This work is aimed at utilization of vibrational spectroscopic techniques for characterization of several
types of structural particles suitable for the construction of chemical robots. Several case studies are presented
and discussed: (i) PNIPAM-coated silica particles, (ii) surface-functionalized magnetic nanoparticles
modified by citric and oleic acid, (iii) nanocomposit SERS-active substrates consisting of self-assembled
monolayers of linear α,ω-aliphatic diammines with different lengths on Ag metal surface and a flat Ag electrode
followed by testing of sensing activity of AD/NPs systems in the detection of the pesticide aldrin.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3515

Matějka, P.

Prokopec, V.

Singh, M.

Čejková, J.

Štěpánek, F.

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 1 No 3, 03PCSI09(4pp) (2012)   2304-1862/2012/1(4)03PCSI09(4) 03PCSI09-1  2012 Sumy State University Use of Vibrational Spectroscopic Techniques for the Characterization of Structured Particles for Chemical Robots   V. Prokopec1,*, J. Čejková2, M. Singh2, P. Matějka1, F. Štěpánek2  1  Department of Analytical chemistry Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic 2 Department of Chemical Engineering, Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic   (Received 19 June 2012; revised manuscript received 21 August 2012; published online 24 August 2012)  This work is aimed at utilization of vibrational spectroscopic techniques for characterization of several types of structural particles suitable for the construction of chemical robots. Several case studies are pre-sented and discussed: (i) PNIPAM-coated silica particles, (ii) surface-functionalized magnetic nanoparticles modified by citric and oleic acid, (iii) nanocomposit SERS-active substrates consisting of self-assembled monolayers of linear α,ω-aliphatic diammines with different lengths on Ag metal surface and a flat Ag elec-trode followed by testing of sensing activity of AD/NPs systems in the detection of the pesticide aldrin.  Keywords: Chemical robot, silica particles, magnetic nanoparticles, SERS substrates   PACS numbers: 82.80.Gk, 68.43. – h, 78.30. – j                                                             * vadym.prokopec@vscht.cz 1. INTRODUCTION  Chemical robots are in principle artificial cells, with the exception of the ability to evolve and self-replicate. The main components of such a synthetic cell are (i) a “body” (shell) that defines properties such a size, shape, hardness and should facilitate the exchange of molecules with the environment similarly as a cell membrane, (ii) the internal space with compartments which should pro-cess absorbed molecules and release or accumulate products of chemical reactions. Chemical robots should also have the ability to move either passively or actively in the surrounding medium, and to adhere to target sub-strates or objects. Chemical robots may be used for tar-geted drug delivery, recovery of valuable chemicals from dilute resources, environmental clean-up, as smart diag-nostic devices, or other applications [1]. The adhesion of chemical robots to substrates or other robots may be affected by several parameters, such as by their shape, size, and surface properties. One possibility how to control particle size and surface properties is to use the so-called smart polymers that change their volume and hydrophilic/hydrophobic properties by external stimu-li, e.g.microcapsules consisting of the thermo-responsive polymer PNIPAM and inorganic nanoparticles. Magnetic nanoparticles have been recently extensive-ly studied because of their extensive applications in bio-chemistry, bioseparation, tissue repair and in vivo drug delivery [2]. The properties of magnetic nanoparticles can be significantly altered by its physical and physico-chemical characteristics, such as morphological and compositional, and the possibility of engineering the