Naphthalene Based Azo Dyes and Its Substituted Derivatives Containing Mono Boronic Acid - Saccharide Sensors

Murugesan Suresh; Narayanasamy Rajendiran; Palanichamy Ramasamy; Sengamalai Senthilmurugan

doi:doi:10.11648/j.sjac.20261402.11

Research Article |

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Naphthalene Based Azo Dyes and Its Substituted Derivatives Containing Mono Boronic Acid - Saccharide Sensors

Murugesan Suresh

, Narayanasamy Rajendiran^*

, Palanichamy Ramasamy

, Sengamalai Senthilmurugan

Published in Science Journal of Analytical Chemistry (Volume 14, Issue 2)

Received: 14 March 2026 Accepted: 26 March 2026 Published: 13 April 2026

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Abstract

Three novel naphthalene-based azo dyes incorporating boronic acid functional groups were synthesized. Their sugar-sensing behavior toward glucose and fructose was systematically investigated using UV-visible, fluorescence, time-resolved fluorescence, pH titration, and cyclic voltammetry techniques. Upon increasing the concentration of the sugars, both the absorbance and fluorescence intensities of the dyes decreased, indicating effective interaction. In the excited state, the dyes exhibited stronger sensing responses to fructose compared to glucose. The fluorescence lifetime measurements further confirmed the compounds' capability to detect sugars. At elevated pH levels, the boronic acid groups exist predominantly in their anionic form [B(OH)₃^-], which induces a change in the boron atom's hybridization from sp² to sp³, facilitating binding with sugar molecules. Among the three compounds, compound 1 exhibited the highest association constant with fructose, suggesting a stronger binding affinity is higher than compared to glucose. To further validate the sugar-sensing behavior, the quantum yields of the compounds were measured in pure water, glucose, and fructose solutions. When higher concentrations of the sensor were introduced into the sugar solution, the oxidation peaks current (Ipa) decreased while the reduction peak current (Ipc) increased. In contrast, Ipa increased in the sensor-only solutions. Based on these observations, a plausible sensing mechanism has been proposed.

Published in	Science Journal of Analytical Chemistry (Volume 14, Issue 2)
DOI	10.11648/j.sjac.20261402.11
Page(s)	18-27
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2026. Published by Science Publishing Group

Keywords

Saccharide Sensor, Boronic Acid, Fluorescence Sensor, Electrochemical Sensor, Glucose, Fructose

1. Introduction

Sugars are vital biological molecules involved in essential processes such as nutrition, metabolism, and the maintenance of cell structure. They also act as physiologically active substances, playing key roles in regulating processes like birth, cellular differentiation, and immune response. Due to their significance, there is a growing need to develop sugar-sensing compounds that function effectively in aqueous solutions

[1]

. Considerable attention has been directed towards creating synthetic molecular receptors capable of recognizing neutral organic molecules, including sugars. Earlier studies have demonstrated that sugars can influence the color of dyes containing boronic acid functionalities

[2-6]

Although boronic acid azo dyes have been known for over five decades, their interactions with sugars have only been systematically explored in the past few years. Over this period, increasing interest has emerged in the unique properties of boron-based chemistry. Boronic acid-appended chromophores have been designed and investigated for detecting carbohydrate molecules at very low concentrations. Shinkai and co-workers

[4-6]

have synthesized several types of receptors incorporating boronic acid groups. The sensing ability of these molecules arises from photoinduced electron transfer, triggered by complex formation between the analyte and the receptor. Naphthyl boronic acid-appended azo dyes exhibit pronounced changes in their absorption and fluorescence spectra in the presence or absence of saccharide molecules

[7]

. Variations in pH can influence the sensing behavior, as evidenced by spectral shifts upon interaction with saccharides

[8]

. Boronic acid receptors are capable of selectively binding saccharides in aqueous media through covalent interactions.

The objective of this study is to design a highly sensitive and selective sugar recognition system in aqueous solution using binary complexes formed between newly synthesized fluorescent sensors and various sugars. In this work, three naphthalene-based boronic azo dyes were synthesized and their sensing abilities were evaluated through absorption and fluorescence spectroscopy. The increasing interest in synthetic chemosensors has driven the development of artificial glucose receptors integrated with fluorescence signal transducers. The sugar-sensing behavior of the synthesized boronic acid compounds was examined over a pH range of 2-12 using phosphate buffer solutions.

