FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
"A Method for Synthesis of Dysprosium Sulfide (Dy2S3) Thin film and Supercapacitive Application
Thereof."
2. APPLICANT
a) NAME: Dr. Vishwanath Vithal Bhosale
b) NATIONALITY: Indian
c) ADDRESS: D.Y. Patil Education Society (Deemed to be University), Kasaba Bawada, Kolhapur 416 006.
3. PREAMBLE TO THE DESCRIPTION
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it is to be
performed
The following specification particularly describes and ascertains the nature of the present invention and the manner in which it is to be performed. Papers Related to work
1. P.P.Kumbhar and C.D.Lokhande, Electrodeposition of dysprosium from non-aqueous ethanol bath, Indian J. Chem. Technol., 1(1994) 194-196.
2. J.Lodermeyer, M.Multerer, M.Zistler, SJordan, HJ.Gores, W.Kipferl, E. Diaconu, M. Sperl,G.Bayreuther, Electroplating of dysprosium, electrochemical investigations, and study of magnetic properties, J. Elec. Soc, 153 (2006) C242-C248 .
3. C.A.Berger, M. Arkhipova, G. Maas, T. Jacob, Dysprosium electrodeposition from a hexaalkylguanidinium-based ionic liquid, Nanoscale, 8 (2016) 13997-14003.
U.S. Patents

Sr.
no. Name of the patent Patent Number Month and year Inventors
1 Method for producing thin films of rare earth chalcogenides 4,575,464 March 11, 1986 Grain et.al. Framingham, MA
2 Protected thermoelectric elements and method of protecting same 3,737,345 June 5, 1973 Kudman, et. al. NJ
3 Phase change memory devices and methods comprising gallium, lanthanide and chalcogenide compounds 8,624,215 January 7, 2014 Hewak et al. Hampshire, GB

The field of invention:
The present investigation concerns with producing thin coating of rare earth chalcogenide,
particularly dysprosium sulfide at low temperature onto solid surfaces usable in energy storage devices.
Background of invention:
Here, the rare earth chalcogenides has been synthesized by electrodeposition and chemical
bath deposition (CBD) method and used for electromagnetic properties as well as supercapacitor properties but in the present investigation first time dysprosium sulfide which belongs to lanthanides series have synthesized by successive ionic layer and reaction (SILAR) method and applicable for supercapacitor application.
As a broad classification of thin film methods, physical and chemical methods are only two classes based on the method of material deposition. In physical methods, vacuum evaporation and sputtering are the basic categories, which are further classified into laser evaporation, electron beam evaporation, RF sputtering, magnetron sputtering etc. Chemical methods are classified according to phase of initial precursor solutions. Solution and gas phases are further couple of routes of chemical methods, which are further classified into chemical vapor deposition (CVD), electrodeposition, chemical bath deposition, hydrothermal, successive ionic layer adsorption and reaction (SILAR) method etc. Physical methods require high working temperature and high vacuum and advanced instruments. Hence these methods suffer from high cost. Moreover, material wastage and cleaning of deposition chamber and small area deposition are crucial things of concern in the physical methods. Comparatively, chemical methods are simple, cheap and convenient to deposit materials on large scale. Different preparative parameters of chemical methods such as the solution pH, concentration of reactants, deposition temperature, and time of deposition can be easily controlled.
One of the newest solution methods for the deposition of thin film is successive ionic layer adsorption and reaction (SILAR) method. As it is a chemical method, a large number of varieties of