particle surface to promote specific interactions with different targets. The key to understanding the proper-ties and stability of magnetic nanoparticles in different environments resides in the elucidation of their surface structure and its respective chemical composition. The interaction between the surfactant and nanoparticle is critical and essential for both synthesis and further ap-plications of nanoparticles [3]. The controlled fabrication of nanostructured junc-tions in SERS substrates is nowadays one of the critical targets in nanotechnology [4]. The functionalization of metal nanoparticles (NPs) by bifunctional agent gives rise to the formation of highly sensitive interparticle junctions by simultaneously creating intermolecular cavities (IC) where the approaching of detected sub-stances is possible, enabling so called single molecule detection (SMD) due to the formation of specified loca-tions with extremely high enhancement abilities, named hot spots (HS) [5]. One of the suitable groups of sub-stances which can serve as bifucntional linkers with promising properties for the creation of HS and IC are α,ω-aliphatic diammines (DA).   In this work several types of structural particles were analysed and characterized by vibrational spectro-scopic techniques: (i) PNIPAM-coated silica particles, (ii) surface-functionalized magnetic nanoparticles modified by citric and oleic acid, (iii) nanocomposit SERS-active substrates consisting of self-assembled monolayers of linear α,ω-aliphatic diammines with different lengths on Ag metal surface and a flat Ag electrode followed by test-ing of sensing activity of AD/NPs systems in the detec-tion of the pesticide aldrin.  2. EXPERIMENTAL  2.1 PNIPAM-coated SiO2 microparticles  For the PNIPAM-coated silica particles preparation commercial microparticles based on silicium dioxide with a mean size of 5 μm (Sigma) were used. The particles were functionalized by silanization by methacryloxypro-pyltrimethoxysilane (MPS, Sigma). The PNIPAM coat-ing was carried out by a conventional polymerization process [6]. The FTIR spectroscope (Nexus, Nicolet) was used to confirm the synthesis of PNIPAM-coated silica microparticles. All measurements were carried out on the ATR accessory. Each spectrum was measured with a resolution 2 cm-1 and 128 scans.   V. PROKOPEC, J. ČEJKOVÁ, M. SINGH, ET AL. PROC. NAP 1, 03PCSI09 (2012)   03PCSI09-2 2.2 Citric acid coated γ-Fe2O3 nanoparticles   The citric acid coated γ-Fe2O3 nanoparticles were synthesised using the in-situ and the ex-situ approach. The uncoated nanoparticles were formed according a procedure by Maity et al. [7]. The ex-situ citrate coated γ-Fe2O3 nanoparticles were synthesised using a similar procedure according to Sahoo et al. [8]. Citric acid coat-ed nanoparticles prepared in this way could be dried, stored under atmospheric conditions, and easily re-dispersed in aqueous media to form stable ferrofluids of the desired concentration. FTIR spectra of the nano-particles were collected using a Nicolet Nexus 670 spec-trometer (Thermo, USA) in the range of 4000 - 400 cm-1 at 4 cm-1 resolution. All presented spectra are the aver-age of 256 scans. The sample powders were mixed with KBr and compressed into a pellet. The baseline correc-tions were performed using OMNIC 7.0 software (Thermo, USA).   Fig. 1 – FTIR spectra of bare silica particles (a), pure NIPAM (b) and silica particles coated by PNIPAM (c)   2.3  Nanocomposit SERS-active substrates  Silver colloids were prepared by reduction of silver nitrate with hydroxylamine hydrochloride at room temperature [9]. SERS measurements on Ag colloidal suspensions were performed by adding an aliquot of aqueous chloride solution to a final concentration 2×10-2 M and, subsequently, by adding aliquots of and solutions up to the desired concentration. The flat elec-trode was subjected to the pretreatment procedure (pol-ishing and cleaning) and