Herein, we report the synthesis and spectroscopic characterization of a novel class of boronic acid-appended azo dyes (Figure 1), in which the boronic acid group is attached to the aromatic ring at the meta-position relative to the azo group. These dyes display pronounced UV-vis and fluorescence spectral changes upon sugar binding, which are also visually detectable. Compounds 1-3 were successfully synthesized via diazo-coupling reactions. In the initial step, the diazonium ion of the respective aniline derivative was generated using sodium nitrite in hydrochloric acid, followed by coupling with naphthyl boronic acid.

2. Materials and Methods

2.1. Synthesis of Boronic Acid Azo Dyes

A series of naphthalene-based boronic acid azo dyes were synthesized with minimal or no purification required. The synthesis began with an azo coupling reaction. Aniline (1 mL, 2 mmol) was dissolved in 20 mL of 1 M HCl and the solution was cooled to 0°C. Sodium nitrite (2 mmol) dissolved in 10 mL of water was then added dropwise, maintaining the temperature below 5°C to form the diazonium salt. After 15-30 min, a solution of 2-naphthalene boronic acid (2 mmol, 0.24 g) in 10 mL of 1 M NaOH was added at 0°C. The mixture was neutralized with a small amount of 1 M NaOH and stirred for 1-2 h at 0°C, yielding an orange-colored solid. The precipitate was collected by filtration and dried. Similarly, 2-aminobenzoic acid (2ABA) and 4-aminobenzoic acid (4ABA) were diazotized and coupled with 2-naphthalene boronic acid (2NBA). The reaction scheme and structures of the synthesized compounds are shown in Figures 1 and 2.

2.2. Preparation of Boronic Acid-sugar Solution

Stock solutions of sugars were prepared in triply distilled water, with concentrations ranging from 1 × 10^-3 to 1 × 10^-2 M. Stock solutions of compounds 1, 2, and 3 were prepared at a concentration of 4 × 10^-5 M. For the measurements, 0.2 mL of the dye solution was mixed with varying volumes of glucose or fructose solutions. The final mixture was diluted to 10 mL with triply distilled water and thoroughly shaken. The solutions were then agitated for 1 h in a shaking bath at a fixed temperature. Absorption and emission spectra were recorded under neutral and varying pH conditions. The sensing performance of the synthesized compounds towards sugars was evaluated by comparing their optical properties in the presence of sugars with those in pure water.

3. Results and Discussion

3.1. Effect on Absorption Spectra

Figure 3 shows the absorption and fluorescence spectra of compounds 1, 2, and 3 in aqueous solution. The absorption and fluorescence spectral parameters, including shifts and band shapes, for the three sensor compounds in the presence of varying concentrations of glucose and fructose are nearly identical. Therefore, only the glucose response spectra are presented in the figures and tables. In neutral pH, compound 1 exhibits absorption maxima at 540, 385, 325, and 270 nm; compound 2 at 487, 324, 310, and 278 nm; and compound 3 at 491, 325, 310, and 278 nm. Upon the addition of glucose or fructose, the absorbance at these maxima decreases, indicating interactions between the sensors and the saccharide molecules.

The decrease in absorbance observed for all three sensor molecules after addition of saccharide solutions can be attributed to spectral or structural modifications of the sensors upon sugar binding. As illustrated in Figure 2, the boronic acid group in its free form is an electron-deficient Lewis acid with an sp²-hybridized boron atom in a trigonal planar geometry. Upon binding to saccharides, it is converted into an anionic form with an sp³-hybridized boron atom in a tetrahedral geometry

[9-12]

. This change in electronic configuration alters the boronic acid group’s electronic properties, leading to observable spectral variations in the absorption profiles.

3.2. Effect on Emission Spectra

The selectivity of the sensors toward glucose and fructose in the excited state at pH ≈ 7 was evaluated. Figure 3 shows the emission spectral variations of compounds 1, 2, and 3 as a function of glucose and fructose concentration. Compound 1 exhibits two emission maxima at 470 and 440 nm, compound 2 at 663 and 687 nm, and compound 3 at 664 and 686 nm. All three compounds display dual luminescence with two well-resolved emission bands in the visible region—one arising from the locally excited (LE) state and the other, a red-shifted long-wavelength band, from the intramolecular charge transfer (ICT) state. The addition of glucose or fructose causes a decrease in emission intensity at these maxima. Among the three, sensor 1 shows the highest association constant for both glucose and fructose. In the excited state, fructose exhibits greater affinity for the sensors compared to glucose. Consequently, only the fructose emission spectra are presented, as glucose binding in the excited state is minimal, as evident from the Benesi-Hildebrand plots.