substrates can be coated, as it can produce coating of variety of surface nanostructures of different materials with three dimensional (3-D), two-dimensional (2-D) and one dimensional (1-D) shapes and sizes, ideal for industrial applications. It is worked in open system at elevated temperature. This method relies on the chemical reactions, further, solubility of substances changes in a sealed heated aqueous solution above ambient temperature and pressure to grow nano-crystals.
The SILAR method has various advantages over other conventional methods such as:
1) This system has been designed to automatic the entire process to avoid operator fatigue and errors associated with it. In manual SILAR process, the operator has to perform hundreds of repetitive dipping into the solution and water. It is very difficult to control dip duration and number of dips in a manual process which can last hours. In the automated unit, the operator need just to clamp the substrate into the holder and program the controller with required dip cycles and duration.
2) It is user friendly, cost-effective, and convenient method to obtain coating of various inorganic materials. Coating of material can be possible on any conducting and non-conducting material and thickness can be easily controlled by manipulating various preparative parameters such as temperature, time of dipping time, drying time, cycles, concentrations of initial precursors, pH of solution etc.
3) It can be worked at low temperature and convenient to obtain large area coating of material.
4) Material wastage is minimized compared with resistive heating and sputtering methods.
5) Variety of nanostructures can be easily produced at the micro-surface of coating material.
Rare earth elements usually exist in trivalent cations, consist of the fifteen lanthanides (from atomic number of 57 to 71) plus yttrium and scandium. In the past, rare earth elements based sulfides (CeS2, LaS2, Dy2S3 etc.) have been prepared with the help of sulfurization technique of their corresponding oxide compounds using H2S or CS2 like toxic gases. Rare earth sulfides are good refractory materials, as these are thermodynamically stable at higher temperatures. Due to

excellent chemical and physical properties, rare earth sulfides are used as optical materials for thermoelectric devices. More importantly, these materials are known to undergo dramatic change in their optical properties, when subjected to changing temperature, pressure or magnetic fields. Recently, thin films of rare earth sulfides, such as Sm2S3, La2S3 and Y-S have been prepared using simple chemical methods such as successive ionic layer adsorption and reaction (SILAR), chemical bath deposition (CBD) and electrodeposition, respectively and used in energy storage devices.
Dysprosium sulfide, one of the rare earth metals is formed in two dominant phases as DyS and Dy2S3 with various crystal structures such as cubic, tetragonal, orthorhombic and monoclinic. Dysprosium is deposited by electrodeposition method on different solid substrates and studied its electrical properties. Further, more electrochemical and magnetic properties are also studied. However, till date, synthesis of Dy2S3 thin films either by physical or chemical methods has not been reported in literature.
Dysprosium sulfide (Dy2S3), one of the rare earth sulfides is formed in two dominant phases as DyS and Dy2S3 with different crystal structures such as cubic, tetragonal, orthorhombic and monoclinic. Prior Art
U.S. Patent no. 4,575,464 describes a method for producing thin films of chalcogenides of the rare earths. Thin films are produced by introducing a rare earth metal vapor into an oxygen less atmosphere, however containing a gaseous chalcogen as well as hydrogen, giving rise to a reaction which formed a gaseous rare earth chalcogenide. The gaseous rare earth chalcogenide was deposited as a thin film on a substrate heated to 200 to 400 °C.
U.S. Patent no. 3,737,345 describes a thermoelectric element, comprising lead telluride and/or lead selenide, provided with a protective coating of a compound of tellurium and/or selenium and one of the rare earth elements, gadolinium, terbium, dysprosium, holmium, erbium, thulium, or ytterbium. The method comprised chemically reacting the heated, unprotected

thermoelectric element, in an evacuated environment, with one of the aforementioned rare earth elements to form the protective coating as a refractory reaction product.
U.S. Patent no. 8,624,215 describes phase change of some rare earth materials based on compounds of Ga; lanthanide; and chalcogenide. This includes compounds of Ga, La, and S (GLS) as well as related compounds in which there is substitution of S with O, Se and/or Te. It has been demonstrated that this class of materials exhibit low energy switching. Objectives of the Invention:
A main purpose of the present invention is to produce thin film of dysprosium sulfide on stainless steel substrate. Another main purpose of the present invention is to produce dysprosium sulfide thin film using chemical method. Another purpose is to obtain dysprosium sulfide (Dy2S3) thin film with orthorhombic crystal structure. Yet another main purpose of present is to produce nanostructured morphology of dysprosium sulfide thin film by optimizing preparative parameters in chemical method namely, Successive Ionic Layer Adsorption and Reaction (SILAR) method. Yet another purpose of invention is to produce dysprosium sulfide thin film on large area of surfaces useful for applications in supercapacitor. Summary of the Invention:
The present invention deals with synthesis of dysprosium sulfide (Dy2S3) thin film onto stainless steel substrates from aqueous acidic bath (pH between 1.5 to 4.5), which comprises (0.2 M-1M) dysprosium compounds Dy(NO3)3 and (0.2-1M) sodium sulfide (Na2S) solutions at temperature between 303 K to 333 K and varying dipping time between 10 to 30 sec and dipping cycles between 10 to 60 sec. Moreover, Dy2S3 thin film on stainless steel substrate is subjected for its electrochemical supercapacitive response as an application. The following examples, according to favored embodiments of the invention, demonstrate the features thereof. However, it is understood that such examples are not to be interpreted as limiting the scope of the invention as defined in the claims.

