カチオン性チオール/ジスルフィド分子の金電極上における電子移動促進効果を見いだし，新たな原理に基づく分子センサーを開発した．神経毒の一種であるネライストキシン（4-N,N-dimethylamino-1,2-dithiolane, NRT）は，分子内にジスルフィド結合と3級アミンを有し，Au-S共有結合を介して金電極表面に結合し自己組織化単分子膜を形成する．これにより電極表面は正に帯電し，アニオン性のフェリシアン化物イオンと金電極との間の電子移動が促進されることがわかった．この電子移動促進効果は支持電解質の塩化カリウム（KCl）濃度を低くすると一層顕著となり，1 mmol L⁻¹ KClの条件下ではNRTの有無によりほぼ0/1のコントラストが得られた．この現象に基づいて新規NRTセンサーを構築し，血清中から十分な感度で定量的に検出することに成功した．同様の電子移動促進効果は，NRTと類似の構造を有するチオコリンについても認められ，コリンエステラーゼ阻害作用を有する神経毒である有機リン剤及びカルバメート剤の検出，並びに血中コリンエステラーゼ活性評価法（中毒の判定法）に応用した．

可視と近赤外の様々な波長の発光ダイオードを光源とする金とアルミニウム蒸着ガラス棒SPRセンサーの屈折率に対する応答特性について測定を行った．また，多層フレネル等式を用いた理論計算を行い，実測による応答特性と比較検討した結果，一部の波長や膜厚において実験誤差を上回る応答特性の違いが存在したが，両金属ともに実測結果と理論計算がよい一致を示した．理論計算に用いた誘電率は，SPRの応答が得られる両金属の膜厚の範囲においては一定の値を用いることができた．また，誘電率の実部と虚部の比率によるセンサーの応答特性の簡易予測が可能であった．本研究により，金だけでなく表面酸化物を持つアルミニウムについても多層フレネル等式を用いた計算による応答特性の予測が可能であり，多層フレネル等式を用いた理論計算は金属蒸着ガラス棒SPRセンサーの応答特性の予測において有用であることが分かった．

六方晶窒化ホウ素（h-BN）をセンサ検知極の補助層として用いた起電力式アンモニアセンサの作製と評価を行った．センサ素子は安定化ジルコニア（YSZ）をベースとして，白金検知極をh-BNでコーティングした．エタノール中でミリングしたh-BN粉末を用いることでアンモニアに対する顕著な応答の増大が見られた．30 ppmアンモニアに対する応答値は，ミリング時間48hで最大値となった．ミリング処理により，h-BNの剥離やB-N結合欠陥の形成により，アンモニア吸着点が増大したためと考えられた．センサ応答はアンモニア濃度の対数に対して直線的に増加したことから，検知極上でのアンモニアの酸化と酸素の還元による混成電位に基づくことが示唆された．一方，ミリング処理を水中で行うと，応答値が大きく低下することが分かった．加湿アンモニアにおいては，乾燥アンモニアに比べてセンサ応答が80％ に減少した．h-BNへのAg担持によりセンサ応答の顕著な増大が起こることが分かった．

In this work, ionic liquid materials composed of pH indicator dyes were synthesized and used as a plasticizer for a plasticized PVC membrane-based ion-selective optode. We chose several triphenylmethane dyes and synthesized ionic liquids with those by an ion-exchange procedure, and found that an ionic liquid composed of bromothymol blue (BTB) realized the highest ion-exchange ratio of approximately 100 % (highest concentration of dye). The absorbance response of the PVC membrane using a BTB-based ionic liquid was decreased by ca. 37 % using the repetitive introduction of acid and base solutions, and reached to exhibit a stable and reproducible response. The concentration of dye was 20∼70-times higher than that of the conventional ones. In addition, the PVC membrane was applied for anion sensing based on the coextraction of protons and anions in aqueous solutions, and it was found that the ion selectivity followed the Hofmeister series. In the future, the present ionic liquid material is expected to be applied for highly-selective and sensitive ion-selective optodes by the modification of functional groups such as ion-recognition or reaction with the target molecule.

A simple DNase I detecting method was achieved under a homogenous medium containing DNA duplex and a newly synthesized ferrocenylnaphthalene diimide derivative (FND) carrying alanine (1) or alanine-lysine residue (2) as an electrochemical indicator. The binding affinity of 1 or 2 with double stranded DNA was 10⁵ M⁻¹ or 10⁶ M⁻¹ order, which was estimated from a Scatchard analysis calculated by its absorption change upon the addition of calf thymus DNA (CT-DNA). It was expected that 1 or 2 intercalated to double stranded DNA with a threading mode and electrostatic interaction of the linker ammonium cations of 1 or 2 with phosphate anions of the DNA duplex backbone. The largest current increase after a DNase I treatment was observed under the mixture in a ratio of [3]:[CT-DNA-bp] = 10 : 1 (bp: DNA concentration per base pair), where the distance between the bound ligands is expected to a 10 bp or 34 Å theoretically. When considering to be ca. 30 Å of DNase I size and decreasing of the current increase under an increased amount of 3, DNase I required over ten base pairs to access and digest with the DNA duplex. The current increase in the case of a mixture of 10 μM 1 or 2 and 100 μM CT-DNA was obtained 340 % or 640 %, respectively, after being treated with DNase I (final concentration: 2.0 × 10⁻³ U μL⁻¹), which might be derived from an apperarent molecular weight or diffusion coefficient of the ligand bound DNA duplex and the detection limit of DNase I in the case of 1 or 2 was 2.0 × 10⁻⁵ or 2.0 × 10⁻⁹ U μL⁻¹, respectively, where the detection limit for 2 was 10⁴-times higher than that for 1.

Horseradish peroxidase (HRP) is used as a sensitizing enzyme to detect a membrane protein with high sensitivity. In this method, the membrane protein is labeled with HRP, and fluorescent group-modified tyramide is used as a substrate for fluorescent signal amplification. However, a high background signal due to a nonspecific adsorption of fluorescent group-modified tyramide to cells is known to compromise high-sensitive detection. Here, we designed a new substrate in which tyramide was changed to tyrosyltaurine. Because the background signal was greatly reduced by the sulfonate group in the new substrate, the signal-to-noise ratio was greatly improved compared with a commercial substrate.

A photochemical decomposition of organosulfur compounds (OSCs), such as allyl methyl sulfide (AMS), dimethyl disulfide (DMDS) and diallyl sulfide (DAS), was performed by oxalate-containing photo-Fenton reaction. The residual concentration ratio of the OSCs was in a descending order: AMS < DMDS ≅ DAS. The AMS of 1.45 μg L⁻¹ was approximately 90 % degraded by a photo-Fenton reaction in 120 min with a hydrogen peroxide concentration of 50 mmol L⁻¹, a sodium oxalate concentration of 3 mmol L⁻¹ and a ferric chloride concentration of 0.7 mmol L⁻¹ under ultraviolet light irradiation. In this reaction, the OSCs in the gas phase are considered to be dissolved in the liquid phase and decomposed by ^•OH from a photo-Fenton reaction at the water interface, whose reactivity would depend on the solubility in water and the chemical structure. This method could be useful for the decomposition of potent odorants of OSCs in a real environment.