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Figure 1. Structures of synthesised compounds 1, 2 and 3.

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Figure 2. Diazotization (1) and coupling reaction (2) methods.

Binding constants (Table 1) for the sensor-sugar complexes were determined by analyzing changes in the absorption and fluorescence maxima with increasing sugar concentration. The stoichiometry of the complexes was established by applying the Benesi-Hildebrand equation, where plots of 1/A-A0 vs 1/ [saccharide] and 1/I-I0 Vs 1/ [saccharide] indicates formation of a 1: 1 sensor sugar complex

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[13-20]

. We have obtained the straight line in the plot which is taken as further evidence of 1: 1 complex formation between glucose and fructose with the sensor molecules

[21, 22]

. The association constant values reveal that the binding process is more favored in the excited state for these compounds than ground state.

3.3. Effect of pH

To investigate the relationship between fluorescence intensity changes and boron ionization states, we examined the pH profiles of both absorption and fluorescence spectra in the absence and presence of glucose and fructose at a fixed concentration (0.01 M). For all sensors, measurements were performed under identical conditions, with and without saccharides. Figure 4 present the absorption and fluorescence changes for all sensors in the presence of glucose and fructose. For sensor 1, the calculated pKa value was 7.9. At low pH, binding affinity is weaker; however, as the pH increases from 4 to 12, the likelihood of interaction with glucose and fructose increases. In the presence of glucose, the pKa decreased to 7.6, while in the presence of fructose it further dropped to 6.6

[21-23]

For sensors 2 and 3, no ionization occurred at very low pH (2-3). At pH ≈ 4 and above, a red shift was observed, attributed to ionization of the -COOH group (pKa ≈ 4.2). At pH ≈ 9 and higher, the pKa for both sensors were found to be around 9.2. In the presence of glucose, the pKa dropped to 7.9, and with fructose, it decreased to 6.8

[24-26]

. In all three sensors, binding affinity was consistently higher for fructose than for glucose.

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Figure 3. Absorption and fluorescence spectra of (a) compound 1 (b) compound 2 and (c) compound 3 (8 x 10-5 M) with increasing concentration of D-glucose and fructose: 1) 0, 2) 0.002, 3) 0.004, 4) 0.006, 5) 0.008, 6) 0.01 measured in phosphate buffer solution at pH ~ 7.0.

Table 1. Absorbance and Fluorescence maxima of compound 1, 2 and 3 at pH 7 in the presence of glucose and fructose.

Concentration of sugars (M)	Compound 1						Compound 2						Compound 3
	with glucose			with fructose			with glucose			with fructose			with glucose			with fructose
	abs	log 	flu	abs	log 	flu	abs	log 	flu	abs	log 	flu	abs	log 	flu	abs	log 	flu
0	540 385 324 269	4.19 4.06 4.33	470 441	540 385 325 269	4.19 4.06 4.33	470 441	488 324 310 278	3.20 3.45 3.46 4.22	687 663	488 324 310 278	3.20 3.45 3.46 4.22	687 663	490 325 310 278	3.34 3.53 3.51 4.23	688 664	490 325 310 278	3.34 3.53 3.51 4.23	688 664
0.002	540 385 325 268	4.18 4.05 4.32	471 440	540 385 325 269	4.19 4.04 4.32	471 440	487 325 310 277	3.18 3.44 3.45 4.22	687 663	488 324 310 278	3.15 3.48 3.47 4.29	687 663	490 324 309 278	3.29 3.51 3.50 4.20	688 664	491 325 310 279	3.32 3.49 3.47 4.21	688 664
0.010	540 386 325 268	4.17 4.05 4.31	470 439	540 385 325 269	4.17 4.01 4.29	470 439	488 324 311 279	3.08 3.38 3.44 4.21	687 663	487 324 310 278	3.06 3.41 3.41 4.24	687 663	490 324 309 278	3.18 3.43 3.41 4.18	688 664	490 324 310 278	3.24 3.42 3.41 4.19	688 664
Exci (nm)			380			380			480			480			480			480
K (1: 1) M-1		176	313		167	688		286	647		168	2482		347	351		344	796

