan/carboxymethyl chitosan [62], chitosan-SS-zein [63], chitosan-sodium lignosulfonate@alkaline lignin-based Pickering emulsion [64], cotton stalk-g-poly(acrylic acid)-polyvinylpyrrolidone-bentonite [65], 3,4-dihydroxyhydrocinnamic acid, N-hydroxysuccinimide ester modified chitosan [66], GO-carboxymethyl chitosan [67], GO@polydopamine [68], HMS-SS-chitosan oligosaccharide [69], HMS@1-tetradecanol@polydopamine [70], isolated soy protein/carboxymethyl chitosan [71], lignosulfonate-chitosan-polydopamine [72], lignosulfonate/dodecyl dimethyl benzyl ammonium chloride/Fe(III) [73], maize bran-g-poly(acrylic acid-co-acrylamide)-montmorillonite [74], mesoporous nano-selenium@polyacrylic acid [75], MoS2@MSN@cyclodextrin polymer [76], O-carboxymethyl chitosan [77], polydopamine-poly(N,N-dimethylaminoethyl methacrylate) [78], porous porphyrinic MOFs@pectin@chitosan [79], poly(acrylic acid)-b-poly(N-isopropyl acrylamide) [80], poly[2-(2-bromoisobutyryloxy)-ethyl methacrylate-g-poly(acrylic acid)-b-poly(N-isopropyl acrylamide)] [81], poly(β-cyclodextrin)-adamantane-grafted poly(acrylic acid) [82], poly(glycidyl methacrylate-co-acrylic acid)-HMS [83], polyethyleneimine-grafted lignin [84], polyacrylamide/methylcellulose/calcic montmorillonite [85], polyethylenimine modified hollow/mesoporous carbon nanoparticle [86], polydopamine-attapulgite-calcium alginate [87], rGO-Cu2–xSe@chitosan [88], sulfonated-carboxymethyl cellulose-g-poly(acrylic acid)-polyvinylpyrrolidone-silica nanoparticle [89], salep-g-poly(acrylic acid)/montmorillonite [90], subabul stem lignin [91], UiO-66-NH2-carboxymethyl cellulose [92]
	(2) Degradation of the nanocarriers due to acid- or base-mediated decomposition of their components	Alginate-Mg–Al LDH [93], bovine serum albumin nanoparticle [94], carboxymethyl chitosan-allyl glycidyl ether-trisiloxane surfactant [95], α-cyclodextrin-HMS [96], α-cyclodextrin/ZIF-8 [97], 2,4-dinitrobenzaldehyde@ZIF-8 [98], Fe-doped MSN/tannic acid [99], γ-FeOOH@biochar [100], glycine methyl ester-conjugated polysuccinimide nanoparticle [101], halloysite nanotube/Ca2+/EDTA2−/calcium alginate [102], 3-mercaptopropyl trimethoxysilane and poly(ethylene glycol) diacrylate functionalized boron nitride nanoplatelet [103], methoxypolyethylene glycol-o-nitrobenzyl [104], Mg–Al LDH [105], MSN-polydopamine-Cu2+ [106], MSN/β-glucan [107], MIL-101(Fe)@silica [108], MIL-101(Fe)-carboxymethyl starch [109], MIL-101(Fe)-polydopamine [110], MIL-101(Fe)-tannic acid [111], MIL-101@carboxymethyl chitosan [112], polydopamine@NH2-MIL-101(Fe) [113], soybean protein isolate-carboxymethyl cellulose [114], trimethylammoniumpillar[5],arene-methyl orange-functionalized mesoporous selenium [115], UiO-66@hydroxypropyl cellulose [116], ZIF-8 [[117], [118], [119]], ZnO@ZIF-8 [120]
	(3) pH-induced cleavage of the chemical or hydrogen bonds linking the nutrients or pesticide AIs and the nanocarriers	Aldehyde-functionalized ZnO quantum dot [121], carboxyl cellulose-attapulgite [122], polydopamine-isocyanatopropyltriethoxysilane-polyethyleneimine [123], sulfonate-functionalized MSN [124], trimethylammonium-functionalized MSN [125]
Temperature	(1) Structural change of nanocarriers composed of temperature-sensitive polymers with an LCST or of liposomes with a suitable phase transition temperature	Alginate-g-poly(N-isopropyl acrylamide-co-N,N-diethylacrylamide)/semi-coke [46], ASO-ethylene oxide/propylene oxide block copolymer-ferroferric oxide-palygorskite [126], carboxymethyl cellulose/poly(N-vinylcaprolactam-co-acrylamide) [127], isopropyl myristate@poly(N-isopropylacrylamide-co-butyl methylacrylate) [128], MSN@poly(N-isopropyl acrylamide) [129] poly(acrylic acid)-b-poly(N-isopropyl acrylamide) [80], poly[2-(2-bromoisobutyryloxy)-ethyl methacrylate-g-poly(acrylic acid)-b-poly(N-isopropyl acrylamide)] [81], poly(β-cyclodextrin)-adamantane-grafted poly(acrylic acid) [82], polydopamine-poly(N-isopropyl acrylamide) [10], polydopamine-poly(N,N-dimethylaminoethyl methacrylate) [78], polyether polyol/polycaprolactone [130], poly(N-isopropyl acrylamide-co-methacrylic acid)-HMS [131], poly(N-isopropyl acrylamide)-GO [132], poly(propylene oxide-co-carbon dioxide-co-allyl glycidyl ether)-poly(N-isopropylacrylamide)-polyethylene glycol monomethyl ether [133], yolk lecithin-cholesterol [134]