Example: 1
The coating of Dy2S3 thin film is carried out at 303 K temperature by SILAR method. In the coating of Dy2S3 thin film, aqueous 0.1 M Dy(NO3)3 solution is used as the cationic precursor and
0.2 M Na2S solution is utilized as the anionic precursor. The cleaned stainless steel substrate (SS) is
immersed in the cationic precursor for 30 s, where Dy ions are adsorbed on the substrate,
followed by 30 s rinsing in double distilled water (DDW) to remove the loosely bound species of
Dy+3 ionic species. Successively, the substrate is dipped in the anionic precursor solution of S"2 ions
for 30 s to build a layer of Dy2S3. Again, the substrate is rinsed for 30 s in DDW to take out the
overloaded or unreacted species. In this way, one SILAR cycle of Dy2S3 deposition is completed
and 20 such deposition cycles are reiterated to get the terminal thickness of the film is 0.4 mg/cm2.
The yellowish white colored coating of Dy2S3 is formed on steel. The yellowish white colored
coating of Dy2S3 is formed on steel and glass plates.
From the X-ray diffraction study, peak positions observed at 20 values of 19,25, 21.65,
23.02, 28.36, 29.23, 30.97, and 32.43° correspond to planes of (102), (311), (202), 210), (211),
(302), and (105), respectively of orthorhombic phase of Dy2S3 (Fig. 1). Scanning electron
microscopy (SEM) study of Dy2S3 film showed uniform distribution of nano particles over the
surface of steel (Fig. 2).

Entity Parameters
Cationic precursor Dy(NO3)3(0.1M)
Anionic precursor Na2S (0.2 M)
pH of cationic solution 1.5=1=0.1
Substrate Stainless steel (5 cm2)
Temperature 303 K
Deposition time (s) 30
Rinsing time (s) 30
Cycles 20
Crystal structure Orthorhombic Dy2S3 (Crystalline size 30 nm)
Structure and morphology thickness Nanocrystalline (50 nm).

Thickness 0.4 mg/cm2
Example: 2
Dysprosium sulfide (Dy2S3)thin film is carried out at 313 K temperature by SILAR method.
In the coating of Dy2S3 thin film, aqueous 0.2 M Dy(NO3)3 solution is used as the cationic precursor and 0.4 M Na2S solution is utilized as the anionic precursor. The cleaned stainless steel substrate (SS) is immersed in the cationic precursor for 25 s, where Dy+3 ions are adsorbed on the substrate, followed by 25 s rinsing in double distilled water (DDW) to remove the loosely bound species of Dy+3 ionic species. Successively, the substrate is dipped in the anionic precursor solution of S"2 ions for 25 s to build a layer of Dy2S3. Again, the substrate is rinsed for 25 s in DDW to take out the overloaded or unreacted species. In this way, one SILAR cycle of Dy2S3 deposition is completed and 30 such deposition cycles are reiterated to get the terminal thickness of the film is 0.8 mg/cm2.