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Figure 4. pH titration curves for sugar sensor vs glucose and fructose in the absorption and fluorescence spectra (0.01M); (a) compound 1, (b) compound 2, and (c) compound 3 (8 x 10-5 M) measured in buffer solutions at room temperature; pKa values are given in the figure. Sugar sensor vs glucose and fructose in the fluorescence intensity; (0.01M) for (a) compound 1 (ex =380 nm, em = 468 nm) (b) compound 2 (ex =480 nm, em = 684 nm) and (c) compound 3 (ex = 480 nm, em = 686 nm (8 x10-5 M) measured in buffer solutions.

Emission spectra pH profiles were also recorded under the same conditions (0.01 M glucose/fructose). In the excited state, photoinduced electron transfer (PET) is widely used for designing fluorescence saccharide sensors

[27-29]

. Boronate ester complex formation between carbohydrates and boronic acid receptors typically results in fluorescence changes via chelation-enhanced quenching (CHEQ) or chelation-enhanced fluorescence (CHEF)

[30, 31]

In the present study, sensor 1 showed minimal fluorescence changes upon glucose or fructose addition, though intensity decreased with increasing saccharide concentration. Conversely, sensors 2 and 3 underwent CHEQ in the presence of saccharides, with fluorescence quenching more pronounced at higher pH (≥9) compared to the sensor alone

[32-35]

. While sensor 1 showed no significant enhancement at high pH, it exhibited marked emission changes under these conditions.

Notably, such large fluorescence changes have rarely been reported for boronic acid-based sugar sensors. Ward et al. proposed that B-C-N interactions significantly influence the spectral changes of boronic acid-linked azobenzene dyes

[36, 37]

. In their case, the B-C-N bond formed between the boronic acid and the nitrogen atom of the azo group. Other studies have also highlighted the role of B-C-N bonding in enhancing the performance of boronic acid-based fluorometric sensors

[38-41]

. In contrast, here the B-C-N bond is directly linked to the nitrogen atom of the chromophoric azo group. The interaction between the chromophore and boronic acid appears to be crucial for inducing the significant UV-vis and fluorescence spectral changes observed.

3.4. Fluorescence Lifetime Analysis

The excited-state lifetimes of sensors 1, 2, and 3 were measured in water, glucose, and fructose solutions (0.01 M) by exciting at 380 nm for sensor 1 and at 480 nm for sensors 2 and 3, while recording emission across 400-700 nm. In the presence of glucose and fructose, all sensors exhibited increased lifetime values compared to those in water. In both aqueous and glucose/fructose media, the fluorescence decay profiles were best fitted with triexponential functions, indicating the presence of heterogeneous species. This suggests that the sensors exist in multiple microenvironments and can interact with sugars in aqueous solution. The three distinct lifetime components correspond to populations with varying degrees of interaction between the sensor molecules and saccharides. Notably, the excited-state lifetimes of sensors 1, 2, and 3 were consistently shorter in water than in glucose or fructose solutions, confirming that sugar binding stabilizes the excited states of the sensors.

Compound 1 (λem- 470 nm): water ≈ τave = 0.17 ns, C1: glucose ≈ τ1 - 0.10 ns, τ2 - 5.62 ns, τ3 - 1.99 ns, τave = 2.57 ns; C1: fructose ≈ τ1 - 1.01 ns, τ2 - 4.37 ns, τ3 - 3.19 ns, τave = 2.99 ns.

Compound 2 (λem - 660 nm): water ≈ τave = 2.02 ns, C2: glucose ≈ τ1- 1.52 ns, τ2 - 4.03 ns, τ3 - 2.32 ns, τave = 2.39 ns, C2: fructose ≈ τ1 - 1.53 ns, τ2 - 5.23 ns, τ3 - 2.57 ns, τave = 2.28 ns).

Compound 3 (λem - 660 nm): water ≈ τave = 2.00 ns, C3: glucose ≈ τ1- 1.53 ns, τ2 - 4.04 ns, τ3 - 2.33 ns, τave = 2.41 ns, C3: fructose ≈ τ1 - 1.54 ns, τ2 - 5.24 ns, τ3 - 2.58 ns, τave = 2.60 ns).