	(2) Accelerated diffusion of nutrients or pesticide AIs within the nanocarrier at higher temperatures	Calcium alginate [135], chitosan [58,75], chitosan-gum Arabic [136], n-hexadecane/nanofibrillated cellulose [137], poly(vinyl alcohol)-ASO-attapulgite [138], trimethylammonium-functionalized MSN [125]
	(3) Bond breaking between a pesticide AI and the nanocarrier at higher temperatures	Aldehyde-functionalized ZnO quantum dot [121], carboxylated porous carbon nanoparticle@chitosan [56]
Light	(1) Near-infrared-induced temperature increase of a photothermal material and subsequent temperature response	Alginate-g-poly(N-isopropyl acrylamide-co-N,N-diethylacrylamide)/semi-coke [46], biochar@soybean oil-polysulfide [139], Cu2-xSe-rGO [140], GO@polydopamine [68], HMS@1-tetradecanol@polydopamine [70], hollow carbon microsphere@polyethylene glycol/α-cyclodextrin [141], MIL-101(Fe)-tannic acid [111], MoS2@MSN@cyclodextrin polymer [76], polydopamine-poly(N-isopropyl acrylamide) [10], polydopamine-Ti3C2Tx [142]
	(2) Structural change of polymers containing photolabile moieties under UV irradiation	Biochar-azobenzene-ASO-attapulgite [143], cucurbit[8]uril/azobenzene derivative [144], 2,4-dinitrobenzaldehyde@ZIF-8 [98], methoxypolyethylene glycol-o-nitrobenzyl [104], 2-nitrobenzyl succinate-carboxymethyl chitosan [145]
	(3) Light-induced bond breaking between a pesticide AI and the nanocarrier	Poly(ethylene glycol)-ο-nitrobenzyl [146], thioacetal o-nitrobenzaldehyde [147]
Redox	Structural change of nanocarriers containing redox moieties [e.g., disulfide bonds, Fe(III)]	Carboxymethyl cellulose/3,3′-dithiobis(propionohydrazide) [54], chitosan-SS-zein [63], disulfide bond-linked and starch-coated MSN [148], HMS-didecyl disulfide [149], HMS-SS-chitosan oligosaccharide [69], iron(III)-based MOFs-pectin [150], MIL-101(Fe)-carboxymethyl starch [109], MIL-101(Fe)-tannic acid [111]
Enzyme	Enzyme-catalyzed degradation of nanocarriers containing enzyme substrates	Cellulose acetate/chitosan/zein/starch/polycaprolactone [151], chitosan-lignosulfonate [60], chitosan-sodium lignosulfonate@alkaline lignin-based Pickering emulsion [64], α-cyclodextrin-HMS [96], α-cyclodextrin/ZIF-8 [97], α-cyclodextrin-phenylamine-functionalized HMS [152], disulfide bond-linked and starch-coated MSN [148], HMS-hydroxypropyl cellulose [153], iron(III)-based MOFs-pectin [150], lignin [154], lignin/polysaccharide/Fe(III) [155], lignosulfonate/dodecyl dimethyl benzyl ammonium chloride/Fe(III) [73], MIL-101(Fe)-carboxymethyl starch [109], MoS2@MSN@cyclodextrin polymer [76], MSN-chitosan [156], MSN/β-glucan [107], MSN-pectin [157], N-succinyl chitosan [158], poly(β-cyclodextrin)-adamantane-grafted poly(acrylic acid) [82], polydopamine-isocyanatopropyl triethoxysilane-polyethyleneimine [123], porous porphyrinic MOFs@pectin@chitosan [79], UiO-66@hydroxypropyl cellulose [116], zein nanocapsule [159], zein nanoparticle [160]

AI, active ingredient; ASO, amino silicon oil; HMS, hollow mesoporous silica; LCST, lower critical solution temperature; LDH, layered double hydroxides; MIL-101, Materials Institute Lavoisier-101; MOFs, metal-organic frameworks; MSN, mesoporous silica nanoparticle; (r)GO, (reduced) graphene oxide; UiO-66, University of Oslo-66; UV, ultraviolet; ZIF-8, zeolitic imidazolate framework-8.