afterwards to ORC treatment in electrochemical cell in order to fabricate the desired nanomorphology of the surface. The electrode was then immersed into and solution for 12 hours and then into the suspension of NPs for 2 hours. Detection of aldrin was performed after immersing the electrode with composite substrate on its surface into the solution of aldrin with concentration 10-4 M for 2 hours. The SERS spectra were collected with a Renishaw Raman Micro-scope System equipped with argon laser at 514,5 nm, a Leica microscope, and an electrically cooled CCD cam-era. The laser power in the sample was 2.0 mW.   3. RESULTS AND DISCUSSION  3.1 PNIPAM-coated SiO2 microparticles  The successful coating procedure was confirmed by comparison of FTIR spectra of both uncoated and coated silica particles. Fig.  1 compares the infrared spectra of unmodified silica, NIPAM monomer and silica particles coated with PNIPAM. The spectra of both uncoated and PNIPAM-modified silica contain a band at 1040 cm-1 that corresponds to Si-O-Si stretching vibration. Be-sides that also bands at 933 cm-1 and 780 cm-1, corre-sponding to Si-O-C and Si-C stretching vibrations, re-spectively, are apparent. The spectrum of PNIPAM-modified silica shows the presence of many characteris-tic peaks corresponding to PNIPAM: N-H group stretch-ing band at 3265 cm-1, CH3 and CH2 groups stretching band at 2972, 2932 and 2877 cm-1, C=O stretching at 1658 resp. 1622 cm-1, N-H bending at ca. 1550 cm-1. All of the IR peaks have confirmed the successful grafting copolymerization of PNIPAM onto the silica.  3.2 Citric acid coated γ-Fe2O3 nanoparticles  Infrared spectroscopy has been used to characterize the iron oxide nanoparticles, as it is a complimentary  USE OF VIBRATIONAL SPECTROSCOPIC TECHNIQUES FOR THE… PROC. NAP 1, 03PCSI09 (2012)   03PCSI09-3 technique to differentiate between different oxide phases i.e. maghemite, magnetite and hematite. The FTIR spec-tra are summarized in Fig. 2. The broad high frequency bands between 3200 and 3600 cm-1 correspond to stretch-ing vibrations of the O-H bond from hydroxyl groups or absorbed water present on the nanoparticle surface.  The peaks at 2922 cm-1 and 2851 cm-1 correspond to stretching vibrations of aliphatic groups (CH3 and CH2). The peak around 1600 cm-1 and 1400 cm-1 in the uncoated   Fig. 2 – FTIR spectra of pure tri-sodium citrate, uncoated γ-Fe2O3 nanoparticles of 14 nm size and citrate coated nanoparticles of 3.2 and 10 nm size  nanoparticles corresponds to stretching vibrations of the O-H bond for H2O and C-O bond for CO2 (from air). The peaks (low frequency bands) at around 630 cm-1 and 446 cm-1 are the stretching vibration in tetrahedral site of the Fe-O bond, which is consistent with those for the ma-ghemite (γ-Fe2O3) phase [7]. A small shift of Fe-O bands known for bulk maghemite may have occurred due to overlapping of bands, giving an average wave number, or due to size effects. It has been observed that the intensity of the peaks increases with the decreasing particle size, showing an increased vacancy ordering with respect to size reduction of the nanoparticles. The presence of citric acid coating is confirmed by the presence of the broad peaks between 1500-1650 cm-1 and around 1400 cm-1 which correspond to asymmetric and symmetric C-O bonds of the citric acid coated nanoparticle surface. The peaks corresponding to citric acid become more intense in the smaller (3.2 nm) nanoparticles compared to 10 nm nanoparticles, which is consistent with their larger specif-ic surface area and therefore higher expected mass frac-tion of citric acid to iron oxide.     