Entity Parameters
Cationic precursor Dy(NO3)3 (0.2M)
Anionic precursor Na2S (0.4 M)
pH of cationic solution 2±0.1
Substrate Stainless steel (10 cm2)
Temperature 313K
Deposition time (s) 25
Rinsing time (s) 25
Cycles 30
Crystal structure Orthorhombic Dy2S3 (Crystalline size 40 nm)
Structure and morphology thickness Nanocrystalline (70 nm).
Thickness 0.6 mg/cm
Example: 3
Dysprosium sulfide (Dy2S3)thin film is carried out at 323 K temperature by SILAR method.
In the coating of Dy2S3 thin film, aqueous 0.4 M Dy(NO3)3 solutions are used as the cationic precursor and 0.5 M Na2S solution is utilized as the anionic precursor. The cleaned stainless steel substrate (SS) is immersed in the cationic precursor for 20 s, where Dy ions are adsorbed on the substrate, followed by 20 s rinsing in double distilled water (DDW) to remove the loosely bound

species of Dy+3 ionic species. Successively, the substrate is dipped in the anionic precursor solution of S"2 ions for 20 s to build a layer of Dy2S3. Again, the substrate is rinsed for 20 s in DDW to take out the overloaded or unreacted species. In this way, one SILAR cycle of Dy2S3 deposition is completed and 40 such deposition cycles are reiterated to get the terminal thickness of the film is 0.8 mg/cm2. The yellowish white colored coating of Dy2S3 is formed on stainless steel substrate.

Entity Parameters
Cationic precursor Dy(NO3)3(0.4M)
Anionic precursor Na2S (0.5 M)
pH of cationic solution 3.5±0.1
Substrate Stainless steel (20 cm2)
Temperature 323 K
Deposition time (s) 20
Rinsing time (s) 20
Cycles 40
Crystal structure Orthorhombic Dy2S3 (Crystalline size 50 nm)
Structure and morphology thickness Nanocrystailine (80 nm).
Thickness 0.8 mg/cm2
Example: 4
Dysprosium sulfide (Dy2S3)thin film is carried out at 323 K temperature by SILAR method.
In the coating of Dy2S3 thin film, aqueous 0.7 M Dy (NO3)3 solution is used as the cationic precursor and 0.8 M Na2S solution is utilized as the anionic precursor. The cleaned stainless steel substrate (SS) is immersed in the cationic precursor for 15 s, where Dy ions are adsorbed on the substrate, followed by 15 s rinsing in double distilled water (DDW) to remove the loosely bound species of Dy ionic species. Successively, the substrate is dipped in the anionic precursor solution of S" ions for 15 s to build a layer of Dy2S3. Again, the substrate is rinsed for 15 s in DDW to take out the overloaded or unreacted species. In this way, one SILAR cycle of Dy2S3 deposition is completed and 50 such deposition cycles are reiterated to get the terminal thickness of the film 0.9 mg/cm . The yellowish white colored coating of Dy2S3 is formed on stainless steel substrate.

Entity Parameters
Cationic precursor Dy(NO3)3 (0.7M)
Anionic precursor Na2S(0.9M)
pH of cationic solution 4.0±0.1
Substrate Stainless steel (25 cm2)
Temperature 323 K
Deposition time (s) 15
Rinsing time (s) 15
Cycles 50
Crystal structure Orthorhombic Dy2S3 (Crystalline size 30 nm)
Structure and morphology thickness Nanocrystalline (50 nm),
Thickness 0.9 mg/cm2
Example: 5
Dysprosium sulfide (Dy2S3) thin film is carried out at 333 K temperature (60) by SILAR
method. In the coating of Dy2S3 thin film, aqueous 0.7 M Dy (NO3)3 solution is used as the cationic precursor and 0.8 M Na2S solution is utilized as the anionic precursor. The cleaned stainless steel substrate (SS) is immersed in the cationic precursor for 10 s, where Dy+3 ions are adsorbed on the substrate, followed by 10 s rinsing in double distilled water (DDW) to remove the loosely bound species of Dy+3 ionic species. Successively, the substrate is dipped in the anionic precursor solution of S' ions for 10 s to build a layer of Dy2S3. Again, the substrate is rinsed for 10 s in DDW to take out the overloaded or unreacted species. In this way, one SILAR cycle of Dy2S3 deposition is completed and 60 such deposition cycles are reiterated to get the terminal thickness of the film 1 mg/cm . The yellowish white colored coating of Dy2S3 is formed on stainless steel substrate.