The increases in lifetimes of the sensors with glucose and fructose demonstrate their interactions with the saccharides.

3.5. Cyclic Voltammetry

Cyclic voltammetry (CV) was employed to investigate the interaction of the sensors with sugars, thereby confirming their sensing and binding modes. At pH ~7, the oxidation peaks of the isolated sensor compounds 1, 2, and 3 were observed at 0.763, 0.800, and 0.851 V, respectively (Figure 5, Tables 2 and 3). To evaluate the interaction between the sensors and glucose or fructose, fixed concentrations of glucose or fructose were mixed with varying amounts of sensor solutions, and the CV profiles were recorded (Tables 2 and 3).

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Figure 5. Cyclic voltammograms of glucose (in carbon electrode) with different concentrations of sensor (a) C1, (b) C2 and (c) C3 (x 10-4 M): 1) 0, 2), 3, 3) 7 and 4) 10.

Table 2. CV for sensor with glucose (scan rate, 100 mV s-1, concentration of glucose - 2×10-6 M; sensor concentration: 0, 3, 5, 7 and 10 ×10-3 M).

Sensor- sugar	Sensor conc’n x 10-3	Epa	Ipa	Epc	Ipc	Epa-Epc/2	Ipa/Ipc
Glucose only	2 x 10-6	373	0.224	-	-	-287	-
C1only	2	763	0.566	-	-	381	-
C1-Glucose	3	776	0.672	-	-	388	-
	5	785	0.637	-	-	392	-
	7	819	0.628	-	-	409	-
	10	844	0.591	-	-	422	-
C2 only	2	800	0.749	-	-	400	-
C2-Glucose	3	893	0.556	-	-	446	-
	5	1010	0.924	-	-	505	-
	7	1069	1.089	-	-	534	-
	10	1116	1.253	-	-	558	-
C3 only	2 x 10-6	851	0.613	-	-	678	-
C3-Glucose	3	773	0.922	-	-	396	-
	5	793	0.880	-	-	386	-
	7	826	0.852	-	-	413	-
	10	869	0.720	-	-	484	-

Table 3. CV for sensor with fructose (scan rate, 100 mV s-1, concentration of fructose - 2×10-6 M; sensor concentration: 0, 3, 5, 7 and 10 ×10-3 M).

Sensor- sugar	Sensor conc’n x 10-3	Epa	Ipa	Epc	Ipc	Epa-Epc/2	Ipa/Ipc
Fructose only		380	0.225	-	-	-290	-
C1only	2	765	0.563	-	-	378	-
C1- Fructose	3	777	0.670	-	-	385	-
	5	786	0.634	-	-	392	-
	7	817	0.624	-	-	407	-
	10	842	0.588	-	-	421	-
C2 only	2	798	0.746	-	-	402	-
C2- Fructose	3	890	0.553	-	-	444	-
	5	1008	0.921	-	-	501	-
	7	1066	1.086	-	-	533	-
	10	1113	1.250	-	-	555	-
C3 only	2 x 10-6	851	0.610	-	-	676	-
C3- Fructose	3	771	0.919	-	-	394	-
	5	790	0.877	-	-	384	-
	7	822	0.848	-	-	411	-
	10	866	0.722	-	-	482	-

Cyclic voltammograms of a carbon electrode in sensor with glucose (sensor concentration - 1x 10-3 M) at different scan rate = (100-500 mV s-1).

With increasing sensor concentration, the oxidation peaks current (Ipa) of the sensor-glucose system increased, accompanied by a positive shift in electrode potential (Epa). A similar trend was observed for the sensor-fructose system, where both oxidation peaks shifted toward higher potentials with a corresponding increase in Ipa. These observations indicate the formation of non-electroactive complexes between the sugars and the sensors. The increase in peak current is attributed mainly to the higher free concentration of the sensors and complex formation with sugars, rather than factors such as: (i) altered electrochemical kinetics of the sensor,

(ii) direct effects of sugar addition or electrode surface blockage,

(iii) adsorption of glucose/fructose onto the electrode surface, or (iv) competitive adsorption between the sensor and sugar at the glassy carbon electrode (GCE).

The observed oxidation peak potential shifts were ascribed to hydrophobic interactions between the sensors and sugars

[42]

. Electrostatic binding modes typically cause a more positive shift in the formal potential (E0), whereas intercalative binding modes also result in a positive E0 shift

[43]

. Therefore, the results suggest that the sensors interact with glucose and fructose via a partial intercalative binding mode.