3.3 Nanocomposit SERS-active substrates  Two main spectral regions are found to be the most sensitive, giving the most useful information about the structural and dynamic properties of ADn/NPs systems. These are regions corresponding to C-C and C-H stretch-ing vibrations. The main chain C-C skeletal stretching region from ca. 1050 cm-1 to ca. 1150 cm-1 is sensitive to the intra-molecular conformation along each chain [10]. For a long chain with all-trans structures, two intense bands appear at ca. 1050 cm-1 and ca. 1130 cm-1 , which can be assigned to symmetric and anti-symmetric C-C stretching vibrations, respectively. With decreasing number of trans C-C bonds in the chain in favor of gauche conformers, the intensity of these two bands low-ers and a strong band at about 1080 cm-1 appears. The spectral features in the C-H stretching region at the range of ca. 2800 cm-1 – 3000 cm-1 are found to be cru-cially affected by the lateral packing interactions due to the re-orientation of the alkyl chains [11]. In this region all the aliphatic diammines with longer chains show a narrow band at ca. 2850 cm-1 corresponding to symmet-ric υ(C-H) mode, and a broad band at ca. 2915 cm-1. The H~2915/H~2850 ratio can be used as an indication of inter-molecular van der Waals interactions.  V. PROKOPEC, J. ČEJKOVÁ, M. SINGH, ET AL. PROC. NAP 1, 03PCSI09 (2012)   03PCSI09-4 The sensing ability of nanocomposit ADn functional-ized substrates was tested by using the polychlorinated insecticide aldrin as an example of a probe molecule. In the absence of diammine, no SERS spectrum of aldrin could be obtained due to its low affinity toward the metal surface, whereas the fabrication of nanocomposite sub-strate functionalized by bifunctional linker enabled its SERS detection due to the formation of the host/guest complex (Fig. 3). The characteristic bands of aldrin which are mainly assigned to C-Cl stretching modes can be seen in the low wavenumber region which is com-pletely free of diammine bands. The comparison with the Raman spectrum of solid aldrin confirms its positive detection with described system.    Fig. 3 – SERS spectra of DA8 (a), surface complex DA8/aldrin (b) and Raman spectrum of aldrin in condensed state (c)  4. CONCLUTIONS  It has been shown that vibrational spectroscopic techniques can be very useful in characterization of different types of structured particles which can serve as compartments for chemical robots. Within the exper-iments with SiO2 microparticles the successful coating of microparticles with thermo-responsive polymer PNIPAM was confirmed by using FTIR spectroscopy. FTIR measurements also confirmed the coating of -Fe2O3 nanoparticles by citric acid their consistence of the maghemite phase. Finally, in the experiments with nanocomposite substrates we have shown that ADn-functionalized Ag NPs systems can act as analyte na-nosensors for SERS detection of polychlorinated pesti-cides.  AKNOWLEDGEMENTS  Financial support from Czech Science Foundation P206/11/P405 is gratefully acknowledged.    REFERENCES  1. J. Čejková, „Design, synthesis and characterization of structural particles for chemical robots, Dissertation, 2010, Institute of Chemical Technology Prague. 2. S.J. Son, J. Reichel, B. He, M. Schuchman, S.B. Lee,  J. Am. Chem. Soc. 127, 7316 (2005). 3. R. Tietze, R. Jurgons, S. Lyer, E. Schreiber, F. Wiekhorst, D. Eberbeck, H. Richter, U. Steinhoff, L. Trahms, C. Alex-iou, J. Magnetism Magnetic Materials 321, 1465 (2009). 4. N.P.W. Pieczonka, R.F. Aroca, Chem. Soc. Rev. 37, 946 (2008). 5. L. Guerrini, J.V. Garcia-Ramos, C. Domingo, S. Sanchez-Cortes, J. Phys. Chem. C 112, 7527 (2008). 6. M. Karg, I. Pastoriza-Santos, L.M. Liz-Marzán, T. Hell-weg, ChemPhysChem 7(11), 2298 (2006). 7. D. Maity, D.C. Agrawal, J. Magn. Magn. Mater. 308, 46 (2007). 8. Y. Sahoo, A. Goodarzi, M. T. Swihart, T. Y. Ohulchanskyy, N. Kaur, E.P. Furlani, P.N. Prasad, J. Phys. Chem. B 109, 3879 (2005). 9. M.V. Canamares, J.V. Garcia-Ramos, J.D. Domez-Varga, C. Domingo, S. Sanchez-Cortes, Langmuir 21, 8546 (2005). 10. M.A. Bryant, J.E. Pemberton, J. Am. Chem. Soc. 113, 8284 (1991). 11. P. T. T. Wong, D. J. Siminovitch, H.H. Mantsch, Biochim. Biophys. Acta 947, 139 (1988).  