Entity Parameters
Cationic precursor Dy(N03)3 (0.7M)
Anionic precursor Na2S (0.9 M)
pH of cationic solution 4.5±0.1
Substrate Stainless steel (25 cm2)
Temperature 333 K

Deposition time (s) 10
Rinsing time (s) 10
Cycles 60
Crystal structure Orthorhombic Dy2S3 (Crystalline size 25 nm)
Structure and morphology thickness Nanocrystalline (55 nm).
Thickness 1 mg/cm
Example: 6
Dysprosium sulfide coating made on stainless steel substarte in example 1 is studied for
supercapacitor application. For this, three electrode cell setup is used. Three electrode cells consists of working electrode as Dy2S3 coated stainless steel substrate, platinum plate as a counter electrode, and saturated calomel electrode (SCE) as reference electrode. Supercapacitive evaluation of Dy2S3 coating is carried using 1 M Na2SO4 electrolyte within potential window of-1 to 0 V/SCE.
Cyclic voltammetry (CV) and galvanostatic charge discharge (GCD) analysis of Dy2S3 is carried out to test charge storage application of material. In CV study, material is scanned for various scan rates from 5 to 100 mVs-1 scan rates showing quasi-rectangular nature of all curves as shown in Fig. 3 (A). Further, highest specific capacitance of 272.7 Fg-1 at scan rate of 5 mVs-1 is calculated for Dy2S3 coating using following equation,
(1)
Cs=ʃv2v1[V(I)dV/mv.{V2-V\)
where, ʃv2v1[V(I)dV is area under the CV curve for corresponding scan rate of v and within potential

window of (V2-V1), and m is coating mass of Dy2S3 on steel plate of 1 cm area.
The galvanostatic charge discharge (GCD) technique is used to test nature of Dy2S3 electrode, either pseudocapacitive or not. GCD measurements of Dy2S3 coated electrode are carried for current densities of 0.1 to 0.4 mAcm-2 as shown in Fig. 3 (B). Firstly sudden potential IR drop is observed in each GCD curve relating intrinsic resistance of coating and subsequent non-linear curve indicates pseudocapacitive behavior of material.

Object Parameters
Electrode material Dy2S3 coating on stainless steel (5 cm2)
Electrolyte 1 M Na2SO4
Scan rate variation 5-100 mVs-1
Highest specific capacitance 272.7 Fg-1 for 5 mVs-1
Dysprosium sulfide is a member of rare earth chalcogenide. The coatings of dysprosium sulfide having Dy2S3 phase, with orthorhombic crystal structure, and nanostructured surface formed on solid surfaces is helpful in different better applications such as thermoelectric devices, solar cell, gas sensor and supercapacitor. One of application of energy storage is exemplified in this investigation.

We claim,
1. A method for synthesis of dysprosium sulfide film on solid substrate, wherein the
method comprises of following steps:
a) Immersion of substrate in aqueous solution of dysprosium nitrate for 10 to 30 seconds so as to form a uniform layer of dysprosium ions on the stainless steel substrate;
b) followed by rinsing of the substrate with double distilled water for 10 to 30 seconds,
c) followed by insertion of the substrate in aqueous solution of sodium sulfide for 10 to 30 seconds for the reaction of dysprosium ions with sulfide ions so as to form dysprosium sulfide film on stainless steel substrate surface; wherein, concentration of dysprosium nitrate in aqueous solution is in between 0.1 to 1 M; wherein concentration of sodium sulfide solution is in between 0.2 to 1 M; wherein, the steps of a to c are repeated to produce dysprosium sulfide film on stainless steel substrate of desired thickness.

2. The method as claimed in claim 1, wherein, the dysprosium sulfide film is coated at temperature between 303 to 333 K.
3. The method as claimed in claim 1, wherein, is dysprosium sulfide film is nano crystalline and uniform.
4. The method as claim 1, wherein, the thickness of dysprosium sulfide film ranges from 0.4 to 1 mg/cm2.
5. The dysprosium sulfide film as described in claim 1 is used for electrochemical energy storage with specific capacitance of 272.7 F g-1.
6. The method as claimed in claim 1, wherein, nano crystalline dysprosium sulfide film on stainless steel substrate stores electrochemical energy substantially as herein described with the help of example no. 6.