CV measurements for sensor-sugar interactions were further performed at various scan rates (Figure 5). Plots of Ep versus υ and Ep versus lnυ yielded well-defined straight lines. From these plots, the value of αn was determined from the slope, while ks was obtained from the intercept. The E0 value was calculated by extrapolating the Ep versus υ plot to υ = 0, where Ep approaches E0. The number of binding sites (n) and the binding constant (βS) for the electrochemical interactions were determined using the following equation:

Log [ΔI/ [ΔImax − ΔI] = Log βs + m log [sensor]

Here, ΔI is the difference in peak current in the presence and absence of sugar, and ΔImax is the value obtained when the sensor concentration slightly exceeds that of the sugar. Csugar, [sugar], and [sugar-msensor] correspond to the total, free, and bound concentrations of sugar in the solution, respectively. A linear plot of log [ΔI/ (ΔImax−ΔI)] vs. log [Q] indicates that the sensor forms a 1: 1 complex with glucose or fructose. The binding ratio and constant were derived from the slope and intercept of this plot, with the binding constant closely matching values obtained from spectroscopic analysis.

These results demonstrate that the incorporation of a boronic acid group in resonance with an azo dye induces a noticeable color change in the dyes. This change is likely due to a conformational switch in the boron atom between its neutral and anionic states. Although the transition between electron-withdrawing and electron-donating properties of the boronic group influences the system, its effect on the intramolecular charge transfer of the dyes remains modest. For dyes 2 and 3, the electronic properties are predominantly governed by the COOH group and are largely unaffected by the boronic group. Notably, when the COOH group is deprotonated at pH < 4, dyes 2 and 3 undergo a pronounced color change from pale yellow to deep red in solution. Dye 1, which lacks a strong electron-donating group, exhibits larger optical changes. Ongoing work aims to explore the impact of boronic acid conformational switching on the optical properties of a broader range of azo dyes to better understand the origin of these color changes and optimize their magnitude.

4. Conclusion

Three naphthalene-based monoboronic acid azo dyes and their carboxylic acid-substituted derivatives were successfully synthesized. The affinity of the monoboronic acid moiety towards glucose and fructose was confirmed through absorption and fluorescence spectroscopy. Compounds 1, 2, and 3 demonstrated high selectivity and low detection limits for glucose and fructose at the optimum pH. At elevated pH values, the sensor molecules exhibited enhanced binding affinity towards both sugars, with association constant values indicating stronger binding for fructose compared to glucose. This increased affinity at higher pH is attributed to the conversion of the boronic acid group into its anionic form [B(OH)₃^-], accompanied by a change in the boron atom configuration from sp² to sp³, facilitating sugar binding. Cyclic voltammetry studies revealed that, at higher sensor concentrations, the oxidation peak current (Ipa) decreased while the reduction peak current (Ipc) increased; in the presence of sugars, however, Ipa showed a significant increase.

Abbreviations

Compound 1	4 (2-phenyl diazenyl phenyl boronicacid)
Compound 2	2 (4-diazenyl phenyl boronyl benzoicacid)
Compound 3	4 (1- diazenyl phenyl boronyl benzoic acid)
CV	Cyclic Voltammetry
A₀	Absorbance of the Solution in Water
IF	Fluorescence Intensity of the Solution in the Sensor
I₀	Fluorescence Intensity of the Solution in Water
A	Absorbance of the Solution in the Sensor
τ	Life Time of the Species in the Excited State
ns	Nanosecond
α	The Electron Transfer Coefficient
ks	The Standard Rate Constant of the Surface Reaction
υ	The Scan Rate
E₀	The Formal Potential
n	The Number of Electrons Transferred
Ep	Electrode Potential
IP_a	Oxidation Peak Current
IP_c	Reduction Peak Current
C_sugar, [sugar], and [sugar-sensor]	Refer to the Total, Free, and Bound Sugar Concentrations in the Solution, Respectively

Author Contributions

Murugesan Suresh: Formal Analysis, Investigation

Narayanasamy Rajendiran: Funding acquisition, Project administration, Methodology, Resources, Software, Supervision, Writing – original draft, Writing – review & editing

Palanichamy Ramasamy: Data curation

Sengamalai Senthilmurugan: Validation, Visualization

Conflicts of Interest

The authors declare no conflict of interest.