Use of Vibrational Spectroscopic Techniques for the Characterization of Structured Particles for Chemical Robots

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 1 No 3, 03PCSI09(4pp) (2012) 
 
 
2304-1862/2012/1(4)03PCSI09(4) 03PCSI09-1  2012 Sumy State University 
Use of Vibrational Spectroscopic Techniques for the Characterization of 
Structured Particles for Chemical Robots  
 
V. Prokopec1,*, J. Čejková2, M. Singh2, P. Matějka1, F. Štěpánek2 
 
1  Department of Analytical chemistry Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6, 
Czech Republic 
2 Department of Chemical Engineering, Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6, 
Czech Republic  
 
(Received 19 June 2012; revised manuscript received 21 August 2012; published online 24 August 2012) 
 
This work is aimed at utilization of vibrational spectroscopic techniques for characterization of several 
types of structural particles suitable for the construction of chemical robots. Several case studies are pre-
sented and discussed: (i) PNIPAM-coated silica particles, (ii) surface-functionalized magnetic nanoparticles 
modified by citric and oleic acid, (iii) nanocomposit SERS-active substrates consisting of self-assembled 
monolayers of linear α,ω-aliphatic diammines with different lengths on Ag metal surface and a flat Ag elec-
trode followed by testing of sensing activity of AD/NPs systems in the detection of the pesticide aldrin. 
 
Keywords: Chemical robot, silica particles, magnetic nanoparticles, SERS substrates 
 
 PACS numbers: 82.80.Gk, 68.43. – h, 78.30. – j 
 
 
                                                          
* vadym.prokopec@vscht.cz 
1. INTRODUCTION 
 
Chemical robots are in principle artificial cells, with 
the exception of the ability to evolve and self-replicate. 
The main components of such a synthetic cell are (i) a 
“body” (shell) that defines properties such a size, shape, 
hardness and should facilitate the exchange of molecules 
with the environment similarly as a cell membrane, (ii) 
the internal space with compartments which should pro-
cess absorbed molecules and release or accumulate 
products of chemical reactions. Chemical robots should 
also have the ability to move either passively or actively 
in the surrounding medium, and to adhere to target sub-
strates or objects. Chemical robots may be used for tar-
geted drug delivery, recovery of valuable chemicals from 
dilute resources, environmental clean-up, as smart diag-
nostic devices, or other applications [1]. 
The adhesion of chemical robots to substrates or other 
robots may be affected by several parameters, such as by 
their shape, size, and surface properties. One possibility 
how to control particle size and surface properties is to use 
the so-called smart polymers that change their volume 
and hydrophilic/hydrophobic properties by external stimu-
li, e.g.microcapsules consisting of the thermo-responsive 
polymer PNIPAM and inorganic nanoparticles. 
Magnetic nanoparticles have been recently extensive-
ly studied because of their extensive applications in bio-
chemistry, bioseparation, tissue repair and in vivo drug 
delivery [2]. The properties of magnetic nanoparticles 
can be significantly altered by its physical and physico-
chemical characteristics, such as morphological and 
compositional, and the possibility of engineering the 
particle surface to promote specific interactions with 
different targets. The key to understanding the proper-
ties and stability of magnetic nanoparticles in different 
environments resides in the elucidation of their surface 
structure and its respective chemical composition. The 
interaction between the surfactant and nanoparticle is 
critical and essential for both synthesis and further ap-
plications of nanoparticles [3]. 
The controlled fabrication of nanostructured junc-
tions in SERS substrates is nowadays one of the critical 
targets in nanotechnology [4]. The functionalization of 
metal nanoparticles (NPs) by bifunctional agent gives 
rise to the formation of highly sensitive interparticle 
junctions by simultaneously creating intermolecular 
cavities (IC) where the approaching of detected sub-
stances is possible, enabling so called single molecule 
detection (SMD) due to the formation of specified loca-
tions with extremely high enhancement abilities, named 
hot spots (HS) [5]. One of the suitable groups of sub-
stances which can serve as bifucntional linkers with 
promising properties for the creation of HS and IC are 
α,ω-aliphatic diammines (DA).   
In this work several types of structural particles 
were analysed and characterized by vibrational spectro-
scopic techniques: (i) PNIPAM-coated silica particles, (ii) 
surface-functionalized magnetic nanoparticles modified 
by citric and oleic acid, (iii) nanocomposit SERS-active 
substrates consisting of self-assembled monolayers of 
linear α,ω-aliphatic diammines with different lengths on 
Ag metal surface and a flat Ag electrode followed by test-
ing of sensing activity of AD/NPs systems in the detec-
tion of the pesticide aldrin. 
 
2. EXPERIMENTAL 
 
2.1 PNIPAM-coated SiO2 microparticles 
 
For the PNIPAM-coated silica particles preparation 
commercial microparticles based on silicium dioxide with 
a mean size of 5 μm (Sigma) were used. The particles 
were functionalized by silanization by methacryloxypro-
pyltrimethoxysilane (MPS, Sigma). The PNIPAM coat-
ing was carried out by a conventional polymerization 
process [6]. The FTIR spectroscope (Nexus, Nicolet) was 
used to confirm the synthesis of PNIPAM-coated silica 
microparticles. All measurements were carried out on 
the ATR accessory. Each spectrum was measured with 
a resolution 2 cm-1 and 128 scans.  
 V. PROKOPEC, J. ČEJKOVÁ, M. SINGH, ET AL. PROC. NAP 1, 03PCSI09 (2012) 
 
 
03PCSI09-2 
2.2 Citric acid coated γ-Fe2O3 nanoparticles  
 
The citric acid coated γ-Fe2O3 nanoparticles were 
synthesised using the in-situ and the ex-situ approach. 
The uncoated nanoparticles were formed according a 
procedure by Maity et al. [7]. The ex-situ citrate coated 
γ-Fe2O3 nanoparticles were synthesised using a similar 
procedure according to Sahoo et al. [8]. Citric acid coat-
ed nanoparticles prepared in this way could be dried, 
stored under atmospheric conditions, and easily re-
dispersed in aqueous media to form stable ferrofluids of 
the desired concentration. FTIR spectra of the nano-
particles were collected using a Nicolet Nexus 670 spec-
trometer (Thermo, USA) in the range of 4000 - 400 cm-1 
at 4 cm-1 resolution. All presented spectra are the aver-
age of 256 scans. The sample powders were mixed with 
KBr and compressed into a pellet. The baseline correc-
tions were performed using OMNIC 7.0 software 
(Thermo, USA).
 
 
 
Fig. 1 – FTIR spectra of bare silica particles (a), pure NIPAM (b) and silica particles coated by PNIPAM (c) 
 
 
2.3  Nanocomposit SERS-active substrates 
 
Silver colloids were prepared by reduction of silver 
nitrate with hydroxylamine hydrochloride at room 
temperature [9]. SERS measurements on Ag colloidal 
suspensions were performed by adding an aliquot of 
aqueous chloride solution to a final concentration 
2×10-2 M and, subsequently, by adding aliquots of and 
solutions up to the desired concentration. The flat elec-
trode was subjected to the pretreatment procedure (pol-
ishing and cleaning) and afterwards to ORC treatment 
in electrochemical cell in order to fabricate the desired 
nanomorphology of the surface. The electrode was then 
immersed into and solution for 12 hours and then into 
the suspension of NPs for 2 hours. Detection of aldrin 
was performed after immersing the electrode with 
composite substrate on its surface into the solution of 
aldrin with concentration 10-4 M for 2 hours. The SERS 
spectra were collected with a Renishaw Raman Micro-
scope System equipped with argon laser at 514,5 nm, a 
Leica microscope, and an electrically cooled CCD cam-
era. The laser power in the sample was 2.0 mW. 
 