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Suresh, M., Rajendiran, N., Ramasamy, P., Senthilmurugan, S. (2026). Naphthalene Based Azo Dyes and Its Substituted Derivatives Containing Mono Boronic Acid - Saccharide Sensors. Science Journal of Analytical Chemistry, 14(2), 18-27. https://doi.org/10.11648/j.sjac.20261402.11

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Suresh, M.; Rajendiran, N.; Ramasamy, P.; Senthilmurugan, S. Naphthalene Based Azo Dyes and Its Substituted Derivatives Containing Mono Boronic Acid - Saccharide Sensors. Sci. J. Anal. Chem. 2026, 14(2), 18-27. doi: 10.11648/j.sjac.20261402.11

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Suresh M, Rajendiran N, Ramasamy P, Senthilmurugan S. Naphthalene Based Azo Dyes and Its Substituted Derivatives Containing Mono Boronic Acid - Saccharide Sensors. Sci J Anal Chem. 2026;14(2):18-27. doi: 10.11648/j.sjac.20261402.11

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@article{10.11648/j.sjac.20261402.11,
  author = {Murugesan Suresh and Narayanasamy Rajendiran and Palanichamy Ramasamy and Sengamalai Senthilmurugan},
  title = {Naphthalene Based Azo Dyes and Its Substituted Derivatives Containing Mono Boronic Acid - Saccharide Sensors},
  journal = {Science Journal of Analytical Chemistry},
  volume = {14},
  number = {2},
  pages = {18-27},
  doi = {10.11648/j.sjac.20261402.11},
  url = {https://doi.org/10.11648/j.sjac.20261402.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.sjac.20261402.11},
  abstract = {Three novel naphthalene-based azo dyes incorporating boronic acid functional groups were synthesized. Their sugar-sensing behavior toward glucose and fructose was systematically investigated using UV-visible, fluorescence, time-resolved fluorescence, pH titration, and cyclic voltammetry techniques. Upon increasing the concentration of the sugars, both the absorbance and fluorescence intensities of the dyes decreased, indicating effective interaction. In the excited state, the dyes exhibited stronger sensing responses to fructose compared to glucose. The fluorescence lifetime measurements further confirmed the compounds' capability to detect sugars. At elevated pH levels, the boronic acid groups exist predominantly in their anionic form [B(OH)3-], which induces a change in the boron atom's hybridization from sp2 to sp3, facilitating binding with sugar molecules. Among the three compounds, compound 1 exhibited the highest association constant with fructose, suggesting a stronger binding affinity is higher than compared to glucose. To further validate the sugar-sensing behavior, the quantum yields of the compounds were measured in pure water, glucose, and fructose solutions. When higher concentrations of the sensor were introduced into the sugar solution, the oxidation peaks current (Ipa) decreased while the reduction peak current (Ipc) increased. In contrast, Ipa increased in the sensor-only solutions. Based on these observations, a plausible sensing mechanism has been proposed.},
 year = {2026}
}

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TY - JOUR
T1 - Naphthalene Based Azo Dyes and Its Substituted Derivatives Containing Mono Boronic Acid - Saccharide Sensors
AU - Murugesan Suresh
AU - Narayanasamy Rajendiran
AU - Palanichamy Ramasamy
AU - Sengamalai Senthilmurugan
Y1 - 2026/04/13
PY - 2026
N1 - https://doi.org/10.11648/j.sjac.20261402.11
DO - 10.11648/j.sjac.20261402.11
T2 - Science Journal of Analytical Chemistry
JF - Science Journal of Analytical Chemistry
JO - Science Journal of Analytical Chemistry
SP - 18
EP - 27
PB - Science Publishing Group
SN - 2376-8053
UR - https://doi.org/10.11648/j.sjac.20261402.11
AB - Three novel naphthalene-based azo dyes incorporating boronic acid functional groups were synthesized. Their sugar-sensing behavior toward glucose and fructose was systematically investigated using UV-visible, fluorescence, time-resolved fluorescence, pH titration, and cyclic voltammetry techniques. Upon increasing the concentration of the sugars, both the absorbance and fluorescence intensities of the dyes decreased, indicating effective interaction. In the excited state, the dyes exhibited stronger sensing responses to fructose compared to glucose. The fluorescence lifetime measurements further confirmed the compounds' capability to detect sugars. At elevated pH levels, the boronic acid groups exist predominantly in their anionic form [B(OH)3-], which induces a change in the boron atom's hybridization from sp2 to sp3, facilitating binding with sugar molecules. Among the three compounds, compound 1 exhibited the highest association constant with fructose, suggesting a stronger binding affinity is higher than compared to glucose. To further validate the sugar-sensing behavior, the quantum yields of the compounds were measured in pure water, glucose, and fructose solutions. When higher concentrations of the sensor were introduced into the sugar solution, the oxidation peaks current (Ipa) decreased while the reduction peak current (Ipc) increased. In contrast, Ipa increased in the sensor-only solutions. Based on these observations, a plausible sensing mechanism has been proposed.
VL - 14
IS - 2
ER -