 
3. RESULTS AND DISCUSSION 
 
3.1 PNIPAM-coated SiO2 microparticles 
 
The successful coating procedure was confirmed by 
comparison of FTIR spectra of both uncoated and coated 
silica particles. Fig.  1 compares the infrared spectra of 
unmodified silica, NIPAM monomer and silica particles 
coated with PNIPAM. The spectra of both uncoated and 
PNIPAM-modified silica contain a band at 1040 cm-1 
that corresponds to Si-O-Si stretching vibration. Be-
sides that also bands at 933 cm-1 and 780 cm-1, corre-
sponding to Si-O-C and Si-C stretching vibrations, re-
spectively, are apparent. The spectrum of PNIPAM-
modified silica shows the presence of many characteris-
tic peaks corresponding to PNIPAM: N-H group stretch-
ing band at 3265 cm-1, CH3 and CH2 groups stretching 
band at 2972, 2932 and 2877 cm-1, C=O stretching at 
1658 resp. 1622 cm-1, N-H bending at ca. 1550 cm-1. All 
of the IR peaks have confirmed the successful grafting 
copolymerization of PNIPAM onto the silica. 
 
3.2 Citric acid coated γ-Fe2O3 nanoparticles 
 
Infrared spectroscopy has been used to characterize 
the iron oxide nanoparticles, as it is a complimentary 
 USE OF VIBRATIONAL SPECTROSCOPIC TECHNIQUES FOR THE… PROC. NAP 1, 03PCSI09 (2012) 
 
 
03PCSI09-3 
technique to differentiate between different oxide phases 
i.e. maghemite, magnetite and hematite. The FTIR spec-
tra are summarized in Fig. 2. The broad high frequency 
bands between 3200 and 3600 cm-1 correspond to stretch-
ing vibrations of the O-H bond from hydroxyl groups or 
absorbed water present on the nanoparticle surface.  The 
peaks at 2922 cm-1 and 2851 cm-1 correspond to stretching 
vibrations of aliphatic groups (CH3 and CH2). The peak 
around 1600 cm-1 and 1400 cm-1 in the uncoated
 
 
 
Fig. 2 – FTIR spectra of pure tri-sodium citrate, uncoated γ-Fe2O3 nanoparticles of 14 nm size and citrate coated nanoparticles of 
3.2 and 10 nm size 
 
nanoparticles corresponds to stretching vibrations of the 
O-H bond for H2O and C-O bond for CO2 (from air). The 
peaks (low frequency bands) at around 630 cm-1 and 
446 cm-1 are the stretching vibration in tetrahedral site of 
the Fe-O bond, which is consistent with those for the ma-
ghemite (γ-Fe2O3) phase [7]. A small shift of Fe-O bands 
known for bulk maghemite may have occurred due to 
overlapping of bands, giving an average wave number, or 
due to size effects. It has been observed that the intensity 
of the peaks increases with the decreasing particle size, 
showing an increased vacancy ordering with respect to 
size reduction of the nanoparticles. The presence of citric 
acid coating is confirmed by the presence of the broad 
peaks between 1500-1650 cm-1 and around 1400 cm-1 
which correspond to asymmetric and symmetric C-O 
bonds of the citric acid coated nanoparticle surface. The 
peaks corresponding to citric acid become more intense in 
the smaller (3.2 nm) nanoparticles compared to 10 nm 
nanoparticles, which is consistent with their larger specif-
ic surface area and therefore higher expected mass frac-
tion of citric acid to iron oxide. 
 
 
 
 
3.3 Nanocomposit SERS-active substrates 
 
Two main spectral regions are found to be the most 
sensitive, giving the most useful information about the 
structural and dynamic properties of ADn/NPs systems. 
These are regions corresponding to C-C and C-H stretch-
ing vibrations. The main chain C-C skeletal stretching 
region from ca. 1050 cm-1 to ca. 1150 cm-1 is sensitive to 
the intra-molecular conformation along each chain [10]. 
For a long chain with all-trans structures, two intense 
bands appear at ca. 1050 cm-1 and ca. 1130 cm-1 , which 
can be assigned to symmetric and anti-symmetric C-C 
stretching vibrations, respectively. With decreasing 
number of trans C-C bonds in the chain in favor of 
gauche conformers, the intensity of these two bands low-
ers and a strong band at about 1080 cm-1 appears. The 
spectral features in the C-H stretching region at the 
range of ca. 2800 cm-1 – 3000 cm-1 are found to be cru-
cially affected by the lateral packing interactions due to 
the re-orientation of the alkyl chains [11]. In this region 
all the aliphatic diammines with longer chains show a 
narrow band at ca. 2850 cm-1 corresponding to symmet-
ric υ(C-H) mode, and a broad band at ca. 2915 cm-1. The 
H~2915/H~2850 ratio can be used as an indication of inter-
molecular van der Waals interactions. 
 V. PROKOPEC, J. ČEJKOVÁ, M. SINGH, ET AL. PROC. NAP 1, 03PCSI09 (2012) 
 
 
03PCSI09-4 
The sensing ability of nanocomposit ADn functional-
ized substrates was tested by using the polychlorinated 
insecticide aldrin as an example of a probe molecule. In 
the absence of diammine, no SERS spectrum of aldrin 
could be obtained due to its low affinity toward the metal 
surface, whereas the fabrication of nanocomposite sub-
strate functionalized by bifunctional linker enabled its 
SERS detection due to the formation of the host/guest 
complex (Fig. 3). The characteristic bands of aldrin 
which are mainly assigned to C-Cl stretching modes can 
be seen in the low wavenumber region which is com-
pletely free of diammine bands. The comparison with the 
Raman spectrum of solid aldrin confirms its positive 
detection with described system. 
 
 
 
Fig. 3 – SERS spectra of DA8 (a), surface complex DA8/aldrin (b) and Raman spectrum of aldrin in condensed state (c) 
 
4. CONCLUTIONS 
 
It has been shown that vibrational spectroscopic 
techniques can be very useful in characterization of 
different types of structured particles which can serve 
as compartments for chemical robots. Within the exper-
iments with SiO2 microparticles the successful coating 
of microparticles with thermo-responsive polymer 
PNIPAM was confirmed by using FTIR spectroscopy. 
FTIR measurements also confirmed the coating of 
-Fe2O3 nanoparticles by citric acid their consistence of 
the maghemite phase. Finally, in the experiments with 
nanocomposite substrates we have shown that ADn-
functionalized Ag NPs systems can act as analyte na-
nosensors for SERS detection of polychlorinated pesti-
cides. 
 
AKNOWLEDGEMENTS 
 
Financial support from Czech Science Foundation 
P206/11/P405 is gratefully acknowledged. 
 
 
 
REFERENCES 
 
1. J. Čejková, „Design, synthesis and characterization of 
structural particles for chemical robots, Dissertation, 2010, 
Institute of Chemical Technology Prague. 
2. S.J. Son, J. Reichel, B. He, M. Schuchman, S.B. Lee,  
J. Am. Chem. Soc. 127, 7316 (2005). 
3. R. Tietze, R. Jurgons, S. Lyer, E. Schreiber, F. Wiekhorst, 
D. Eberbeck, H. Richter, U. Steinhoff, L. Trahms, C. Alex-
iou, J. Magnetism Magnetic Materials 321, 1465 (2009). 
4. N.P.W. Pieczonka, R.F. Aroca, Chem. Soc. Rev. 37, 946 
(2008). 
5. L. Guerrini, J.V. Garcia-Ramos, C. Domingo, S. Sanchez-
Cortes, J. Phys. Chem. C 112, 7527 (2008). 
6. M. Karg, I. Pastoriza-Santos, L.M. Liz-Marzán, T. Hell-
weg, ChemPhysChem 7(11), 2298 (2006). 
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https://essuir.sumdu.edu.ua/bitstream/123456789/35158/1/princon_2012_1_3_54.pdf

Use of Vibrational Spectroscopic Techniques for the Characterization of Structured Particles for Chemical Robots

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