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Murugesan Suresh

Department of Chemistry, MRG Arts College, Mannargudi, India

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http://orcid.org/0000-0002-5346-6926
Narayanasamy Rajendiran

Department of Chemistry, Annamalai University, Annamalai Nagar, India

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http://orcid.org/0000-0002-5860-6609
Palanichamy Ramasamy

Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India

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http://orcid.org/0000-0003-0393-0417
Sengamalai Senthilmurugan

Department of Zoology, Annamalai University, Annamalai Nagar, India

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http://orcid.org/0000-0003-0204-4245

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Suresh, M., Rajendiran, N., Ramasamy, P., Senthilmurugan, S. (2026). Naphthalene Based Azo Dyes and Its Substituted Derivatives Containing Mono Boronic Acid - Saccharide Sensors. Science Journal of Analytical Chemistry, 14(2), 18-27. https://doi.org/10.11648/j.sjac.20261402.11

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ACS Style

Suresh, M.; Rajendiran, N.; Ramasamy, P.; Senthilmurugan, S. Naphthalene Based Azo Dyes and Its Substituted Derivatives Containing Mono Boronic Acid - Saccharide Sensors. Sci. J. Anal. Chem. 2026, 14(2), 18-27. doi: 10.11648/j.sjac.20261402.11

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AMA Style

Suresh M, Rajendiran N, Ramasamy P, Senthilmurugan S. Naphthalene Based Azo Dyes and Its Substituted Derivatives Containing Mono Boronic Acid - Saccharide Sensors. Sci J Anal Chem. 2026;14(2):18-27. doi: 10.11648/j.sjac.20261402.11

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@article{10.11648/j.sjac.20261402.11,
  author = {Murugesan Suresh and Narayanasamy Rajendiran and Palanichamy Ramasamy and Sengamalai Senthilmurugan},
  title = {Naphthalene Based Azo Dyes and Its Substituted Derivatives Containing Mono Boronic Acid - Saccharide Sensors},
  journal = {Science Journal of Analytical Chemistry},
  volume = {14},
  number = {2},
  pages = {18-27},
  doi = {10.11648/j.sjac.20261402.11},
  url = {https://doi.org/10.11648/j.sjac.20261402.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.sjac.20261402.11},
  abstract = {Three novel naphthalene-based azo dyes incorporating boronic acid functional groups were synthesized. Their sugar-sensing behavior toward glucose and fructose was systematically investigated using UV-visible, fluorescence, time-resolved fluorescence, pH titration, and cyclic voltammetry techniques. Upon increasing the concentration of the sugars, both the absorbance and fluorescence intensities of the dyes decreased, indicating effective interaction. In the excited state, the dyes exhibited stronger sensing responses to fructose compared to glucose. The fluorescence lifetime measurements further confirmed the compounds' capability to detect sugars. At elevated pH levels, the boronic acid groups exist predominantly in their anionic form [B(OH)3-], which induces a change in the boron atom's hybridization from sp2 to sp3, facilitating binding with sugar molecules. Among the three compounds, compound 1 exhibited the highest association constant with fructose, suggesting a stronger binding affinity is higher than compared to glucose. To further validate the sugar-sensing behavior, the quantum yields of the compounds were measured in pure water, glucose, and fructose solutions. When higher concentrations of the sensor were introduced into the sugar solution, the oxidation peaks current (Ipa) decreased while the reduction peak current (Ipc) increased. In contrast, Ipa increased in the sensor-only solutions. Based on these observations, a plausible sensing mechanism has been proposed.},
 year = {2026}
}

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